On Mon, Oct 06, 2014 at 06:10:40PM +0300, Michael S. Tsirkin wrote:
> 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.
Tested suspend to ram with virtio net and blk.
>
> Cc: stable@xxxxxxxxxxxxxxx
> Cc: Amit Shah <amit.shah@xxxxxxxxxx>
> Signed-off-by: Michael S. Tsirkin <mst@xxxxxxxxxx>
> ---
> drivers/virtio/virtio_pci.c | 36 ++++++++++++++++++++++++++++++++----
> 1 file changed, 32 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/virtio/virtio_pci.c b/drivers/virtio/virtio_pci.c
> index 3d1463c..0f2db51 100644
> --- a/drivers/virtio/virtio_pci.c
> +++ b/drivers/virtio/virtio_pci.c
> @@ -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 +800,41 @@ 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)
> - ret = drv->restore(&vp_dev->vdev);
> + if (!drv->restore)
> + return 0;
As Amit points out, this is a bug: for a driver without restore
callback we should still set DRIVER_OK.
Will post v3.
> +
> + 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;
> }
> --
> MST
>
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