Re: [dpdk-dev] [PATCH v4] vhost: use SMP barriers instead of compiler ones.

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

On Fri, Mar 18, 2016 at 03:23:53PM +0300, Ilya Maximets wrote:
> Since commit 4c02e453cc62 ("eal: introduce SMP memory barriers") virtio
> uses architecture dependent SMP barriers. vHost should use them too.
> 
> Fixes: 4c02e453cc62 ("eal: introduce SMP memory barriers")
> 
> Signed-off-by: Ilya Maximets <i.maximets@samsung.com>
> ---
>  lib/librte_vhost/vhost_rxtx.c | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/lib/librte_vhost/vhost_rxtx.c b/lib/librte_vhost/vhost_rxtx.c
> index b4da665..859c669 100644
> --- a/lib/librte_vhost/vhost_rxtx.c
> +++ b/lib/librte_vhost/vhost_rxtx.c
> @@ -315,7 +315,7 @@ virtio_dev_rx(struct virtio_net *dev, uint16_t queue_id,
>  			rte_prefetch0(&vq->desc[desc_indexes[i+1]]);
>  	}
>  
> -	rte_compiler_barrier();
> +	rte_smp_wmb();
>  
>  	/* Wait until it's our turn to add our buffer to the used ring. */
>  	while (unlikely(vq->last_used_idx != res_start_idx))
> @@ -565,7 +565,7 @@ virtio_dev_merge_rx(struct virtio_net *dev, uint16_t queue_id,
>  
>  		nr_used = copy_mbuf_to_desc_mergeable(dev, vq, start, end,
>  						      pkts[pkt_idx]);
> -		rte_compiler_barrier();
> +		rte_smp_wmb();
>  
>  		/*
>  		 * Wait until it's our turn to add our buffer
> @@ -923,7 +923,8 @@ rte_vhost_dequeue_burst(struct virtio_net *dev, uint16_t queue_id,
>  				sizeof(vq->used->ring[used_idx]));
>  	}
>  
> -	rte_compiler_barrier();
> +	rte_smp_wmb();
> +	rte_smp_rmb();

rte_smp_mb?

	--yliu