Re: [dpdk-dev] [PATCH] vhost: restore IOTLB mempool allocation

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

> -----Original Message-----
> From: David Marchand <david.marchand@redhat.com>
> Sent: Monday, May 17, 2021 5:00 PM
> To: dev@dpdk.org
> Cc: thomas@monjalon.net; Yigit, Ferruh <ferruh.yigit@intel.com>; Maxime
> Coquelin <maxime.coquelin@redhat.com>; Xia, Chenbo <chenbo.xia@intel.com>;
> Zhihong Wang <wangzhihong.wzh@bytedance.com>; Junjie Wan
> <wanjunjie@bytedance.com>
> Subject: [PATCH] vhost: restore IOTLB mempool allocation
> 
> As explained by Chenbo, IOTLB messages will be sent when some queues
> are not enabled. If we initialize IOTLB in vhost_user_set_vring_num,
> it could happen that IOTLB update comes when IOTLB pool of disabled
> queues are not initialized.
> 
> Fixes: 968bbc7e2e50 ("vhost: avoid IOTLB mempool allocation while IOMMU
> disabled")
> 
> Signed-off-by: David Marchand <david.marchand@redhat.com>
> ---
> Summary of a discussion with Maxime:
> 
> To keep the mempool allocation optimization, we could try to initialise
> the per-vring mempools at reception of the first IOTLB message.
> Since those pools are used as caches, it is not an issue if some vrings
> received more IOTLB updates than others.
> 
> But looking/testing this now is too late for 21.05, hence reverting is
> the safer.
> 
> ---
>  lib/vhost/vhost.c      | 5 +++--
>  lib/vhost/vhost_user.c | 6 +-----
>  2 files changed, 4 insertions(+), 7 deletions(-)
> 
> diff --git a/lib/vhost/vhost.c b/lib/vhost/vhost.c
> index 9cbcf650b6..c96f6335c8 100644
> --- a/lib/vhost/vhost.c
> +++ b/lib/vhost/vhost.c
> @@ -365,8 +365,7 @@ free_vq(struct virtio_net *dev, struct vhost_virtqueue
> *vq)
> 
>  	vhost_free_async_mem(vq);
>  	rte_free(vq->batch_copy_elems);
> -	if (vq->iotlb_pool)
> -		rte_mempool_free(vq->iotlb_pool);
> +	rte_mempool_free(vq->iotlb_pool);
>  	rte_free(vq->log_cache);
>  	rte_free(vq);
>  }
> @@ -570,6 +569,8 @@ init_vring_queue(struct virtio_net *dev, uint32_t
> vring_idx)
>  	vq->kickfd = VIRTIO_UNINITIALIZED_EVENTFD;
>  	vq->callfd = VIRTIO_UNINITIALIZED_EVENTFD;
>  	vq->notif_enable = VIRTIO_UNINITIALIZED_NOTIF;
> +
> +	vhost_user_iotlb_init(dev, vring_idx);
>  }
> 
>  static void
> diff --git a/lib/vhost/vhost_user.c b/lib/vhost/vhost_user.c
> index 611ff209e3..8f0eba6412 100644
> --- a/lib/vhost/vhost_user.c
> +++ b/lib/vhost/vhost_user.c
> @@ -469,10 +469,6 @@ vhost_user_set_vring_num(struct virtio_net **pdev,
>  		return RTE_VHOST_MSG_RESULT_ERR;
>  	}
> 
> -	if (dev->features & (1ULL << VIRTIO_F_IOMMU_PLATFORM)) {
> -		if (vhost_user_iotlb_init(dev, msg->payload.state.index))
> -			return RTE_VHOST_MSG_RESULT_ERR;
> -	}
>  	return RTE_VHOST_MSG_RESULT_OK;
>  }
> 
> @@ -578,7 +574,7 @@ numa_realloc(struct virtio_net *dev, int index)
>  	dev->virtqueue[index] = vq;
>  	vhost_devices[dev->vid] = dev;
> 
> -	if (old_vq != vq && (dev->features & (1ULL <<
> VIRTIO_F_IOMMU_PLATFORM)))
> +	if (old_vq != vq)
>  		vhost_user_iotlb_init(dev, index);
> 
>  	return dev;
> --
> 2.23.0

Reviewed-by: Chenbo Xia <chenbo.xia@intel.com>