Linux Virtualization - Sep 2019 - [PATCH V2 6/8] mdev: introduce virtio device and its device ops

Hi all:

There are hardware that can do virtio datapath offloading while having
its own control path. This path tries to implement a mdev based
unified API to support using kernel virtio driver to drive those
devices. This is done by introducing a new mdev transport for virtio
(virtio_mdev) and register itself as a new kind of mdev driver. Then
it provides a unified way for kernel virtio driver to talk with mdev
device implementation.

Though the series only contains kernel driver support, the goal is to
make the transport generic enough to support userspace drivers. This
means vhost-mdev[1] could be built on top as well by resuing the
transport.

A sample driver is also implemented which simulate a virito-net
loopback ethernet device on top of vringh + workqueue. This could be
used as a reference implementation for real hardware driver.

Consider mdev framework only support VFIO device and driver right now,
this series also extend it to support other types. This is done
through introducing class id to the device and pairing it with
id_talbe claimed by the driver. On top, this seris also decouple
device specific parents ops out of the common ones.

Pktgen test was done with virito-net + mvnet loop back device.

Please review.

[1] https://lkml.org/lkml/2019/9/16/869

Changes from V1:

- move virtio_mdev.c to drivers/virtio
- store class_id in mdev_device instead of mdev_parent
- store device_ops in mdev_device instead of mdev_parent
- reorder the patch, vringh fix comes first
- really silent compiling warnings
- really switch to use u16 for class_id
- uevent and modpost support for mdev class_id
- vraious tweaks per comments from Parav

Changes from RFC-V2:

- silent compile warnings on some specific configuration
- use u16 instead u8 for class id
- reseve MDEV_ID_VHOST for future vhost-mdev work
- introduce "virtio" type for mvnet and make "vhost" type
for future
  work
- add entries in MAINTAINER
- tweak and typos fixes in commit log

Changes from RFC-V1:

- rename device id to class id
- add docs for class id and device specific ops (device_ops)
- split device_ops into seperate headers
- drop the mdev_set_dma_ops()
- use device_ops to implement the transport API, then it's not a part
  of UAPI any more
- use GFP_ATOMIC in mvnet sample device and other tweaks
- set_vring_base/get_vring_base support for mvnet device

Jason Wang (8):
  vringh: fix copy direction of vringh_iov_push_kern()
  mdev: class id support
  mdev: bus uevent support
  modpost: add support for mdev class id
  mdev: introduce device specific ops
  mdev: introduce virtio device and its device ops
  virtio: introduce a mdev based transport
  docs: sample driver to demonstrate how to implement virtio-mdev
    framework

 .../driver-api/vfio-mediated-device.rst       |   7 +-
 MAINTAINERS                                   |   2 +
 drivers/gpu/drm/i915/gvt/kvmgt.c              |  18 +-
 drivers/s390/cio/vfio_ccw_ops.c               |  18 +-
 drivers/s390/crypto/vfio_ap_ops.c             |  14 +-
 drivers/vfio/mdev/mdev_core.c                 |  19 +
 drivers/vfio/mdev/mdev_driver.c               |  22 +
 drivers/vfio/mdev/mdev_private.h              |   2 +
 drivers/vfio/mdev/vfio_mdev.c                 |  45 +-
 drivers/vhost/vringh.c                        |   8 +-
 drivers/virtio/Kconfig                        |   7 +
 drivers/virtio/Makefile                       |   1 +
 drivers/virtio/virtio_mdev.c                  | 417 +++++++++++
 include/linux/mdev.h                          |  52 +-
 include/linux/mod_devicetable.h               |   8 +
 include/linux/vfio_mdev.h                     |  52 ++
 include/linux/virtio_mdev.h                   | 145 ++++
 samples/Kconfig                               |   7 +
 samples/vfio-mdev/Makefile                    |   1 +
 samples/vfio-mdev/mbochs.c                    |  20 +-
 samples/vfio-mdev/mdpy.c                      |  20 +-
 samples/vfio-mdev/mtty.c                      |  18 +-
 samples/vfio-mdev/mvnet.c                     | 692 ++++++++++++++++++
 scripts/mod/devicetable-offsets.c             |   3 +
 scripts/mod/file2alias.c                      |  10 +
 25 files changed, 1524 insertions(+), 84 deletions(-)
 create mode 100644 drivers/virtio/virtio_mdev.c
 create mode 100644 include/linux/vfio_mdev.h
 create mode 100644 include/linux/virtio_mdev.h
 create mode 100644 samples/vfio-mdev/mvnet.c

-- 
2.19.1

We want to copy from iov to buf, so the direction was wrong.

Signed-off-by: Jason Wang <jasowang at redhat.com>
---
 drivers/vhost/vringh.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/vhost/vringh.c b/drivers/vhost/vringh.c
index 08ad0d1f0476..a0a2d74967ef 100644
--- a/drivers/vhost/vringh.c
+++ b/drivers/vhost/vringh.c
@@ -852,6 +852,12 @@ static inline int xfer_kern(void *src, void *dst, size_t
len)
 	return 0;
 }
 
+static inline int kern_xfer(void *dst, void *src, size_t len)
+{
+	memcpy(dst, src, len);
+	return 0;
+}
+
 /**
  * vringh_init_kern - initialize a vringh for a kernelspace vring.
  * @vrh: the vringh to initialize.
@@ -958,7 +964,7 @@ EXPORT_SYMBOL(vringh_iov_pull_kern);
 ssize_t vringh_iov_push_kern(struct vringh_kiov *wiov,
 			     const void *src, size_t len)
 {
-	return vringh_iov_xfer(wiov, (void *)src, len, xfer_kern);
+	return vringh_iov_xfer(wiov, (void *)src, len, kern_xfer);
 }
 EXPORT_SYMBOL(vringh_iov_push_kern);
 
-- 
2.19.1

Mdev bus only supports vfio driver right now, so it doesn't implement
match method. But in the future, we may add drivers other than vfio,
the first driver could be virtio-mdev. This means we need to add
device class id support in bus match method to pair the mdev device
and mdev driver correctly.

So this patch adds id_table to mdev_driver and class_id for mdev
parent with the match method for mdev bus.

Signed-off-by: Jason Wang <jasowang at redhat.com>
---
 Documentation/driver-api/vfio-mediated-device.rst |  3 +++
 drivers/gpu/drm/i915/gvt/kvmgt.c                  |  1 +
 drivers/s390/cio/vfio_ccw_ops.c                   |  1 +
 drivers/s390/crypto/vfio_ap_ops.c                 |  1 +
 drivers/vfio/mdev/mdev_core.c                     |  7 +++++++
 drivers/vfio/mdev/mdev_driver.c                   | 14 ++++++++++++++
 drivers/vfio/mdev/mdev_private.h                  |  1 +
 drivers/vfio/mdev/vfio_mdev.c                     |  6 ++++++
 include/linux/mdev.h                              |  8 ++++++++
 include/linux/mod_devicetable.h                   |  8 ++++++++
 samples/vfio-mdev/mbochs.c                        |  1 +
 samples/vfio-mdev/mdpy.c                          |  1 +
 samples/vfio-mdev/mtty.c                          |  1 +
 13 files changed, 53 insertions(+)

diff --git a/Documentation/driver-api/vfio-mediated-device.rst
b/Documentation/driver-api/vfio-mediated-device.rst
index 25eb7d5b834b..a5bdc60d62a1 100644
--- a/Documentation/driver-api/vfio-mediated-device.rst
+++ b/Documentation/driver-api/vfio-mediated-device.rst
@@ -102,12 +102,14 @@ structure to represent a mediated device's driver::
       * @probe: called when new device created
       * @remove: called when device removed
       * @driver: device driver structure
+      * @id_table: the ids serviced by this driver
       */
      struct mdev_driver {
 	     const char *name;
 	     int  (*probe)  (struct device *dev);
 	     void (*remove) (struct device *dev);
 	     struct device_driver    driver;
+	     const struct mdev_class_id *id_table;
      };
 
 A mediated bus driver for mdev should use this structure in the function calls
@@ -165,6 +167,7 @@ register itself with the mdev core driver::
 	extern int  mdev_register_device(struct device *dev,
 	                                 const struct mdev_parent_ops *ops);
 
+
 However, the mdev_parent_ops structure is not required in the function call
 that a driver should use to unregister itself with the mdev core driver::
 
diff --git a/drivers/gpu/drm/i915/gvt/kvmgt.c b/drivers/gpu/drm/i915/gvt/kvmgt.c
index 23aa3e50cbf8..f793252a3d2a 100644
--- a/drivers/gpu/drm/i915/gvt/kvmgt.c
+++ b/drivers/gpu/drm/i915/gvt/kvmgt.c
@@ -678,6 +678,7 @@ static int intel_vgpu_create(struct kobject *kobj, struct
mdev_device *mdev)
 		     dev_name(mdev_dev(mdev)));
 	ret = 0;
 
+	mdev_set_class_id(mdev, MDEV_ID_VFIO);
 out:
 	return ret;
 }
diff --git a/drivers/s390/cio/vfio_ccw_ops.c b/drivers/s390/cio/vfio_ccw_ops.c
index f0d71ab77c50..d258ef1fedb9 100644
--- a/drivers/s390/cio/vfio_ccw_ops.c
+++ b/drivers/s390/cio/vfio_ccw_ops.c
@@ -129,6 +129,7 @@ static int vfio_ccw_mdev_create(struct kobject *kobj, struct
mdev_device *mdev)
 			   private->sch->schid.ssid,
 			   private->sch->schid.sch_no);
 
+	mdev_set_class_id(mdev, MDEV_ID_VFIO);
 	return 0;
 }
 
diff --git a/drivers/s390/crypto/vfio_ap_ops.c
b/drivers/s390/crypto/vfio_ap_ops.c
index 5c0f53c6dde7..2cfd96112aa0 100644
--- a/drivers/s390/crypto/vfio_ap_ops.c
+++ b/drivers/s390/crypto/vfio_ap_ops.c
@@ -343,6 +343,7 @@ static int vfio_ap_mdev_create(struct kobject *kobj, struct
mdev_device *mdev)
 	list_add(&matrix_mdev->node, &matrix_dev->mdev_list);
 	mutex_unlock(&matrix_dev->lock);
 
+	mdev_set_class_id(mdev, MDEV_ID_VFIO);
 	return 0;
 }
 
diff --git a/drivers/vfio/mdev/mdev_core.c b/drivers/vfio/mdev/mdev_core.c
index b558d4cfd082..8764cf4a276d 100644
--- a/drivers/vfio/mdev/mdev_core.c
+++ b/drivers/vfio/mdev/mdev_core.c
@@ -45,6 +45,12 @@ void mdev_set_drvdata(struct mdev_device *mdev, void *data)
 }
 EXPORT_SYMBOL(mdev_set_drvdata);
 
+void mdev_set_class_id(struct mdev_device *mdev, u16 id)
+{
+	mdev->class_id = id;
+}
+EXPORT_SYMBOL(mdev_set_class_id);
+
 struct device *mdev_dev(struct mdev_device *mdev)
 {
 	return &mdev->dev;
@@ -135,6 +141,7 @@ static int mdev_device_remove_cb(struct device *dev, void
*data)
  * mdev_register_device : Register a device
  * @dev: device structure representing parent device.
  * @ops: Parent device operation structure to be registered.
+ * @id: device id.
  *
  * Add device to list of registered parent devices.
  * Returns a negative value on error, otherwise 0.
diff --git a/drivers/vfio/mdev/mdev_driver.c b/drivers/vfio/mdev/mdev_driver.c
index 0d3223aee20b..b7c40ce86ee3 100644
--- a/drivers/vfio/mdev/mdev_driver.c
+++ b/drivers/vfio/mdev/mdev_driver.c
@@ -69,8 +69,22 @@ static int mdev_remove(struct device *dev)
 	return 0;
 }
 
+static int mdev_match(struct device *dev, struct device_driver *drv)
+{
+	unsigned int i;
+	struct mdev_device *mdev = to_mdev_device(dev);
+	struct mdev_driver *mdrv = to_mdev_driver(drv);
+	const struct mdev_class_id *ids = mdrv->id_table;
+
+	for (i = 0; ids[i].id; i++)
+		if (ids[i].id == mdev->class_id)
+			return 1;
+	return 0;
+}
+
 struct bus_type mdev_bus_type = {
 	.name		= "mdev",
+	.match		= mdev_match,
 	.probe		= mdev_probe,
 	.remove		= mdev_remove,
 };
diff --git a/drivers/vfio/mdev/mdev_private.h b/drivers/vfio/mdev/mdev_private.h
index 7d922950caaf..c65f436c1869 100644
--- a/drivers/vfio/mdev/mdev_private.h
+++ b/drivers/vfio/mdev/mdev_private.h
@@ -33,6 +33,7 @@ struct mdev_device {
 	struct kobject *type_kobj;
 	struct device *iommu_device;
 	bool active;
+	u16 class_id;
 };
 
 #define to_mdev_device(dev)	container_of(dev, struct mdev_device, dev)
diff --git a/drivers/vfio/mdev/vfio_mdev.c b/drivers/vfio/mdev/vfio_mdev.c
index 30964a4e0a28..fd2a4d9a3f26 100644
--- a/drivers/vfio/mdev/vfio_mdev.c
+++ b/drivers/vfio/mdev/vfio_mdev.c
@@ -120,10 +120,16 @@ static void vfio_mdev_remove(struct device *dev)
 	vfio_del_group_dev(dev);
 }
 
+static struct mdev_class_id id_table[] = {
+	{ MDEV_ID_VFIO },
+	{ 0 },
+};
+
 static struct mdev_driver vfio_mdev_driver = {
 	.name	= "vfio_mdev",
 	.probe	= vfio_mdev_probe,
 	.remove	= vfio_mdev_remove,
+	.id_table = id_table,
 };
 
 static int __init vfio_mdev_init(void)
diff --git a/include/linux/mdev.h b/include/linux/mdev.h
index 0ce30ca78db0..3974650c074f 100644
--- a/include/linux/mdev.h
+++ b/include/linux/mdev.h
@@ -118,6 +118,7 @@ struct mdev_type_attribute mdev_type_attr_##_name =		\
  * @probe: called when new device created
  * @remove: called when device removed
  * @driver: device driver structure
+ * @id_table: the ids serviced by this driver.
  *
  **/
 struct mdev_driver {
@@ -125,12 +126,14 @@ struct mdev_driver {
 	int  (*probe)(struct device *dev);
 	void (*remove)(struct device *dev);
 	struct device_driver driver;
+	const struct mdev_class_id *id_table;
 };
 
 #define to_mdev_driver(drv)	container_of(drv, struct mdev_driver, driver)
 
 void *mdev_get_drvdata(struct mdev_device *mdev);
 void mdev_set_drvdata(struct mdev_device *mdev, void *data);
+void mdev_set_class_id(struct mdev_device *mdev, u16 id);
 const guid_t *mdev_uuid(struct mdev_device *mdev);
 
 extern struct bus_type mdev_bus_type;
@@ -145,4 +148,9 @@ struct device *mdev_parent_dev(struct mdev_device *mdev);
 struct device *mdev_dev(struct mdev_device *mdev);
 struct mdev_device *mdev_from_dev(struct device *dev);
 
+enum {
+	MDEV_ID_VFIO = 1,
+	/* New entries must be added here */
+};
+
 #endif /* MDEV_H */
diff --git a/include/linux/mod_devicetable.h b/include/linux/mod_devicetable.h
index 5714fd35a83c..f32c6e44fb1a 100644
--- a/include/linux/mod_devicetable.h
+++ b/include/linux/mod_devicetable.h
@@ -821,4 +821,12 @@ struct wmi_device_id {
 	const void *context;
 };
 
+/**
+ * struct mdev_class_id - MDEV device class identifier
+ * @id: Used to identify a specific class of device, e.g vfio-mdev device.
+ */
+struct mdev_class_id {
+	__u16 id;
+};
+
 #endif /* LINUX_MOD_DEVICETABLE_H */
diff --git a/samples/vfio-mdev/mbochs.c b/samples/vfio-mdev/mbochs.c
index ac5c8c17b1ff..8a8583c892b2 100644
--- a/samples/vfio-mdev/mbochs.c
+++ b/samples/vfio-mdev/mbochs.c
@@ -561,6 +561,7 @@ static int mbochs_create(struct kobject *kobj, struct
mdev_device *mdev)
 	mbochs_reset(mdev);
 
 	mbochs_used_mbytes += type->mbytes;
+	mdev_set_class_id(mdev, MDEV_ID_VFIO);
 	return 0;
 
 err_mem:
diff --git a/samples/vfio-mdev/mdpy.c b/samples/vfio-mdev/mdpy.c
index cc86bf6566e4..88d7e76f3836 100644
--- a/samples/vfio-mdev/mdpy.c
+++ b/samples/vfio-mdev/mdpy.c
@@ -269,6 +269,7 @@ static int mdpy_create(struct kobject *kobj, struct
mdev_device *mdev)
 	mdpy_reset(mdev);
 
 	mdpy_count++;
+	mdev_set_class_id(mdev, MDEV_ID_VFIO);
 	return 0;
 }
 
diff --git a/samples/vfio-mdev/mtty.c b/samples/vfio-mdev/mtty.c
index 92e770a06ea2..4e0735143b69 100644
--- a/samples/vfio-mdev/mtty.c
+++ b/samples/vfio-mdev/mtty.c
@@ -770,6 +770,7 @@ static int mtty_create(struct kobject *kobj, struct
mdev_device *mdev)
 	list_add(&mdev_state->next, &mdev_devices_list);
 	mutex_unlock(&mdev_list_lock);
 
+	mdev_set_class_id(mdev, MDEV_ID_VFIO);
 	return 0;
 }
 
-- 
2.19.1

This patch adds bus uevent support for mdev bus in order to allow
cooperation with userspace.

Signed-off-by: Jason Wang <jasowang at redhat.com>
---
 drivers/vfio/mdev/mdev_driver.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/vfio/mdev/mdev_driver.c b/drivers/vfio/mdev/mdev_driver.c
index b7c40ce86ee3..319d886ffaf7 100644
--- a/drivers/vfio/mdev/mdev_driver.c
+++ b/drivers/vfio/mdev/mdev_driver.c
@@ -82,9 +82,17 @@ static int mdev_match(struct device *dev, struct
device_driver *drv)
 	return 0;
 }
 
+static int mdev_uevent(struct device *dev, struct kobj_uevent_env *env)
+{
+	struct mdev_device *mdev = to_mdev_device(dev);
+
+	return add_uevent_var(env, "MODALIAS=mdev:c%02X",
mdev->class_id);
+}
+
 struct bus_type mdev_bus_type = {
 	.name		= "mdev",
 	.match		= mdev_match,
+	.uevent		= mdev_uevent,
 	.probe		= mdev_probe,
 	.remove		= mdev_remove,
 };
-- 
2.19.1

Add support to parse mdev class id table.

Signed-off-by: Jason Wang <jasowang at redhat.com>
---
 drivers/vfio/mdev/vfio_mdev.c     |  2 ++
 scripts/mod/devicetable-offsets.c |  3 +++
 scripts/mod/file2alias.c          | 10 ++++++++++
 3 files changed, 15 insertions(+)

diff --git a/drivers/vfio/mdev/vfio_mdev.c b/drivers/vfio/mdev/vfio_mdev.c
index fd2a4d9a3f26..891cf83a2d9a 100644
--- a/drivers/vfio/mdev/vfio_mdev.c
+++ b/drivers/vfio/mdev/vfio_mdev.c
@@ -125,6 +125,8 @@ static struct mdev_class_id id_table[] = {
 	{ 0 },
 };
 
+MODULE_DEVICE_TABLE(mdev, id_table);
+
 static struct mdev_driver vfio_mdev_driver = {
 	.name	= "vfio_mdev",
 	.probe	= vfio_mdev_probe,
diff --git a/scripts/mod/devicetable-offsets.c
b/scripts/mod/devicetable-offsets.c
index 054405b90ba4..6cbb1062488a 100644
--- a/scripts/mod/devicetable-offsets.c
+++ b/scripts/mod/devicetable-offsets.c
@@ -231,5 +231,8 @@ int main(void)
 	DEVID(wmi_device_id);
 	DEVID_FIELD(wmi_device_id, guid_string);
 
+	DEVID(mdev_class_id);
+	DEVID_FIELD(mdev_class_id, id);
+
 	return 0;
 }
diff --git a/scripts/mod/file2alias.c b/scripts/mod/file2alias.c
index e17a29ae2e97..6805f87a1149 100644
--- a/scripts/mod/file2alias.c
+++ b/scripts/mod/file2alias.c
@@ -1330,6 +1330,15 @@ static int do_wmi_entry(const char *filename, void
*symval, char *alias)
 	return 1;
 }
 
+/* looks like: "mdev:cN" */
+static int do_mdev_entry(const char *filename, void *symval, char *alias)
+{
+	DEF_FIELD(symval, mdev_class_id, id);
+
+	sprintf(alias, "mdev:c%02X", id);
+	return 1;
+}
+
 /* Does namelen bytes of name exactly match the symbol? */
 static bool sym_is(const char *name, unsigned namelen, const char *symbol)
 {
@@ -1402,6 +1411,7 @@ static const struct devtable devtable[] = {
 	{"typec", SIZE_typec_device_id, do_typec_entry},
 	{"tee", SIZE_tee_client_device_id, do_tee_entry},
 	{"wmi", SIZE_wmi_device_id, do_wmi_entry},
+	{"mdev", SIZE_mdev_class_id, do_mdev_entry},
 };
 
 /* Create MODULE_ALIAS() statements.
-- 
2.19.1

Currently, except for the create and remove, the rest of
mdev_parent_ops is designed for vfio-mdev driver only and may not help
for kernel mdev driver. With the help of class id, this patch
introduces device specific callbacks inside mdev_device
structure. This allows different set of callback to be used by
vfio-mdev and virtio-mdev.

Signed-off-by: Jason Wang <jasowang at redhat.com>
---
 .../driver-api/vfio-mediated-device.rst       |  4 +-
 MAINTAINERS                                   |  1 +
 drivers/gpu/drm/i915/gvt/kvmgt.c              | 17 +++---
 drivers/s390/cio/vfio_ccw_ops.c               | 17 ++++--
 drivers/s390/crypto/vfio_ap_ops.c             | 13 +++--
 drivers/vfio/mdev/mdev_core.c                 | 12 +++++
 drivers/vfio/mdev/mdev_private.h              |  1 +
 drivers/vfio/mdev/vfio_mdev.c                 | 37 ++++++-------
 include/linux/mdev.h                          | 42 ++++-----------
 include/linux/vfio_mdev.h                     | 52 +++++++++++++++++++
 samples/vfio-mdev/mbochs.c                    | 19 ++++---
 samples/vfio-mdev/mdpy.c                      | 19 ++++---
 samples/vfio-mdev/mtty.c                      | 17 ++++--
 13 files changed, 168 insertions(+), 83 deletions(-)
 create mode 100644 include/linux/vfio_mdev.h

diff --git a/Documentation/driver-api/vfio-mediated-device.rst
b/Documentation/driver-api/vfio-mediated-device.rst
index a5bdc60d62a1..d50425b368bb 100644
--- a/Documentation/driver-api/vfio-mediated-device.rst
+++ b/Documentation/driver-api/vfio-mediated-device.rst
@@ -152,7 +152,9 @@ callbacks per mdev parent device, per mdev type, or any
other categorization.
 Vendor drivers are expected to be fully asynchronous in this respect or
 provide their own internal resource protection.)
 
