Linux Virtualization - Dec 2014 - [PATCH RFC v2 1/4] virtio: add API to detect legacy devices

transports need to be able to detect legacy-only
devices (ATM balloon only) to use legacy path
to drive them.

Add a core API to do just that.
The implementation just blacklists balloon:
not too pretty, but let's not over-engineer.

Signed-off-by: Michael S. Tsirkin <mst at redhat.com>
Acked-by: Cornelia Huck <cornelia.huck at de.ibm.com>
---
 include/linux/virtio.h  | 2 ++
 drivers/virtio/virtio.c | 6 ++++++
 2 files changed, 8 insertions(+)

diff --git a/include/linux/virtio.h b/include/linux/virtio.h
index 2bbf626..d666bcb 100644
--- a/include/linux/virtio.h
+++ b/include/linux/virtio.h
@@ -108,6 +108,8 @@ struct virtio_device {
 	void *priv;
 };
 
+bool virtio_device_is_legacy_only(struct virtio_device_id id);
+
 static inline struct virtio_device *dev_to_virtio(struct device *_dev)
 {
 	return container_of(_dev, struct virtio_device, dev);
diff --git a/drivers/virtio/virtio.c b/drivers/virtio/virtio.c
index fa6b75d..6b4c1113 100644
--- a/drivers/virtio/virtio.c
+++ b/drivers/virtio/virtio.c
@@ -267,6 +267,12 @@ static struct bus_type virtio_bus = {
 	.remove = virtio_dev_remove,
 };
 
+bool virtio_device_is_legacy_only(struct virtio_device_id id)
+{
+	return id.device == VIRTIO_ID_BALLOON;
+}
+EXPORT_SYMBOL_GPL(register_virtio_driver);
+
 int register_virtio_driver(struct virtio_driver *driver)
 {
 	/* Catch this early. */
-- 
MST

Legacy balloon device doesn't pretend to support revision 1 or 64 bit
features.

But just in case someone implements a broken one that does, let's not
even try to drive legacy only devices using revision 1, and let's not
give them a chance to say they support VIRTIO_F_VERSION_1 by not reading
high feature bits.

Signed-off-by: Michael S. Tsirkin <mst at redhat.com>
---
 drivers/s390/kvm/virtio_ccw.c | 16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)

diff --git a/drivers/s390/kvm/virtio_ccw.c b/drivers/s390/kvm/virtio_ccw.c
index 4a3e6e5..c792b5f 100644
--- a/drivers/s390/kvm/virtio_ccw.c
+++ b/drivers/s390/kvm/virtio_ccw.c
@@ -733,6 +733,9 @@ static u64 virtio_ccw_get_features(struct virtio_device
*vdev)
 
 	rc = le32_to_cpu(features->features);
 
+	if (vcdev->revision == 0)
+		goto out_free;
+
 	/* Read second half of the feature bits from the host. */
 	features->index = 1;
 	ccw->cmd_code = CCW_CMD_READ_FEAT;
@@ -775,6 +778,9 @@ static void virtio_ccw_finalize_features(struct
virtio_device *vdev)
 	ccw->cda = (__u32)(unsigned long)features;
 	ccw_io_helper(vcdev, ccw, VIRTIO_CCW_DOING_WRITE_FEAT);
 
+	if (vcdev->revision == 0)
+		goto out_free;
+
 	features->index = 1;
 	features->features = cpu_to_le32(vdev->features >> 32);
 	/* Write the second half of the feature bits to the host. */
@@ -1182,9 +1188,13 @@ static int virtio_ccw_online(struct ccw_device *cdev)
 	vcdev->vdev.id.vendor = cdev->id.cu_type;
 	vcdev->vdev.id.device = cdev->id.cu_model;
 
-	ret = virtio_ccw_set_transport_rev(vcdev);
-	if (ret)
-		goto out_free;
+	if (virtio_device_is_legacy_only(vcdev->vdev.id)) {
+		vcdev->revision = 0;
+	} else {
+		ret = virtio_ccw_set_transport_rev(vcdev);
+		if (ret)
+			goto out_free;
+	}
 
 	ret = register_virtio_device(&vcdev->vdev);
 	if (ret) {
-- 
MST

This will make it easy for transports to validate features and return
failure.

