Re: [dpdk-dev] [PATCH v4 4/7] vhost: fix NUMA reallocation with multiqueue

["Xia, Chenbo" <chenbo.xia@intel.com>]

Hi Maxime,

> -----Original Message-----
> From: Maxime Coquelin <maxime.coquelin@redhat.com>
> Sent: Thursday, June 17, 2021 11:38 PM
> To: dev@dpdk.org; david.marchand@redhat.com; Xia, Chenbo <chenbo.xia@intel.com>
> Cc: Maxime Coquelin <maxime.coquelin@redhat.com>; stable@dpdk.org
> Subject: [PATCH v4 4/7] vhost: fix NUMA reallocation with multiqueue
> 
> Since the Vhost-user device initialization has been reworked,
> enabling the application to start using the device as soon as
> the first queue pair is ready, NUMA reallocation no more
> happened on queue pairs other than the first one since
> numa_realloc() was returning early if the device was running.
> 
> This patch fixes this issue by only preventing the device
> metadata to be allocated if the device is running. For the
> virtqueues, a vring state change notification is sent to
> notify the application of its disablement. Since the callback
> is supposed to be blocking, it is safe to reallocate it
> afterwards.

Is there a corner case? Numa_realloc may happen during vhost-user msg
set_vring_addr/kick, set_mem_table and iotlb msg. And iotlb msg will
not take vq access lock. It could happen when numa_realloc happens on
iotlb msg and app accesses vq in the meantime?

Thanks,
Chenbo

> 
> Fixes: d0fcc38f5fa4 ("vhost: improve device readiness notifications")
> Cc: stable@dpdk.org
> 
> Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
> ---
>  lib/vhost/vhost_user.c | 11 ++++++++---
>  1 file changed, 8 insertions(+), 3 deletions(-)
> 
> diff --git a/lib/vhost/vhost_user.c b/lib/vhost/vhost_user.c
> index 0e9e26ebe0..6e7b327ef8 100644
> --- a/lib/vhost/vhost_user.c
> +++ b/lib/vhost/vhost_user.c
> @@ -488,9 +488,6 @@ numa_realloc(struct virtio_net *dev, int index)
>  	struct batch_copy_elem *new_batch_copy_elems;
>  	int ret;
> 
> -	if (dev->flags & VIRTIO_DEV_RUNNING)
> -		return dev;
> -
>  	old_dev = dev;
>  	vq = old_vq = dev->virtqueue[index];
> 
> @@ -506,6 +503,11 @@ numa_realloc(struct virtio_net *dev, int index)
>  		return dev;
>  	}
>  	if (oldnode != newnode) {
> +		if (vq->ready) {
> +			vq->ready = false;
> +			vhost_user_notify_queue_state(dev, index, 0);
> +		}
> +
>  		VHOST_LOG_CONFIG(INFO,
>  			"reallocate vq from %d to %d node\n", oldnode, newnode);
>  		vq = rte_malloc_socket(NULL, sizeof(*vq), 0, newnode);
> @@ -558,6 +560,9 @@ numa_realloc(struct virtio_net *dev, int index)
>  		rte_free(old_vq);
>  	}
> 
> +	if (dev->flags & VIRTIO_DEV_RUNNING)
> +		goto out;
> +
>  	/* check if we need to reallocate dev */
>  	ret = get_mempolicy(&oldnode, NULL, 0, old_dev,
>  			    MPOL_F_NODE | MPOL_F_ADDR);
> --
> 2.31.1