Re: [PATCH v5 02/10] vhost: use SVQ element ndescs instead of opaque data for desc validation

[Jason Wang]

在 2022/8/3 01:57, Eugenio Pérez 写道:
> Since we're going to allow SVQ to add elements without the guest's
> knowledge and without its own VirtQueueElement, it's easier to check if
> an element is a valid head checking a different thing than the
> VirtQueueElement.
>
> Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
> ---


Patch looks good to me. But I spot several other issues:

1) vhost_svq_add() use size_t for in_num and out_num, is this intended?
2) do we need to fail vhost_svq_add() if in_num + out_num == 0?

Thanks


>   hw/virtio/vhost-shadow-virtqueue.c | 3 ++-
>   1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/hw/virtio/vhost-shadow-virtqueue.c 
> b/hw/virtio/vhost-shadow-virtqueue.c
> index ffd2b2c972..e6eebd0e8d 100644
> --- a/hw/virtio/vhost-shadow-virtqueue.c
> +++ b/hw/virtio/vhost-shadow-virtqueue.c
> @@ -414,7 +414,7 @@ static VirtQueueElement 
> *vhost_svq_get_buf(VhostShadowVirtqueue *svq,
>           return NULL;
>       }
>   
> -    if (unlikely(!svq->desc_state[used_elem.id].elem)) {
> +    if (unlikely(!svq->desc_state[used_elem.id].ndescs)) {
>           qemu_log_mask(LOG_GUEST_ERROR,
>               "Device %s says index %u is used, but it was not available",
>               svq->vdev->name, used_elem.id);
> @@ -422,6 +422,7 @@ static VirtQueueElement 
> *vhost_svq_get_buf(VhostShadowVirtqueue *svq,
>       }
>   
>       num = svq->desc_state[used_elem.id].ndescs;
> +    svq->desc_state[used_elem.id].ndescs = 0;
>       last_used_chain = vhost_svq_last_desc_of_chain(svq, num, used_elem.id);
>       svq->desc_next[last_used_chain] = svq->free_head;
>       svq->free_head = used_elem.id;