-The callbacks in the mdev_parent_ops structure are as follows:
+The device specific callbacks are referred through device_ops pointer
+in mdev_parent_ops. For vfio-mdev device, its callbacks in device_ops
+are as follows:
 
 * open: open callback of mediated device
 * close: close callback of mediated device
diff --git a/MAINTAINERS b/MAINTAINERS
index b2326dece28e..89832b316500 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -17075,6 +17075,7 @@ S:	Maintained
 F:	Documentation/driver-api/vfio-mediated-device.rst
 F:	drivers/vfio/mdev/
 F:	include/linux/mdev.h
+F:	include/linux/vfio_mdev.h
 F:	samples/vfio-mdev/
 
 VFIO PLATFORM DRIVER
diff --git a/drivers/gpu/drm/i915/gvt/kvmgt.c b/drivers/gpu/drm/i915/gvt/kvmgt.c
index f793252a3d2a..b274f5ee481f 100644
--- a/drivers/gpu/drm/i915/gvt/kvmgt.c
+++ b/drivers/gpu/drm/i915/gvt/kvmgt.c
@@ -42,6 +42,7 @@
 #include <linux/kvm_host.h>
 #include <linux/vfio.h>
 #include <linux/mdev.h>
+#include <linux/vfio_mdev.h>
 #include <linux/debugfs.h>
 
 #include <linux/nospec.h>
@@ -643,6 +644,8 @@ static void kvmgt_put_vfio_device(void *vgpu)
 	vfio_device_put(((struct intel_vgpu *)vgpu)->vdev.vfio_device);
 }
 
+static struct vfio_mdev_device_ops intel_vfio_vgpu_dev_ops;
+
 static int intel_vgpu_create(struct kobject *kobj, struct mdev_device *mdev)
 {
 	struct intel_vgpu *vgpu = NULL;
@@ -679,6 +682,7 @@ static int intel_vgpu_create(struct kobject *kobj, struct
mdev_device *mdev)
 	ret = 0;
 
 	mdev_set_class_id(mdev, MDEV_ID_VFIO);
+	mdev_set_dev_ops(mdev, &intel_vfio_vgpu_dev_ops);
 out:
 	return ret;
 }
@@ -1601,20 +1605,21 @@ static const struct attribute_group *intel_vgpu_groups[]
= {
 	NULL,
 };
 
-static struct mdev_parent_ops intel_vgpu_ops = {
-	.mdev_attr_groups       = intel_vgpu_groups,
-	.create			= intel_vgpu_create,
-	.remove			= intel_vgpu_remove,
-
+static struct vfio_mdev_device_ops intel_vfio_vgpu_dev_ops = {
 	.open			= intel_vgpu_open,
 	.release		= intel_vgpu_release,
-
 	.read			= intel_vgpu_read,
 	.write			= intel_vgpu_write,
 	.mmap			= intel_vgpu_mmap,
 	.ioctl			= intel_vgpu_ioctl,
 };
 
+static struct mdev_parent_ops intel_vgpu_ops = {
+	.mdev_attr_groups       = intel_vgpu_groups,
+	.create			= intel_vgpu_create,
+	.remove			= intel_vgpu_remove,
+};
+
 static int kvmgt_host_init(struct device *dev, void *gvt, const void *ops)
 {
 	struct attribute **kvm_type_attrs;
diff --git a/drivers/s390/cio/vfio_ccw_ops.c b/drivers/s390/cio/vfio_ccw_ops.c
index d258ef1fedb9..329d53c1f46b 100644
--- a/drivers/s390/cio/vfio_ccw_ops.c
+++ b/drivers/s390/cio/vfio_ccw_ops.c
@@ -12,6 +12,7 @@
 
 #include <linux/vfio.h>
 #include <linux/mdev.h>
+#include <linux/vfio_mdev.h>
 #include <linux/nospec.h>
 #include <linux/slab.h>
 
@@ -110,6 +111,8 @@ static struct attribute_group *mdev_type_groups[] = {
 	NULL,
 };
 
+static const struct vfio_mdev_device_ops vfio_mdev_ops;
+
 static int vfio_ccw_mdev_create(struct kobject *kobj, struct mdev_device *mdev)
 {
 	struct vfio_ccw_private *private @@ -130,6 +133,7 @@ static int
vfio_ccw_mdev_create(struct kobject *kobj, struct mdev_device *mdev)
 			   private->sch->schid.sch_no);
 
 	mdev_set_class_id(mdev, MDEV_ID_VFIO);
+	mdev_set_dev_ops(mdev, &vfio_mdev_ops);
 	return 0;
 }
 
@@ -575,11 +579,7 @@ static ssize_t vfio_ccw_mdev_ioctl(struct mdev_device
*mdev,
 	}
 }
 
-static const struct mdev_parent_ops vfio_ccw_mdev_ops = {
-	.owner			= THIS_MODULE,
-	.supported_type_groups  = mdev_type_groups,
-	.create			= vfio_ccw_mdev_create,
-	.remove			= vfio_ccw_mdev_remove,
+static const struct vfio_mdev_device_ops vfio_mdev_ops = {
 	.open			= vfio_ccw_mdev_open,
 	.release		= vfio_ccw_mdev_release,
 	.read			= vfio_ccw_mdev_read,
@@ -587,6 +587,13 @@ static const struct mdev_parent_ops vfio_ccw_mdev_ops = {
 	.ioctl			= vfio_ccw_mdev_ioctl,
 };
 
+static const struct mdev_parent_ops vfio_ccw_mdev_ops = {
+	.owner			= THIS_MODULE,
+	.supported_type_groups  = mdev_type_groups,
+	.create			= vfio_ccw_mdev_create,
+	.remove			= vfio_ccw_mdev_remove,
+};
+
 int vfio_ccw_mdev_reg(struct subchannel *sch)
 {
 	return mdev_register_device(&sch->dev, &vfio_ccw_mdev_ops);
diff --git a/drivers/s390/crypto/vfio_ap_ops.c
b/drivers/s390/crypto/vfio_ap_ops.c
index 2cfd96112aa0..3a89933f0d3e 100644
--- a/drivers/s390/crypto/vfio_ap_ops.c
+++ b/drivers/s390/crypto/vfio_ap_ops.c
@@ -16,6 +16,7 @@
 #include <linux/bitops.h>
 #include <linux/kvm_host.h>
 #include <linux/module.h>
+#include <linux/vfio_mdev.h>
 #include <asm/kvm.h>
 #include <asm/zcrypt.h>
 
@@ -321,6 +322,8 @@ static void vfio_ap_matrix_init(struct ap_config_info *info,
 	matrix->adm_max = info->apxa ? info->Nd : 15;
 }
 
+static const struct vfio_mdev_device_ops vfio_mdev_ops;
+
 static int vfio_ap_mdev_create(struct kobject *kobj, struct mdev_device *mdev)
 {
 	struct ap_matrix_mdev *matrix_mdev;
@@ -344,6 +347,7 @@ static int vfio_ap_mdev_create(struct kobject *kobj, struct
mdev_device *mdev)
 	mutex_unlock(&matrix_dev->lock);
 
 	mdev_set_class_id(mdev, MDEV_ID_VFIO);
+	mdev_set_dev_ops(mdev, &vfio_mdev_ops);
 	return 0;
 }
 
@@ -1281,15 +1285,18 @@ static ssize_t vfio_ap_mdev_ioctl(struct mdev_device
*mdev,
 	return ret;
 }
 
+static const struct vfio_mdev_device_ops vfio_mdev_ops = {
+	.open			= vfio_ap_mdev_open,
+	.release		= vfio_ap_mdev_release,
+	.ioctl			= vfio_ap_mdev_ioctl,
+};
+
 static const struct mdev_parent_ops vfio_ap_matrix_ops = {
 	.owner			= THIS_MODULE,
 	.supported_type_groups	= vfio_ap_mdev_type_groups,
 	.mdev_attr_groups	= vfio_ap_mdev_attr_groups,
 	.create			= vfio_ap_mdev_create,
 	.remove			= vfio_ap_mdev_remove,
-	.open			= vfio_ap_mdev_open,
-	.release		= vfio_ap_mdev_release,
-	.ioctl			= vfio_ap_mdev_ioctl,
 };
 
 int vfio_ap_mdev_register(void)
diff --git a/drivers/vfio/mdev/mdev_core.c b/drivers/vfio/mdev/mdev_core.c
index 8764cf4a276d..6f35f2ced2c9 100644
--- a/drivers/vfio/mdev/mdev_core.c
+++ b/drivers/vfio/mdev/mdev_core.c
@@ -51,6 +51,18 @@ void mdev_set_class_id(struct mdev_device *mdev, u16 id)
 }
 EXPORT_SYMBOL(mdev_set_class_id);
 
+const void *mdev_get_dev_ops(struct mdev_device *mdev)
+{
+	return mdev->device_ops;
+}
+EXPORT_SYMBOL(mdev_get_dev_ops);
+
+void mdev_set_dev_ops(struct mdev_device *mdev, const void *ops)
+{
+	mdev->device_ops = ops;
+}
+EXPORT_SYMBOL(mdev_set_dev_ops);
+
 struct device *mdev_dev(struct mdev_device *mdev)
 {
 	return &mdev->dev;
diff --git a/drivers/vfio/mdev/mdev_private.h b/drivers/vfio/mdev/mdev_private.h
index c65f436c1869..b666805f0b1f 100644
--- a/drivers/vfio/mdev/mdev_private.h
+++ b/drivers/vfio/mdev/mdev_private.h
@@ -34,6 +34,7 @@ struct mdev_device {
 	struct device *iommu_device;
 	bool active;
 	u16 class_id;
+	const void *device_ops;
 };
 
 #define to_mdev_device(dev)	container_of(dev, struct mdev_device, dev)
diff --git a/drivers/vfio/mdev/vfio_mdev.c b/drivers/vfio/mdev/vfio_mdev.c
index 891cf83a2d9a..95efa054442f 100644
--- a/drivers/vfio/mdev/vfio_mdev.c
+++ b/drivers/vfio/mdev/vfio_mdev.c
@@ -14,6 +14,7 @@
 #include <linux/slab.h>
 #include <linux/vfio.h>
 #include <linux/mdev.h>
+#include <linux/vfio_mdev.h>
 
 #include "mdev_private.h"
 
@@ -24,16 +25,16 @@
 static int vfio_mdev_open(void *device_data)
 {
 	struct mdev_device *mdev = device_data;
-	struct mdev_parent *parent = mdev->parent;
+	const struct vfio_mdev_device_ops *ops = mdev_get_dev_ops(mdev);
 	int ret;
 
-	if (unlikely(!parent->ops->open))
+	if (unlikely(!ops->open))
 		return -EINVAL;
 
 	if (!try_module_get(THIS_MODULE))
 		return -ENODEV;
 
-	ret = parent->ops->open(mdev);
+	ret = ops->open(mdev);
 	if (ret)
 		module_put(THIS_MODULE);
 
@@ -43,10 +44,10 @@ static int vfio_mdev_open(void *device_data)
 static void vfio_mdev_release(void *device_data)
 {
 	struct mdev_device *mdev = device_data;
-	struct mdev_parent *parent = mdev->parent;
+	const struct vfio_mdev_device_ops *ops = mdev_get_dev_ops(mdev);
 
-	if (likely(parent->ops->release))
-		parent->ops->release(mdev);
+	if (likely(ops->release))
+		ops->release(mdev);
 
 	module_put(THIS_MODULE);
 }
@@ -55,47 +56,47 @@ static long vfio_mdev_unlocked_ioctl(void *device_data,
 				     unsigned int cmd, unsigned long arg)
 {
 	struct mdev_device *mdev = device_data;
-	struct mdev_parent *parent = mdev->parent;
+	const struct vfio_mdev_device_ops *ops = mdev_get_dev_ops(mdev);
 
-	if (unlikely(!parent->ops->ioctl))
+	if (unlikely(!ops->ioctl))
 		return -EINVAL;
 
-	return parent->ops->ioctl(mdev, cmd, arg);
+	return ops->ioctl(mdev, cmd, arg);
 }
 
 static ssize_t vfio_mdev_read(void *device_data, char __user *buf,
 			      size_t count, loff_t *ppos)
 {
 	struct mdev_device *mdev = device_data;
-	struct mdev_parent *parent = mdev->parent;
+	const struct vfio_mdev_device_ops *ops = mdev_get_dev_ops(mdev);
 
-	if (unlikely(!parent->ops->read))
+	if (unlikely(!ops->read))
 		return -EINVAL;
 
-	return parent->ops->read(mdev, buf, count, ppos);
+	return ops->read(mdev, buf, count, ppos);
 }
 
 static ssize_t vfio_mdev_write(void *device_data, const char __user *buf,
 			       size_t count, loff_t *ppos)
 {
 	struct mdev_device *mdev = device_data;
-	struct mdev_parent *parent = mdev->parent;
+	const struct vfio_mdev_device_ops *ops = mdev_get_dev_ops(mdev);
 
-	if (unlikely(!parent->ops->write))
+	if (unlikely(!ops->write))
 		return -EINVAL;
 
-	return parent->ops->write(mdev, buf, count, ppos);
+	return ops->write(mdev, buf, count, ppos);
 }
 
 static int vfio_mdev_mmap(void *device_data, struct vm_area_struct *vma)
 {
 	struct mdev_device *mdev = device_data;
-	struct mdev_parent *parent = mdev->parent;
+	const struct vfio_mdev_device_ops *ops = mdev_get_dev_ops(mdev);
 
-	if (unlikely(!parent->ops->mmap))
+	if (unlikely(!ops->mmap))
 		return -EINVAL;
 
-	return parent->ops->mmap(mdev, vma);
+	return ops->mmap(mdev, vma);
 }
 
 static const struct vfio_device_ops vfio_mdev_dev_ops = {
diff --git a/include/linux/mdev.h b/include/linux/mdev.h
index 3974650c074f..3414307311f1 100644
--- a/include/linux/mdev.h
+++ b/include/linux/mdev.h
@@ -10,6 +10,11 @@
 #ifndef MDEV_H
 #define MDEV_H
 
+#include <linux/types.h>
+#include <linux/device.h>
+#include <linux/mdev.h>
+#include <uapi/linux/uuid.h>
+
 struct mdev_device;
 
 /*
@@ -48,30 +53,8 @@ struct device *mdev_get_iommu_device(struct device *dev);
  *			@mdev: mdev_device device structure which is being
  *			       destroyed
  *			Returns integer: success (0) or error (< 0)
- * @open:		Open mediated device.
- *			@mdev: mediated device.
- *			Returns integer: success (0) or error (< 0)
- * @release:		release mediated device
- *			@mdev: mediated device.
- * @read:		Read emulation callback
- *			@mdev: mediated device structure
- *			@buf: read buffer
- *			@count: number of bytes to read
- *			@ppos: address.
- *			Retuns number on bytes read on success or error.
- * @write:		Write emulation callback
- *			@mdev: mediated device structure
- *			@buf: write buffer
- *			@count: number of bytes to be written
- *			@ppos: address.
- *			Retuns number on bytes written on success or error.
- * @ioctl:		IOCTL callback
- *			@mdev: mediated device structure
- *			@cmd: ioctl command
- *			@arg: arguments to ioctl
- * @mmap:		mmap callback
- *			@mdev: mediated device structure
- *			@vma: vma structure
+ * @device_ops:         Device specific emulation callback.
+ *
  * Parent device that support mediated device should be registered with mdev
  * module with mdev_parent_ops structure.
  **/
@@ -83,15 +66,6 @@ struct mdev_parent_ops {
 
 	int     (*create)(struct kobject *kobj, struct mdev_device *mdev);
 	int     (*remove)(struct mdev_device *mdev);
-	int     (*open)(struct mdev_device *mdev);
-	void    (*release)(struct mdev_device *mdev);
-	ssize_t (*read)(struct mdev_device *mdev, char __user *buf,
-			size_t count, loff_t *ppos);
-	ssize_t (*write)(struct mdev_device *mdev, const char __user *buf,
-			 size_t count, loff_t *ppos);
-	long	(*ioctl)(struct mdev_device *mdev, unsigned int cmd,
-			 unsigned long arg);
-	int	(*mmap)(struct mdev_device *mdev, struct vm_area_struct *vma);
 };
 
 /* interface for exporting mdev supported type attributes */
@@ -133,6 +107,8 @@ struct mdev_driver {
 
 void *mdev_get_drvdata(struct mdev_device *mdev);
 void mdev_set_drvdata(struct mdev_device *mdev, void *data);
+const void *mdev_get_dev_ops(struct mdev_device *mdev);
+void mdev_set_dev_ops(struct mdev_device *mdev, const void *ops);
 void mdev_set_class_id(struct mdev_device *mdev, u16 id);
 const guid_t *mdev_uuid(struct mdev_device *mdev);
 
diff --git a/include/linux/vfio_mdev.h b/include/linux/vfio_mdev.h
new file mode 100644
index 000000000000..3907c5371c2b
--- /dev/null
+++ b/include/linux/vfio_mdev.h
@@ -0,0 +1,52 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * VFIO Mediated device definition
+ */
+
+#ifndef VFIO_MDEV_H
+#define VFIO_MDEV_H
+
+#include <linux/mdev.h>
+
+/**
+ * struct vfio_mdev_device_ops - Structure to be registered for each
+ * mdev device to register the device to vfio-mdev module.
+ *
+ * @open:		Open mediated device.
+ *			@mdev: mediated device.
+ *			Returns integer: success (0) or error (< 0)
+ * @release:		release mediated device
+ *			@mdev: mediated device.
+ * @read:		Read emulation callback
+ *			@mdev: mediated device structure
+ *			@buf: read buffer
+ *			@count: number of bytes to read
+ *			@ppos: address.
+ *			Retuns number on bytes read on success or error.
+ * @write:		Write emulation callback
+ *			@mdev: mediated device structure
+ *			@buf: write buffer
+ *			@count: number of bytes to be written
+ *			@ppos: address.
+ *			Retuns number on bytes written on success or error.
+ * @ioctl:		IOCTL callback
+ *			@mdev: mediated device structure
+ *			@cmd: ioctl command
+ *			@arg: arguments to ioctl
+ * @mmap:		mmap callback
+ *			@mdev: mediated device structure
+ *			@vma: vma structure
+ */
+struct vfio_mdev_device_ops {
+	int     (*open)(struct mdev_device *mdev);
+	void    (*release)(struct mdev_device *mdev);
+	ssize_t (*read)(struct mdev_device *mdev, char __user *buf,
+			size_t count, loff_t *ppos);
+	ssize_t (*write)(struct mdev_device *mdev, const char __user *buf,
+			 size_t count, loff_t *ppos);
+	long	(*ioctl)(struct mdev_device *mdev, unsigned int cmd,
+			 unsigned long arg);
+	int	(*mmap)(struct mdev_device *mdev, struct vm_area_struct *vma);
+};
+
+#endif
diff --git a/samples/vfio-mdev/mbochs.c b/samples/vfio-mdev/mbochs.c
index 8a8583c892b2..b4bf29c6136c 100644
--- a/samples/vfio-mdev/mbochs.c
+++ b/samples/vfio-mdev/mbochs.c
@@ -30,6 +30,7 @@
 #include <linux/iommu.h>
 #include <linux/sysfs.h>
 #include <linux/mdev.h>
+#include <linux/vfio_mdev.h>
 #include <linux/pci.h>
 #include <linux/dma-buf.h>
 #include <linux/highmem.h>
@@ -516,6 +517,8 @@ static int mbochs_reset(struct mdev_device *mdev)
 	return 0;
 }
 
+static const struct vfio_mdev_device_ops vfio_mdev_ops;
+
 static int mbochs_create(struct kobject *kobj, struct mdev_device *mdev)
 {
 	const struct mbochs_type *type = mbochs_find_type(kobj);
@@ -562,6 +565,7 @@ static int mbochs_create(struct kobject *kobj, struct
mdev_device *mdev)
 
 	mbochs_used_mbytes += type->mbytes;
 	mdev_set_class_id(mdev, MDEV_ID_VFIO);
+	mdev_set_dev_ops(mdev, &vfio_mdev_ops);
 	return 0;
 
 err_mem:
@@ -1419,12 +1423,7 @@ static struct attribute_group *mdev_type_groups[] = {
 	NULL,
 };
 
-static const struct mdev_parent_ops mdev_fops = {
-	.owner			= THIS_MODULE,
-	.mdev_attr_groups	= mdev_dev_groups,
-	.supported_type_groups	= mdev_type_groups,
-	.create			= mbochs_create,
-	.remove			= mbochs_remove,
+static const struct vfio_mdev_device_ops vfio_mdev_ops = {
 	.open			= mbochs_open,
 	.release		= mbochs_close,
 	.read			= mbochs_read,
@@ -1433,6 +1432,14 @@ static const struct mdev_parent_ops mdev_fops = {
 	.mmap			= mbochs_mmap,
 };
 
+static const struct mdev_parent_ops mdev_fops = {
+	.owner			= THIS_MODULE,
+	.mdev_attr_groups	= mdev_dev_groups,
+	.supported_type_groups	= mdev_type_groups,
+	.create			= mbochs_create,
+	.remove			= mbochs_remove,
+};
+
 static const struct file_operations vd_fops = {
 	.owner		= THIS_MODULE,
 };
diff --git a/samples/vfio-mdev/mdpy.c b/samples/vfio-mdev/mdpy.c
index 88d7e76f3836..80c2df531326 100644
--- a/samples/vfio-mdev/mdpy.c
+++ b/samples/vfio-mdev/mdpy.c
@@ -26,6 +26,7 @@
 #include <linux/iommu.h>
 #include <linux/sysfs.h>
 #include <linux/mdev.h>
+#include <linux/vfio_mdev.h>
 #include <linux/pci.h>
 #include <drm/drm_fourcc.h>
 #include "mdpy-defs.h"
@@ -226,6 +227,8 @@ static int mdpy_reset(struct mdev_device *mdev)
 	return 0;
 }
 
+static const struct vfio_mdev_device_ops vfio_mdev_ops;
+
 static int mdpy_create(struct kobject *kobj, struct mdev_device *mdev)
 {
 	const struct mdpy_type *type = mdpy_find_type(kobj);
@@ -270,6 +273,7 @@ static int mdpy_create(struct kobject *kobj, struct
mdev_device *mdev)
 
 	mdpy_count++;
 	mdev_set_class_id(mdev, MDEV_ID_VFIO);
+	mdev_set_dev_ops(mdev, &vfio_mdev_ops);
 	return 0;
 }
 
@@ -726,12 +730,7 @@ static struct attribute_group *mdev_type_groups[] = {
 	NULL,
 };
 
-static const struct mdev_parent_ops mdev_fops = {
-	.owner			= THIS_MODULE,
-	.mdev_attr_groups	= mdev_dev_groups,
-	.supported_type_groups	= mdev_type_groups,
-	.create			= mdpy_create,
-	.remove			= mdpy_remove,
+static const struct vfio_mdev_device_ops vfio_mdev_ops = {
 	.open			= mdpy_open,
 	.release		= mdpy_close,
 	.read			= mdpy_read,
@@ -740,6 +739,14 @@ static const struct mdev_parent_ops mdev_fops = {
 	.mmap			= mdpy_mmap,
 };
 
+static const struct mdev_parent_ops mdev_fops = {
+	.owner			= THIS_MODULE,
+	.mdev_attr_groups	= mdev_dev_groups,
+	.supported_type_groups	= mdev_type_groups,
+	.create			= mdpy_create,
+	.remove			= mdpy_remove,
+};
+
 static const struct file_operations vd_fops = {
 	.owner		= THIS_MODULE,
 };
diff --git a/samples/vfio-mdev/mtty.c b/samples/vfio-mdev/mtty.c
index 4e0735143b69..2db860ccb02c 100644
--- a/samples/vfio-mdev/mtty.c
+++ b/samples/vfio-mdev/mtty.c
@@ -27,6 +27,7 @@
 #include <linux/ctype.h>
 #include <linux/file.h>
 #include <linux/mdev.h>
+#include <linux/vfio_mdev.h>
 #include <linux/pci.h>
 #include <linux/serial.h>
 #include <uapi/linux/serial_reg.h>
@@ -723,6 +724,8 @@ static ssize_t mdev_access(struct mdev_device *mdev, u8
*buf, size_t count,
 	return ret;
 }
 
+static const struct vfio_mdev_device_ops vfio_dev_ops;
+
 static int mtty_create(struct kobject *kobj, struct mdev_device *mdev)
 {
 	struct mdev_state *mdev_state;
@@ -771,6 +774,7 @@ static int mtty_create(struct kobject *kobj, struct
mdev_device *mdev)
 	mutex_unlock(&mdev_list_lock);
 
 	mdev_set_class_id(mdev, MDEV_ID_VFIO);
+	mdev_set_dev_ops(mdev, &vfio_dev_ops);
 	return 0;
 }
 
@@ -1411,6 +1415,14 @@ static struct attribute_group *mdev_type_groups[] = {
 	NULL,
 };
 
+static const struct vfio_mdev_device_ops vfio_dev_ops = {
+	.open                   = mtty_open,
+	.release                = mtty_close,
+	.read                   = mtty_read,
+	.write                  = mtty_write,
+	.ioctl		        = mtty_ioctl,
+};
+
 static const struct mdev_parent_ops mdev_fops = {
 	.owner                  = THIS_MODULE,
 	.dev_attr_groups        = mtty_dev_groups,
@@ -1418,11 +1430,6 @@ static const struct mdev_parent_ops mdev_fops = {
 	.supported_type_groups  = mdev_type_groups,
 	.create                 = mtty_create,
 	.remove			= mtty_remove,
-	.open                   = mtty_open,
-	.release                = mtty_close,
-	.read                   = mtty_read,
-	.write                  = mtty_write,
-	.ioctl		        = mtty_ioctl,
 };
 
 static void mtty_device_release(struct device *dev)
-- 
2.19.1

This patch implements basic support for mdev driver that supports
virtio transport for kernel virtio driver.

