From mboxrd@z Thu Jan  1 00:00:00 1970
From: Yuanhan Liu <yuanhan.liu@linux.intel.com>
Subject: Re: [PATCH] virito: fix reuse index in nested loop
Date: Mon, 13 Jun 2016 16:57:49 +0800
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To: Jianfeng Tan <jianfeng.tan@intel.com>
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On Sun, Jun 12, 2016 at 10:05:45AM +0000, Jianfeng Tan wrote:
> This patches fixes problem of reusing index of outmost loop in nested
> loops. This bug will lead to failure when starting a multi queue
> virtio device: rx queues (except from the first one) cannot be started,
> expecially their vq_ring cannot be initialized, so that when invoking
> rx func on these queues, segment fault happens.
> 
> Fixes: a900472aedef ("virtio: split virtio Rx/Tx queue")

Good catch!

> Signed-off-by: Jianfeng Tan <jianfeng.tan@intel.com>
> ---
>  drivers/net/virtio/virtio_rxtx.c | 36 ++++++++++++++++++++----------------
>  1 file changed, 20 insertions(+), 16 deletions(-)
> 
> diff --git a/drivers/net/virtio/virtio_rxtx.c b/drivers/net/virtio/virtio_rxtx.c
> index 2e7205b..b96d0cb 100644
> --- a/drivers/net/virtio/virtio_rxtx.c
> +++ b/drivers/net/virtio/virtio_rxtx.c
> @@ -331,7 +331,7 @@ virtio_dev_rxtx_start(struct rte_eth_dev *dev)
>  	 * -	Allocate blank mbufs for the each rx descriptor
>  	 *
>  	 */
> -	int i;
> +	int i, j;

However, I don't quite like using "i, j, k" stuff. So, how about
renaming "j" to "ring_idx"?

>  	PMD_INIT_FUNC_TRACE();
>  
> @@ -352,15 +352,18 @@ virtio_dev_rxtx_start(struct rte_eth_dev *dev)
>  		error = ENOSPC;
>  
>  #ifdef RTE_MACHINE_CPUFLAG_SSSE3
> -		if (use_simple_rxtx)
> -			for (i = 0; i < vq->vq_nentries; i++) {
> -				vq->vq_ring.avail->ring[i] = i;
> -				vq->vq_ring.desc[i].flags = VRING_DESC_F_WRITE;
> +		if (use_simple_rxtx) {
> +			uint16_t k;

We could reuse "ring_idx" here; no need to define yet another iterate var
for that.

	--yliu