> >
> > The IN_ORDER feature uses additional software state to track the next
> > available descriptor and in-flight descriptor batches.
> >
> > virtqueue_init() resets the common virtqueue state, but free_head and
> > batch_last.id are initialized only when the virtqueue is created. When
> > an IN_ORDER virtqueue is reset, these fields can retain state from the
> > previous queue instance.
> >
> > Reset free_head and invalidate batch_last when initializing an
> > IN_ORDER virtqueue. Keep this in virtqueue_init() so the state is
> > initialized consistently for both newly created and reset virtqueues.
> >
> > Fixes: f6a15d854986 ("virtio_ring: add in order support")
>
> I think this is needed for -stable.
>
> > Signed-off-by: Li RongQing <[email protected]>
> > ---
> > drivers/virtio/virtio_ring.c | 5 +++++
> > 1 file changed, 5 insertions(+)
> >
> > diff --git a/drivers/virtio/virtio_ring.c
> > b/drivers/virtio/virtio_ring.c index db678f5..d0dc464 100644
> > --- a/drivers/virtio/virtio_ring.c
> > +++ b/drivers/virtio/virtio_ring.c
> > @@ -559,6 +559,11 @@ static void virtqueue_init(struct vring_virtqueue *vq,
> u32 num)
> > vq->in_use = false;
> > vq->last_add_time_valid = false; #endif
> > +
> > + if (virtqueue_is_in_order(vq)) {
> > + vq->free_head = 0;
> > + vq->batch_last.id = UINT_MAX;
> > + }
>
> I would try to reuse or refactor virtqueue_vring_attach_split() to reduce code
> duplication.
>
> Btw have you checked Qemu shadow virtqueue as it might suffer from the same
> issue.
>
I checked QEMU's shadow virtqueue implementation. batch_last is reinitialized
in vhost_svq_start(),
but free_head is not. Since the SVQ object can be reused across stop/start,
free_head may retain stale
state. So a corresponding fix should be needed
void vhost_svq_start(VhostShadowVirtqueue *svq, VirtIODevice *vdev,
VirtQueue *vq, VhostIOVATree *iova_tree)
{
...
svq->shadow_avail_idx = 0;
svq->shadow_used_idx = 0;
+ svq->free_head = 0;
memset(&svq->batch_last, 0, sizeof(svq->batch_last));
svq->last_used = 0;
svq->last_used_idx = 0;
thanks
[Li,Rongqing]
> Thanks
>
> > }
> >
> >
> > --
> > 2.9.4
> >