Signed-off-by: Jason Wang <jasowang at redhat.com>
---
 include/linux/mdev.h        |   2 +
 include/linux/virtio_mdev.h | 145 ++++++++++++++++++++++++++++++++++++
 2 files changed, 147 insertions(+)
 create mode 100644 include/linux/virtio_mdev.h

diff --git a/include/linux/mdev.h b/include/linux/mdev.h
index 3414307311f1..73ac27b3b868 100644
--- a/include/linux/mdev.h
+++ b/include/linux/mdev.h
@@ -126,6 +126,8 @@ struct mdev_device *mdev_from_dev(struct device *dev);
 
 enum {
 	MDEV_ID_VFIO = 1,
+	MDEV_ID_VIRTIO = 2,
+	MDEV_ID_VHOST = 3,
 	/* New entries must be added here */
 };
 
diff --git a/include/linux/virtio_mdev.h b/include/linux/virtio_mdev.h
new file mode 100644
index 000000000000..d1a40a739266
--- /dev/null
+++ b/include/linux/virtio_mdev.h
@@ -0,0 +1,145 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Virtio mediated device driver
+ *
+ * Copyright 2019, Red Hat Corp.
+ *     Author: Jason Wang <jasowang at redhat.com>
+ */
+#ifndef _LINUX_VIRTIO_MDEV_H
+#define _LINUX_VIRTIO_MDEV_H
+
+#include <linux/interrupt.h>
+#include <linux/mdev.h>
+#include <uapi/linux/vhost.h>
+
+#define VIRTIO_MDEV_DEVICE_API_STRING		"virtio-mdev"
+#define VIRTIO_MDEV_VERSION 0x1
+
+struct virtio_mdev_callback {
+	irqreturn_t (*callback)(void *data);
+	void *private;
+};
+
+/**
+ * struct vfio_mdev_device_ops - Structure to be registered for each
+ * mdev device to register the device to virtio-mdev module.
+ *
+ * @set_vq_address:		Set the address of virtqueue
+ *				@mdev: mediated device
+ *				@idx: virtqueue index
+ *				@desc_area: address of desc area
+ *				@driver_area: address of driver area
+ *				@device_area: address of device area
+ *				Returns integer: success (0) or error (< 0)
+ * @set_vq_num:		Set the size of virtqueue
+ *				@mdev: mediated device
+ *				@idx: virtqueue index
+ *				@num: the size of virtqueue
+ * @kick_vq:			Kick the virtqueue
+ *				@mdev: mediated device
+ *				@idx: virtqueue index
+ * @set_vq_cb:			Set the interrut calback function for
+ *				a virtqueue
+ *				@mdev: mediated device
+ *				@idx: virtqueue index
+ *				@cb: virtio-mdev interrupt callback structure
+ * @set_vq_ready:		Set ready status for a virtqueue
+ *				@mdev: mediated device
+ *				@idx: virtqueue index
+ *				@ready: ready (true) not ready(false)
+ * @get_vq_ready:		Get ready status for a virtqueue
+ *				@mdev: mediated device
+ *				@idx: virtqueue index
+ *				Returns boolean: ready (true) or not (false)
+ * @set_vq_state:		Set the state for a virtqueue
+ *				@mdev: mediated device
+ *				@idx: virtqueue index
+ *				@state: virtqueue state (last_avail_idx)
+ *				Returns integer: success (0) or error (< 0)
+ * @get_vq_state:		Get the state for a virtqueue
+ *				@mdev: mediated device
+ *				@idx: virtqueue index
+ *				Returns virtqueue state (last_avail_idx)
+ * @get_vq_align:		Get the virtqueue align requirement
+ *				for the device
+ *				@mdev: mediated device
+ *				Returns virtqueue algin requirement
+ * @get_features:		Get virtio features supported by the device
+ *				@mdev: mediated device
+ *				Returns the features support by the
+ *				device
+ * @get_features:		Set virtio features supported by the driver
+ *				@mdev: mediated device
+ *				@features: feature support by the driver
+ *				Returns integer: success (0) or error (< 0)
+ * @set_config_cb:		Set the config interrupt callback
+ *				@mdev: mediated device
+ *				@cb: virtio-mdev interrupt callback structure
+ * @get_device_id:		Get virtio device id
+ *				@mdev: mediated device
+ *				Returns u32: virtio device id
+ * @get_vendor_id:		Get virtio vendor id
+ *				@mdev: mediated device
+ *				Returns u32: virtio vendor id
+ * @get_status:		Get the device status
+ *				@mdev: mediated device
+ *				Returns u8: virtio device status
+ * @set_status:		Set the device status
+ *				@mdev: mediated device
+ *				@status: virtio device status
+ * @get_config:		Read from device specific confiugration space
+ *				@mdev: mediated device
+ *				@offset: offset from the beginning of
+ *				configuration space
+ *				@buf: buffer used to read to
+ *				@len: the length to read from
+ *				configration space
+ * @set_config:		Write to device specific confiugration space
+ *				@mdev: mediated device
+ *				@offset: offset from the beginning of
+ *				configuration space
+ *				@buf: buffer used to write from
+ *				@len: the length to write to
+ *				configration space
+ * @get_version:		Get the version of virtio mdev device
+ *				@mdev: mediated device
+ *				Returns integer: version of the device
+ * @get_generation:		Get device generaton
+ *				@mdev: mediated device
+ *				Returns u32: device generation
+ */
+struct virtio_mdev_device_ops {
+	/* Virtqueue ops */
+	int (*set_vq_address)(struct mdev_device *mdev,
+			      u16 idx, u64 desc_area, u64 driver_area,
+			      u64 device_area);
+	void (*set_vq_num)(struct mdev_device *mdev, u16 idx, u32 num);
+	void (*kick_vq)(struct mdev_device *mdev, u16 idx);
+	void (*set_vq_cb)(struct mdev_device *mdev, u16 idx,
+			  struct virtio_mdev_callback *cb);
+	void (*set_vq_ready)(struct mdev_device *mdev, u16 idx, bool ready);
+	bool (*get_vq_ready)(struct mdev_device *mdev, u16 idx);
+	int (*set_vq_state)(struct mdev_device *mdev, u16 idx, u64 state);
+	u64 (*get_vq_state)(struct mdev_device *mdev, u16 idx);
+
+	/* Device ops */
+	u16 (*get_vq_align)(struct mdev_device *mdev);
+	u64 (*get_features)(struct mdev_device *mdev);
+	int (*set_features)(struct mdev_device *mdev, u64 features);
+	void (*set_config_cb)(struct mdev_device *mdev,
+			      struct virtio_mdev_callback *cb);
+	u16 (*get_queue_max)(struct mdev_device *mdev);
+	u32 (*get_device_id)(struct mdev_device *mdev);
+	u32 (*get_vendor_id)(struct mdev_device *mdev);
+	u8 (*get_status)(struct mdev_device *mdev);
+	void (*set_status)(struct mdev_device *mdev, u8 status);
+	void (*get_config)(struct mdev_device *mdev, unsigned int offset,
+			   void *buf, unsigned int len);
+	void (*set_config)(struct mdev_device *mdev, unsigned int offset,
+			   const void *buf, unsigned int len);
+	int (*get_version)(struct mdev_device *mdev);
+	u32 (*get_generation)(struct mdev_device *mdev);
+};
+
+#endif
+
-- 
2.19.1

This patch introduces a new mdev transport for virtio. This is used to
use kernel virtio driver to drive the mediated device that is capable
of populating virtqueue directly.

A new virtio-mdev driver will be registered to the mdev bus, when a
new virtio-mdev device is probed, it will register the device with
mdev based config ops. This means it is a software transport between
mdev driver and mdev device. The transport was implemented through
device specific opswhich is a part of mdev_parent_ops now.

Signed-off-by: Jason Wang <jasowang at redhat.com>
---
 drivers/virtio/Kconfig       |   7 +
 drivers/virtio/Makefile      |   1 +
 drivers/virtio/virtio_mdev.c | 417 +++++++++++++++++++++++++++++++++++
 3 files changed, 425 insertions(+)
 create mode 100644 drivers/virtio/virtio_mdev.c

diff --git a/drivers/virtio/Kconfig b/drivers/virtio/Kconfig
index 078615cf2afc..8d18722ab572 100644
--- a/drivers/virtio/Kconfig
+++ b/drivers/virtio/Kconfig
@@ -43,6 +43,13 @@ config VIRTIO_PCI_LEGACY
 
 	  If unsure, say Y.
 
+config VIRTIO_MDEV_DEVICE
+	tristate "VIRTIO driver for Mediated devices"
+	depends on VFIO_MDEV && VIRTIO
+	default n
+	help
+	  VIRTIO based driver for Mediated devices.
+
 config VIRTIO_PMEM
 	tristate "Support for virtio pmem driver"
 	depends on VIRTIO
diff --git a/drivers/virtio/Makefile b/drivers/virtio/Makefile
index 3a2b5c5dcf46..ebc7fa15ae82 100644
--- a/drivers/virtio/Makefile
+++ b/drivers/virtio/Makefile
@@ -6,3 +6,4 @@ virtio_pci-y := virtio_pci_modern.o virtio_pci_common.o
 virtio_pci-$(CONFIG_VIRTIO_PCI_LEGACY) += virtio_pci_legacy.o
 obj-$(CONFIG_VIRTIO_BALLOON) += virtio_balloon.o
 obj-$(CONFIG_VIRTIO_INPUT) += virtio_input.o
+obj-$(CONFIG_VIRTIO_MDEV_DEVICE) += virtio_mdev.o
diff --git a/drivers/virtio/virtio_mdev.c b/drivers/virtio/virtio_mdev.c
new file mode 100644
index 000000000000..c2f3cb2738bd
--- /dev/null
+++ b/drivers/virtio/virtio_mdev.c
@@ -0,0 +1,417 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * VIRTIO based driver for Mediated device
+ *
+ * Copyright (c) 2019, Red Hat. All rights reserved.
+ *     Author: Jason Wang <jasowang at redhat.com>
+ *
+ */
+
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/device.h>
+#include <linux/kernel.h>
+#include <linux/slab.h>
+#include <linux/uuid.h>
+#include <linux/mdev.h>
+#include <linux/virtio_mdev.h>
+#include <linux/virtio.h>
+#include <linux/virtio_config.h>
+#include <linux/virtio_ring.h>
+
+#define DRIVER_VERSION  "0.1"
+#define DRIVER_AUTHOR   "Red Hat Corporation"
+#define DRIVER_DESC     "VIRTIO based driver for Mediated device"
+
+#define to_virtio_mdev_device(dev) \
+	container_of(dev, struct virtio_mdev_device, vdev)
+
+struct virtio_mdev_device {
+	struct virtio_device vdev;
+	struct mdev_device *mdev;
+	unsigned long version;
+
+	struct virtqueue **vqs;
+	/* The lock to protect virtqueue list */
+	spinlock_t lock;
+	struct list_head virtqueues;
+};
+
+struct virtio_mdev_vq_info {
+	/* the actual virtqueue */
+	struct virtqueue *vq;
+
+	/* the list node for the virtqueues list */
+	struct list_head node;
+};
+
+static struct mdev_device *vm_get_mdev(struct virtio_device *vdev)
+{
+	struct virtio_mdev_device *vm_dev = to_virtio_mdev_device(vdev);
+	struct mdev_device *mdev = vm_dev->mdev;
+
+	return mdev;
+}
+
+static void virtio_mdev_get(struct virtio_device *vdev, unsigned offset,
+			    void *buf, unsigned len)
+{
+	struct mdev_device *mdev = vm_get_mdev(vdev);
+	const struct virtio_mdev_device_ops *ops = mdev_get_dev_ops(mdev);
+
+	ops->get_config(mdev, offset, buf, len);
+}
+
+static void virtio_mdev_set(struct virtio_device *vdev, unsigned offset,
+			    const void *buf, unsigned len)
+{
+	struct mdev_device *mdev = vm_get_mdev(vdev);
+	const struct virtio_mdev_device_ops *ops = mdev_get_dev_ops(mdev);
+
+	ops->set_config(mdev, offset, buf, len);
+}
+
+static u32 virtio_mdev_generation(struct virtio_device *vdev)
+{
+	struct mdev_device *mdev = vm_get_mdev(vdev);
+	const struct virtio_mdev_device_ops *ops = mdev_get_dev_ops(mdev);
+
+	return ops->get_generation(mdev);
+}
+
+static u8 virtio_mdev_get_status(struct virtio_device *vdev)
+{
+	struct mdev_device *mdev = vm_get_mdev(vdev);
+	const struct virtio_mdev_device_ops *ops = mdev_get_dev_ops(mdev);
+
+	return ops->get_status(mdev);
+}
+
+static void virtio_mdev_set_status(struct virtio_device *vdev, u8 status)
+{
+	struct mdev_device *mdev = vm_get_mdev(vdev);
+	const struct virtio_mdev_device_ops *ops = mdev_get_dev_ops(mdev);
+
+	return ops->set_status(mdev, status);
+}
+
+static void virtio_mdev_reset(struct virtio_device *vdev)
+{
+	struct mdev_device *mdev = vm_get_mdev(vdev);
+	const struct virtio_mdev_device_ops *ops = mdev_get_dev_ops(mdev);
+
+	return ops->set_status(mdev, 0);
+}
+
+static bool virtio_mdev_notify(struct virtqueue *vq)
+{
+	struct mdev_device *mdev = vm_get_mdev(vq->vdev);
+	const struct virtio_mdev_device_ops *ops = mdev_get_dev_ops(mdev);
+
+	ops->kick_vq(mdev, vq->index);
+
+	return true;
+}
+
+static irqreturn_t virtio_mdev_config_cb(void *private)
+{
+	struct virtio_mdev_device *vm_dev = private;
+
+	virtio_config_changed(&vm_dev->vdev);
+
+	return IRQ_HANDLED;
+}
+
+static irqreturn_t virtio_mdev_virtqueue_cb(void *private)
+{
+	struct virtio_mdev_vq_info *info = private;
+
+	return vring_interrupt(0, info->vq);
+}
+
+static struct virtqueue *
+virtio_mdev_setup_vq(struct virtio_device *vdev, unsigned index,
+		     void (*callback)(struct virtqueue *vq),
+		     const char *name, bool ctx)
+{
+	struct virtio_mdev_device *vm_dev = to_virtio_mdev_device(vdev);
+	struct mdev_device *mdev = vm_get_mdev(vdev);
+	const struct virtio_mdev_device_ops *ops = mdev_get_dev_ops(mdev);
+	struct virtio_mdev_vq_info *info;
+	struct virtio_mdev_callback cb;
+	struct virtqueue *vq;
+	u64 desc_addr, driver_addr, device_addr;
+	unsigned long flags;
+	u32 align, num;
+	int err;
+
+	if (!name)
+		return NULL;
+
+	/* Queue shouldn't already be set up. */
+	if (ops->get_vq_ready(mdev, index))
+		return ERR_PTR(-ENOENT);
+
+	/* Allocate and fill out our active queue description */
+	info = kmalloc(sizeof(*info), GFP_KERNEL);
+	if (!info)
+		return ERR_PTR(-ENOMEM);
+
+	num = ops->get_queue_max(mdev);
+	if (num == 0) {
+		err = -ENOENT;
+		goto error_new_virtqueue;
+	}
+
+	/* Create the vring */
+	align = ops->get_vq_align(mdev);
+	vq = vring_create_virtqueue(index, num, align, vdev,
+				    true, true, ctx,
+				    virtio_mdev_notify, callback, name);
+	if (!vq) {
+		err = -ENOMEM;
+		goto error_new_virtqueue;
+	}
+
+	/* Setup virtqueue callback */
+	cb.callback = virtio_mdev_virtqueue_cb;
+	cb.private = info;
+	ops->set_vq_cb(mdev, index, &cb);
+	ops->set_vq_num(mdev, index, virtqueue_get_vring_size(vq));
+
+	desc_addr = virtqueue_get_desc_addr(vq);
+	driver_addr = virtqueue_get_avail_addr(vq);
+	device_addr = virtqueue_get_used_addr(vq);
+
+	if (ops->set_vq_address(mdev, index,
+				desc_addr, driver_addr,
+				device_addr)) {
+		err = -EINVAL;
+		goto err_vq;
+	}
+
+	ops->set_vq_ready(mdev, index, 1);
+
+	vq->priv = info;
+	info->vq = vq;
+
+	spin_lock_irqsave(&vm_dev->lock, flags);
+	list_add(&info->node, &vm_dev->virtqueues);
+	spin_unlock_irqrestore(&vm_dev->lock, flags);
+
+	return vq;
+
+err_vq:
+	vring_del_virtqueue(vq);
+error_new_virtqueue:
+	ops->set_vq_ready(mdev, index, 0);
+	WARN_ON(ops->get_vq_ready(mdev, index));
+	kfree(info);
+	return ERR_PTR(err);
+
+}
+
+static void virtio_mdev_del_vq(struct virtqueue *vq)
+{
+	struct virtio_mdev_device *vm_dev = to_virtio_mdev_device(vq->vdev);
+	struct mdev_device *mdev = vm_dev->mdev;
+	const struct virtio_mdev_device_ops *ops = mdev_get_dev_ops(mdev);
+	struct virtio_mdev_vq_info *info = vq->priv;
+	unsigned int index = vq->index;
+	unsigned long flags;
+
+	spin_lock_irqsave(&vm_dev->lock, flags);
+	list_del(&info->node);
+	spin_unlock_irqrestore(&vm_dev->lock, flags);
+
+	/* Select and deactivate the queue */
+	ops->set_vq_ready(mdev, index, 0);
+	WARN_ON(ops->get_vq_ready(mdev, index));
+
+	vring_del_virtqueue(vq);
+
+	kfree(info);
+}
+
+static void virtio_mdev_del_vqs(struct virtio_device *vdev)
+{
+	struct virtqueue *vq, *n;
+
+	list_for_each_entry_safe(vq, n, &vdev->vqs, list)
+		virtio_mdev_del_vq(vq);
+}
+
+static int virtio_mdev_find_vqs(struct virtio_device *vdev, unsigned nvqs,
+				struct virtqueue *vqs[],
+				vq_callback_t *callbacks[],
+				const char * const names[],
+				const bool *ctx,
+				struct irq_affinity *desc)
+{
+	struct virtio_mdev_device *vm_dev = to_virtio_mdev_device(vdev);
+	struct mdev_device *mdev = vm_get_mdev(vdev);
+	const struct virtio_mdev_device_ops *ops = mdev_get_dev_ops(mdev);
+	struct virtio_mdev_callback cb;
+	int i, err, queue_idx = 0;
+
+	vm_dev->vqs = kmalloc_array(queue_idx, sizeof(*vm_dev->vqs),
+				    GFP_KERNEL);
+	if (!vm_dev->vqs)
+		return -ENOMEM;
+
+	for (i = 0; i < nvqs; ++i) {
+		if (!names[i]) {
+			vqs[i] = NULL;
+			continue;
+		}
+
+		vqs[i] = virtio_mdev_setup_vq(vdev, queue_idx++,
+					      callbacks[i], names[i], ctx ?
+					      ctx[i] : false);
+		if (IS_ERR(vqs[i])) {
+			err = PTR_ERR(vqs[i]);
+			goto err_setup_vq;
+		}
+	}
+
+	cb.callback = virtio_mdev_config_cb;
+	cb.private = vm_dev;
+	ops->set_config_cb(mdev, &cb);
+
+	return 0;
+
+err_setup_vq:
+	kfree(vm_dev->vqs);
+	virtio_mdev_del_vqs(vdev);
+	return err;
+}
+
+static u64 virtio_mdev_get_features(struct virtio_device *vdev)
+{
+	struct mdev_device *mdev = vm_get_mdev(vdev);
+	const struct virtio_mdev_device_ops *ops = mdev_get_dev_ops(mdev);
+
+	return ops->get_features(mdev);
+}
+
+static int virtio_mdev_finalize_features(struct virtio_device *vdev)
+{
+	struct mdev_device *mdev = vm_get_mdev(vdev);
+	const struct virtio_mdev_device_ops *ops = mdev_get_dev_ops(mdev);
+
+	/* Give virtio_ring a chance to accept features. */
+	vring_transport_features(vdev);
+
+	return ops->set_features(mdev, vdev->features);
+}
+
+static const char *virtio_mdev_bus_name(struct virtio_device *vdev)
+{
+	struct virtio_mdev_device *vm_dev = to_virtio_mdev_device(vdev);
+	struct mdev_device *mdev = vm_dev->mdev;
+
+	return dev_name(mdev_dev(mdev));
+}
+
+static const struct virtio_config_ops virtio_mdev_config_ops = {
+	.get		= virtio_mdev_get,
+	.set		= virtio_mdev_set,
+	.generation	= virtio_mdev_generation,
+	.get_status	= virtio_mdev_get_status,
+	.set_status	= virtio_mdev_set_status,
+	.reset		= virtio_mdev_reset,
+	.find_vqs	= virtio_mdev_find_vqs,
+	.del_vqs	= virtio_mdev_del_vqs,
+	.get_features	= virtio_mdev_get_features,
+	.finalize_features = virtio_mdev_finalize_features,
+	.bus_name	= virtio_mdev_bus_name,
+};
+
+static void virtio_mdev_release_dev(struct device *_d)
+{
+	struct virtio_device *vdev +	       container_of(_d, struct virtio_device,
dev);
+	struct virtio_mdev_device *vm_dev +	       container_of(vdev, struct
virtio_mdev_device, vdev);
+
+	devm_kfree(_d, vm_dev);
+}
+
+static int virtio_mdev_probe(struct device *dev)
+{
+	struct mdev_device *mdev = mdev_from_dev(dev);
+	const struct virtio_mdev_device_ops *ops = mdev_get_dev_ops(mdev);
+	struct virtio_mdev_device *vm_dev;
+	int rc;
+
+	vm_dev = devm_kzalloc(dev, sizeof(*vm_dev), GFP_KERNEL);
+	if (!vm_dev)
+		return -ENOMEM;
+
+	vm_dev->vdev.dev.parent = dev;
+	vm_dev->vdev.dev.release = virtio_mdev_release_dev;
+	vm_dev->vdev.config = &virtio_mdev_config_ops;
+	vm_dev->mdev = mdev;
+	vm_dev->vqs = NULL;
+	INIT_LIST_HEAD(&vm_dev->virtqueues);
+	spin_lock_init(&vm_dev->lock);
+
+	vm_dev->version = ops->get_version(mdev);
+	if (vm_dev->version != 1) {
+		dev_err(dev, "Version %ld not supported!\n",
+			vm_dev->version);
+		return -ENXIO;
+	}
+
+	vm_dev->vdev.id.device = ops->get_device_id(mdev);
+	if (vm_dev->vdev.id.device == 0)
+		return -ENODEV;
+
+	vm_dev->vdev.id.vendor = ops->get_vendor_id(mdev);
+	rc = register_virtio_device(&vm_dev->vdev);
+	if (rc)
+		put_device(dev);
+	else
+		dev_set_drvdata(dev, vm_dev);
+
+	return rc;
+}
+
+static void virtio_mdev_remove(struct device *dev)
+{
+	struct virtio_mdev_device *vm_dev = dev_get_drvdata(dev);
+
+	unregister_virtio_device(&vm_dev->vdev);
+}
+
+static struct mdev_class_id id_table[] = {
+	{ MDEV_ID_VIRTIO },
+	{ 0 },
+};
+
+MODULE_DEVICE_TABLE(mdev, id_table);
+
+static struct mdev_driver virtio_mdev_driver = {
+	.name	= "virtio_mdev",
+	.probe	= virtio_mdev_probe,
+	.remove = virtio_mdev_remove,
+	.id_table = id_table,
+};
+
+static int __init virtio_mdev_init(void)
+{
+	return mdev_register_driver(&virtio_mdev_driver, THIS_MODULE);
+}
+
+static void __exit virtio_mdev_exit(void)
+{
+	mdev_unregister_driver(&virtio_mdev_driver);
+}
+
+module_init(virtio_mdev_init)
+module_exit(virtio_mdev_exit)
+
+MODULE_VERSION(DRIVER_VERSION);
+MODULE_LICENSE("GPL v2");
+MODULE_AUTHOR(DRIVER_AUTHOR);
+MODULE_DESCRIPTION(DRIVER_DESC);
-- 
2.19.1

This sample driver creates mdev device that simulate virtio net device
over virtio mdev transport. The device is implemented through vringh
and workqueue. A device specific dma ops is to make sure HVA is used
directly as the IOVA. This should be sufficient for kernel virtio
driver to work.

