Re: [RFC PATCH 09/12] vdpa: Extract vhost_vdpa_net_svq_add from vhost_vdpa_net_handle_ctrl_avail

[Jason Wang <jasowang@redhat.com>]

在 2022/7/16 19:34, Eugenio Pérez 写道:
> So we can reuse to inject state messages.
>
> Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
> ---
>   net/vhost-vdpa.c | 89 +++++++++++++++++++++++++++---------------------
>   1 file changed, 51 insertions(+), 38 deletions(-)
>
> diff --git a/net/vhost-vdpa.c b/net/vhost-vdpa.c
> index 211bd0468b..aaae51a778 100644
> --- a/net/vhost-vdpa.c
> +++ b/net/vhost-vdpa.c
> @@ -334,6 +334,54 @@ static bool vhost_vdpa_net_cvq_map_elem(VhostVDPAState *s,
>       return true;
>   }
>   
> +static virtio_net_ctrl_ack vhost_vdpa_net_svq_add(VhostShadowVirtqueue *svq,
> +                                               const struct iovec *dev_buffers)


The name should be tweaked since it is used only for cvq.


> +{
> +    /* in buffer used for device model */
> +    virtio_net_ctrl_ack status;
> +    const struct iovec in = {
> +        .iov_base = &status,
> +        .iov_len = sizeof(status),
> +    };
> +    size_t dev_written;
> +    int r;
> +    void *unused = (void *)1;
> +
> +    r = vhost_svq_add(svq, &dev_buffers[0], 1, &dev_buffers[1], 1, unused);
> +    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
> +     */


This reminds me that, do we need a upper limit of the time on the 
polling here. (Avoid taking BQL for too long time).

Thanks


> +    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;
> +    }
> +
> +    status = VIRTIO_NET_ERR;
> +    virtio_net_handle_ctrl_iov(svq->vdev, &in, 1, dev_buffers, 1);
> +    if (status != VIRTIO_NET_OK) {
> +        error_report("Bad CVQ processing in model");
> +        return VIRTIO_NET_ERR;
> +    }
> +
> +    return VIRTIO_NET_OK;
> +}
> +
>   static int vhost_vdpa_start_control_svq(struct vhost_vdpa *v)
>   {
>       struct vhost_vring_state state = {
> @@ -392,19 +440,13 @@ 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 */
> -    const struct iovec in = {
> -        .iov_base = &status,
> -        .iov_len = sizeof(status),
> -    };
> -    int r;
>       bool ok;
>   
>       ok = vhost_vdpa_net_cvq_map_elem(s, elem, dev_buffers);
> @@ -417,36 +459,7 @@ 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));
> -    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) {
> -        error_report("Bad CVQ processing in model");
> -    }
> +    status = vhost_vdpa_net_svq_add(svq, dev_buffers);
>   
>   out:
>       in_len = iov_from_buf(elem->in_sg, elem->in_num, 0, &status,
> @@ -462,7 +475,7 @@ 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 = {