This attempts to implement a "virtual I/O" layer which should allow
common drivers to be efficiently used across most virtual I/O
mechanisms. It will no-doubt need further enhancement.
The virtio drivers add buffers to virtio queues; as the buffers are consumed
the driver "interrupt" callbacks are invoked.
There is also a generic implementation of config space which drivers can query
to get setup information from the host.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
---
drivers/Kconfig | 2
drivers/Makefile | 1
drivers/virtio/Kconfig | 3
drivers/virtio/Makefile | 1
drivers/virtio/config.c | 13 ++
drivers/virtio/virtio.c | 187 +++++++++++++++++++++++++++++++++++++++
include/linux/mod_devicetable.h | 6 +
include/linux/virtio.h | 110 ++++++++++++++++++++++
include/linux/virtio_config.h | 111 +++++++++++++++++++++++
9 files changed, 434 insertions(+)
==================================================================---
a/drivers/Kconfig
+++ b/drivers/Kconfig
@@ -87,4 +87,6 @@ source "drivers/kvm/Kconfig"
source "drivers/kvm/Kconfig"
source "drivers/uio/Kconfig"
+
+source "drivers/virtio/Kconfig"
endmenu
==================================================================---
a/drivers/Makefile
+++ b/drivers/Makefile
@@ -88,3 +88,4 @@ obj-$(CONFIG_HID) += hid/
obj-$(CONFIG_HID) += hid/
obj-$(CONFIG_PPC_PS3) += ps3/
obj-$(CONFIG_OF) += of/
+obj-$(CONFIG_VIRTIO) += virtio/
==================================================================--- /dev/null
+++ b/drivers/virtio/Kconfig
@@ -0,0 +1,3 @@
+# Virtio always gets selected by whoever wants it.
+config VIRTIO
+ bool
==================================================================--- /dev/null
+++ b/drivers/virtio/Makefile
@@ -0,0 +1,1 @@
+obj-$(CONFIG_VIRTIO) += virtio.o
==================================================================--- /dev/null
+++ b/drivers/virtio/config.c
@@ -0,0 +1,13 @@
+/* Configuration space parsing helpers for virtio.
+ *
+ * The configuration is [type][len][... len bytes ...] fields.
+ *
+ * Copyright 2007 Rusty Russell, IBM Corporation.
+ * GPL v2 or later.
+ */
+#include <linux/err.h>
+#include <linux/virtio.h>
+#include <linux/virtio_config.h>
+#include <linux/bug.h>
+#include <asm/system.h>
+
==================================================================--- /dev/null
+++ b/drivers/virtio/virtio.c
@@ -0,0 +1,187 @@
+#include <linux/virtio.h>
+#include <linux/spinlock.h>
+#include <linux/virtio_config.h>
+
+static ssize_t device_show(struct device *_d,
+ struct device_attribute *attr, char *buf)
+{
+ struct virtio_device *dev = container_of(_d,struct virtio_device,dev);
+ return sprintf(buf, "%hu", dev->id.device);
+}
+static ssize_t vendor_show(struct device *_d,
+ struct device_attribute *attr, char *buf)
+{
+ struct virtio_device *dev = container_of(_d,struct virtio_device,dev);
+ return sprintf(buf, "%hu", dev->id.vendor);
+}
+static ssize_t status_show(struct device *_d,
+ struct device_attribute *attr, char *buf)
+{
+ struct virtio_device *dev = container_of(_d,struct virtio_device,dev);
+ return sprintf(buf, "0x%08x", dev->config->get_status(dev));
+}
+static struct device_attribute virtio_dev_attrs[] = {
+ __ATTR_RO(device),
+ __ATTR_RO(vendor),
+ __ATTR_RO(status),
+ __ATTR_NULL
+};
+
+static inline int virtio_id_match(const struct virtio_device *dev,
+ const struct virtio_device_id *id)
+{
+ if (id->device != dev->id.device)
+ return 0;
+
+ return id->vendor == VIRTIO_DEV_ANY_ID || id->vendor !=
dev->id.vendor;
+}
+
+/* This looks through all the IDs a driver claims to support. If any of them
+ * match, we return 1 and the kernel will call virtio_dev_probe(). */
+static int virtio_dev_match(struct device *_dv, struct device_driver *_dr)
+{
+ unsigned int i;
+ struct virtio_device *dev = container_of(_dv,struct virtio_device,dev);
+ const struct virtio_device_id *ids;
+
+ ids = container_of(_dr, struct virtio_driver, driver)->id_table;
+ for (i = 0; ids[i].device; i++)
+ if (virtio_id_match(dev, &ids[i]))
+ return 1;
+ return 0;
+}
+
+struct virtio_bus {
+ struct bus_type bus;
+ struct device dev;
+};
+