Only 'virtio' type is supported right now. I plan to add 'vhost'
type
on top which requires some virtual IOMMU implemented in this sample
driver.

Signed-off-by: Jason Wang <jasowang at redhat.com>
---
 MAINTAINERS                |   1 +
 samples/Kconfig            |   7 +
 samples/vfio-mdev/Makefile |   1 +
 samples/vfio-mdev/mvnet.c  | 692 +++++++++++++++++++++++++++++++++++++
 4 files changed, 701 insertions(+)
 create mode 100644 samples/vfio-mdev/mvnet.c

diff --git a/MAINTAINERS b/MAINTAINERS
index 89832b316500..347dc64cdc23 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -17202,6 +17202,7 @@ F:	include/linux/virtio*.h
 F:	include/uapi/linux/virtio_*.h
 F:	drivers/crypto/virtio/
 F:	mm/balloon_compaction.c
+F:	samples/vfio-mdev/mvnet.c
 
 VIRTIO BLOCK AND SCSI DRIVERS
 M:	"Michael S. Tsirkin" <mst at redhat.com>
diff --git a/samples/Kconfig b/samples/Kconfig
index c8dacb4dda80..a1a1ca2c00b7 100644
--- a/samples/Kconfig
+++ b/samples/Kconfig
@@ -131,6 +131,13 @@ config SAMPLE_VFIO_MDEV_MDPY
 	  mediated device.  It is a simple framebuffer and supports
 	  the region display interface (VFIO_GFX_PLANE_TYPE_REGION).
 
+config SAMPLE_VIRTIO_MDEV_NET
+        tristate "Build virtio mdev net example mediated device sample
code -- loadable modules only"
+	depends on VIRTIO_MDEV_DEVICE && VHOST_RING && m
+	help
+	  Build a networking sample device for use as a virtio
+	  mediated device.
+
 config SAMPLE_VFIO_MDEV_MDPY_FB
 	tristate "Build VFIO mdpy example guest fbdev driver -- loadable module
only"
 	depends on FB && m
diff --git a/samples/vfio-mdev/Makefile b/samples/vfio-mdev/Makefile
index 10d179c4fdeb..f34af90ed0a0 100644
--- a/samples/vfio-mdev/Makefile
+++ b/samples/vfio-mdev/Makefile
@@ -3,3 +3,4 @@ obj-$(CONFIG_SAMPLE_VFIO_MDEV_MTTY) += mtty.o
 obj-$(CONFIG_SAMPLE_VFIO_MDEV_MDPY) += mdpy.o
 obj-$(CONFIG_SAMPLE_VFIO_MDEV_MDPY_FB) += mdpy-fb.o
 obj-$(CONFIG_SAMPLE_VFIO_MDEV_MBOCHS) += mbochs.o
+obj-$(CONFIG_SAMPLE_VIRTIO_MDEV_NET) += mvnet.o
diff --git a/samples/vfio-mdev/mvnet.c b/samples/vfio-mdev/mvnet.c
new file mode 100644
index 000000000000..53a39f0f3460
--- /dev/null
+++ b/samples/vfio-mdev/mvnet.c
@@ -0,0 +1,692 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Mediated virtual virtio-net device driver.
+ *
+ * Copyright (c) 2019, Red Hat Inc. All rights reserved.
+ *     Author: Jason Wang <jasowang at redhat.com>
+ *
+ * Sample driver that creates mdev device that simulates ethernet loopback
+ * device.
+ *
+ * Usage:
+ *
+ * # modprobe virtio_mdev
+ * # modprobe mvnet
+ * # cd /sys/devices/virtual/mvnet/mvnet/mdev_supported_types/mvnet-virtio
+ * # echo "83b8f4f2-509f-382f-3c1e-e6bfe0fa1001" > ./create
+ * # cd devices/83b8f4f2-509f-382f-3c1e-e6bfe0fa1001
+ * # ls -d virtio0
+ * virtio0
+ */
+
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/device.h>
+#include <linux/kernel.h>
+#include <linux/fs.h>
+#include <linux/poll.h>
+#include <linux/slab.h>
+#include <linux/sched.h>
+#include <linux/wait.h>
+#include <linux/uuid.h>
+#include <linux/iommu.h>
+#include <linux/sysfs.h>
+#include <linux/file.h>
+#include <linux/etherdevice.h>
+#include <linux/mdev.h>
+#include <linux/vringh.h>
+#include <linux/virtio_mdev.h>
+#include <uapi/linux/virtio_config.h>
+#include <uapi/linux/virtio_net.h>
+
+#define VERSION_STRING  "0.1"
+#define DRIVER_AUTHOR   "Red Hat Corporation"
+
+#define MVNET_CLASS_NAME "mvnet"
+#define MVNET_NAME       "mvnet"
+
+/*
+ * Global Structures
+ */
+
+static struct mvnet_dev {
+	struct class	*vd_class;
+	struct idr	vd_idr;
+	struct device	dev;
+} mvnet_dev;
+
+struct mvnet_virtqueue {
+	struct vringh vring;
+	struct vringh_kiov iov;
+	unsigned short head;
+	bool ready;
+	u64 desc_addr;
+	u64 device_addr;
+	u64 driver_addr;
+	u32 num;
+	void *private;
+	irqreturn_t (*cb)(void *data);
+};
+
+#define MVNET_QUEUE_ALIGN PAGE_SIZE
+#define MVNET_QUEUE_MAX 256
+#define MVNET_DEVICE_ID 0x1
+#define MVNET_VENDOR_ID 0
+
+u64 mvnet_features = (1ULL << VIRTIO_F_ANY_LAYOUT) |
+		     (1ULL << VIRTIO_F_VERSION_1) |
+		     (1ULL << VIRTIO_F_IOMMU_PLATFORM);
+
+/* State of each mdev device */
+struct mvnet_state {
+	struct mvnet_virtqueue vqs[2];
+	struct work_struct work;
+	spinlock_t lock;
+	struct mdev_device *mdev;
+	struct virtio_net_config config;
+	void *buffer;
+	u32 status;
+	u32 generation;
+	u64 features;
+	struct list_head next;
+};
+
+static struct mutex mdev_list_lock;
+static struct list_head mdev_devices_list;
+
+static void mvnet_queue_ready(struct mvnet_state *mvnet, unsigned int idx)
+{
+	struct mvnet_virtqueue *vq = &mvnet->vqs[idx];
+	int ret;
+
+	ret = vringh_init_kern(&vq->vring, mvnet_features, MVNET_QUEUE_MAX,
+			       false, (struct vring_desc *)vq->desc_addr,
+			       (struct vring_avail *)vq->driver_addr,
+			       (struct vring_used *)vq->device_addr);
+}
+
+static void mvnet_vq_reset(struct mvnet_virtqueue *vq)
+{
+	vq->ready = 0;
+	vq->desc_addr = 0;
+	vq->driver_addr = 0;
+	vq->device_addr = 0;
+	vq->cb = NULL;
+	vq->private = NULL;
+	vringh_init_kern(&vq->vring, mvnet_features, MVNET_QUEUE_MAX,
+			false, 0, 0, 0);
+}
+
+static void mvnet_reset(struct mvnet_state *mvnet)
+{
+	int i;
+
+	for (i = 0; i < 2; i++)
+		mvnet_vq_reset(&mvnet->vqs[i]);
+
+	mvnet->features = 0;
+	mvnet->status = 0;
+	++mvnet->generation;
+}
+
+static void mvnet_work(struct work_struct *work)
+{
+	struct mvnet_state *mvnet = container_of(work, struct
+						 mvnet_state, work);
+	struct mvnet_virtqueue *txq = &mvnet->vqs[1];
+	struct mvnet_virtqueue *rxq = &mvnet->vqs[0];
+	size_t read, write, total_write;
+	int err;
+	int pkts = 0;
+
+	spin_lock(&mvnet->lock);
+
+	if (!txq->ready || !rxq->ready)
+		goto out;
+
+	while (true) {
+		total_write = 0;
+		err = vringh_getdesc_kern(&txq->vring, &txq->iov, NULL,
+					  &txq->head, GFP_ATOMIC);
+		if (err <= 0)
+			break;
+
+		err = vringh_getdesc_kern(&rxq->vring, NULL, &rxq->iov,
+					  &rxq->head, GFP_ATOMIC);
+		if (err <= 0) {
+			vringh_complete_kern(&txq->vring, txq->head, 0);
+			break;
+		}
+
+		while (true) {
+			read = vringh_iov_pull_kern(&txq->iov, mvnet->buffer,
+						    PAGE_SIZE);
+			if (read <= 0)
+				break;
+
+			write = vringh_iov_push_kern(&rxq->iov, mvnet->buffer,
+						     read);
+			if (write <= 0)
+				break;
+
+			total_write += write;
+		}
+
+		/* Make sure data is wrote before advancing index */
+		smp_wmb();
+
+		vringh_complete_kern(&txq->vring, txq->head, 0);
+		vringh_complete_kern(&rxq->vring, rxq->head, total_write);
+
+		/* Make sure used is visible before rasing the interrupt. */
+		smp_wmb();
+
+		local_bh_disable();
+		if (txq->cb)
+			txq->cb(txq->private);
+		if (rxq->cb)
+			rxq->cb(rxq->private);
+		local_bh_enable();
+
+		if (++pkts > 4) {
+			schedule_work(&mvnet->work);
+			goto out;
+		}
+	}
+
+out:
+	spin_unlock(&mvnet->lock);
+}
+
+static dma_addr_t mvnet_map_page(struct device *dev, struct page *page,
+				 unsigned long offset, size_t size,
+				 enum dma_data_direction dir,
+				 unsigned long attrs)
+{
+	/* Vringh can only use HVA */
+	return (dma_addr_t)(page_address(page) + offset);
+}
+
+static void mvnet_unmap_page(struct device *dev, dma_addr_t dma_addr,
+			     size_t size, enum dma_data_direction dir,
+			     unsigned long attrs)
+{
+}
+
+static void *mvnet_alloc_coherent(struct device *dev, size_t size,
+				  dma_addr_t *dma_addr, gfp_t flag,
+				  unsigned long attrs)
+{
+	void *addr = kmalloc(size, flag);
+
+	if (addr == NULL)
+		*dma_addr = DMA_MAPPING_ERROR;
+	else
+		*dma_addr = (dma_addr_t) addr;
+
+	return addr;
+}
+
+static void mvnet_free_coherent(struct device *dev, size_t size,
+				void *vaddr, dma_addr_t dma_addr,
+				unsigned long attrs)
+{
+	kfree((void *)dma_addr);
+}
+
+static const struct dma_map_ops mvnet_dma_ops = {
+	.map_page = mvnet_map_page,
+	.unmap_page = mvnet_unmap_page,
+	.alloc = mvnet_alloc_coherent,
+	.free = mvnet_free_coherent,
+};
+
+static const struct virtio_mdev_device_ops virtio_mdev_ops;
+
+static int mvnet_create(struct kobject *kobj, struct mdev_device *mdev)
+{
+	struct mvnet_state *mvnet;
+	struct virtio_net_config *config;
+	struct device *dev = mdev_dev(mdev);
+
+	if (!mdev)
+		return -EINVAL;
+
+	mvnet = kzalloc(sizeof(struct mvnet_state), GFP_KERNEL);
+	if (mvnet == NULL)
+		return -ENOMEM;
+
+	mvnet->buffer = kmalloc(PAGE_SIZE, GFP_KERNEL);
+	if (!mvnet->buffer) {
+		kfree(mvnet);
+		return -ENOMEM;
+	}
+
+	config = &mvnet->config;
+	config->mtu = 1500;
+	config->status = VIRTIO_NET_S_LINK_UP;
+	eth_random_addr(config->mac);
+
+	INIT_WORK(&mvnet->work, mvnet_work);
+
+	spin_lock_init(&mvnet->lock);
+	mvnet->mdev = mdev;
+	mdev_set_drvdata(mdev, mvnet);
+
+	mutex_lock(&mdev_list_lock);
+	list_add(&mvnet->next, &mdev_devices_list);
+	mutex_unlock(&mdev_list_lock);
+
+	dev->coherent_dma_mask = DMA_BIT_MASK(64);
+	set_dma_ops(dev, &mvnet_dma_ops);
+
+	mdev_set_class_id(mdev, MDEV_ID_VIRTIO);
+	mdev_set_dev_ops(mdev, &virtio_mdev_ops);
+
+	return 0;
+}
+
+static int mvnet_remove(struct mdev_device *mdev)
+{
+	struct mvnet_state *mds, *tmp_mds;
+	struct mvnet_state *mvnet = mdev_get_drvdata(mdev);
+	int ret = -EINVAL;
+
+	mutex_lock(&mdev_list_lock);
+	list_for_each_entry_safe(mds, tmp_mds, &mdev_devices_list, next) {
+		if (mvnet == mds) {
+			list_del(&mvnet->next);
+			mdev_set_drvdata(mdev, NULL);
+			kfree(mvnet->buffer);
+			kfree(mvnet);
+			ret = 0;
+			break;
+		}
+	}
+	mutex_unlock(&mdev_list_lock);
+
+	return ret;
+}
+
+static ssize_t
+sample_mvnet_dev_show(struct device *dev, struct device_attribute *attr,
+		     char *buf)
+{
+	if (mdev_from_dev(dev))
+		return sprintf(buf, "This is MDEV %s\n", dev_name(dev));
+
+	return sprintf(buf, "\n");
+}
+
+static DEVICE_ATTR_RO(sample_mvnet_dev);
+
+static struct attribute *mvnet_dev_attrs[] = {
+	&dev_attr_sample_mvnet_dev.attr,
+	NULL,
+};
+
+static const struct attribute_group mvnet_dev_group = {
+	.name  = "mvnet_dev",
+	.attrs = mvnet_dev_attrs,
+};
+
+static const struct attribute_group *mvnet_dev_groups[] = {
+	&mvnet_dev_group,
+	NULL,
+};
+
+static ssize_t
+sample_mdev_dev_show(struct device *dev, struct device_attribute *attr,
+		     char *buf)
+{
+	if (mdev_from_dev(dev))
+		return sprintf(buf, "This is MDEV %s\n", dev_name(dev));
+
+	return sprintf(buf, "\n");
+}
+
+static DEVICE_ATTR_RO(sample_mdev_dev);
+
+static struct attribute *mdev_dev_attrs[] = {
+	&dev_attr_sample_mdev_dev.attr,
+	NULL,
+};
+
+static const struct attribute_group mdev_dev_group = {
+	.name  = "vendor",
+	.attrs = mdev_dev_attrs,
+};
+
+static const struct attribute_group *mdev_dev_groups[] = {
+	&mdev_dev_group,
+	NULL,
+};
+
+#define MVNET_STRING_LEN 16
+
+static ssize_t
+name_show(struct kobject *kobj, struct device *dev, char *buf)
+{
+	char name[MVNET_STRING_LEN];
+	const char *name_str = "virtio-net";
+
+	snprintf(name, MVNET_STRING_LEN, "%s", dev_driver_string(dev));
+	if (!strcmp(kobj->name, name))
+		return sprintf(buf, "%s\n", name_str);
+
+	return -EINVAL;
+}
+
+static MDEV_TYPE_ATTR_RO(name);
+
+static ssize_t
+available_instances_show(struct kobject *kobj, struct device *dev, char *buf)
+{
+	return sprintf(buf, "%d\n", INT_MAX);
+}
+
+static MDEV_TYPE_ATTR_RO(available_instances);
+
+static ssize_t device_api_show(struct kobject *kobj, struct device *dev,
+			       char *buf)
+{
+	return sprintf(buf, "%s\n", VIRTIO_MDEV_DEVICE_API_STRING);
+}
+
+static MDEV_TYPE_ATTR_RO(device_api);
+
+static struct attribute *mdev_types_attrs[] = {
+	&mdev_type_attr_name.attr,
+	&mdev_type_attr_device_api.attr,
+	&mdev_type_attr_available_instances.attr,
+	NULL,
+};
+
+static struct attribute_group mdev_type_group = {
+	.name  = "virtio",
+	.attrs = mdev_types_attrs,
+};
+
+/* TBD: "vhost" type */
+
+static struct attribute_group *mdev_type_groups[] = {
+	&mdev_type_group,
+	NULL,
+};
+
+static int mvnet_set_vq_address(struct mdev_device *mdev, u16 idx,
+				u64 desc_area, u64 driver_area, u64 device_area)
+{
+	struct mvnet_state *mvnet = mdev_get_drvdata(mdev);
+	struct mvnet_virtqueue *vq = &mvnet->vqs[idx];
+
+	vq->desc_addr = desc_area;
+	vq->driver_addr = driver_area;
+	vq->device_addr = device_area;
+
+	return 0;
+}
+
+static void mvnet_set_vq_num(struct mdev_device *mdev, u16 idx, u32 num)
+{
+	struct mvnet_state *mvnet = mdev_get_drvdata(mdev);
+	struct mvnet_virtqueue *vq = &mvnet->vqs[idx];
+
+	vq->num = num;
+}
+
+static void mvnet_kick_vq(struct mdev_device *mdev, u16 idx)
+{
+	struct mvnet_state *mvnet = mdev_get_drvdata(mdev);
+	struct mvnet_virtqueue *vq = &mvnet->vqs[idx];
+
+	if (vq->ready)
+		schedule_work(&mvnet->work);
+}
+
+static void mvnet_set_vq_cb(struct mdev_device *mdev, u16 idx,
+			    struct virtio_mdev_callback *cb)
+{
+	struct mvnet_state *mvnet = mdev_get_drvdata(mdev);
+	struct mvnet_virtqueue *vq = &mvnet->vqs[idx];
+
+	vq->cb = cb->callback;
+	vq->private = cb->private;
+}
+
+static void mvnet_set_vq_ready(struct mdev_device *mdev, u16 idx, bool ready)
+{
+	struct mvnet_state *mvnet = mdev_get_drvdata(mdev);
+	struct mvnet_virtqueue *vq = &mvnet->vqs[idx];
+
+	spin_lock(&mvnet->lock);
+	vq->ready = ready;
+	if (vq->ready)
+		mvnet_queue_ready(mvnet, idx);
+	spin_unlock(&mvnet->lock);
+}
+
+static bool mvnet_get_vq_ready(struct mdev_device *mdev, u16 idx)
+{
+	struct mvnet_state *mvnet = mdev_get_drvdata(mdev);
+	struct mvnet_virtqueue *vq = &mvnet->vqs[idx];
+
+	return vq->ready;
+}
+
+static int mvnet_set_vq_state(struct mdev_device *mdev, u16 idx, u64 state)
+{
+	struct mvnet_state *mvnet = mdev_get_drvdata(mdev);
+	struct mvnet_virtqueue *vq = &mvnet->vqs[idx];
+	struct vringh *vrh = &vq->vring;
+
+	spin_lock(&mvnet->lock);
+	vrh->last_avail_idx = state;
+	spin_unlock(&mvnet->lock);
+
+	return 0;
+}
+
+static u64 mvnet_get_vq_state(struct mdev_device *mdev, u16 idx)
+{
+	struct mvnet_state *mvnet = mdev_get_drvdata(mdev);
+	struct mvnet_virtqueue *vq = &mvnet->vqs[idx];
+	struct vringh *vrh = &vq->vring;
+
+	return vrh->last_avail_idx;
+}
+
+static u16 mvnet_get_vq_align(struct mdev_device *mdev)
+{
+	return MVNET_QUEUE_ALIGN;
+}
+
+static u64 mvnet_get_features(struct mdev_device *mdev)
+{
+	return mvnet_features;
+}
+
+static int mvnet_set_features(struct mdev_device *mdev, u64 features)
+{
+	struct mvnet_state *mvnet = mdev_get_drvdata(mdev);
+
+	/* DMA mapping must be done by driver */
+	if (!(features & (1ULL << VIRTIO_F_IOMMU_PLATFORM)))
+		return -EINVAL;
+
+	mvnet->features = features & mvnet_features;
+
+	return 0;
+}
+
+static void mvnet_set_config_cb(struct mdev_device *mdev,
+				struct virtio_mdev_callback *cb)
+{
+	/* We don't support config interrupt */
+}
+
+static u16 mvnet_get_queue_max(struct mdev_device *mdev)
+{
+	return MVNET_QUEUE_MAX;
+}
+
+static u32 mvnet_get_device_id(struct mdev_device *mdev)
+{
+	return MVNET_DEVICE_ID;
+}
+
+static u32 mvnet_get_vendor_id(struct mdev_device *mdev)
+{
+	return MVNET_VENDOR_ID;
+}
+
+static u8 mvnet_get_status(struct mdev_device *mdev)
+{
+	struct mvnet_state *mvnet = mdev_get_drvdata(mdev);
+
+	return mvnet->status;
+}
+
+static void mvnet_set_status(struct mdev_device *mdev, u8 status)
+{
+	struct mvnet_state *mvnet = mdev_get_drvdata(mdev);
+
+	mvnet->status = status;
+
+	if (status == 0) {
+		spin_lock(&mvnet->lock);
+		mvnet_reset(mvnet);
+		spin_unlock(&mvnet->lock);
+	}
+}
+
+static void mvnet_get_config(struct mdev_device *mdev, unsigned int offset,
+			     void *buf, unsigned int len)
+{
+	struct mvnet_state *mvnet = mdev_get_drvdata(mdev);
+
+	if (offset + len < sizeof(struct virtio_net_config))
+		memcpy(buf, &mvnet->config + offset, len);
+}
+
+static void mvnet_set_config(struct mdev_device *mdev, unsigned int offset,
+			     const void *buf, unsigned int len)
+{
+	/* No writable config supportted by mvnet */
+}
+
+static int mvnet_get_version(struct mdev_device *mdev)
+{
+	return 0x1;
+}
+
+static u32 mvnet_get_generation(struct mdev_device *mdev)
+{
+	struct mvnet_state *mvnet = mdev_get_drvdata(mdev);
+
+	return mvnet->generation;
+}
+
+static const struct virtio_mdev_device_ops virtio_mdev_ops = {
+	.set_vq_address         = mvnet_set_vq_address,
+	.set_vq_num             = mvnet_set_vq_num,
+	.kick_vq                = mvnet_kick_vq,
+	.set_vq_cb              = mvnet_set_vq_cb,
+	.set_vq_ready           = mvnet_set_vq_ready,
+	.get_vq_ready           = mvnet_get_vq_ready,
+	.set_vq_state           = mvnet_set_vq_state,
+	.get_vq_state           = mvnet_get_vq_state,
+	.get_vq_align           = mvnet_get_vq_align,
+	.get_features           = mvnet_get_features,
+	.set_features           = mvnet_set_features,
+	.set_config_cb          = mvnet_set_config_cb,
+	.get_queue_max          = mvnet_get_queue_max,
+	.get_device_id          = mvnet_get_device_id,
+	.get_vendor_id          = mvnet_get_vendor_id,
+	.get_status             = mvnet_get_status,
+	.set_status             = mvnet_set_status,
+	.get_config             = mvnet_get_config,
+	.set_config             = mvnet_set_config,
+	.get_version            = mvnet_get_version,
+	.get_generation         = mvnet_get_generation,
+};
+
+static const struct mdev_parent_ops mdev_fops = {
+	.owner                  = THIS_MODULE,
+	.dev_attr_groups        = mvnet_dev_groups,
+	.mdev_attr_groups       = mdev_dev_groups,
+	.supported_type_groups  = mdev_type_groups,
+	.create                 = mvnet_create,
+	.remove			= mvnet_remove,
+};
+
+static void mvnet_device_release(struct device *dev)
+{
+	dev_dbg(dev, "mvnet: released\n");
+}
+
+static int __init mvnet_dev_init(void)
+{
+	int ret = 0;
+
+	pr_info("mvnet_dev: %s\n", __func__);
+
+	memset(&mvnet_dev, 0, sizeof(mvnet_dev));
+
+	idr_init(&mvnet_dev.vd_idr);
+
+	mvnet_dev.vd_class = class_create(THIS_MODULE, MVNET_CLASS_NAME);
+
+	if (IS_ERR(mvnet_dev.vd_class)) {
+		pr_err("Error: failed to register mvnet_dev class\n");
+		ret = PTR_ERR(mvnet_dev.vd_class);
+		goto failed1;
+	}
+
+	mvnet_dev.dev.class = mvnet_dev.vd_class;
+	mvnet_dev.dev.release = mvnet_device_release;
+	dev_set_name(&mvnet_dev.dev, "%s", MVNET_NAME);
+
+	ret = device_register(&mvnet_dev.dev);
+	if (ret)
+		goto failed2;
+
+	ret = mdev_register_device(&mvnet_dev.dev, &mdev_fops);
+	if (ret)
+		goto failed3;
+
+	mutex_init(&mdev_list_lock);
+	INIT_LIST_HEAD(&mdev_devices_list);
+
+	goto all_done;
+
+failed3:
+
+	device_unregister(&mvnet_dev.dev);
+failed2:
+	class_destroy(mvnet_dev.vd_class);
+
+failed1:
+all_done:
+	return ret;
+}
+
+static void __exit mvnet_dev_exit(void)
+{
+	mvnet_dev.dev.bus = NULL;
+	mdev_unregister_device(&mvnet_dev.dev);
+
+	device_unregister(&mvnet_dev.dev);
+	idr_destroy(&mvnet_dev.vd_idr);
+	class_destroy(mvnet_dev.vd_class);
+	mvnet_dev.vd_class = NULL;
+	pr_info("mvnet_dev: Unloaded!\n");
+}
+
+module_init(mvnet_dev_init)
+module_exit(mvnet_dev_exit)
+
+MODULE_LICENSE("GPL v2");
+MODULE_INFO(supported, "Simulate loopback ethernet device over
mdev");
+MODULE_VERSION(VERSION_STRING);
+MODULE_AUTHOR(DRIVER_AUTHOR);
-- 
2.19.1