Signed-off-by: Michael S. Tsirkin <mst at redhat.com>
---
 include/linux/virtio_config.h          | 3 ++-
 drivers/lguest/lguest_device.c         | 4 +++-
 drivers/misc/mic/card/mic_virtio.c     | 4 +++-
 drivers/remoteproc/remoteproc_virtio.c | 4 +++-
 drivers/s390/kvm/kvm_virtio.c          | 4 +++-
 drivers/s390/kvm/virtio_ccw.c          | 6 ++++--
 drivers/virtio/virtio.c                | 4 +++-
 drivers/virtio/virtio_mmio.c           | 4 +++-
 drivers/virtio/virtio_pci.c            | 4 +++-
 9 files changed, 27 insertions(+), 10 deletions(-)

diff --git a/include/linux/virtio_config.h b/include/linux/virtio_config.h
index 1fa5faa..7979f85 100644
--- a/include/linux/virtio_config.h
+++ b/include/linux/virtio_config.h
@@ -47,6 +47,7 @@
  *	vdev: the virtio_device
  *	This gives the final feature bits for the device: it can change
  *	the dev->feature bits if it wants.
+ *	Returns 0 on success or error status
  * @bus_name: return the bus name associated with the device
  *	vdev: the virtio_device
  *      This returns a pointer to the bus name a la pci_name from which
@@ -68,7 +69,7 @@ struct virtio_config_ops {
 			const char *names[]);
 	void (*del_vqs)(struct virtio_device *);
 	u64 (*get_features)(struct virtio_device *vdev);
-	void (*finalize_features)(struct virtio_device *vdev);
+	int (*finalize_features)(struct virtio_device *vdev);
 	const char *(*bus_name)(struct virtio_device *vdev);
 	int (*set_vq_affinity)(struct virtqueue *vq, int cpu);
 };
diff --git a/drivers/lguest/lguest_device.c b/drivers/lguest/lguest_device.c
index 9b77b66..89088d6 100644
--- a/drivers/lguest/lguest_device.c
+++ b/drivers/lguest/lguest_device.c
@@ -126,7 +126,7 @@ static void status_notify(struct virtio_device *vdev)
  * sorted out, this routine is called so we can tell the Host which features we
  * understand and accept.
  */
-static void lg_finalize_features(struct virtio_device *vdev)
+static int lg_finalize_features(struct virtio_device *vdev)
 {
 	unsigned int i, bits;
 	struct lguest_device_desc *desc = to_lgdev(vdev)->desc;
@@ -153,6 +153,8 @@ static void lg_finalize_features(struct virtio_device *vdev)
 
 	/* Tell Host we've finished with this device's feature negotiation */
 	status_notify(vdev);
+
+	return 0;
 }
 
 /* Once they've found a field, getting a copy of it is easy. */
diff --git a/drivers/misc/mic/card/mic_virtio.c
b/drivers/misc/mic/card/mic_virtio.c
index d027d29..e486a0c 100644
--- a/drivers/misc/mic/card/mic_virtio.c
+++ b/drivers/misc/mic/card/mic_virtio.c
@@ -84,7 +84,7 @@ static u64 mic_get_features(struct virtio_device *vdev)
 	return features;
 }
 
-static void mic_finalize_features(struct virtio_device *vdev)
+static int mic_finalize_features(struct virtio_device *vdev)
 {
 	unsigned int i, bits;
 	struct mic_device_desc __iomem *desc = to_micvdev(vdev)->desc;
@@ -107,6 +107,8 @@ static void mic_finalize_features(struct virtio_device
*vdev)
 			iowrite8(ioread8(&out_features[i / 8]) | (1 << (i % 8)),
 				 &out_features[i / 8]);
 	}
+
+	return 0;
 }
 
 /*
diff --git a/drivers/remoteproc/remoteproc_virtio.c
b/drivers/remoteproc/remoteproc_virtio.c
index 627737e..e1a1023 100644
--- a/drivers/remoteproc/remoteproc_virtio.c
+++ b/drivers/remoteproc/remoteproc_virtio.c
@@ -217,7 +217,7 @@ static u64 rproc_virtio_get_features(struct virtio_device
*vdev)
 	return rsc->dfeatures;
 }
 
-static void rproc_virtio_finalize_features(struct virtio_device *vdev)
+static int rproc_virtio_finalize_features(struct virtio_device *vdev)
 {
 	struct rproc_vdev *rvdev = vdev_to_rvdev(vdev);
 	struct fw_rsc_vdev *rsc;
@@ -235,6 +235,8 @@ static void rproc_virtio_finalize_features(struct
virtio_device *vdev)
 	 * to the remote processor once it is powered on.
 	 */
 	rsc->gfeatures = vdev->features;
+
+	return 0;
 }
 
 static void rproc_virtio_get(struct virtio_device *vdev, unsigned offset,
diff --git a/drivers/s390/kvm/kvm_virtio.c b/drivers/s390/kvm/kvm_virtio.c
index f5575cc..dd65c8b 100644
--- a/drivers/s390/kvm/kvm_virtio.c
+++ b/drivers/s390/kvm/kvm_virtio.c
@@ -93,7 +93,7 @@ static u64 kvm_get_features(struct virtio_device *vdev)
 	return features;
 }
 
