On Mon, Jul 25, 2022 at 3:07 PM Jason Wang <jasow...@redhat.com> wrote:
>
> On Mon, Jul 18, 2022 at 8:05 PM Eugenio Pérez <epere...@redhat.com> wrote:
> >
> > The SVQ vring used idx usually match with the guest visible one, as long
> > as all the guest buffers (GPA) maps to exactly one buffer within qemu's
> > VA. However, as we can see in virtqueue_map_desc, a single guest buffer
> > could map to many buffers in SVQ vring.
> >
> > Also, its also a mistake to rewind them at the source of migration.
> > Since VirtQueue is able to migrate the inflight descriptors, its
> > responsability of the destination to perform the rewind just in case it
> > cannot report the inflight descriptors to the device.
> >
> > This makes easier to migrate between backends or to recover them in
> > vhost devices that support set in flight descriptors.
> >
> > Fixes: 6d0b22266633 ("vdpa: Adapt vhost_vdpa_get_vring_base to SVQ")
> > Signed-off-by: Eugenio Pérez <epere...@redhat.com>
>
> Acked-by: Jason Wang <jasow...@redhat.com>
I've queued this for hard-freeze.
Thanks
>
> >
> > --
> > v2: Squash both fixes in one.
> > ---
> > hw/virtio/vhost-vdpa.c | 24 ++++++++++++------------
> > 1 file changed, 12 insertions(+), 12 deletions(-)
> >
> > diff --git a/hw/virtio/vhost-vdpa.c b/hw/virtio/vhost-vdpa.c
> > index 795ed5a049..4458c8d23e 100644
> > --- a/hw/virtio/vhost-vdpa.c
> > +++ b/hw/virtio/vhost-vdpa.c
> > @@ -1178,7 +1178,18 @@ static int vhost_vdpa_set_vring_base(struct
> > vhost_dev *dev,
> > struct vhost_vring_state *ring)
> > {
> > struct vhost_vdpa *v = dev->opaque;
> > + VirtQueue *vq = virtio_get_queue(dev->vdev, ring->index);
> >
> > + /*
> > + * vhost-vdpa devices does not support in-flight requests. Set all of
> > them
> > + * as available.
> > + *
> > + * TODO: This is ok for networking, but other kinds of devices might
> > + * have problems with these retransmissions.
> > + */
> > + while (virtqueue_rewind(vq, 1)) {
> > + continue;
> > + }
> > if (v->shadow_vqs_enabled) {
> > /*
> > * Device vring base was set at device start. SVQ base is handled
> > by
> > @@ -1194,21 +1205,10 @@ static int vhost_vdpa_get_vring_base(struct
> > vhost_dev *dev,
> > struct vhost_vring_state *ring)
> > {
> > struct vhost_vdpa *v = dev->opaque;
> > - int vdpa_idx = ring->index - dev->vq_index;
> > int ret;
> >
> > if (v->shadow_vqs_enabled) {
> > - VhostShadowVirtqueue *svq = g_ptr_array_index(v->shadow_vqs,
> > vdpa_idx);
> > -
> > - /*
> > - * Setting base as last used idx, so destination will see as
> > available
> > - * all the entries that the device did not use, including the
> > in-flight
> > - * processing ones.
> > - *
> > - * TODO: This is ok for networking, but other kinds of devices
> > might
> > - * have problems with these retransmissions.
> > - */
> > - ring->num = svq->last_used_idx;
> > + ring->num = virtio_queue_get_last_avail_idx(dev->vdev,
> > ring->index);
> > return 0;
> > }
> >
> > --
> > 2.31.1
> >