On Tue, 24 Sep 2019 21:53:26 +0800
Jason Wang <jasowang at redhat.com> wrote:
> Mdev bus only supports vfio driver right now, so it doesn't implement
> match method. But in the future, we may add drivers other than vfio,
> the first driver could be virtio-mdev. This means we need to add
> device class id support in bus match method to pair the mdev device
> and mdev driver correctly.
> 
> So this patch adds id_table to mdev_driver and class_id for mdev
> parent with the match method for mdev bus.
Description needs to be revised from v1, class_id is no longer on the
parent.
> Signed-off-by: Jason Wang <jasowang at redhat.com>
> ---
>  Documentation/driver-api/vfio-mediated-device.rst |  3 +++
>  drivers/gpu/drm/i915/gvt/kvmgt.c                  |  1 +
>  drivers/s390/cio/vfio_ccw_ops.c                   |  1 +
>  drivers/s390/crypto/vfio_ap_ops.c                 |  1 +
>  drivers/vfio/mdev/mdev_core.c                     |  7 +++++++
>  drivers/vfio/mdev/mdev_driver.c                   | 14 ++++++++++++++
>  drivers/vfio/mdev/mdev_private.h                  |  1 +
>  drivers/vfio/mdev/vfio_mdev.c                     |  6 ++++++
>  include/linux/mdev.h                              |  8 ++++++++
>  include/linux/mod_devicetable.h                   |  8 ++++++++
>  samples/vfio-mdev/mbochs.c                        |  1 +
>  samples/vfio-mdev/mdpy.c                          |  1 +
>  samples/vfio-mdev/mtty.c                          |  1 +
>  13 files changed, 53 insertions(+)
> 
> diff --git a/Documentation/driver-api/vfio-mediated-device.rst
b/Documentation/driver-api/vfio-mediated-device.rst
> index 25eb7d5b834b..a5bdc60d62a1 100644
> --- a/Documentation/driver-api/vfio-mediated-device.rst
> +++ b/Documentation/driver-api/vfio-mediated-device.rst
> @@ -102,12 +102,14 @@ structure to represent a mediated device's
driver::
>        * @probe: called when new device created
>        * @remove: called when device removed
>        * @driver: device driver structure
> +      * @id_table: the ids serviced by this driver
>        */
>       struct mdev_driver {
>  	     const char *name;
>  	     int  (*probe)  (struct device *dev);
>  	     void (*remove) (struct device *dev);
>  	     struct device_driver    driver;
> +	     const struct mdev_class_id *id_table;
>       };
>  
>  A mediated bus driver for mdev should use this structure in the function
calls
> @@ -165,6 +167,7 @@ register itself with the mdev core driver::
>  	extern int  mdev_register_device(struct device *dev,
>  	                                 const struct mdev_parent_ops *ops);
>  
> +
>  However, the mdev_parent_ops structure is not required in the function
call
>  that a driver should use to unregister itself with the mdev core driver::
Unintended extra line?  Doesn't seem to match surrounding formatting.

Calling mdev_set_class_id() as part of create seems relatively
fundamental to the vendor driver with this change, it should be added
to the documentation.
> diff --git a/drivers/gpu/drm/i915/gvt/kvmgt.c
b/drivers/gpu/drm/i915/gvt/kvmgt.c
> index 23aa3e50cbf8..f793252a3d2a 100644
> --- a/drivers/gpu/drm/i915/gvt/kvmgt.c
> +++ b/drivers/gpu/drm/i915/gvt/kvmgt.c
> @@ -678,6 +678,7 @@ static int intel_vgpu_create(struct kobject *kobj,
struct mdev_device *mdev)
>  		     dev_name(mdev_dev(mdev)));
>  	ret = 0;
>  
> +	mdev_set_class_id(mdev, MDEV_ID_VFIO);
>  out:
>  	return ret;
>  }
> diff --git a/drivers/s390/cio/vfio_ccw_ops.c
b/drivers/s390/cio/vfio_ccw_ops.c
> index f0d71ab77c50..d258ef1fedb9 100644
> --- a/drivers/s390/cio/vfio_ccw_ops.c
> +++ b/drivers/s390/cio/vfio_ccw_ops.c
> @@ -129,6 +129,7 @@ static int vfio_ccw_mdev_create(struct kobject *kobj,
struct mdev_device *mdev)
>  			   private->sch->schid.ssid,
>  			   private->sch->schid.sch_no);
>  
> +	mdev_set_class_id(mdev, MDEV_ID_VFIO);
>  	return 0;
>  }
>  
> diff --git a/drivers/s390/crypto/vfio_ap_ops.c
b/drivers/s390/crypto/vfio_ap_ops.c
> index 5c0f53c6dde7..2cfd96112aa0 100644
> --- a/drivers/s390/crypto/vfio_ap_ops.c
> +++ b/drivers/s390/crypto/vfio_ap_ops.c
> @@ -343,6 +343,7 @@ static int vfio_ap_mdev_create(struct kobject *kobj,
struct mdev_device *mdev)
>  	list_add(&matrix_mdev->node, &matrix_dev->mdev_list);
>  	mutex_unlock(&matrix_dev->lock);
>  
> +	mdev_set_class_id(mdev, MDEV_ID_VFIO);
>  	return 0;
>  }
>  
> diff --git a/drivers/vfio/mdev/mdev_core.c b/drivers/vfio/mdev/mdev_core.c
> index b558d4cfd082..8764cf4a276d 100644
> --- a/drivers/vfio/mdev/mdev_core.c
> +++ b/drivers/vfio/mdev/mdev_core.c
> @@ -45,6 +45,12 @@ void mdev_set_drvdata(struct mdev_device *mdev, void
*data)
>  }
>  EXPORT_SYMBOL(mdev_set_drvdata);
>  
> +void mdev_set_class_id(struct mdev_device *mdev, u16 id)
> +{
> +	mdev->class_id = id;
> +}
> +EXPORT_SYMBOL(mdev_set_class_id);
> +
>  struct device *mdev_dev(struct mdev_device *mdev)
>  {
>  	return &mdev->dev;
> @@ -135,6 +141,7 @@ static int mdev_device_remove_cb(struct device *dev,
void *data)
>   * mdev_register_device : Register a device
>   * @dev: device structure representing parent device.
>   * @ops: Parent device operation structure to be registered.
> + * @id: device id.
>   *
>   * Add device to list of registered parent devices.
>   * Returns a negative value on error, otherwise 0.
> diff --git a/drivers/vfio/mdev/mdev_driver.c
b/drivers/vfio/mdev/mdev_driver.c
> index 0d3223aee20b..b7c40ce86ee3 100644
> --- a/drivers/vfio/mdev/mdev_driver.c
> +++ b/drivers/vfio/mdev/mdev_driver.c
> @@ -69,8 +69,22 @@ static int mdev_remove(struct device *dev)
>  	return 0;
>  }
>  
> +static int mdev_match(struct device *dev, struct device_driver *drv)
> +{
> +	unsigned int i;
> +	struct mdev_device *mdev = to_mdev_device(dev);
> +	struct mdev_driver *mdrv = to_mdev_driver(drv);
> +	const struct mdev_class_id *ids = mdrv->id_table;
> +
> +	for (i = 0; ids[i].id; i++)
> +		if (ids[i].id == mdev->class_id)
With the proposed API here, mdev->class_id can be NULL, do we allow
devices to exist in that state or should mdev_device_create() generate
an error if the .create() callback doesn't register a type?  Or a
warn_once and assume MDEV_ID_VFIO?  The latter seems pretty sketchy
when we get to patch 5/8.  Thanks,

Alex
> +			return 1;
> +	return 0;
> +}
> +
>  struct bus_type mdev_bus_type = {
>  	.name		= "mdev",
> +	.match		= mdev_match,
>  	.probe		= mdev_probe,
>  	.remove		= mdev_remove,
>  };
> diff --git a/drivers/vfio/mdev/mdev_private.h
b/drivers/vfio/mdev/mdev_private.h
> index 7d922950caaf..c65f436c1869 100644
> --- a/drivers/vfio/mdev/mdev_private.h
> +++ b/drivers/vfio/mdev/mdev_private.h
> @@ -33,6 +33,7 @@ struct mdev_device {
>  	struct kobject *type_kobj;
>  	struct device *iommu_device;
>  	bool active;
> +	u16 class_id;
>  };
>  
>  #define to_mdev_device(dev)	container_of(dev, struct mdev_device, dev)
> diff --git a/drivers/vfio/mdev/vfio_mdev.c b/drivers/vfio/mdev/vfio_mdev.c
> index 30964a4e0a28..fd2a4d9a3f26 100644
> --- a/drivers/vfio/mdev/vfio_mdev.c
> +++ b/drivers/vfio/mdev/vfio_mdev.c
> @@ -120,10 +120,16 @@ static void vfio_mdev_remove(struct device *dev)
>  	vfio_del_group_dev(dev);
>  }
>  
> +static struct mdev_class_id id_table[] = {
> +	{ MDEV_ID_VFIO },
> +	{ 0 },
> +};
> +
>  static struct mdev_driver vfio_mdev_driver = {
>  	.name	= "vfio_mdev",
>  	.probe	= vfio_mdev_probe,
>  	.remove	= vfio_mdev_remove,
> +	.id_table = id_table,
>  };
>  
>  static int __init vfio_mdev_init(void)
> diff --git a/include/linux/mdev.h b/include/linux/mdev.h
> index 0ce30ca78db0..3974650c074f 100644
> --- a/include/linux/mdev.h
> +++ b/include/linux/mdev.h
> @@ -118,6 +118,7 @@ struct mdev_type_attribute mdev_type_attr_##_name =		\
>   * @probe: called when new device created
>   * @remove: called when device removed
>   * @driver: device driver structure
> + * @id_table: the ids serviced by this driver.
>   *
>   **/
>  struct mdev_driver {
> @@ -125,12 +126,14 @@ struct mdev_driver {
>  	int  (*probe)(struct device *dev);
>  	void (*remove)(struct device *dev);
>  	struct device_driver driver;
> +	const struct mdev_class_id *id_table;
>  };
>  
>  #define to_mdev_driver(drv)	container_of(drv, struct mdev_driver, driver)
>  
>  void *mdev_get_drvdata(struct mdev_device *mdev);
>  void mdev_set_drvdata(struct mdev_device *mdev, void *data);
> +void mdev_set_class_id(struct mdev_device *mdev, u16 id);
>  const guid_t *mdev_uuid(struct mdev_device *mdev);
>  
>  extern struct bus_type mdev_bus_type;
> @@ -145,4 +148,9 @@ struct device *mdev_parent_dev(struct mdev_device
*mdev);
>  struct device *mdev_dev(struct mdev_device *mdev);
>  struct mdev_device *mdev_from_dev(struct device *dev);
>  
> +enum {
> +	MDEV_ID_VFIO = 1,
> +	/* New entries must be added here */
> +};
> +
>  #endif /* MDEV_H */
> diff --git a/include/linux/mod_devicetable.h
b/include/linux/mod_devicetable.h
> index 5714fd35a83c..f32c6e44fb1a 100644
> --- a/include/linux/mod_devicetable.h
> +++ b/include/linux/mod_devicetable.h
> @@ -821,4 +821,12 @@ struct wmi_device_id {
>  	const void *context;
>  };
>  
> +/**
> + * struct mdev_class_id - MDEV device class identifier
> + * @id: Used to identify a specific class of device, e.g vfio-mdev device.
> + */
> +struct mdev_class_id {
> +	__u16 id;
> +};
> +
>  #endif /* LINUX_MOD_DEVICETABLE_H */
> diff --git a/samples/vfio-mdev/mbochs.c b/samples/vfio-mdev/mbochs.c
> index ac5c8c17b1ff..8a8583c892b2 100644
> --- a/samples/vfio-mdev/mbochs.c
> +++ b/samples/vfio-mdev/mbochs.c
> @@ -561,6 +561,7 @@ static int mbochs_create(struct kobject *kobj, struct
mdev_device *mdev)
>  	mbochs_reset(mdev);
>  
>  	mbochs_used_mbytes += type->mbytes;
> +	mdev_set_class_id(mdev, MDEV_ID_VFIO);
>  	return 0;
>  
>  err_mem:
> diff --git a/samples/vfio-mdev/mdpy.c b/samples/vfio-mdev/mdpy.c
> index cc86bf6566e4..88d7e76f3836 100644
> --- a/samples/vfio-mdev/mdpy.c
> +++ b/samples/vfio-mdev/mdpy.c
> @@ -269,6 +269,7 @@ static int mdpy_create(struct kobject *kobj, struct
mdev_device *mdev)
>  	mdpy_reset(mdev);
>  
>  	mdpy_count++;
> +	mdev_set_class_id(mdev, MDEV_ID_VFIO);
>  	return 0;
>  }
>  
> diff --git a/samples/vfio-mdev/mtty.c b/samples/vfio-mdev/mtty.c
> index 92e770a06ea2..4e0735143b69 100644
> --- a/samples/vfio-mdev/mtty.c
> +++ b/samples/vfio-mdev/mtty.c
> @@ -770,6 +770,7 @@ static int mtty_create(struct kobject *kobj, struct
mdev_device *mdev)
>  	list_add(&mdev_state->next, &mdev_devices_list);
>  	mutex_unlock(&mdev_list_lock);
>  
> +	mdev_set_class_id(mdev, MDEV_ID_VFIO);
>  	return 0;
>  }
>

On Tue, 24 Sep 2019 21:53:29 +0800
Jason Wang <jasowang at redhat.com> wrote:
> Currently, except for the create and remove, the rest of
> mdev_parent_ops is designed for vfio-mdev driver only and may not help
> for kernel mdev driver. With the help of class id, this patch
> introduces device specific callbacks inside mdev_device
> structure. This allows different set of callback to be used by
> vfio-mdev and virtio-mdev.
> 
> Signed-off-by: Jason Wang <jasowang at redhat.com>
> ---
>  .../driver-api/vfio-mediated-device.rst       |  4 +-
>  MAINTAINERS                                   |  1 +
>  drivers/gpu/drm/i915/gvt/kvmgt.c              | 17 +++---
>  drivers/s390/cio/vfio_ccw_ops.c               | 17 ++++--
>  drivers/s390/crypto/vfio_ap_ops.c             | 13 +++--
>  drivers/vfio/mdev/mdev_core.c                 | 12 +++++
>  drivers/vfio/mdev/mdev_private.h              |  1 +
>  drivers/vfio/mdev/vfio_mdev.c                 | 37 ++++++-------
>  include/linux/mdev.h                          | 42 ++++-----------
>  include/linux/vfio_mdev.h                     | 52 +++++++++++++++++++
>  samples/vfio-mdev/mbochs.c                    | 19 ++++---
>  samples/vfio-mdev/mdpy.c                      | 19 ++++---
>  samples/vfio-mdev/mtty.c                      | 17 ++++--
>  13 files changed, 168 insertions(+), 83 deletions(-)
>  create mode 100644 include/linux/vfio_mdev.h
> 
> diff --git a/Documentation/driver-api/vfio-mediated-device.rst
b/Documentation/driver-api/vfio-mediated-device.rst
> index a5bdc60d62a1..d50425b368bb 100644
> --- a/Documentation/driver-api/vfio-mediated-device.rst
> +++ b/Documentation/driver-api/vfio-mediated-device.rst
> @@ -152,7 +152,9 @@ callbacks per mdev parent device, per mdev type, or any
other categorization.
>  Vendor drivers are expected to be fully asynchronous in this respect or
>  provide their own internal resource protection.)
>  
> -The callbacks in the mdev_parent_ops structure are as follows:
> +The device specific callbacks are referred through device_ops pointer
> +in mdev_parent_ops. For vfio-mdev device, its callbacks in device_ops
> +are as follows:
This is not accurate.  device_ops is now on the mdev_device and is an
mdev bus driver specific structure of callbacks that must be registered
for each mdev device by the parent driver during the create callback.
There's a one to one mapping of class_id to mdev_device_ops callbacks.

That also suggests to me that we could be more clever in registering
both of these with mdev-core.  Can we embed the class_id in the ops
structure in a common way so that the core can extract it and the bus
drivers can access their specific callbacks?
>  * open: open callback of mediated device
>  * close: close callback of mediated device
> diff --git a/MAINTAINERS b/MAINTAINERS
> index b2326dece28e..89832b316500 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -17075,6 +17075,7 @@ S:	Maintained
>  F:	Documentation/driver-api/vfio-mediated-device.rst
>  F:	drivers/vfio/mdev/
>  F:	include/linux/mdev.h
> +F:	include/linux/vfio_mdev.h
>  F:	samples/vfio-mdev/
>  
>  VFIO PLATFORM DRIVER
> diff --git a/drivers/gpu/drm/i915/gvt/kvmgt.c
b/drivers/gpu/drm/i915/gvt/kvmgt.c
> index f793252a3d2a..b274f5ee481f 100644
> --- a/drivers/gpu/drm/i915/gvt/kvmgt.c
> +++ b/drivers/gpu/drm/i915/gvt/kvmgt.c
> @@ -42,6 +42,7 @@
>  #include <linux/kvm_host.h>
>  #include <linux/vfio.h>
>  #include <linux/mdev.h>
> +#include <linux/vfio_mdev.h>
>  #include <linux/debugfs.h>
>  
>  #include <linux/nospec.h>
> @@ -643,6 +644,8 @@ static void kvmgt_put_vfio_device(void *vgpu)
>  	vfio_device_put(((struct intel_vgpu *)vgpu)->vdev.vfio_device);
>  }
>  
> +static struct vfio_mdev_device_ops intel_vfio_vgpu_dev_ops;
> +
>  static int intel_vgpu_create(struct kobject *kobj, struct mdev_device
*mdev)
>  {
>  	struct intel_vgpu *vgpu = NULL;
> @@ -679,6 +682,7 @@ static int intel_vgpu_create(struct kobject *kobj,
struct mdev_device *mdev)
>  	ret = 0;
>  
>  	mdev_set_class_id(mdev, MDEV_ID_VFIO);
> +	mdev_set_dev_ops(mdev, &intel_vfio_vgpu_dev_ops);
This seems rather unrefined.  We're registering interdependent data in
separate calls.  All drivers need to make both of these calls.  I'm not
sure if this is a good idea, but what if we had:

static const struct vfio_mdev_device_ops intel_vfio_vgpu_dev_ops = {
	.id			= MDEV_ID_VFIO,
 	.open			= intel_vgpu_open,
 	.release		= intel_vgpu_release,
        ...