-static void kvm_finalize_features(struct virtio_device *vdev)
+static int kvm_finalize_features(struct virtio_device *vdev)
 {
 	unsigned int i, bits;
 	struct kvm_device_desc *desc = to_kvmdev(vdev)->desc;
@@ -112,6 +112,8 @@ static void kvm_finalize_features(struct virtio_device
*vdev)
 		if (__virtio_test_bit(vdev, i))
 			out_features[i / 8] |= (1 << (i % 8));
 	}
+
+	return 0;
 }
 
 /*
diff --git a/drivers/s390/kvm/virtio_ccw.c b/drivers/s390/kvm/virtio_ccw.c
index c792b5f..789275f 100644
--- a/drivers/s390/kvm/virtio_ccw.c
+++ b/drivers/s390/kvm/virtio_ccw.c
@@ -752,7 +752,7 @@ out_free:
 	return rc;
 }
 
-static void virtio_ccw_finalize_features(struct virtio_device *vdev)
+static int virtio_ccw_finalize_features(struct virtio_device *vdev)
 {
 	struct virtio_ccw_device *vcdev = to_vc_device(vdev);
 	struct virtio_feature_desc *features;
@@ -760,7 +760,7 @@ static void virtio_ccw_finalize_features(struct
virtio_device *vdev)
 
 	ccw = kzalloc(sizeof(*ccw), GFP_DMA | GFP_KERNEL);
 	if (!ccw)
-		return;
+		return 0;
 
 	features = kzalloc(sizeof(*features), GFP_DMA | GFP_KERNEL);
 	if (!features)
@@ -793,6 +793,8 @@ static void virtio_ccw_finalize_features(struct
virtio_device *vdev)
 out_free:
 	kfree(features);
 	kfree(ccw);
+
+	return 0;
 }
 
 static void virtio_ccw_get_config(struct virtio_device *vdev,
diff --git a/drivers/virtio/virtio.c b/drivers/virtio/virtio.c
index 6b4c1113..7ddebbc 100644
--- a/drivers/virtio/virtio.c
+++ b/drivers/virtio/virtio.c
@@ -211,7 +211,9 @@ static int virtio_dev_probe(struct device *_d)
 		if (device_features & (1ULL << i))
 			__virtio_set_bit(dev, i);
 
-	dev->config->finalize_features(dev);
+	err = dev->config->finalize_features(dev);
+	if (err)
+		goto err;
 
 	if (virtio_has_feature(dev, VIRTIO_F_VERSION_1)) {
 		add_status(dev, VIRTIO_CONFIG_S_FEATURES_OK);
diff --git a/drivers/virtio/virtio_mmio.c b/drivers/virtio/virtio_mmio.c
index aec1dae..5219210 100644
--- a/drivers/virtio/virtio_mmio.c
+++ b/drivers/virtio/virtio_mmio.c
@@ -152,7 +152,7 @@ static u64 vm_get_features(struct virtio_device *vdev)
 	return readl(vm_dev->base + VIRTIO_MMIO_HOST_FEATURES);
 }
 
-static void vm_finalize_features(struct virtio_device *vdev)
+static int vm_finalize_features(struct virtio_device *vdev)
 {
 	struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vdev);
 
@@ -164,6 +164,8 @@ static void vm_finalize_features(struct virtio_device *vdev)
 
 	writel(0, vm_dev->base + VIRTIO_MMIO_GUEST_FEATURES_SEL);
 	writel(vdev->features, vm_dev->base + VIRTIO_MMIO_GUEST_FEATURES);
+
+	return 0;
 }
 
 static void vm_get(struct virtio_device *vdev, unsigned offset,
diff --git a/drivers/virtio/virtio_pci.c b/drivers/virtio/virtio_pci.c
index 98f9c6e..c7649f3 100644
--- a/drivers/virtio/virtio_pci.c
+++ b/drivers/virtio/virtio_pci.c
@@ -111,7 +111,7 @@ static u64 vp_get_features(struct virtio_device *vdev)
 }
 
 /* virtio config->finalize_features() implementation */
-static void vp_finalize_features(struct virtio_device *vdev)
+static int vp_finalize_features(struct virtio_device *vdev)
 {
 	struct virtio_pci_device *vp_dev = to_vp_device(vdev);
 
@@ -124,6 +124,8 @@ static void vp_finalize_features(struct virtio_device *vdev)
 	/* We only support 32 feature bits. */
 	iowrite32(vdev->features, vp_dev->ioaddr +
 		  VIRTIO_PCI_LEGACY_GUEST_FEATURES);
+
+	return 0;
 }
 
 /* virtio config->get() implementation */
-- 
MST

What does it mean if rev 1 device does not set
VIRTIO_F_VERSION_1? E.g. is it native endian?