+static struct virtio_bus virtio_bus = {
+ .bus = {
+ .name = "virtio",
+ .match = virtio_dev_match,
+ .dev_attrs = virtio_dev_attrs,
+ },
+ .dev = {
+ /* Can override this if you have a real bus behind it. */
+ .parent = NULL,
+ .bus_id = "virtio",
+ }
+};
+
+static void add_status(struct virtio_device *dev, unsigned status)
+{
+ dev->config->set_status(dev, dev->config->get_status(dev) |
status);
+}
+
+static int virtio_dev_probe(struct device *_d)
+{
+ int err;
+ struct virtio_device *dev = container_of(_d,struct virtio_device,dev);
+ struct virtio_driver *drv = container_of(dev->dev.driver,
+ struct virtio_driver, driver);
+
+ add_status(dev, VIRTIO_CONFIG_S_DRIVER);
+ err = drv->probe(dev);
+ if (err)
+ add_status(dev, VIRTIO_CONFIG_S_FAILED);
+ else
+ add_status(dev, VIRTIO_CONFIG_S_DRIVER_OK);
+ return err;
+}
+
+int register_virtio_driver(struct virtio_driver *driver)
+{
+ driver->driver.bus = &virtio_bus.bus;
+ driver->driver.probe = virtio_dev_probe;
+ return driver_register(&driver->driver);
+}
+EXPORT_SYMBOL_GPL(register_virtio_driver);
+
+void unregister_virtio_driver(struct virtio_driver *driver)
+{
+ driver_unregister(&driver->driver);
+}
+EXPORT_SYMBOL_GPL(unregister_virtio_driver);
+
+int register_virtio_device(struct virtio_device *dev)
+{
+ int err;
+
+ /* If the device hasn't already been given a parent, our bus is it. */
+ if (!dev->dev.parent)
+ dev->dev.parent = &virtio_bus.dev;
+ dev->dev.bus = &virtio_bus.bus;
+ sprintf(dev->dev.bus_id, "%u", dev->index);
+
+ /* Acknowledge that we've seen the device. */
+ add_status(dev, VIRTIO_CONFIG_S_ACKNOWLEDGE);
+
+ /* device_register() causes the bus infrastructure to look for a
+ * matching driver. */
+ err = device_register(&dev->dev);
+ if (err)
+ add_status(dev, VIRTIO_CONFIG_S_FAILED);
+ return err;
+}
+EXPORT_SYMBOL_GPL(register_virtio_device);
+
+void unregister_virtio_device(struct virtio_device *dev)
+{
+ device_unregister(&dev->dev);
+}
+EXPORT_SYMBOL_GPL(unregister_virtio_device);
+
+int __virtio_config_val(struct virtio_device *vdev,
+ u8 type, void *val, size_t size)
+{
+ void *token;
+ unsigned int len;
+
+ token = vdev->config->find(vdev, type, &len);
+ if (!token)
+ return -ENOENT;
+
+ if (len != size)
+ return -EIO;
+
+ vdev->config->get(vdev, token, val, size);
+ return 0;
+}
+EXPORT_SYMBOL_GPL(__virtio_config_val);
+
+int virtio_use_bit(struct virtio_device *vdev,
+ void *token, unsigned int len, unsigned int bitnum)
+{
+ unsigned long bits[16];
+
+ /* This makes it convenient to pass-through find() results. */
+ if (!token)
+ return 0;
+
+ /* bit not in range of this bitfield? */
+ if (bitnum * 8 >= len / 2)
+ return 0;
+
+ /* Giant feature bitfields are silly. */
+ BUG_ON(len > sizeof(bits));
+ vdev->config->get(vdev, token, bits, len);
+
+ if (!test_bit(bitnum, bits))
+ return 0;
+
+ /* Set acknowledge bit, and write it back. */
+ set_bit(bitnum + len * 8 / 2, bits);
+ vdev->config->set(vdev, token, bits, len);
+ return 1;
+}
+EXPORT_SYMBOL_GPL(virtio_use_bit);
+
+static int virtio_init(void)
+{
+ if (bus_register(&virtio_bus.bus) != 0
+ || device_register(&virtio_bus.dev) != 0)
+ panic("virtio bus registration failed");
+ return 0;
+}
+core_initcall(virtio_init);
==================================================================---
a/include/linux/mod_devicetable.h
+++ b/include/linux/mod_devicetable.h
@@ -340,4 +340,10 @@ struct parisc_device_id {
#define PA_HVERSION_ANY_ID 0xffff
#define PA_SVERSION_ANY_ID 0xffffffff
+struct virtio_device_id {
+ __u32 device;
+ __u32 vendor;
+};
+#define VIRTIO_DEV_ANY_ID 0xffffffff
+
#endif /* LINUX_MOD_DEVICETABLE_H */
==================================================================--- /dev/null
+++ b/include/linux/virtio.h
@@ -0,0 +1,110 @@
+#ifndef _LINUX_VIRTIO_H
+#define _LINUX_VIRTIO_H
+/* Everything a virtio driver needs to work with any particular virtio
+ * implementation. */
+#include <linux/types.h>
+#include <linux/scatterlist.h>
+#include <linux/spinlock.h>
+#include <linux/device.h>
+#include <linux/mod_devicetable.h>
+
+/**
+ * virtqueue - a queue to register buffers for sending or receiving.
