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>
diff --git a/drivers/virtio/virtio_pci.c b/drivers/virtio/virtio_pci.c
index 3d1463c..add40d0 100644
--- a/drivers/virtio/virtio_pci.c
+++ b/drivers/virtio/virtio_pci.c
@@ -789,6 +789,7 @@
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 @@
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;
}
