Subject: Re: [PATCH 08/12] net: ll_temac: Fix iommu/swiotlb leak

From: Andrew Lunn <[email-masked]>
Date: Fri, 26 Apr 2019 16:21:03 +0200

On Fri, Apr 26, 2019 at 09:32:27AM +0200, Esben Haabendal wrote:
> Unmap the actual buffer length, not the amount of data received.

Hi Esben

The patch Subject does not seem to match the content?

Also, there can be performance advantages of just unmapping the
received length. The unmap operation does a cache invalidate, which
can be expensive. Consider the effort of unmapping a 64 byte ACK vs 9K
jumbo frame?

      Andrew
 
> Signed-off-by: Esben Haabendal <[email-masked]>
> ---
>  drivers/net/ethernet/xilinx/ll_temac_main.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/net/ethernet/xilinx/ll_temac_main.c b/drivers/net/ethernet/xilinx/ll_temac_main.c
> index 309f149..56d8077 100644
> --- a/drivers/net/ethernet/xilinx/ll_temac_main.c
> +++ b/drivers/net/ethernet/xilinx/ll_temac_main.c
> @@ -821,7 +821,7 @@ static void ll_temac_recv(struct net_device *ndev)
>  		length = be32_to_cpu(cur_p->app4) & 0x3FFF;
>  
>  		dma_unmap_single(ndev->dev.parent, be32_to_cpu(cur_p->phys),
> -				 length, DMA_FROM_DEVICE);
> +				 XTE_MAX_JUMBO_FRAME_SIZE, DMA_FROM_DEVICE);
>  
>  		skb_put(skb, length);
>  		skb->protocol = eth_type_trans(skb, ndev);
> -- 
> 2.4.11
>