On 10/21/2015 11:48 AM, Yuanhan Liu wrote:
> All queue pairs, including the default (the first) queue pair,
> are allocated dynamically, when a vring_call message is received
> first time for a specific queue pair.
>
> This is a refactor work for enabling vhost-user multiple queue;
> it should not break anything as it does no functional changes:
> we don't support mq set, so there is only one mq at max.
>
> This patch is based on Changchun's patch.
>
[...]
>
> void
> @@ -290,13 +298,9 @@ user_get_vring_base(struct vhost_device_ctx ctx,
> * sent and only sent in vhost_vring_stop.
> * TODO: cleanup the vring, it isn't usable since here.
> */
> - if ((dev->virtqueue[VIRTIO_RXQ]->kickfd) >= 0) {
> - close(dev->virtqueue[VIRTIO_RXQ]->kickfd);
> - dev->virtqueue[VIRTIO_RXQ]->kickfd = -1;
> - }
> - if ((dev->virtqueue[VIRTIO_TXQ]->kickfd) >= 0) {
> - close(dev->virtqueue[VIRTIO_TXQ]->kickfd);
> - dev->virtqueue[VIRTIO_TXQ]->kickfd = -1;
> + if ((dev->virtqueue[state->index]->kickfd) >= 0) {
> + close(dev->virtqueue[state->index]->kickfd);
> + dev->virtqueue[state->index]->kickfd = -1;
> }
Since we change the behavior here, better list in the commit message as
well.
>
>
> @@ -680,13 +704,21 @@ set_vring_call(struct vhost_device_ctx ctx, struct
> vhost_vring_file *file)
> {
> struct virtio_net *dev;
> struct vhost_virtqueue *vq;
> + uint32_t cur_qp_idx = file->index / VIRTIO_QNUM;
>
> dev = get_device(ctx);
> if (dev == NULL)
> return -1;
>
> + /* alloc vring queue pair if it is a new queue pair */
> + if (cur_qp_idx + 1 > dev->virt_qp_nb) {
> + if (alloc_vring_queue_pair(dev, cur_qp_idx) < 0)
> + return -1;
> + }
> +
Here we rely on the fact that this set_vring_call message is sent in the
continuous ascending order of queue idx 0, 1, 2, ...
> /* file->index refers to the queue index. The txq is 1, rxq is 0. */
> vq = dev->virtqueue[file->index];
> + assert(vq != NULL);
>
If we allocate the queue until the we receive the first vring message,
better add comment that we rely on this fact.
Could we add the vhost-user message to tell us the queue number QEMU
allocates before vring message?
> if (vq->callfd >= 0)
> close(vq->callfd);
