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virtio_pci: fix virtio spec compliance on restore 

On restore, virtio pci does the following:
+ set features
+ init vqs etc - device can be used at this point!
+ set ACKNOWLEDGE,DRIVER and DRIVER_OK status bits

This is in violation of the virtio spec, which
requires the following order:
- ACKNOWLEDGE
- DRIVER
- init vqs
- DRIVER_OK

This behaviour will break with hypervisors that assume spec compliant
behaviour.  It seems like a good idea to have this patch applied to
stable branches to reduce the support butden for the hypervisors.

Cc: stable@vger.kernel.org
Cc: Amit Shah <amit.shah@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
This commit is contained in:
Michael S. Tsirkin 2014-10-14 10:40:29 +10:30 committed by Rusty Russell
parent 7ec62d421b
commit 6fbc198cf6
1 changed files with 30 additions and 3 deletions
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33
drivers/virtio/virtio_pci.c
View File

@ -789,6 +789,7 @@ static int virtio_pci_restore(struct device *dev)
struct pci_dev *pci_dev = to_pci_dev(dev);
struct virtio_pci_device *vp_dev = pci_get_drvdata(pci_dev);
struct virtio_driver *drv;
unsigned status = 0;
int ret;
drv = container_of(vp_dev->vdev.dev.driver,
@ -799,14 +800,40 @@ static int virtio_pci_restore(struct device *dev)
return ret;
pci_set_master(pci_dev);
/* We always start by resetting the device, in case a previous
* driver messed it up. */
vp_reset(&vp_dev->vdev);
/* Acknowledge that we've seen the device. */
status |= VIRTIO_CONFIG_S_ACKNOWLEDGE;
vp_set_status(&vp_dev->vdev, status);
/* Maybe driver failed before freeze.
* Restore the failed status, for debugging. */
status |= vp_dev->saved_status & VIRTIO_CONFIG_S_FAILED;
vp_set_status(&vp_dev->vdev, status);
if (!drv)
return 0;
/* We have a driver! */
status |= VIRTIO_CONFIG_S_DRIVER;
vp_set_status(&vp_dev->vdev, status);
vp_finalize_features(&vp_dev->vdev);
if (drv && drv->restore)
if (drv->restore) {
ret = drv->restore(&vp_dev->vdev);
if (ret) {
status |= VIRTIO_CONFIG_S_FAILED;
vp_set_status(&vp_dev->vdev, status);
return ret;
}
}
/* Finally, tell the device we're all set */
if (!ret)
vp_set_status(&vp_dev->vdev, vp_dev->saved_status);
status |= VIRTIO_CONFIG_S_DRIVER_OK;
vp_set_status(&vp_dev->vdev, status);
return ret;
}