And the set function passed &intel_vfio_vgpu_dev_ops.id and the mdev
bus drivers used container_of to get to their callbacks?
>  out:
>  	return ret;
>  }
> @@ -1601,20 +1605,21 @@ static const struct attribute_group
*intel_vgpu_groups[] = {
>  	NULL,
>  };
>  
> -static struct mdev_parent_ops intel_vgpu_ops = {
> -	.mdev_attr_groups       = intel_vgpu_groups,
> -	.create			= intel_vgpu_create,
> -	.remove			= intel_vgpu_remove,
> -
> +static struct vfio_mdev_device_ops intel_vfio_vgpu_dev_ops = {
>  	.open			= intel_vgpu_open,
>  	.release		= intel_vgpu_release,
> -
>  	.read			= intel_vgpu_read,
>  	.write			= intel_vgpu_write,
>  	.mmap			= intel_vgpu_mmap,
>  	.ioctl			= intel_vgpu_ioctl,
>  };
>  
> +static struct mdev_parent_ops intel_vgpu_ops = {
These could maybe be made const at the same time.  Thanks,

Alex
> +	.mdev_attr_groups       = intel_vgpu_groups,
> +	.create			= intel_vgpu_create,
> +	.remove			= intel_vgpu_remove,
> +};
> +
>  static int kvmgt_host_init(struct device *dev, void *gvt, const void *ops)
>  {
>  	struct attribute **kvm_type_attrs;
> diff --git a/drivers/s390/cio/vfio_ccw_ops.c
b/drivers/s390/cio/vfio_ccw_ops.c
> index d258ef1fedb9..329d53c1f46b 100644
> --- a/drivers/s390/cio/vfio_ccw_ops.c
> +++ b/drivers/s390/cio/vfio_ccw_ops.c
> @@ -12,6 +12,7 @@
>  
>  #include <linux/vfio.h>
>  #include <linux/mdev.h>
> +#include <linux/vfio_mdev.h>
>  #include <linux/nospec.h>
>  #include <linux/slab.h>
>  
> @@ -110,6 +111,8 @@ static struct attribute_group *mdev_type_groups[] = {
>  	NULL,
>  };
>  
> +static const struct vfio_mdev_device_ops vfio_mdev_ops;
> +
>  static int vfio_ccw_mdev_create(struct kobject *kobj, struct mdev_device
*mdev)
>  {
>  	struct vfio_ccw_private *private > @@ -130,6 +133,7 @@ static int
vfio_ccw_mdev_create(struct kobject *kobj, struct mdev_device *mdev)
>  			   private->sch->schid.sch_no);
>  
>  	mdev_set_class_id(mdev, MDEV_ID_VFIO);
> +	mdev_set_dev_ops(mdev, &vfio_mdev_ops);
>  	return 0;
>  }
>  
> @@ -575,11 +579,7 @@ static ssize_t vfio_ccw_mdev_ioctl(struct mdev_device
*mdev,
>  	}
>  }
>  
> -static const struct mdev_parent_ops vfio_ccw_mdev_ops = {
> -	.owner			= THIS_MODULE,
> -	.supported_type_groups  = mdev_type_groups,
> -	.create			= vfio_ccw_mdev_create,
> -	.remove			= vfio_ccw_mdev_remove,
> +static const struct vfio_mdev_device_ops vfio_mdev_ops = {
>  	.open			= vfio_ccw_mdev_open,
>  	.release		= vfio_ccw_mdev_release,
>  	.read			= vfio_ccw_mdev_read,
> @@ -587,6 +587,13 @@ static const struct mdev_parent_ops vfio_ccw_mdev_ops
= {
>  	.ioctl			= vfio_ccw_mdev_ioctl,
>  };
>  
> +static const struct mdev_parent_ops vfio_ccw_mdev_ops = {
> +	.owner			= THIS_MODULE,
> +	.supported_type_groups  = mdev_type_groups,
> +	.create			= vfio_ccw_mdev_create,
> +	.remove			= vfio_ccw_mdev_remove,
> +};
> +
>  int vfio_ccw_mdev_reg(struct subchannel *sch)
>  {
>  	return mdev_register_device(&sch->dev, &vfio_ccw_mdev_ops);
> diff --git a/drivers/s390/crypto/vfio_ap_ops.c
b/drivers/s390/crypto/vfio_ap_ops.c
> index 2cfd96112aa0..3a89933f0d3e 100644
> --- a/drivers/s390/crypto/vfio_ap_ops.c
> +++ b/drivers/s390/crypto/vfio_ap_ops.c
> @@ -16,6 +16,7 @@
>  #include <linux/bitops.h>
>  #include <linux/kvm_host.h>
>  #include <linux/module.h>
> +#include <linux/vfio_mdev.h>
>  #include <asm/kvm.h>
>  #include <asm/zcrypt.h>
>  
> @@ -321,6 +322,8 @@ static void vfio_ap_matrix_init(struct ap_config_info
*info,
>  	matrix->adm_max = info->apxa ? info->Nd : 15;
>  }
>  
> +static const struct vfio_mdev_device_ops vfio_mdev_ops;
> +
>  static int vfio_ap_mdev_create(struct kobject *kobj, struct mdev_device
*mdev)
>  {
>  	struct ap_matrix_mdev *matrix_mdev;
> @@ -344,6 +347,7 @@ static int vfio_ap_mdev_create(struct kobject *kobj,
struct mdev_device *mdev)
>  	mutex_unlock(&matrix_dev->lock);
>  
>  	mdev_set_class_id(mdev, MDEV_ID_VFIO);
> +	mdev_set_dev_ops(mdev, &vfio_mdev_ops);
>  	return 0;
>  }
>  
> @@ -1281,15 +1285,18 @@ static ssize_t vfio_ap_mdev_ioctl(struct
mdev_device *mdev,
>  	return ret;
>  }
>  
> +static const struct vfio_mdev_device_ops vfio_mdev_ops = {
> +	.open			= vfio_ap_mdev_open,
> +	.release		= vfio_ap_mdev_release,
> +	.ioctl			= vfio_ap_mdev_ioctl,
> +};
> +
>  static const struct mdev_parent_ops vfio_ap_matrix_ops = {
>  	.owner			= THIS_MODULE,
>  	.supported_type_groups	= vfio_ap_mdev_type_groups,
>  	.mdev_attr_groups	= vfio_ap_mdev_attr_groups,
>  	.create			= vfio_ap_mdev_create,
>  	.remove			= vfio_ap_mdev_remove,
> -	.open			= vfio_ap_mdev_open,
> -	.release		= vfio_ap_mdev_release,
> -	.ioctl			= vfio_ap_mdev_ioctl,
>  };
>  
>  int vfio_ap_mdev_register(void)
> diff --git a/drivers/vfio/mdev/mdev_core.c b/drivers/vfio/mdev/mdev_core.c
> index 8764cf4a276d..6f35f2ced2c9 100644
> --- a/drivers/vfio/mdev/mdev_core.c
> +++ b/drivers/vfio/mdev/mdev_core.c
> @@ -51,6 +51,18 @@ void mdev_set_class_id(struct mdev_device *mdev, u16 id)
>  }
>  EXPORT_SYMBOL(mdev_set_class_id);
>  
> +const void *mdev_get_dev_ops(struct mdev_device *mdev)
> +{
> +	return mdev->device_ops;
> +}
> +EXPORT_SYMBOL(mdev_get_dev_ops);
> +
> +void mdev_set_dev_ops(struct mdev_device *mdev, const void *ops)
> +{
> +	mdev->device_ops = ops;
> +}
> +EXPORT_SYMBOL(mdev_set_dev_ops);
> +
>  struct device *mdev_dev(struct mdev_device *mdev)
>  {
>  	return &mdev->dev;
> diff --git a/drivers/vfio/mdev/mdev_private.h
b/drivers/vfio/mdev/mdev_private.h
> index c65f436c1869..b666805f0b1f 100644
> --- a/drivers/vfio/mdev/mdev_private.h
> +++ b/drivers/vfio/mdev/mdev_private.h
> @@ -34,6 +34,7 @@ struct mdev_device {
>  	struct device *iommu_device;
>  	bool active;
>  	u16 class_id;
> +	const void *device_ops;
>  };
>  
>  #define to_mdev_device(dev)	container_of(dev, struct mdev_device, dev)
> diff --git a/drivers/vfio/mdev/vfio_mdev.c b/drivers/vfio/mdev/vfio_mdev.c
> index 891cf83a2d9a..95efa054442f 100644
> --- a/drivers/vfio/mdev/vfio_mdev.c
> +++ b/drivers/vfio/mdev/vfio_mdev.c
> @@ -14,6 +14,7 @@
>  #include <linux/slab.h>
>  #include <linux/vfio.h>
>  #include <linux/mdev.h>
> +#include <linux/vfio_mdev.h>
>  
>  #include "mdev_private.h"
>  
> @@ -24,16 +25,16 @@
>  static int vfio_mdev_open(void *device_data)
>  {
>  	struct mdev_device *mdev = device_data;
> -	struct mdev_parent *parent = mdev->parent;
> +	const struct vfio_mdev_device_ops *ops = mdev_get_dev_ops(mdev);
>  	int ret;
>  
> -	if (unlikely(!parent->ops->open))
> +	if (unlikely(!ops->open))
>  		return -EINVAL;
>  
>  	if (!try_module_get(THIS_MODULE))
>  		return -ENODEV;
>  
> -	ret = parent->ops->open(mdev);
> +	ret = ops->open(mdev);
>  	if (ret)
>  		module_put(THIS_MODULE);
>  
> @@ -43,10 +44,10 @@ static int vfio_mdev_open(void *device_data)
>  static void vfio_mdev_release(void *device_data)
>  {
>  	struct mdev_device *mdev = device_data;
> -	struct mdev_parent *parent = mdev->parent;
> +	const struct vfio_mdev_device_ops *ops = mdev_get_dev_ops(mdev);
>  
> -	if (likely(parent->ops->release))
> -		parent->ops->release(mdev);
> +	if (likely(ops->release))
> +		ops->release(mdev);
>  
>  	module_put(THIS_MODULE);
>  }
> @@ -55,47 +56,47 @@ static long vfio_mdev_unlocked_ioctl(void *device_data,
>  				     unsigned int cmd, unsigned long arg)
>  {
>  	struct mdev_device *mdev = device_data;
> -	struct mdev_parent *parent = mdev->parent;
> +	const struct vfio_mdev_device_ops *ops = mdev_get_dev_ops(mdev);
>  
> -	if (unlikely(!parent->ops->ioctl))
> +	if (unlikely(!ops->ioctl))
>  		return -EINVAL;
>  
> -	return parent->ops->ioctl(mdev, cmd, arg);
> +	return ops->ioctl(mdev, cmd, arg);
>  }
>  
>  static ssize_t vfio_mdev_read(void *device_data, char __user *buf,
>  			      size_t count, loff_t *ppos)
>  {
>  	struct mdev_device *mdev = device_data;
> -	struct mdev_parent *parent = mdev->parent;
> +	const struct vfio_mdev_device_ops *ops = mdev_get_dev_ops(mdev);
>  
> -	if (unlikely(!parent->ops->read))
> +	if (unlikely(!ops->read))
>  		return -EINVAL;
>  
> -	return parent->ops->read(mdev, buf, count, ppos);
> +	return ops->read(mdev, buf, count, ppos);
>  }
>  
>  static ssize_t vfio_mdev_write(void *device_data, const char __user *buf,
>  			       size_t count, loff_t *ppos)
>  {
>  	struct mdev_device *mdev = device_data;
> -	struct mdev_parent *parent = mdev->parent;
> +	const struct vfio_mdev_device_ops *ops = mdev_get_dev_ops(mdev);
>  
> -	if (unlikely(!parent->ops->write))
> +	if (unlikely(!ops->write))
>  		return -EINVAL;
>  
> -	return parent->ops->write(mdev, buf, count, ppos);
> +	return ops->write(mdev, buf, count, ppos);
>  }
>  
>  static int vfio_mdev_mmap(void *device_data, struct vm_area_struct *vma)
>  {
>  	struct mdev_device *mdev = device_data;
> -	struct mdev_parent *parent = mdev->parent;
> +	const struct vfio_mdev_device_ops *ops = mdev_get_dev_ops(mdev);
>  
> -	if (unlikely(!parent->ops->mmap))
> +	if (unlikely(!ops->mmap))
>  		return -EINVAL;
>  
> -	return parent->ops->mmap(mdev, vma);
> +	return ops->mmap(mdev, vma);
>  }
>  
>  static const struct vfio_device_ops vfio_mdev_dev_ops = {
> diff --git a/include/linux/mdev.h b/include/linux/mdev.h
> index 3974650c074f..3414307311f1 100644
> --- a/include/linux/mdev.h
> +++ b/include/linux/mdev.h
> @@ -10,6 +10,11 @@
>  #ifndef MDEV_H
>  #define MDEV_H
>  
> +#include <linux/types.h>
> +#include <linux/device.h>
> +#include <linux/mdev.h>
> +#include <uapi/linux/uuid.h>
> +
>  struct mdev_device;
>  
>  /*
> @@ -48,30 +53,8 @@ struct device *mdev_get_iommu_device(struct device
*dev);
>   *			@mdev: mdev_device device structure which is being
>   *			       destroyed
>   *			Returns integer: success (0) or error (< 0)
> - * @open:		Open mediated device.
> - *			@mdev: mediated device.
> - *			Returns integer: success (0) or error (< 0)
> - * @release:		release mediated device
> - *			@mdev: mediated device.
> - * @read:		Read emulation callback
> - *			@mdev: mediated device structure
> - *			@buf: read buffer
> - *			@count: number of bytes to read
> - *			@ppos: address.
> - *			Retuns number on bytes read on success or error.
> - * @write:		Write emulation callback
> - *			@mdev: mediated device structure
> - *			@buf: write buffer
> - *			@count: number of bytes to be written
> - *			@ppos: address.
> - *			Retuns number on bytes written on success or error.
> - * @ioctl:		IOCTL callback
> - *			@mdev: mediated device structure
> - *			@cmd: ioctl command
> - *			@arg: arguments to ioctl
> - * @mmap:		mmap callback
> - *			@mdev: mediated device structure
> - *			@vma: vma structure
> + * @device_ops:         Device specific emulation callback.
> + *
>   * Parent device that support mediated device should be registered with
mdev
>   * module with mdev_parent_ops structure.
>   **/
> @@ -83,15 +66,6 @@ struct mdev_parent_ops {
>  
>  	int     (*create)(struct kobject *kobj, struct mdev_device *mdev);
>  	int     (*remove)(struct mdev_device *mdev);
> -	int     (*open)(struct mdev_device *mdev);
> -	void    (*release)(struct mdev_device *mdev);
> -	ssize_t (*read)(struct mdev_device *mdev, char __user *buf,
> -			size_t count, loff_t *ppos);
> -	ssize_t (*write)(struct mdev_device *mdev, const char __user *buf,
> -			 size_t count, loff_t *ppos);
> -	long	(*ioctl)(struct mdev_device *mdev, unsigned int cmd,
> -			 unsigned long arg);
> -	int	(*mmap)(struct mdev_device *mdev, struct vm_area_struct *vma);
>  };
>  
>  /* interface for exporting mdev supported type attributes */
> @@ -133,6 +107,8 @@ struct mdev_driver {
>  
>  void *mdev_get_drvdata(struct mdev_device *mdev);
>  void mdev_set_drvdata(struct mdev_device *mdev, void *data);
> +const void *mdev_get_dev_ops(struct mdev_device *mdev);
> +void mdev_set_dev_ops(struct mdev_device *mdev, const void *ops);
>  void mdev_set_class_id(struct mdev_device *mdev, u16 id);
>  const guid_t *mdev_uuid(struct mdev_device *mdev);
>  
> diff --git a/include/linux/vfio_mdev.h b/include/linux/vfio_mdev.h
> new file mode 100644
> index 000000000000..3907c5371c2b
> --- /dev/null
> +++ b/include/linux/vfio_mdev.h
> @@ -0,0 +1,52 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/*
> + * VFIO Mediated device definition
> + */
> +
> +#ifndef VFIO_MDEV_H
> +#define VFIO_MDEV_H
> +
> +#include <linux/mdev.h>
> +
> +/**
> + * struct vfio_mdev_device_ops - Structure to be registered for each
> + * mdev device to register the device to vfio-mdev module.
> + *
> + * @open:		Open mediated device.
> + *			@mdev: mediated device.
> + *			Returns integer: success (0) or error (< 0)
> + * @release:		release mediated device
> + *			@mdev: mediated device.
> + * @read:		Read emulation callback
> + *			@mdev: mediated device structure
> + *			@buf: read buffer
> + *			@count: number of bytes to read
> + *			@ppos: address.
> + *			Retuns number on bytes read on success or error.
> + * @write:		Write emulation callback
> + *			@mdev: mediated device structure
> + *			@buf: write buffer
> + *			@count: number of bytes to be written
> + *			@ppos: address.
> + *			Retuns number on bytes written on success or error.
> + * @ioctl:		IOCTL callback
> + *			@mdev: mediated device structure
> + *			@cmd: ioctl command
> + *			@arg: arguments to ioctl
> + * @mmap:		mmap callback
> + *			@mdev: mediated device structure
> + *			@vma: vma structure
> + */
> +struct vfio_mdev_device_ops {
> +	int     (*open)(struct mdev_device *mdev);
> +	void    (*release)(struct mdev_device *mdev);
> +	ssize_t (*read)(struct mdev_device *mdev, char __user *buf,
> +			size_t count, loff_t *ppos);
> +	ssize_t (*write)(struct mdev_device *mdev, const char __user *buf,
> +			 size_t count, loff_t *ppos);
> +	long	(*ioctl)(struct mdev_device *mdev, unsigned int cmd,
> +			 unsigned long arg);
> +	int	(*mmap)(struct mdev_device *mdev, struct vm_area_struct *vma);
> +};
> +
> +#endif
> diff --git a/samples/vfio-mdev/mbochs.c b/samples/vfio-mdev/mbochs.c
> index 8a8583c892b2..b4bf29c6136c 100644
> --- a/samples/vfio-mdev/mbochs.c
> +++ b/samples/vfio-mdev/mbochs.c
> @@ -30,6 +30,7 @@
>  #include <linux/iommu.h>
>  #include <linux/sysfs.h>
>  #include <linux/mdev.h>
> +#include <linux/vfio_mdev.h>
>  #include <linux/pci.h>
>  #include <linux/dma-buf.h>
>  #include <linux/highmem.h>
> @@ -516,6 +517,8 @@ static int mbochs_reset(struct mdev_device *mdev)
>  	return 0;
>  }
>  
> +static const struct vfio_mdev_device_ops vfio_mdev_ops;
> +
>  static int mbochs_create(struct kobject *kobj, struct mdev_device *mdev)
>  {
>  	const struct mbochs_type *type = mbochs_find_type(kobj);
> @@ -562,6 +565,7 @@ static int mbochs_create(struct kobject *kobj, struct
mdev_device *mdev)
>  
>  	mbochs_used_mbytes += type->mbytes;
>  	mdev_set_class_id(mdev, MDEV_ID_VFIO);
> +	mdev_set_dev_ops(mdev, &vfio_mdev_ops);
>  	return 0;
>  
>  err_mem:
> @@ -1419,12 +1423,7 @@ static struct attribute_group *mdev_type_groups[] =
{
>  	NULL,
>  };
>  
> -static const struct mdev_parent_ops mdev_fops = {
> -	.owner			= THIS_MODULE,
> -	.mdev_attr_groups	= mdev_dev_groups,
> -	.supported_type_groups	= mdev_type_groups,
> -	.create			= mbochs_create,
> -	.remove			= mbochs_remove,
> +static const struct vfio_mdev_device_ops vfio_mdev_ops = {
>  	.open			= mbochs_open,
>  	.release		= mbochs_close,
>  	.read			= mbochs_read,
> @@ -1433,6 +1432,14 @@ static const struct mdev_parent_ops mdev_fops = {
>  	.mmap			= mbochs_mmap,
>  };
>  
> +static const struct mdev_parent_ops mdev_fops = {
> +	.owner			= THIS_MODULE,
> +	.mdev_attr_groups	= mdev_dev_groups,
> +	.supported_type_groups	= mdev_type_groups,
> +	.create			= mbochs_create,
> +	.remove			= mbochs_remove,
> +};
> +
>  static const struct file_operations vd_fops = {
>  	.owner		= THIS_MODULE,
>  };
> diff --git a/samples/vfio-mdev/mdpy.c b/samples/vfio-mdev/mdpy.c
> index 88d7e76f3836..80c2df531326 100644
> --- a/samples/vfio-mdev/mdpy.c
> +++ b/samples/vfio-mdev/mdpy.c
> @@ -26,6 +26,7 @@
>  #include <linux/iommu.h>
>  #include <linux/sysfs.h>
>  #include <linux/mdev.h>
> +#include <linux/vfio_mdev.h>
>  #include <linux/pci.h>
>  #include <drm/drm_fourcc.h>
>  #include "mdpy-defs.h"
> @@ -226,6 +227,8 @@ static int mdpy_reset(struct mdev_device *mdev)
>  	return 0;
>  }
>  
> +static const struct vfio_mdev_device_ops vfio_mdev_ops;
> +
>  static int mdpy_create(struct kobject *kobj, struct mdev_device *mdev)
>  {
>  	const struct mdpy_type *type = mdpy_find_type(kobj);
> @@ -270,6 +273,7 @@ static int mdpy_create(struct kobject *kobj, struct
mdev_device *mdev)
>  
>  	mdpy_count++;
>  	mdev_set_class_id(mdev, MDEV_ID_VFIO);
> +	mdev_set_dev_ops(mdev, &vfio_mdev_ops);
>  	return 0;
>  }
>  
> @@ -726,12 +730,7 @@ static struct attribute_group *mdev_type_groups[] = {
>  	NULL,
>  };
>  
> -static const struct mdev_parent_ops mdev_fops = {
> -	.owner			= THIS_MODULE,
> -	.mdev_attr_groups	= mdev_dev_groups,
> -	.supported_type_groups	= mdev_type_groups,
> -	.create			= mdpy_create,
> -	.remove			= mdpy_remove,
> +static const struct vfio_mdev_device_ops vfio_mdev_ops = {
>  	.open			= mdpy_open,
>  	.release		= mdpy_close,
>  	.read			= mdpy_read,
> @@ -740,6 +739,14 @@ static const struct mdev_parent_ops mdev_fops = {
>  	.mmap			= mdpy_mmap,
>  };
>  
> +static const struct mdev_parent_ops mdev_fops = {
> +	.owner			= THIS_MODULE,
> +	.mdev_attr_groups	= mdev_dev_groups,
> +	.supported_type_groups	= mdev_type_groups,
> +	.create			= mdpy_create,
> +	.remove			= mdpy_remove,
> +};
> +
>  static const struct file_operations vd_fops = {
>  	.owner		= THIS_MODULE,
>  };
> diff --git a/samples/vfio-mdev/mtty.c b/samples/vfio-mdev/mtty.c
> index 4e0735143b69..2db860ccb02c 100644
> --- a/samples/vfio-mdev/mtty.c
> +++ b/samples/vfio-mdev/mtty.c
> @@ -27,6 +27,7 @@
>  #include <linux/ctype.h>
>  #include <linux/file.h>
>  #include <linux/mdev.h>
> +#include <linux/vfio_mdev.h>
>  #include <linux/pci.h>
>  #include <linux/serial.h>
>  #include <uapi/linux/serial_reg.h>
> @@ -723,6 +724,8 @@ static ssize_t mdev_access(struct mdev_device *mdev, u8
*buf, size_t count,
>  	return ret;
>  }
>  
> +static const struct vfio_mdev_device_ops vfio_dev_ops;
> +
>  static int mtty_create(struct kobject *kobj, struct mdev_device *mdev)
>  {
>  	struct mdev_state *mdev_state;
> @@ -771,6 +774,7 @@ static int mtty_create(struct kobject *kobj, struct
mdev_device *mdev)
>  	mutex_unlock(&mdev_list_lock);
>  
>  	mdev_set_class_id(mdev, MDEV_ID_VFIO);
> +	mdev_set_dev_ops(mdev, &vfio_dev_ops);
>  	return 0;
>  }
>  
> @@ -1411,6 +1415,14 @@ static struct attribute_group *mdev_type_groups[] =
{
>  	NULL,
>  };
>  
> +static const struct vfio_mdev_device_ops vfio_dev_ops = {
> +	.open                   = mtty_open,
> +	.release                = mtty_close,
> +	.read                   = mtty_read,
> +	.write                  = mtty_write,
> +	.ioctl		        = mtty_ioctl,
> +};
> +
>  static const struct mdev_parent_ops mdev_fops = {
>  	.owner                  = THIS_MODULE,
>  	.dev_attr_groups        = mtty_dev_groups,
> @@ -1418,11 +1430,6 @@ static const struct mdev_parent_ops mdev_fops = {
>  	.supported_type_groups  = mdev_type_groups,
>  	.create                 = mtty_create,
>  	.remove			= mtty_remove,
> -	.open                   = mtty_open,
> -	.release                = mtty_close,
> -	.read                   = mtty_read,
> -	.write                  = mtty_write,
> -	.ioctl		        = mtty_ioctl,
>  };
>  
>  static void mtty_device_release(struct device *dev)

