Re: [PATCH v4 2/7] vdpa: Extract vhost_vdpa_net_cvq_add from vhost_vdpa_net_handle_ctrl_avail

[Jason Wang]

在 2022/7/22 19:12, Eugenio Pérez 写道:
> So we can reuse to inject state messages.
>
> Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
> ---
>   net/vhost-vdpa.c | 74 ++++++++++++++++++++++++++++++------------------
>   1 file changed, 47 insertions(+), 27 deletions(-)
>
> diff --git a/net/vhost-vdpa.c b/net/vhost-vdpa.c
> index 6abad276a6..1b82ac2e07 100644
> --- a/net/vhost-vdpa.c
> +++ b/net/vhost-vdpa.c
> @@ -334,6 +334,46 @@ static bool vhost_vdpa_net_cvq_map_elem(VhostVDPAState *s,
>       return true;
>   }
>   
> +static virtio_net_ctrl_ack vhost_vdpa_net_cvq_add(VhostShadowVirtqueue *svq,
> +                                               const struct iovec *dev_buffers)


Let's make this support any layout by accepting in/out sg.


> +{
> +    /* in buffer used for device model */
> +    virtio_net_ctrl_ack status;
> +    size_t dev_written;
> +    int r;
> +
> +    /*
> +     * Add a fake non-NULL VirtQueueElement since we'll remove before SVQ
> +     * event loop can get it.
> +     */
> +    r = vhost_svq_add(svq, &dev_buffers[0], 1, &dev_buffers[1], 1, (void *)1);


I'd suggest to avoid the trick like (void *)1, which is usually a hint 
of the defect of the API.

We can either:

1) make vhost_svq_get() check ndescs instead of elem

or

2) simple pass sg

Thanks


> +    if (unlikely(r != 0)) {
> +        if (unlikely(r == -ENOSPC)) {
> +            qemu_log_mask(LOG_GUEST_ERROR, "%s: No space on device queue\n",
> +                          __func__);
> +        }
> +        return VIRTIO_NET_ERR;
> +    }
> +
> +    /*
> +     * We can poll here since we've had BQL from the time we sent the
> +     * descriptor. Also, we need to take the answer before SVQ pulls by itself,
> +     * when BQL is released
> +     */
> +    dev_written = vhost_svq_poll(svq);
> +    if (unlikely(dev_written < sizeof(status))) {
> +        error_report("Insufficient written data (%zu)", dev_written);
> +        return VIRTIO_NET_ERR;
> +    }
> +
> +    memcpy(&status, dev_buffers[1].iov_base, sizeof(status));
> +    if (status != VIRTIO_NET_OK) {
> +        return VIRTIO_NET_ERR;
> +    }
> +
> +    return VIRTIO_NET_OK;
> +}
> +
>   /**
>    * Do not forward commands not supported by SVQ. Otherwise, the device could
>    * accept it and qemu would not know how to update the device model.
> @@ -380,19 +420,18 @@ static int 
> vhost_vdpa_net_handle_ctrl_avail(VhostShadowVirtqueue *svq,
>                                               void *opaque)
>   {
>       VhostVDPAState *s = opaque;
> -    size_t in_len, dev_written;
> +    size_t in_len;
>       virtio_net_ctrl_ack status = VIRTIO_NET_ERR;
>       /* out and in buffers sent to the device */
>       struct iovec dev_buffers[2] = {
>           { .iov_base = s->cvq_cmd_out_buffer },
>           { .iov_base = s->cvq_cmd_in_buffer },
>       };
> -    /* in buffer used for device model */
> +    /* in buffer seen by virtio-net device model */
>       const struct iovec in = {
>           .iov_base = &status,
>           .iov_len = sizeof(status),
>       };
> -    int r = -EINVAL;
>       bool ok;
>   
>       ok = vhost_vdpa_net_cvq_map_elem(s, elem, dev_buffers);
> @@ -405,35 +444,16 @@ static int 
> vhost_vdpa_net_handle_ctrl_avail(VhostShadowVirtqueue *svq,
>           goto out;
>       }
>   
> -    r = vhost_svq_add(svq, &dev_buffers[0], 1, &dev_buffers[1], 1, elem);
> -    if (unlikely(r != 0)) {
> -        if (unlikely(r == -ENOSPC)) {
> -            qemu_log_mask(LOG_GUEST_ERROR, "%s: No space on device queue\n",
> -                          __func__);
> -        }
> -        goto out;
> -    }
> -
> -    /*
> -     * We can poll here since we've had BQL from the time we sent the
> -     * descriptor. Also, we need to take the answer before SVQ pulls by itself,
> -     * when BQL is released
> -     */
> -    dev_written = vhost_svq_poll(svq);
> -    if (unlikely(dev_written < sizeof(status))) {
> -        error_report("Insufficient written data (%zu)", dev_written);
> -        goto out;
> -    }
> -
> -    memcpy(&status, dev_buffers[1].iov_base, sizeof(status));
> +    status = vhost_vdpa_net_cvq_add(svq, dev_buffers);
>       if (status != VIRTIO_NET_OK) {
>           goto out;
>       }
>   
>       status = VIRTIO_NET_ERR;
> -    virtio_net_handle_ctrl_iov(svq->vdev, &in, 1, dev_buffers, 1);
> -    if (status != VIRTIO_NET_OK) {
> +    in_len = virtio_net_handle_ctrl_iov(svq->vdev, &in, 1, dev_buffers, 1);
> +    if (in_len != sizeof(status) || status != VIRTIO_NET_OK) {
>           error_report("Bad CVQ processing in model");
> +        return VIRTIO_NET_ERR;
>       }
>   
>   out:
> @@ -450,7 +470,7 @@ out:
>       if (dev_buffers[1].iov_base) {
>           vhost_vdpa_cvq_unmap_buf(&s->vhost_vdpa, dev_buffers[1].iov_base);
>       }
> -    return r;
> +    return status == VIRTIO_NET_OK ? 0 : 1;
>   }
>   
>   static const VhostShadowVirtqueueOps vhost_vdpa_net_svq_ops = {