On Fri, Jul 15, 2022 at 6:10 AM Jason Wang <jasowang@redhat.com> wrote:
>
> On Fri, Jul 15, 2022 at 12:32 AM Eugenio Pérez <eperezma@redhat.com> wrote:
> >
> > Since CVQ will be able to modify elements, the number of descriptors in
> > the guest may not match with the number of descriptors exposed. Track
> > separately.
> >
> > Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
> > ---
> > hw/virtio/vhost-shadow-virtqueue.h | 6 ++++++
> > hw/virtio/vhost-shadow-virtqueue.c | 10 +++++-----
> > 2 files changed, 11 insertions(+), 5 deletions(-)
> >
> > diff --git a/hw/virtio/vhost-shadow-virtqueue.h b/hw/virtio/vhost-shadow-virtqueue.h
> > index f35d4b8f90..143c86a568 100644
> > --- a/hw/virtio/vhost-shadow-virtqueue.h
> > +++ b/hw/virtio/vhost-shadow-virtqueue.h
> > @@ -17,6 +17,12 @@
> >
> > typedef struct SVQElement {
> > VirtQueueElement elem;
> > +
> > + /*
> > + * Number of descriptors exposed to the device. May or may not match
> > + * guest's
> > + */
> > + unsigned int ndescs;
> > } SVQElement;
>
> Can we simplify things furtherly by moving ndscs into a dedicated array at svq?
>
> Then we don't need to bother with introducing SVQElement.
>
Yes, I'll move to a desc_state.
Thanks!
> Thanks
>
> >
> > /* Shadow virtqueue to relay notifications */
> > diff --git a/hw/virtio/vhost-shadow-virtqueue.c b/hw/virtio/vhost-shadow-virtqueue.c
> > index 442ca3cbd3..3b112c4ec8 100644
> > --- a/hw/virtio/vhost-shadow-virtqueue.c
> > +++ b/hw/virtio/vhost-shadow-virtqueue.c
> > @@ -243,10 +243,10 @@ static int vhost_svq_add(VhostShadowVirtqueue *svq, const struct iovec *out_sg,
> > size_t in_num, SVQElement *svq_elem)
> > {
> > unsigned qemu_head;
> > - unsigned ndescs = in_num + out_num;
> > + svq_elem->ndescs = in_num + out_num;
> > bool ok;
> >
> > - if (unlikely(ndescs > vhost_svq_available_slots(svq))) {
> > + if (unlikely(svq_elem->ndescs > vhost_svq_available_slots(svq))) {
> > return -ENOSPC;
> > }
> >
> > @@ -393,7 +393,7 @@ static SVQElement *vhost_svq_get_buf(VhostShadowVirtqueue *svq,
> > SVQElement *elem;
> > const vring_used_t *used = svq->vring.used;
> > vring_used_elem_t used_elem;
> > - uint16_t last_used, last_used_chain, num;
> > + uint16_t last_used, last_used_chain;
> >
> > if (!vhost_svq_more_used(svq)) {
> > return NULL;
> > @@ -420,8 +420,8 @@ static SVQElement *vhost_svq_get_buf(VhostShadowVirtqueue *svq,
> > }
> >
> > elem = svq->ring_id_maps[used_elem.id];
> > - num = elem->elem.in_num + elem->elem.out_num;
> > - last_used_chain = vhost_svq_last_desc_of_chain(svq, num, used_elem.id);
> > + last_used_chain = vhost_svq_last_desc_of_chain(svq, elem->ndescs,
> > + used_elem.id);
> > svq->desc_next[last_used_chain] = svq->free_head;
> > svq->free_head = used_elem.id;
> >
> > --
> > 2.31.1
> >
>