On Tue, 24 Sep 2019 21:53:30 +0800
Jason Wang <jasowang at redhat.com> wrote:
> This patch implements basic support for mdev driver that supports
> virtio transport for kernel virtio driver.
> 
> Signed-off-by: Jason Wang <jasowang at redhat.com>
> ---
>  include/linux/mdev.h        |   2 +
>  include/linux/virtio_mdev.h | 145 ++++++++++++++++++++++++++++++++++++
>  2 files changed, 147 insertions(+)
>  create mode 100644 include/linux/virtio_mdev.h
> 
> diff --git a/include/linux/mdev.h b/include/linux/mdev.h
> index 3414307311f1..73ac27b3b868 100644
> --- a/include/linux/mdev.h
> +++ b/include/linux/mdev.h
> @@ -126,6 +126,8 @@ struct mdev_device *mdev_from_dev(struct device *dev);
>  
>  enum {
>  	MDEV_ID_VFIO = 1,
> +	MDEV_ID_VIRTIO = 2,
> +	MDEV_ID_VHOST = 3,
MDEV_ID_VHOST isn't used yet here.  Also, given the strong
interdependence between the class_id and the ops structure, we might
wand to define them in the same place.  Thanks,

Alex
>  	/* New entries must be added here */
>  };
>  
> diff --git a/include/linux/virtio_mdev.h b/include/linux/virtio_mdev.h
> new file mode 100644
> index 000000000000..d1a40a739266
> --- /dev/null
> +++ b/include/linux/virtio_mdev.h
> @@ -0,0 +1,145 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/*
> + * Virtio mediated device driver
> + *
> + * Copyright 2019, Red Hat Corp.
> + *     Author: Jason Wang <jasowang at redhat.com>
> + */
> +#ifndef _LINUX_VIRTIO_MDEV_H
> +#define _LINUX_VIRTIO_MDEV_H
> +
> +#include <linux/interrupt.h>
> +#include <linux/mdev.h>
> +#include <uapi/linux/vhost.h>
> +
> +#define VIRTIO_MDEV_DEVICE_API_STRING		"virtio-mdev"
> +#define VIRTIO_MDEV_VERSION 0x1
> +
> +struct virtio_mdev_callback {
> +	irqreturn_t (*callback)(void *data);
> +	void *private;
> +};
> +
> +/**
> + * struct vfio_mdev_device_ops - Structure to be registered for each
> + * mdev device to register the device to virtio-mdev module.
> + *
> + * @set_vq_address:		Set the address of virtqueue
> + *				@mdev: mediated device
> + *				@idx: virtqueue index
> + *				@desc_area: address of desc area
> + *				@driver_area: address of driver area
> + *				@device_area: address of device area
> + *				Returns integer: success (0) or error (< 0)
> + * @set_vq_num:		Set the size of virtqueue
> + *				@mdev: mediated device
> + *				@idx: virtqueue index
> + *				@num: the size of virtqueue
> + * @kick_vq:			Kick the virtqueue
> + *				@mdev: mediated device
> + *				@idx: virtqueue index
> + * @set_vq_cb:			Set the interrut calback function for
> + *				a virtqueue
> + *				@mdev: mediated device
> + *				@idx: virtqueue index
> + *				@cb: virtio-mdev interrupt callback structure
> + * @set_vq_ready:		Set ready status for a virtqueue
> + *				@mdev: mediated device
> + *				@idx: virtqueue index
> + *				@ready: ready (true) not ready(false)
> + * @get_vq_ready:		Get ready status for a virtqueue
> + *				@mdev: mediated device
> + *				@idx: virtqueue index
> + *				Returns boolean: ready (true) or not (false)
> + * @set_vq_state:		Set the state for a virtqueue
> + *				@mdev: mediated device
> + *				@idx: virtqueue index
> + *				@state: virtqueue state (last_avail_idx)
> + *				Returns integer: success (0) or error (< 0)
> + * @get_vq_state:		Get the state for a virtqueue
> + *				@mdev: mediated device
> + *				@idx: virtqueue index
> + *				Returns virtqueue state (last_avail_idx)
> + * @get_vq_align:		Get the virtqueue align requirement
> + *				for the device
> + *				@mdev: mediated device
> + *				Returns virtqueue algin requirement
> + * @get_features:		Get virtio features supported by the device
> + *				@mdev: mediated device
> + *				Returns the features support by the
> + *				device
> + * @get_features:		Set virtio features supported by the driver
> + *				@mdev: mediated device
> + *				@features: feature support by the driver
> + *				Returns integer: success (0) or error (< 0)
> + * @set_config_cb:		Set the config interrupt callback
> + *				@mdev: mediated device
> + *				@cb: virtio-mdev interrupt callback structure
> + * @get_device_id:		Get virtio device id
> + *				@mdev: mediated device
> + *				Returns u32: virtio device id
> + * @get_vendor_id:		Get virtio vendor id
> + *				@mdev: mediated device
> + *				Returns u32: virtio vendor id
> + * @get_status:		Get the device status
> + *				@mdev: mediated device
> + *				Returns u8: virtio device status
> + * @set_status:		Set the device status
> + *				@mdev: mediated device
> + *				@status: virtio device status
> + * @get_config:		Read from device specific confiugration space
> + *				@mdev: mediated device
> + *				@offset: offset from the beginning of
> + *				configuration space
> + *				@buf: buffer used to read to
> + *				@len: the length to read from
> + *				configration space
> + * @set_config:		Write to device specific confiugration space
> + *				@mdev: mediated device
> + *				@offset: offset from the beginning of
> + *				configuration space
> + *				@buf: buffer used to write from
> + *				@len: the length to write to
> + *				configration space
> + * @get_version:		Get the version of virtio mdev device
> + *				@mdev: mediated device
> + *				Returns integer: version of the device
> + * @get_generation:		Get device generaton
> + *				@mdev: mediated device
> + *				Returns u32: device generation
> + */
> +struct virtio_mdev_device_ops {
> +	/* Virtqueue ops */
> +	int (*set_vq_address)(struct mdev_device *mdev,
> +			      u16 idx, u64 desc_area, u64 driver_area,
> +			      u64 device_area);
> +	void (*set_vq_num)(struct mdev_device *mdev, u16 idx, u32 num);
> +	void (*kick_vq)(struct mdev_device *mdev, u16 idx);
> +	void (*set_vq_cb)(struct mdev_device *mdev, u16 idx,
> +			  struct virtio_mdev_callback *cb);
> +	void (*set_vq_ready)(struct mdev_device *mdev, u16 idx, bool ready);
> +	bool (*get_vq_ready)(struct mdev_device *mdev, u16 idx);
> +	int (*set_vq_state)(struct mdev_device *mdev, u16 idx, u64 state);
> +	u64 (*get_vq_state)(struct mdev_device *mdev, u16 idx);
> +
> +	/* Device ops */
> +	u16 (*get_vq_align)(struct mdev_device *mdev);
> +	u64 (*get_features)(struct mdev_device *mdev);
> +	int (*set_features)(struct mdev_device *mdev, u64 features);
> +	void (*set_config_cb)(struct mdev_device *mdev,
> +			      struct virtio_mdev_callback *cb);
> +	u16 (*get_queue_max)(struct mdev_device *mdev);
> +	u32 (*get_device_id)(struct mdev_device *mdev);
> +	u32 (*get_vendor_id)(struct mdev_device *mdev);
> +	u8 (*get_status)(struct mdev_device *mdev);
> +	void (*set_status)(struct mdev_device *mdev, u8 status);
> +	void (*get_config)(struct mdev_device *mdev, unsigned int offset,
> +			   void *buf, unsigned int len);
> +	void (*set_config)(struct mdev_device *mdev, unsigned int offset,
> +			   const void *buf, unsigned int len);
> +	int (*get_version)(struct mdev_device *mdev);
> +	u32 (*get_generation)(struct mdev_device *mdev);
> +};
> +
> +#endif
> +

> From: Jason Wang [mailto:jasowang at redhat.com]
> Sent: Tuesday, September 24, 2019 9:53 PM
> 
> Hi all:
> 
> There are hardware that can do virtio datapath offloading while having
> its own control path. This path tries to implement a mdev based
> unified API to support using kernel virtio driver to drive those
> devices. This is done by introducing a new mdev transport for virtio
> (virtio_mdev) and register itself as a new kind of mdev driver. Then
> it provides a unified way for kernel virtio driver to talk with mdev
> device implementation.
> 
> Though the series only contains kernel driver support, the goal is to
> make the transport generic enough to support userspace drivers. This
> means vhost-mdev[1] could be built on top as well by resuing the
> transport.
> 
> A sample driver is also implemented which simulate a virito-net
> loopback ethernet device on top of vringh + workqueue. This could be
> used as a reference implementation for real hardware driver.
> 
> Consider mdev framework only support VFIO device and driver right now,
> this series also extend it to support other types. This is done
> through introducing class id to the device and pairing it with
> id_talbe claimed by the driver. On top, this seris also decouple
id_table claimed ... this series ...
> device specific parents ops out of the common ones.
> 
> Pktgen test was done with virito-net + mvnet loop back device.
> 
> Please review.
> 
> [1] https://lkml.org/lkml/2019/9/16/869
> 
> Changes from V1:
> 
> - move virtio_mdev.c to drivers/virtio
> - store class_id in mdev_device instead of mdev_parent
> - store device_ops in mdev_device instead of mdev_parent
> - reorder the patch, vringh fix comes first
> - really silent compiling warnings
> - really switch to use u16 for class_id
> - uevent and modpost support for mdev class_id
> - vraious tweaks per comments from Parav
> 
> Changes from RFC-V2:
> 
> - silent compile warnings on some specific configuration
> - use u16 instead u8 for class id
> - reseve MDEV_ID_VHOST for future vhost-mdev work
> - introduce "virtio" type for mvnet and make "vhost"
type for future
>   work
> - add entries in MAINTAINER
> - tweak and typos fixes in commit log
> 
> Changes from RFC-V1:
> 
> - rename device id to class id
> - add docs for class id and device specific ops (device_ops)
> - split device_ops into seperate headers
> - drop the mdev_set_dma_ops()
> - use device_ops to implement the transport API, then it's not a part
>   of UAPI any more
> - use GFP_ATOMIC in mvnet sample device and other tweaks
> - set_vring_base/get_vring_base support for mvnet device
> 
> Jason Wang (8):
>   vringh: fix copy direction of vringh_iov_push_kern()
>   mdev: class id support
>   mdev: bus uevent support
>   modpost: add support for mdev class id
>   mdev: introduce device specific ops
>   mdev: introduce virtio device and its device ops
>   virtio: introduce a mdev based transport
>   docs: sample driver to demonstrate how to implement virtio-mdev
>     framework
> 
>  .../driver-api/vfio-mediated-device.rst       |   7 +-
>  MAINTAINERS                                   |   2 +
>  drivers/gpu/drm/i915/gvt/kvmgt.c              |  18 +-
>  drivers/s390/cio/vfio_ccw_ops.c               |  18 +-
>  drivers/s390/crypto/vfio_ap_ops.c             |  14 +-
>  drivers/vfio/mdev/mdev_core.c                 |  19 +
>  drivers/vfio/mdev/mdev_driver.c               |  22 +
>  drivers/vfio/mdev/mdev_private.h              |   2 +
>  drivers/vfio/mdev/vfio_mdev.c                 |  45 +-
>  drivers/vhost/vringh.c                        |   8 +-
>  drivers/virtio/Kconfig                        |   7 +
>  drivers/virtio/Makefile                       |   1 +
>  drivers/virtio/virtio_mdev.c                  | 417 +++++++++++
>  include/linux/mdev.h                          |  52 +-
>  include/linux/mod_devicetable.h               |   8 +
>  include/linux/vfio_mdev.h                     |  52 ++
>  include/linux/virtio_mdev.h                   | 145 ++++
>  samples/Kconfig                               |   7 +
>  samples/vfio-mdev/Makefile                    |   1 +
>  samples/vfio-mdev/mbochs.c                    |  20 +-
>  samples/vfio-mdev/mdpy.c                      |  20 +-
>  samples/vfio-mdev/mtty.c                      |  18 +-
>  samples/vfio-mdev/mvnet.c                     | 692 ++++++++++++++++++
>  scripts/mod/devicetable-offsets.c             |   3 +
>  scripts/mod/file2alias.c                      |  10 +
>  25 files changed, 1524 insertions(+), 84 deletions(-)
>  create mode 100644 drivers/virtio/virtio_mdev.c
>  create mode 100644 include/linux/vfio_mdev.h
>  create mode 100644 include/linux/virtio_mdev.h
>  create mode 100644 samples/vfio-mdev/mvnet.c
> 
> --
> 2.19.1

> From: Jason Wang
> Sent: Tuesday, September 24, 2019 9:53 PM
> 
> Mdev bus only supports vfio driver right now, so it doesn't implement
> match method. But in the future, we may add drivers other than vfio,
> the first driver could be virtio-mdev. This means we need to add
> device class id support in bus match method to pair the mdev device
> and mdev driver correctly.
> 
> So this patch adds id_table to mdev_driver and class_id for mdev
> parent with the match method for mdev bus.
> 
> Signed-off-by: Jason Wang <jasowang at redhat.com>
> ---
>  Documentation/driver-api/vfio-mediated-device.rst |  3 +++
>  drivers/gpu/drm/i915/gvt/kvmgt.c                  |  1 +
>  drivers/s390/cio/vfio_ccw_ops.c                   |  1 +
>  drivers/s390/crypto/vfio_ap_ops.c                 |  1 +
>  drivers/vfio/mdev/mdev_core.c                     |  7 +++++++
>  drivers/vfio/mdev/mdev_driver.c                   | 14 ++++++++++++++
>  drivers/vfio/mdev/mdev_private.h                  |  1 +
>  drivers/vfio/mdev/vfio_mdev.c                     |  6 ++++++
>  include/linux/mdev.h                              |  8 ++++++++
>  include/linux/mod_devicetable.h                   |  8 ++++++++
>  samples/vfio-mdev/mbochs.c                        |  1 +
>  samples/vfio-mdev/mdpy.c                          |  1 +
>  samples/vfio-mdev/mtty.c                          |  1 +
>  13 files changed, 53 insertions(+)
> 
> diff --git a/Documentation/driver-api/vfio-mediated-device.rst
> b/Documentation/driver-api/vfio-mediated-device.rst
> index 25eb7d5b834b..a5bdc60d62a1 100644
> --- a/Documentation/driver-api/vfio-mediated-device.rst
> +++ b/Documentation/driver-api/vfio-mediated-device.rst
> @@ -102,12 +102,14 @@ structure to represent a mediated device's
> driver::
>        * @probe: called when new device created
>        * @remove: called when device removed
>        * @driver: device driver structure
> +      * @id_table: the ids serviced by this driver
>        */
>       struct mdev_driver {
>  	     const char *name;
>  	     int  (*probe)  (struct device *dev);
>  	     void (*remove) (struct device *dev);
>  	     struct device_driver    driver;
> +	     const struct mdev_class_id *id_table;
>       };
> 
>  A mediated bus driver for mdev should use this structure in the function
> calls
> @@ -165,6 +167,7 @@ register itself with the mdev core driver::
>  	extern int  mdev_register_device(struct device *dev,
>  	                                 const struct mdev_parent_ops *ops);
> 
> +
>  However, the mdev_parent_ops structure is not required in the function
> call
>  that a driver should use to unregister itself with the mdev core driver::
> 
> diff --git a/drivers/gpu/drm/i915/gvt/kvmgt.c
> b/drivers/gpu/drm/i915/gvt/kvmgt.c
> index 23aa3e50cbf8..f793252a3d2a 100644
> --- a/drivers/gpu/drm/i915/gvt/kvmgt.c
> +++ b/drivers/gpu/drm/i915/gvt/kvmgt.c
> @@ -678,6 +678,7 @@ static int intel_vgpu_create(struct kobject *kobj,
> struct mdev_device *mdev)
>  		     dev_name(mdev_dev(mdev)));
>  	ret = 0;
> 
> +	mdev_set_class_id(mdev, MDEV_ID_VFIO);
>  out:
>  	return ret;
>  }
> diff --git a/drivers/s390/cio/vfio_ccw_ops.c
> b/drivers/s390/cio/vfio_ccw_ops.c
> index f0d71ab77c50..d258ef1fedb9 100644
> --- a/drivers/s390/cio/vfio_ccw_ops.c
> +++ b/drivers/s390/cio/vfio_ccw_ops.c
> @@ -129,6 +129,7 @@ static int vfio_ccw_mdev_create(struct kobject
> *kobj, struct mdev_device *mdev)
>  			   private->sch->schid.ssid,
>  			   private->sch->schid.sch_no);
> 
> +	mdev_set_class_id(mdev, MDEV_ID_VFIO);
>  	return 0;
>  }
> 
> diff --git a/drivers/s390/crypto/vfio_ap_ops.c
> b/drivers/s390/crypto/vfio_ap_ops.c
> index 5c0f53c6dde7..2cfd96112aa0 100644
> --- a/drivers/s390/crypto/vfio_ap_ops.c
> +++ b/drivers/s390/crypto/vfio_ap_ops.c
> @@ -343,6 +343,7 @@ static int vfio_ap_mdev_create(struct kobject *kobj,
> struct mdev_device *mdev)
>  	list_add(&matrix_mdev->node, &matrix_dev->mdev_list);
>  	mutex_unlock(&matrix_dev->lock);
> 
> +	mdev_set_class_id(mdev, MDEV_ID_VFIO);
>  	return 0;
>  }
> 
> diff --git a/drivers/vfio/mdev/mdev_core.c
> b/drivers/vfio/mdev/mdev_core.c
> index b558d4cfd082..8764cf4a276d 100644
> --- a/drivers/vfio/mdev/mdev_core.c
> +++ b/drivers/vfio/mdev/mdev_core.c
> @@ -45,6 +45,12 @@ void mdev_set_drvdata(struct mdev_device *mdev,
> void *data)
>  }
>  EXPORT_SYMBOL(mdev_set_drvdata);
> 
> +void mdev_set_class_id(struct mdev_device *mdev, u16 id)
> +{
> +	mdev->class_id = id;
> +}
> +EXPORT_SYMBOL(mdev_set_class_id);
> +
>  struct device *mdev_dev(struct mdev_device *mdev)
>  {
>  	return &mdev->dev;
> @@ -135,6 +141,7 @@ static int mdev_device_remove_cb(struct device
> *dev, void *data)
>   * mdev_register_device : Register a device
>   * @dev: device structure representing parent device.
>   * @ops: Parent device operation structure to be registered.
> + * @id: device id.
class id.
>   *
>   * Add device to list of registered parent devices.
>   * Returns a negative value on error, otherwise 0.
> diff --git a/drivers/vfio/mdev/mdev_driver.c
> b/drivers/vfio/mdev/mdev_driver.c
> index 0d3223aee20b..b7c40ce86ee3 100644
> --- a/drivers/vfio/mdev/mdev_driver.c
> +++ b/drivers/vfio/mdev/mdev_driver.c
> @@ -69,8 +69,22 @@ static int mdev_remove(struct device *dev)
>  	return 0;
>  }
> 
> +static int mdev_match(struct device *dev, struct device_driver *drv)
> +{
> +	unsigned int i;
> +	struct mdev_device *mdev = to_mdev_device(dev);
> +	struct mdev_driver *mdrv = to_mdev_driver(drv);
> +	const struct mdev_class_id *ids = mdrv->id_table;
> +
> +	for (i = 0; ids[i].id; i++)
> +		if (ids[i].id == mdev->class_id)
> +			return 1;
> +	return 0;
> +}
> +
>  struct bus_type mdev_bus_type = {
>  	.name		= "mdev",
> +	.match		= mdev_match,
>  	.probe		= mdev_probe,
>  	.remove		= mdev_remove,
>  };
> diff --git a/drivers/vfio/mdev/mdev_private.h
> b/drivers/vfio/mdev/mdev_private.h
> index 7d922950caaf..c65f436c1869 100644
> --- a/drivers/vfio/mdev/mdev_private.h
> +++ b/drivers/vfio/mdev/mdev_private.h
> @@ -33,6 +33,7 @@ struct mdev_device {
>  	struct kobject *type_kobj;
>  	struct device *iommu_device;
>  	bool active;
> +	u16 class_id;
>  };
> 
>  #define to_mdev_device(dev)	container_of(dev, struct mdev_device, dev)
> diff --git a/drivers/vfio/mdev/vfio_mdev.c
> b/drivers/vfio/mdev/vfio_mdev.c
> index 30964a4e0a28..fd2a4d9a3f26 100644
> --- a/drivers/vfio/mdev/vfio_mdev.c
> +++ b/drivers/vfio/mdev/vfio_mdev.c
> @@ -120,10 +120,16 @@ static void vfio_mdev_remove(struct device *dev)
>  	vfio_del_group_dev(dev);
>  }
> 
> +static struct mdev_class_id id_table[] = {
> +	{ MDEV_ID_VFIO },
> +	{ 0 },
> +};
> +
>  static struct mdev_driver vfio_mdev_driver = {
>  	.name	= "vfio_mdev",
>  	.probe	= vfio_mdev_probe,
>  	.remove	= vfio_mdev_remove,
> +	.id_table = id_table,
>  };
> 
>  static int __init vfio_mdev_init(void)
> diff --git a/include/linux/mdev.h b/include/linux/mdev.h
> index 0ce30ca78db0..3974650c074f 100644
> --- a/include/linux/mdev.h
> +++ b/include/linux/mdev.h
> @@ -118,6 +118,7 @@ struct mdev_type_attribute
> mdev_type_attr_##_name =		\
>   * @probe: called when new device created
>   * @remove: called when device removed
>   * @driver: device driver structure
> + * @id_table: the ids serviced by this driver.
>   *
>   **/
>  struct mdev_driver {
> @@ -125,12 +126,14 @@ struct mdev_driver {
>  	int  (*probe)(struct device *dev);
>  	void (*remove)(struct device *dev);
>  	struct device_driver driver;
> +	const struct mdev_class_id *id_table;
>  };
> 
>  #define to_mdev_driver(drv)	container_of(drv, struct mdev_driver, driver)
> 
>  void *mdev_get_drvdata(struct mdev_device *mdev);
>  void mdev_set_drvdata(struct mdev_device *mdev, void *data);
> +void mdev_set_class_id(struct mdev_device *mdev, u16 id);
>  const guid_t *mdev_uuid(struct mdev_device *mdev);
> 
>  extern struct bus_type mdev_bus_type;
> @@ -145,4 +148,9 @@ struct device *mdev_parent_dev(struct
> mdev_device *mdev);
>  struct device *mdev_dev(struct mdev_device *mdev);
>  struct mdev_device *mdev_from_dev(struct device *dev);
> 
> +enum {
> +	MDEV_ID_VFIO = 1,
> +	/* New entries must be added here */
> +};
> +
>  #endif /* MDEV_H */
> diff --git a/include/linux/mod_devicetable.h
> b/include/linux/mod_devicetable.h
> index 5714fd35a83c..f32c6e44fb1a 100644
> --- a/include/linux/mod_devicetable.h
> +++ b/include/linux/mod_devicetable.h
> @@ -821,4 +821,12 @@ struct wmi_device_id {
>  	const void *context;
>  };
> 
> +/**
> + * struct mdev_class_id - MDEV device class identifier
> + * @id: Used to identify a specific class of device, e.g vfio-mdev device.
> + */
> +struct mdev_class_id {
> +	__u16 id;
> +};
> +
>  #endif /* LINUX_MOD_DEVICETABLE_H */
> diff --git a/samples/vfio-mdev/mbochs.c b/samples/vfio-mdev/mbochs.c
> index ac5c8c17b1ff..8a8583c892b2 100644
> --- a/samples/vfio-mdev/mbochs.c
> +++ b/samples/vfio-mdev/mbochs.c
> @@ -561,6 +561,7 @@ static int mbochs_create(struct kobject *kobj, struct
> mdev_device *mdev)
>  	mbochs_reset(mdev);
> 
>  	mbochs_used_mbytes += type->mbytes;
> +	mdev_set_class_id(mdev, MDEV_ID_VFIO);
>  	return 0;
> 
>  err_mem:
> diff --git a/samples/vfio-mdev/mdpy.c b/samples/vfio-mdev/mdpy.c
> index cc86bf6566e4..88d7e76f3836 100644
> --- a/samples/vfio-mdev/mdpy.c
> +++ b/samples/vfio-mdev/mdpy.c
> @@ -269,6 +269,7 @@ static int mdpy_create(struct kobject *kobj, struct
> mdev_device *mdev)
>  	mdpy_reset(mdev);
> 
>  	mdpy_count++;
> +	mdev_set_class_id(mdev, MDEV_ID_VFIO);
>  	return 0;
>  }
> 
> diff --git a/samples/vfio-mdev/mtty.c b/samples/vfio-mdev/mtty.c
> index 92e770a06ea2..4e0735143b69 100644
> --- a/samples/vfio-mdev/mtty.c
> +++ b/samples/vfio-mdev/mtty.c
> @@ -770,6 +770,7 @@ static int mtty_create(struct kobject *kobj, struct
> mdev_device *mdev)
>  	list_add(&mdev_state->next, &mdev_devices_list);
>  	mutex_unlock(&mdev_list_lock);
> 
> +	mdev_set_class_id(mdev, MDEV_ID_VFIO);
>  	return 0;
>  }
> 
> --
> 2.19.1

