Re: [RFC PATCH v9 13/23] vhost: Add vhost_svq_inject

[Jason Wang]

在 2022/7/7 02:39, Eugenio Pérez 写道:
> This allows qemu to inject buffers to the device.


Not a native speaker but we probably need a better terminology than 
inject here.

Since the CVQ is totally under the control of the Qemu anyhow.


> Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
> ---
>   hw/virtio/vhost-shadow-virtqueue.h |  2 ++
>   hw/virtio/vhost-shadow-virtqueue.c | 34 ++++++++++++++++++++++++++++++
>   2 files changed, 36 insertions(+)
>
> diff --git a/hw/virtio/vhost-shadow-virtqueue.h 
> b/hw/virtio/vhost-shadow-virtqueue.h
> index a811f90e01..d01d2370db 100644
> --- a/hw/virtio/vhost-shadow-virtqueue.h
> +++ b/hw/virtio/vhost-shadow-virtqueue.h
> @@ -98,6 +98,8 @@ bool vhost_svq_valid_features(uint64_t features, Error 
> **errp);
>   
>   void vhost_svq_push_elem(VhostShadowVirtqueue *svq,
>                            const VirtQueueElement *elem, uint32_t len);
> +int vhost_svq_inject(VhostShadowVirtqueue *svq, const struct iovec *iov,
> +                     size_t out_num, size_t in_num, void *opaque);
>   void vhost_svq_set_svq_kick_fd(VhostShadowVirtqueue *svq, int svq_kick_fd);
>   void vhost_svq_set_svq_call_fd(VhostShadowVirtqueue *svq, int call_fd);
>   void vhost_svq_get_vring_addr(const VhostShadowVirtqueue *svq,
> diff --git a/hw/virtio/vhost-shadow-virtqueue.c 
> b/hw/virtio/vhost-shadow-virtqueue.c
> index 492bb12b5f..bd9e34b413 100644
> --- a/hw/virtio/vhost-shadow-virtqueue.c
> +++ b/hw/virtio/vhost-shadow-virtqueue.c
> @@ -283,6 +283,40 @@ static bool vhost_svq_add_element(VhostShadowVirtqueue 
> *svq,
>       return ok;
>   }
>   
> +/**
> + * Inject a chain of buffers to the device
> + *
> + * @svq: Shadow VirtQueue
> + * @iov: I/O vector
> + * @out_num: Number of front out descriptors
> + * @in_num: Number of last input descriptors
> + * @opaque: Contextual data to store in descriptor
> + *
> + * Return 0 on success, -ENOMEM if cannot inject
> + */
> +int vhost_svq_inject(VhostShadowVirtqueue *svq, const struct iovec *iov,
> +                     size_t out_num, size_t in_num, void *opaque)


If we manage to embed opaque into VirtqueueElement, we can simply use 
vhost_svq_add() here.

Thanks


> +{
> +    bool ok;
> +
> +    /*
> +     * All vhost_svq_inject calls are controlled by qemu so we won't hit this
> +     * assertions.
> +     */
> +    assert(out_num || in_num);
> +    assert(svq->ops);
> +
> +    if (unlikely(svq->next_guest_avail_elem)) {
> +        error_report("Injecting in a full queue");
> +        return -ENOMEM;
> +    }
> +
> +    ok = vhost_svq_add(svq, iov, out_num, iov + out_num, in_num, opaque);
> +    assert(ok);
> +    vhost_svq_kick(svq);
> +    return 0;
> +}
> +
>   /**
>    * Forward available buffers.
>    *