Let's not even try to drive such devices:
fail attempts to finalize features.
virtio core will detect this and bail out.

Signed-off-by: Michael S. Tsirkin <mst at redhat.com>
---
 drivers/s390/kvm/virtio_ccw.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/s390/kvm/virtio_ccw.c b/drivers/s390/kvm/virtio_ccw.c
index 789275f..f9f87ba 100644
--- a/drivers/s390/kvm/virtio_ccw.c
+++ b/drivers/s390/kvm/virtio_ccw.c
@@ -758,6 +758,13 @@ static int virtio_ccw_finalize_features(struct
virtio_device *vdev)
 	struct virtio_feature_desc *features;
 	struct ccw1 *ccw;
 
+	if (vcdev->revision == 1 &&
+	    !__virtio_test_bit(vdev, VIRTIO_F_VERSION_1)) {
+		dev_err(&vdev->dev, "virtio: device uses revision 1 "
+			"but does not have VIRTIO_F_VERSION_1\n");
+		return -EINVAL;
+	}
+
 	ccw = kzalloc(sizeof(*ccw), GFP_DMA | GFP_KERNEL);
 	if (!ccw)
 		return 0;
-- 
MST

> This will make it easy for transports to validate features and return
> failure.
> 
> Signed-off-by: Michael S. Tsirkin <mst at redhat.com>
> ---
>  include/linux/virtio_config.h          | 3 ++-
>  drivers/lguest/lguest_device.c         | 4 +++-
>  drivers/misc/mic/card/mic_virtio.c     | 4 +++-
>  drivers/remoteproc/remoteproc_virtio.c | 4 +++-
>  drivers/s390/kvm/kvm_virtio.c          | 4 +++-
>  drivers/s390/kvm/virtio_ccw.c          | 6 ++++--
>  drivers/virtio/virtio.c                | 4 +++-
>  drivers/virtio/virtio_mmio.c           | 4 +++-
>  drivers/virtio/virtio_pci.c            | 4 +++-
>  9 files changed, 27 insertions(+), 10 deletions(-)
> 
> diff --git a/include/linux/virtio_config.h b/include/linux/virtio_config.h
> index 1fa5faa..7979f85 100644
> --- a/include/linux/virtio_config.h
> +++ b/include/linux/virtio_config.h
> @@ -47,6 +47,7 @@
>   *	vdev: the virtio_device
>   *	This gives the final feature bits for the device: it can change
>   *	the dev->feature bits if it wants.
> + *	Returns 0 on success or error status
"Returns 0 on success, otherwise the error status."
>   * @bus_name: return the bus name associated with the device
>   *	vdev: the virtio_device
>   *      This returns a pointer to the bus name a la pci_name from which
> @@ -68,7 +69,7 @@ struct virtio_config_ops {
>  			const char *names[]);
>  	void (*del_vqs)(struct virtio_device *);
>  	u64 (*get_features)(struct virtio_device *vdev);
> -	void (*finalize_features)(struct virtio_device *vdev);
> +	int (*finalize_features)(struct virtio_device *vdev);
>  	const char *(*bus_name)(struct virtio_device *vdev);
>  	int (*set_vq_affinity)(struct virtqueue *vq, int cpu);
>  };
...
> 
>  static void virtio_ccw_get_config(struct virtio_device *vdev,
> diff --git a/drivers/virtio/virtio.c b/drivers/virtio/virtio.c
> index 6b4c1113..7ddebbc 100644
> --- a/drivers/virtio/virtio.c
> +++ b/drivers/virtio/virtio.c
> @@ -211,7 +211,9 @@ static int virtio_dev_probe(struct device *_d)
>  		if (device_features & (1ULL << i))
>  			__virtio_set_bit(dev, i);
> 
> -	dev->config->finalize_features(dev);
> +	err = dev->config->finalize_features(dev);
> +	if (err)
> +		goto err;
> 
>  	if (virtio_has_feature(dev, VIRTIO_F_VERSION_1)) {
>  		add_status(dev, VIRTIO_CONFIG_S_FEATURES_OK);
> diff --git a/drivers/virtio/virtio_mmio.c b/drivers/virtio/virtio_mmio.c
> index aec1dae..5219210 100644
> --- a/drivers/virtio/virtio_mmio.c
> +++ b/drivers/virtio/virtio_mmio.c
> @@ -152,7 +152,7 @@ static u64 vm_get_features(struct virtio_device *vdev)
>  	return readl(vm_dev->base + VIRTIO_MMIO_HOST_FEATURES);
>  }
> 
Do we have to take care of fails in virtio_device_restore()?

Otherwise looks good to me.

David