Re: [PATCH] virtio: reset device on bad guest index in virtio_load()

[Michael S. Tsirkin]

No, but how about sending the patch to me and the mailing list?
I didn't get it through either channel.

On Mon, Nov 30, 2020 at 03:51:13PM +0000, John Levon wrote:
> On Fri, Nov 20, 2020 at 06:51:07PM +0000, John Levon wrote:
> 
> > If we find a queue with an inconsistent guest index value, explicitly mark 
> > the
> > device as needing a reset - and broken - via virtio_error().
> > 
> > There's at least one driver implementation - the virtio-win NetKVM driver - 
> > that
> > is able to handle a VIRTIO_CONFIG_S_NEEDS_RESET notification and 
> > successfully
> > restore the device to a working state. Other implementations do not 
> > correctly
> > handle this, but as the VQ is not in a functional state anyway, this is 
> > still
> > worth doing.
> 
> Ping, anyone have issues with doing this?
> 
> cheers
> john
> 
> > Signed-off-by: John Levon <john.levon@nutanix.com>
> > ---
> >  hw/virtio/virtio.c | 15 +++++++++------
> >  1 file changed, 9 insertions(+), 6 deletions(-)
> > 
> > diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
> > index ceb58fda6c..eff35fab7c 100644
> > --- a/hw/virtio/virtio.c
> > +++ b/hw/virtio/virtio.c
> > @@ -3161,12 +3161,15 @@ int virtio_load(VirtIODevice *vdev, QEMUFile *f, 
> > int version_id)
> >              nheads = vring_avail_idx(&vdev->vq[i]) - 
> > vdev->vq[i].last_avail_idx;
> >              /* Check it isn't doing strange things with descriptor 
> > numbers. */
> >              if (nheads > vdev->vq[i].vring.num) {
> > -                qemu_log_mask(LOG_GUEST_ERROR,
> > -                              "VQ %d size 0x%x Guest index 0x%x "
> > -                              "inconsistent with Host index 0x%x: delta 
> > 0x%x",
> > -                              i, vdev->vq[i].vring.num,
> > -                              vring_avail_idx(&vdev->vq[i]),
> > -                              vdev->vq[i].last_avail_idx, nheads);
> > +                virtio_error(vdev, "VQ %d size 0x%x Guest index 0x%x "
> > +                             "inconsistent with Host index 0x%x: delta 
> > 0x%x",
> > +                             i, vdev->vq[i].vring.num,
> > +                             vring_avail_idx(&vdev->vq[i]),
> > +                             vdev->vq[i].last_avail_idx, nheads);
> > +                vdev->vq[i].used_idx = 0;
> > +                vdev->vq[i].shadow_avail_idx = 0;
> > +                vdev->vq[i].inuse = 0;
> > +                continue;
> >              }
> >              vdev->vq[i].used_idx = vring_used_idx(&vdev->vq[i]);
> >              vdev->vq[i].shadow_avail_idx = vring_avail_idx(&vdev->vq[i]);