> From: Jason Wang [mailto:jasowang at redhat.com]
> Sent: Tuesday, September 24, 2019 9:54 PM
> 
> This patch implements basic support for mdev driver that supports
> virtio transport for kernel virtio driver.
> 
> Signed-off-by: Jason Wang <jasowang at redhat.com>
> ---
>  include/linux/mdev.h        |   2 +
>  include/linux/virtio_mdev.h | 145
> ++++++++++++++++++++++++++++++++++++
>  2 files changed, 147 insertions(+)
>  create mode 100644 include/linux/virtio_mdev.h
> 
> diff --git a/include/linux/mdev.h b/include/linux/mdev.h
> index 3414307311f1..73ac27b3b868 100644
> --- a/include/linux/mdev.h
> +++ b/include/linux/mdev.h
> @@ -126,6 +126,8 @@ struct mdev_device *mdev_from_dev(struct device
> *dev);
> 
>  enum {
>  	MDEV_ID_VFIO = 1,
> +	MDEV_ID_VIRTIO = 2,
> +	MDEV_ID_VHOST = 3,
>  	/* New entries must be added here */
>  };
> 
> diff --git a/include/linux/virtio_mdev.h b/include/linux/virtio_mdev.h
> new file mode 100644
> index 000000000000..d1a40a739266
> --- /dev/null
> +++ b/include/linux/virtio_mdev.h
> @@ -0,0 +1,145 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/*
> + * Virtio mediated device driver
> + *
> + * Copyright 2019, Red Hat Corp.
> + *     Author: Jason Wang <jasowang at redhat.com>
> + */
> +#ifndef _LINUX_VIRTIO_MDEV_H
> +#define _LINUX_VIRTIO_MDEV_H
> +
> +#include <linux/interrupt.h>
> +#include <linux/mdev.h>
> +#include <uapi/linux/vhost.h>
> +
> +#define VIRTIO_MDEV_DEVICE_API_STRING		"virtio-mdev"
> +#define VIRTIO_MDEV_VERSION 0x1
Just be curious. is this version identical to virtio spec version that below
callbacks are created for, or just irrelevant?
> +
> +struct virtio_mdev_callback {
> +	irqreturn_t (*callback)(void *data);
> +	void *private;
> +};
> +
> +/**
> + * struct vfio_mdev_device_ops - Structure to be registered for each
> + * mdev device to register the device to virtio-mdev module.
> + *
> + * @set_vq_address:		Set the address of virtqueue
> + *				@mdev: mediated device
> + *				@idx: virtqueue index
> + *				@desc_area: address of desc area
> + *				@driver_area: address of driver area
> + *				@device_area: address of device area
> + *				Returns integer: success (0) or error (< 0)
> + * @set_vq_num:		Set the size of virtqueue
> + *				@mdev: mediated device
> + *				@idx: virtqueue index
> + *				@num: the size of virtqueue
> + * @kick_vq:			Kick the virtqueue
> + *				@mdev: mediated device
> + *				@idx: virtqueue index
> + * @set_vq_cb:			Set the interrut calback function for
> + *				a virtqueue
> + *				@mdev: mediated device
> + *				@idx: virtqueue index
> + *				@cb: virtio-mdev interrupt callback
> structure
> + * @set_vq_ready:		Set ready status for a virtqueue
> + *				@mdev: mediated device
> + *				@idx: virtqueue index
> + *				@ready: ready (true) not ready(false)
> + * @get_vq_ready:		Get ready status for a virtqueue
> + *				@mdev: mediated device
> + *				@idx: virtqueue index
> + *				Returns boolean: ready (true) or not (false)
> + * @set_vq_state:		Set the state for a virtqueue
> + *				@mdev: mediated device
> + *				@idx: virtqueue index
> + *				@state: virtqueue state (last_avail_idx)
> + *				Returns integer: success (0) or error (< 0)
> + * @get_vq_state:		Get the state for a virtqueue
> + *				@mdev: mediated device
> + *				@idx: virtqueue index
> + *				Returns virtqueue state (last_avail_idx)
> + * @get_vq_align:		Get the virtqueue align requirement
> + *				for the device
> + *				@mdev: mediated device
> + *				Returns virtqueue algin requirement
> + * @get_features:		Get virtio features supported by the device
> + *				@mdev: mediated device
> + *				Returns the features support by the
> + *				device
> + * @get_features:		Set virtio features supported by the driver
> + *				@mdev: mediated device
> + *				@features: feature support by the driver
> + *				Returns integer: success (0) or error (< 0)
> + * @set_config_cb:		Set the config interrupt callback
> + *				@mdev: mediated device
> + *				@cb: virtio-mdev interrupt callback
> structure
> + * @get_device_id:		Get virtio device id
> + *				@mdev: mediated device
> + *				Returns u32: virtio device id
> + * @get_vendor_id:		Get virtio vendor id
> + *				@mdev: mediated device
> + *				Returns u32: virtio vendor id
> + * @get_status:		Get the device status
> + *				@mdev: mediated device
> + *				Returns u8: virtio device status
> + * @set_status:		Set the device status
> + *				@mdev: mediated device
> + *				@status: virtio device status
> + * @get_config:		Read from device specific confiugration
> space
configuration (and similar typos downward)
> + *				@mdev: mediated device
> + *				@offset: offset from the beginning of
> + *				configuration space
> + *				@buf: buffer used to read to
> + *				@len: the length to read from
> + *				configration space
> + * @set_config:		Write to device specific confiugration space
> + *				@mdev: mediated device
> + *				@offset: offset from the beginning of
> + *				configuration space
> + *				@buf: buffer used to write from
> + *				@len: the length to write to
> + *				configration space
> + * @get_version:		Get the version of virtio mdev device
> + *				@mdev: mediated device
> + *				Returns integer: version of the device
> + * @get_generation:		Get device generaton
> + *				@mdev: mediated device
> + *				Returns u32: device generation
> + */
> +struct virtio_mdev_device_ops {
> +	/* Virtqueue ops */
> +	int (*set_vq_address)(struct mdev_device *mdev,
> +			      u16 idx, u64 desc_area, u64 driver_area,
> +			      u64 device_area);
> +	void (*set_vq_num)(struct mdev_device *mdev, u16 idx, u32 num);
> +	void (*kick_vq)(struct mdev_device *mdev, u16 idx);
> +	void (*set_vq_cb)(struct mdev_device *mdev, u16 idx,
> +			  struct virtio_mdev_callback *cb);
> +	void (*set_vq_ready)(struct mdev_device *mdev, u16 idx, bool
> ready);
> +	bool (*get_vq_ready)(struct mdev_device *mdev, u16 idx);
> +	int (*set_vq_state)(struct mdev_device *mdev, u16 idx, u64 state);
> +	u64 (*get_vq_state)(struct mdev_device *mdev, u16 idx);
> +
> +	/* Device ops */
> +	u16 (*get_vq_align)(struct mdev_device *mdev);
> +	u64 (*get_features)(struct mdev_device *mdev);
> +	int (*set_features)(struct mdev_device *mdev, u64 features);
> +	void (*set_config_cb)(struct mdev_device *mdev,
> +			      struct virtio_mdev_callback *cb);
> +	u16 (*get_queue_max)(struct mdev_device *mdev);
> +	u32 (*get_device_id)(struct mdev_device *mdev);
> +	u32 (*get_vendor_id)(struct mdev_device *mdev);
> +	u8 (*get_status)(struct mdev_device *mdev);
> +	void (*set_status)(struct mdev_device *mdev, u8 status);
> +	void (*get_config)(struct mdev_device *mdev, unsigned int offset,
> +			   void *buf, unsigned int len);
> +	void (*set_config)(struct mdev_device *mdev, unsigned int offset,
> +			   const void *buf, unsigned int len);
> +	int (*get_version)(struct mdev_device *mdev);
> +	u32 (*get_generation)(struct mdev_device *mdev);
> +};
I'm not sure how stable above ops are. Does it make sense if defining
just two callbacks here, e.g. vq_ctrl and device_ctrl, and then let the
vendor driver to handle specific ops in each category (similar to how
ioctl works)?

Thanks
Kevin

On 2019/9/25 ??4:24, Tian, Kevin wrote:
>> From: Jason Wang [mailto:jasowang at redhat.com]
>> Sent: Tuesday, September 24, 2019 9:53 PM
>>
>> Hi all:
>>
>> There are hardware that can do virtio datapath offloading while having
>> its own control path. This path tries to implement a mdev based
>> unified API to support using kernel virtio driver to drive those
>> devices. This is done by introducing a new mdev transport for virtio
>> (virtio_mdev) and register itself as a new kind of mdev driver. Then
>> it provides a unified way for kernel virtio driver to talk with mdev
>> device implementation.
>>
>> Though the series only contains kernel driver support, the goal is to
>> make the transport generic enough to support userspace drivers. This
>> means vhost-mdev[1] could be built on top as well by resuing the
>> transport.
>>
>> A sample driver is also implemented which simulate a virito-net
>> loopback ethernet device on top of vringh + workqueue. This could be
>> used as a reference implementation for real hardware driver.
>>
>> Consider mdev framework only support VFIO device and driver right now,
>> this series also extend it to support other types. This is done
>> through introducing class id to the device and pairing it with
>> id_talbe claimed by the driver. On top, this seris also decouple
> id_table claimed ... this series ...

Let me fix in V3.

Thanks

>
>> device specific parents ops out of the common ones.
>>
>> Pktgen test was done with virito-net + mvnet loop back device.
>>
>> Please review.
>>
>> [1] https://lkml.org/lkml/2019/9/16/869
>>
>> Changes from V1:
>>
>> - move virtio_mdev.c to drivers/virtio
>> - store class_id in mdev_device instead of mdev_parent
>> - store device_ops in mdev_device instead of mdev_parent
>> - reorder the patch, vringh fix comes first
>> - really silent compiling warnings
>> - really switch to use u16 for class_id
>> - uevent and modpost support for mdev class_id
>> - vraious tweaks per comments from Parav
>>
>> Changes from RFC-V2:
>>
>> - silent compile warnings on some specific configuration
>> - use u16 instead u8 for class id
>> - reseve MDEV_ID_VHOST for future vhost-mdev work
>> - introduce "virtio" type for mvnet and make
"vhost" type for future
>>   work
>> - add entries in MAINTAINER
>> - tweak and typos fixes in commit log
>>
>> Changes from RFC-V1:
>>
>> - rename device id to class id
>> - add docs for class id and device specific ops (device_ops)
>> - split device_ops into seperate headers
>> - drop the mdev_set_dma_ops()
>> - use device_ops to implement the transport API, then it's not a
part
>>   of UAPI any more
>> - use GFP_ATOMIC in mvnet sample device and other tweaks
>> - set_vring_base/get_vring_base support for mvnet device
>>
>> Jason Wang (8):
>>   vringh: fix copy direction of vringh_iov_push_kern()
>>   mdev: class id support
>>   mdev: bus uevent support
>>   modpost: add support for mdev class id
>>   mdev: introduce device specific ops
>>   mdev: introduce virtio device and its device ops
>>   virtio: introduce a mdev based transport
>>   docs: sample driver to demonstrate how to implement virtio-mdev
>>     framework
>>
>>  .../driver-api/vfio-mediated-device.rst       |   7 +-
>>  MAINTAINERS                                   |   2 +
>>  drivers/gpu/drm/i915/gvt/kvmgt.c              |  18 +-
>>  drivers/s390/cio/vfio_ccw_ops.c               |  18 +-
>>  drivers/s390/crypto/vfio_ap_ops.c             |  14 +-
>>  drivers/vfio/mdev/mdev_core.c                 |  19 +
>>  drivers/vfio/mdev/mdev_driver.c               |  22 +
>>  drivers/vfio/mdev/mdev_private.h              |   2 +
>>  drivers/vfio/mdev/vfio_mdev.c                 |  45 +-
>>  drivers/vhost/vringh.c                        |   8 +-
>>  drivers/virtio/Kconfig                        |   7 +
>>  drivers/virtio/Makefile                       |   1 +
>>  drivers/virtio/virtio_mdev.c                  | 417 +++++++++++
>>  include/linux/mdev.h                          |  52 +-
>>  include/linux/mod_devicetable.h               |   8 +
>>  include/linux/vfio_mdev.h                     |  52 ++
>>  include/linux/virtio_mdev.h                   | 145 ++++
>>  samples/Kconfig                               |   7 +
>>  samples/vfio-mdev/Makefile                    |   1 +
>>  samples/vfio-mdev/mbochs.c                    |  20 +-
>>  samples/vfio-mdev/mdpy.c                      |  20 +-
>>  samples/vfio-mdev/mtty.c                      |  18 +-
>>  samples/vfio-mdev/mvnet.c                     | 692 ++++++++++++++++++
>>  scripts/mod/devicetable-offsets.c             |   3 +
>>  scripts/mod/file2alias.c                      |  10 +
>>  25 files changed, 1524 insertions(+), 84 deletions(-)
>>  create mode 100644 drivers/virtio/virtio_mdev.c
>>  create mode 100644 include/linux/vfio_mdev.h
>>  create mode 100644 include/linux/virtio_mdev.h
>>  create mode 100644 samples/vfio-mdev/mvnet.c
>>
>> --
>> 2.19.1

On Fri, 27 Sep 2019 16:25:13 +0000
Parav Pandit <parav at mellanox.com> wrote:
> Hi Alex,
> 
> 
> > -----Original Message-----
> > From: Alex Williamson <alex.williamson at redhat.com>
> > Sent: Tuesday, September 24, 2019 6:07 PM
> > To: Jason Wang <jasowang at redhat.com>
> > Cc: kvm at vger.kernel.org; linux-s390 at vger.kernel.org; linux-
> > kernel at vger.kernel.org; dri-devel at lists.freedesktop.org; intel-
> > gfx at lists.freedesktop.org; intel-gvt-dev at lists.freedesktop.org;
> > kwankhede at nvidia.com; mst at redhat.com; tiwei.bie at intel.com;
> > virtualization at lists.linux-foundation.org; netdev at
vger.kernel.org;
> > cohuck at redhat.com; maxime.coquelin at redhat.com;
> > cunming.liang at intel.com; zhihong.wang at intel.com;
> > rob.miller at broadcom.com; xiao.w.wang at intel.com;
> > haotian.wang at sifive.com; zhenyuw at linux.intel.com; zhi.a.wang at
intel.com;
> > jani.nikula at linux.intel.com; joonas.lahtinen at linux.intel.com;
> > rodrigo.vivi at intel.com; airlied at linux.ie; daniel at ffwll.ch;
> > farman at linux.ibm.com; pasic at linux.ibm.com; sebott at
linux.ibm.com;
> > oberpar at linux.ibm.com; heiko.carstens at de.ibm.com; gor at
linux.ibm.com;
> > borntraeger at de.ibm.com; akrowiak at linux.ibm.com; freude at
linux.ibm.com;
> > lingshan.zhu at intel.com; Ido Shamay <idos at mellanox.com>;
> > eperezma at redhat.com; lulu at redhat.com; Parav Pandit
> > <parav at mellanox.com>; christophe.de.dinechin at gmail.com;
> > kevin.tian at intel.com
> > Subject: Re: [PATCH V2 6/8] mdev: introduce virtio device and its
device ops
> > 
> > On Tue, 24 Sep 2019 21:53:30 +0800
> > Jason Wang <jasowang at redhat.com> wrote:
> >   
> > > This patch implements basic support for mdev driver that supports
> > > virtio transport for kernel virtio driver.
> > >
> > > Signed-off-by: Jason Wang <jasowang at redhat.com>
> > > ---
> > >  include/linux/mdev.h        |   2 +
> > >  include/linux/virtio_mdev.h | 145
> > > ++++++++++++++++++++++++++++++++++++
> > >  2 files changed, 147 insertions(+)
> > >  create mode 100644 include/linux/virtio_mdev.h
> > >
> > > diff --git a/include/linux/mdev.h b/include/linux/mdev.h index
> > > 3414307311f1..73ac27b3b868 100644
> > > --- a/include/linux/mdev.h
> > > +++ b/include/linux/mdev.h
> > > @@ -126,6 +126,8 @@ struct mdev_device *mdev_from_dev(struct
device
> > > *dev);
> > >
> > >  enum {
> > >  	MDEV_ID_VFIO = 1,
> > > +	MDEV_ID_VIRTIO = 2,
> > > +	MDEV_ID_VHOST = 3,  
> > 
> > MDEV_ID_VHOST isn't used yet here.  Also, given the strong
interdependence
> > between the class_id and the ops structure, we might wand to define
them in
> > the same place.  Thanks,
> >   
> 
> When mlx5_core creates mdevs (parent->ops->create() and it wants to
> bind to mlx5 mdev driver (which does mdev_register_driver()), mlx5
> core driver will publish MDEV_ID_MLX5_NET defined in central place as
> include/linux/mdev.h without any ops structure. Because such ops are
> not relevant. It uses usual, standard ops probe() remove() on the
> mdev (similar to a regular PCI device). So for VHOST case ops may be
> closely related to ID, but not for other type of ID.
> 
> Just want to make sure, that scope of ID covers this case.
AIUI, these device-ops are primarily meant to have 1:N multiplexing of
the mdev bus driver.  One mdev bus driver supports N vendor drivers via
a common "protocol" defined by this structure.  vfio-mdev supports
GVT-g, GRID, and several sample drivers.  I think Jason and Tiwei are
attempting something similar if we have multiple vendors that may
provide virtio/vhost parent drivers.  If you have a 1:1 model with
mlx5 where you're not trying to abstract a common channel between the
mdev bus driver and the mdev vendor driver, then I suppose you might
not use the device-ops capabilities of the mdev-core.  Did I interpret
the question correctly?  I think that's probably fine, mdev-core
shouldn't have any dependencies on the device-ops and we shouldn't
really be dictating the bus/vendor link through mdev.  Thanks,

Alex

On 2019/10/1 ??5:36, Alex Williamson wrote:
> On Fri, 27 Sep 2019 16:25:13 +0000
> Parav Pandit <parav at mellanox.com> wrote:
>
>> Hi Alex,
>>
>>
>>> -----Original Message-----
>>> From: Alex Williamson <alex.williamson at redhat.com>
>>> Sent: Tuesday, September 24, 2019 6:07 PM
>>> To: Jason Wang <jasowang at redhat.com>
>>> Cc: kvm at vger.kernel.org; linux-s390 at vger.kernel.org; linux-
>>> kernel at vger.kernel.org; dri-devel at lists.freedesktop.org;
intel-
>>> gfx at lists.freedesktop.org; intel-gvt-dev at
lists.freedesktop.org;
>>> kwankhede at nvidia.com; mst at redhat.com; tiwei.bie at intel.com;
>>> virtualization at lists.linux-foundation.org; netdev at
vger.kernel.org;
>>> cohuck at redhat.com; maxime.coquelin at redhat.com;
>>> cunming.liang at intel.com; zhihong.wang at intel.com;
>>> rob.miller at broadcom.com; xiao.w.wang at intel.com;
>>> haotian.wang at sifive.com; zhenyuw at linux.intel.com; zhi.a.wang
at intel.com;
>>> jani.nikula at linux.intel.com; joonas.lahtinen at linux.intel.com;
>>> rodrigo.vivi at intel.com; airlied at linux.ie; daniel at ffwll.ch;
>>> farman at linux.ibm.com; pasic at linux.ibm.com; sebott at
linux.ibm.com;
>>> oberpar at linux.ibm.com; heiko.carstens at de.ibm.com; gor at
linux.ibm.com;
>>> borntraeger at de.ibm.com; akrowiak at linux.ibm.com; freude at
linux.ibm.com;
>>> lingshan.zhu at intel.com; Ido Shamay <idos at mellanox.com>;
>>> eperezma at redhat.com; lulu at redhat.com; Parav Pandit
>>> <parav at mellanox.com>; christophe.de.dinechin at gmail.com;
>>> kevin.tian at intel.com
>>> Subject: Re: [PATCH V2 6/8] mdev: introduce virtio device and its
device ops
>>>
>>> On Tue, 24 Sep 2019 21:53:30 +0800
>>> Jason Wang <jasowang at redhat.com> wrote:
>>>    
>>>> This patch implements basic support for mdev driver that
supports
>>>> virtio transport for kernel virtio driver.
>>>>
>>>> Signed-off-by: Jason Wang <jasowang at redhat.com>
>>>> ---
>>>>   include/linux/mdev.h        |   2 +
>>>>   include/linux/virtio_mdev.h | 145
>>>> ++++++++++++++++++++++++++++++++++++
>>>>   2 files changed, 147 insertions(+)
>>>>   create mode 100644 include/linux/virtio_mdev.h
>>>>
>>>> diff --git a/include/linux/mdev.h b/include/linux/mdev.h index
>>>> 3414307311f1..73ac27b3b868 100644
>>>> --- a/include/linux/mdev.h
>>>> +++ b/include/linux/mdev.h
>>>> @@ -126,6 +126,8 @@ struct mdev_device *mdev_from_dev(struct
device
>>>> *dev);
>>>>
>>>>   enum {
>>>>   	MDEV_ID_VFIO = 1,
>>>> +	MDEV_ID_VIRTIO = 2,
>>>> +	MDEV_ID_VHOST = 3,
>>> MDEV_ID_VHOST isn't used yet here.  Also, given the strong
interdependence
>>> between the class_id and the ops structure, we might wand to define
them in
>>> the same place.  Thanks,
>>>    
>> When mlx5_core creates mdevs (parent->ops->create() and it wants
to
>> bind to mlx5 mdev driver (which does mdev_register_driver()), mlx5
>> core driver will publish MDEV_ID_MLX5_NET defined in central place as
>> include/linux/mdev.h without any ops structure. Because such ops are
>> not relevant. It uses usual, standard ops probe() remove() on the
>> mdev (similar to a regular PCI device). So for VHOST case ops may be
>> closely related to ID, but not for other type of ID.
>>
>> Just want to make sure, that scope of ID covers this case.
> AIUI, these device-ops are primarily meant to have 1:N multiplexing of
> the mdev bus driver.  One mdev bus driver supports N vendor drivers via
> a common "protocol" defined by this structure.  vfio-mdev
supports
> GVT-g, GRID, and several sample drivers.  I think Jason and Tiwei are
> attempting something similar if we have multiple vendors that may
> provide virtio/vhost parent drivers.

Exactly.

>   If you have a 1:1 model with
> mlx5 where you're not trying to abstract a common channel between the
> mdev bus driver and the mdev vendor driver, then I suppose you might
> not use the device-ops capabilities of the mdev-core.

Yes, current proposed API allows NULL to be passed as device ops.

Thanks

>   Did I interpret
> the question correctly?  I think that's probably fine, mdev-core
> shouldn't have any dependencies on the device-ops and we shouldn't
> really be dictating the bus/vendor link through mdev.  Thanks,
>
> Alex