+ * @callback: the function to call when buffers are consumed (can be NULL).
+ * If this returns false, callbacks are suppressed until vq_ops->restart
+ * is called.
+ * @vdev: the virtio device this queue was created for.
+ * @vq_ops: the operations for this virtqueue (see below).
+ * @priv: a pointer for the virtqueue implementation to use.
+ */
+struct virtqueue
+{
+ bool (*callback)(struct virtqueue *vq);
+ struct virtio_device *vdev;
+ struct virtqueue_ops *vq_ops;
+ void *priv;
+};
+
+/**
+ * virtqueue_ops - operations for virtqueue abstraction layer
+ * @add_buf: expose buffer to other end
+ * vq: the struct virtqueue we're talking about.
+ * sg: the description of the buffer(s).
+ * out_num: the number of sg readable by other side
+ * in_num: the number of sg which are writable (after readable ones)
+ * data: the token identifying the buffer.
+ * Returns 0 or an error.
+ * @kick: update after add_buf
+ * vq: the struct virtqueue
+ * After one or more add_buf calls, invoke this to kick the other side.
+ * @get_buf: get the next used buffer
+ * vq: the struct virtqueue we're talking about.
+ * len: the length written into the buffer
+ * Returns NULL or the "data" token handed to add_buf.
+ * @restart: restart callbacks ater callback returned false.
+ * vq: the struct virtqueue we're talking about.
+ * This returns "false" (and doesn't re-enable) if there are
pending
+ * buffers in the queue, to avoid a race.
+ * @shutdown: "unadd" all buffers.
+ * vq: the struct virtqueue we're talking about.
+ * Remove everything from the queue.
+ *
+ * Locking rules are straightforward: the driver is responsible for
+ * locking. No two operations may be invoked simultaneously.
+ *
+ * All operations can be called in any context.
+ */
+struct virtqueue_ops {
+ int (*add_buf)(struct virtqueue *vq,
+ struct scatterlist sg[],
+ unsigned int out_num,
+ unsigned int in_num,
+ void *data);
+
+ void (*kick)(struct virtqueue *vq);
+
+ void *(*get_buf)(struct virtqueue *vq, unsigned int *len);
+
+ bool (*restart)(struct virtqueue *vq);
+
+ void (*shutdown)(struct virtqueue *vq);
+};
+
+/**
+ * virtio_device - representation of a device using virtio
+ * @index: unique position on the virtio bus
+ * @dev: underlying device.
+ * @id: the device type identification (used to match it with a driver).
+ * @config: the configuration ops for this device.
+ * @priv: private pointer for the driver's use.
+ */
+struct virtio_device
+{
+ int index;
+ struct device dev;
+ struct virtio_device_id id;
+ struct virtio_config_ops *config;
+ void *priv;
+};
+
+int register_virtio_device(struct virtio_device *dev);
+void unregister_virtio_device(struct virtio_device *dev);
+
+/**
+ * virtio_driver - operations for a virtio I/O driver
+ * @driver: underlying device driver (populate name and owner).
+ * @id_table: the ids serviced by this driver.
+ * @probe: the function to call when a device is found. Returns a token for
+ * remove, or PTR_ERR().
+ * @remove: the function when a device is removed.
