Re: [dpdk-dev] [PATCH] vhost-user: fix enabling of queue pair

[Yuanhan Liu <yuanhan.liu@linux.intel.com>]

On Fri, Nov 20, 2015 at 03:45:00PM +0200, Victor Kaplansky wrote:
> The VHOST_USER_SET_VRING_ENABLE request is sent for each queue in
> queue-pair separately. So, a queue-pair should be considered
> enabled only when both RX and TX queues are enabled.

Hi Victor,

It was sent per queue-pair, and I found that Michael changed it to
per vring. The reason I made it per queue-pair is that the backend
can handle both queues in one queue-pair. However, I agree that
making it per queue (vring) is better here, to keep the consistency
of sending all requests (say vring_call) per vring.

> 
> The old code caused segfault when last TX queue was enabled.
> 
> Signed-off-by: Victor Kaplansky <victork@redhat.com>
> ---
>  lib/librte_vhost/vhost_user/virtio-net-user.c | 14 +++++++++-----
>  1 file changed, 9 insertions(+), 5 deletions(-)
> 
> diff --git a/lib/librte_vhost/vhost_user/virtio-net-user.c b/lib/librte_vhost/vhost_user/virtio-net-user.c
> index d07452a..c06e53e 100644
> --- a/lib/librte_vhost/vhost_user/virtio-net-user.c
> +++ b/lib/librte_vhost/vhost_user/virtio-net-user.c
> @@ -317,21 +317,25 @@ user_set_vring_enable(struct vhost_device_ctx ctx,
>  		      struct vhost_vring_state *state)
>  {
>  	struct virtio_net *dev = get_device(ctx);
> -	uint16_t base_idx = state->index;
> +	uint16_t idx = state->index;
> +	uint16_t base_idx = (idx / VIRTIO_QNUM) * VIRTIO_QNUM;
>  	int enable = (int)state->num;
> +	int qpair_enabled;
>  
>  	RTE_LOG(INFO, VHOST_CONFIG,
>  		"set queue enable: %d to qp idx: %d\n",
>  		enable, state->index);
>  
> +	dev->virtqueue[idx]->enabled = enable;
> +	qpair_enabled =
> +		dev->virtqueue[base_idx + VIRTIO_RXQ]->enabled &&
> +		dev->virtqueue[base_idx + VIRTIO_TXQ]->enabled;
> +
>  	if (notify_ops->vring_state_changed) {
>  		notify_ops->vring_state_changed(dev, base_idx / VIRTIO_QNUM,
> -						enable);
> +						qpair_enabled);

Here we could make the vring_state_changed callback be per vring then,
instead of per queue-pair. That make the code simpler, as well as more
consistent.

Thanks.

	--yliu
>  	}
>  
> -	dev->virtqueue[base_idx + VIRTIO_RXQ]->enabled = enable;
> -	dev->virtqueue[base_idx + VIRTIO_TXQ]->enabled = enable;
> -
>  	return 0;
>  }
>  
> -- 
> --Victor