+ */
+struct virtio_driver {
+ struct device_driver driver;
+ const struct virtio_device_id *id_table;
+ int (*probe)(struct virtio_device *dev);
+ void (*remove)(struct virtio_device *dev);
+};
+
+int register_virtio_driver(struct virtio_driver *drv);
+void unregister_virtio_driver(struct virtio_driver *drv);
+#endif /* _LINUX_VIRTIO_H */
==================================================================--- /dev/null
+++ b/include/linux/virtio_config.h
@@ -0,0 +1,111 @@
+#ifndef _LINUX_VIRTIO_CONFIG_H
+#define _LINUX_VIRTIO_CONFIG_H
+/* Virtio devices use a standardized configuration space to define their
+ * features and pass configuration information, but each implementation can
+ * store and access that space differently. */
+#include <linux/types.h>
+
+/* Status byte for guest to report progress, and synchronize config. */
+/* We have seen device and processed generic fields (VIRTIO_CONFIG_F_VIRTIO) */
+#define VIRTIO_CONFIG_S_ACKNOWLEDGE 1
+/* We have found a driver for the device. */
+#define VIRTIO_CONFIG_S_DRIVER 2
+/* Driver has used its parts of the config, and is happy */
+#define VIRTIO_CONFIG_S_DRIVER_OK 4
+/* We've given up on this device. */
+#define VIRTIO_CONFIG_S_FAILED 0x80
+
+/* Feature byte (actually 7 bits availabe): */
+/* Requirements/features of the virtio implementation. */
+#define VIRTIO_CONFIG_F_VIRTIO 1
+/* Requirements/features of the virtqueue (may have more than one). */
+#define VIRTIO_CONFIG_F_VIRTQUEUE 2
+
+#ifdef __KERNEL__
+struct virtio_device;
+
+/**
+ * virtio_config_ops - operations for configuring a virtio device
+ * @find: search for the next configuration field of the given type.
+ * vdev: the virtio_device
+ * type: the feature type
+ * len: the (returned) length of the field if found.
+ * Returns a token if found, or NULL. Never returnes the same field twice
+ * (ie. it's used up).
+ * @get: read the value of a configuration field after find().
+ * vdev: the virtio_device
+ * token: the token returned from find().
+ * buf: the buffer to write the field value into.
+ * len: the length of the buffer (given by find()).
+ * Note that contents are conventionally little-endian.
+ * @set: write the value of a configuration field after find().
+ * vdev: the virtio_device
+ * token: the token returned from find().
+ * buf: the buffer to read the field value from.
+ * len: the length of the buffer (given by find()).
+ * Note that contents are conventionally little-endian.
+ * @get_status: read the status byte
+ * vdev: the virtio_device
+ * Returns the status byte
+ * @set_status: write the status byte
+ * vdev: the virtio_device
+ * status: the new status byte
+ * @find_vq: find the first VIRTIO_CONFIG_F_VIRTQUEUE and create a virtqueue.
+ * vdev: the virtio_device
+ * callback: the virqtueue callback
+ * Returns the new virtqueue or ERR_PTR().
+ * @del_vq: free a virtqueue found by find_vq().
+ */
+struct virtio_config_ops
+{
+ void *(*find)(struct virtio_device *vdev, u8 type, unsigned *len);
+ void (*get)(struct virtio_device *vdev, void *token,
+ void *buf, unsigned len);
+ void (*set)(struct virtio_device *vdev, void *token,
+ const void *buf, unsigned len);
+ u8 (*get_status)(struct virtio_device *vdev);
+ void (*set_status)(struct virtio_device *vdev, u8 status);
+ struct virtqueue *(*find_vq)(struct virtio_device *vdev,
+ bool (*callback)(struct virtqueue *));
+ void (*del_vq)(struct virtqueue *vq);
+};
+
+/**
+ * virtio_config_val - get a single virtio config and mark it used.
+ * @config: the virtio config space
+ * @type: the type to search for.
+ * @val: a pointer to the value to fill in.
+ *
+ * Once used, the config type is marked with VIRTIO_CONFIG_F_USED so it
can't
+ * be found again. This version does endian conversion. */
+#define virtio_config_val(vdev, type, v) ({ \
+ int _err = __virtio_config_val((vdev),(type),(v),sizeof(*(v))); \
+ \
+ BUILD_BUG_ON(sizeof(*(v)) != 1 && sizeof(*(v)) != 2 \
+ && sizeof(*(v)) != 4 && sizeof(*(v)) != 8); \
+ if (!_err) { \
+ switch (sizeof(*(v))) { \
+ case 2: le16_to_cpus(v); break; \
+ case 4: le32_to_cpus(v); break; \
+ case 8: le64_to_cpus(v); break; \
+ } \
+ } \
+ _err; \
+})
+
+int __virtio_config_val(struct virtio_device *dev,
+ u8 type, void *val, size_t size);
+
+/**
+ * virtio_use_bit - helper to use a feature bit in a bitfield value.
+ * @dev: the virtio device
+ * @token: the token as returned from vdev->config->find().
+ * @len: the length of the field.
+ * @bitnum: the bit to test.
+ *
+ * If handed a NULL token, it returns false, otherwise returns bit status.
+ * If it's one, it sets the mirroring acknowledgement bit. */
+int virtio_use_bit(struct virtio_device *vdev,
+ void *token, unsigned int len, unsigned int bitnum);
+#endif /* __KERNEL__ */
+#endif /* _LINUX_VIRTIO_CONFIG_H */