netdev - Re: [PATCH v3 1/2] net: macb: Check DMA mappings for error

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Date:	Wed, 05 Mar 2014 23:25:17 +0000
From:	Ben Hutchings <ben@...adent.org.uk>
To:	Soren Brinkmann <soren.brinkmann@...inx.com>
Cc:	Nicolas Ferre <nicolas.ferre@...el.com>, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, Vinod Koul <vinod.koul@...el.com>,
	Dan Williams <dan.j.williams@...el.com>,
	"David S. Miller" <davem@...emloft.net>,
	Michal Simek <michal.simek@...inx.com>
Subject: Re: [PATCH v3 1/2] net: macb: Check DMA mappings for error

On Tue, 2014-03-04 at 08:46 -0800, Soren Brinkmann wrote:
> With CONFIG_DMA_API_DEBUG enabled the following warning is printed:
>  WARNING: CPU: 0 PID: 619 at lib/dma-debug.c:1101 check_unmap+0x758/0x894()
>  macb e000b000.ethernet: DMA-API: device driver failed to check map error[device address=0x000000002d171c02] [size=322 bytes] [mapped as single]
>  Modules linked in:
>  CPU: 0 PID: 619 Comm: udhcpc Not tainted 3.14.0-rc3-xilinx-00219-gd158fc7f36a2 #63
>  [<c001516c>] (unwind_backtrace) from [<c0011df8>] (show_stack+0x10/0x14)
>  [<c0011df8>] (show_stack) from [<c03c7714>] (dump_stack+0x7c/0xc8)
>  [<c03c7714>] (dump_stack) from [<c00245cc>] (warn_slowpath_common+0x60/0x84)
>  [<c00245cc>] (warn_slowpath_common) from [<c0024670>] (warn_slowpath_fmt+0x2c/0x3c)
>  [<c0024670>] (warn_slowpath_fmt) from [<c0228244>] (check_unmap+0x758/0x894)
>  [<c0228244>] (check_unmap) from [<c0228588>] (debug_dma_unmap_page+0x64/0x70)
>  [<c0228588>] (debug_dma_unmap_page) from [<c02aba64>] (macb_interrupt+0x1f8/0x2dc)
>  [<c02aba64>] (macb_interrupt) from [<c006c6e4>] (handle_irq_event_percpu+0x2c/0x178)
>  [<c006c6e4>] (handle_irq_event_percpu) from [<c006c86c>] (handle_irq_event+0x3c/0x5c)
>  [<c006c86c>] (handle_irq_event) from [<c006f548>] (handle_fasteoi_irq+0xb8/0x100)
>  [<c006f548>] (handle_fasteoi_irq) from [<c006c148>] (generic_handle_irq+0x20/0x30)
>  [<c006c148>] (generic_handle_irq) from [<c000f35c>] (handle_IRQ+0x64/0x8c)
>  [<c000f35c>] (handle_IRQ) from [<c0008528>] (gic_handle_irq+0x3c/0x60)
>  [<c0008528>] (gic_handle_irq) from [<c0012904>] (__irq_svc+0x44/0x78)
>  Exception stack(0xed197f60 to 0xed197fa8)
>  7f60: 00000134 60000013 bd94362e bd94362e be96b37c 00000014 fffffd72 00000122
>  7f80: c000ebe4 ed196000 00000000 00000011 c032c0d8 ed197fa8 c0064008 c000ea20
>  7fa0: 60000013 ffffffff
>  [<c0012904>] (__irq_svc) from [<c000ea20>] (ret_fast_syscall+0x0/0x48)
>  ---[ end trace 478f921d0d542d1e ]---
>  Mapped at:
>   [<c0227184>] debug_dma_map_page+0x48/0x11c
>   [<c02aaca0>] macb_start_xmit+0x184/0x2a8
>   [<c03143c0>] dev_hard_start_xmit+0x334/0x470
>   [<c032c09c>] sch_direct_xmit+0x78/0x2f8
>   [<c0314814>] __dev_queue_xmit+0x318/0x708
> 
> due to missing checks of the dma mapping. Add the appropriate checks to fix
> this.
> 
> Signed-off-by: Soren Brinkmann <soren.brinkmann@...inx.com>

Reviewed-by: Ben Hutchings <ben@...adent.org.uk>

> ---
> v3:
>  - move tx_head pointer increment to after the DMA error check
> v2:
>  - unlock spinlock when mapping error is detected in start_xmit()
>  - use kfree_skb() instead of dev_kfree_skb in start_xmit()
> ---
>  drivers/net/ethernet/cadence/macb.c | 14 ++++++++++++--
>  1 file changed, 12 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/ethernet/cadence/macb.c b/drivers/net/ethernet/cadence/macb.c
> index 3190d38e16fb..1f03e2041e86 100644
> --- a/drivers/net/ethernet/cadence/macb.c
> +++ b/drivers/net/ethernet/cadence/macb.c
> @@ -632,11 +632,16 @@ static void gem_rx_refill(struct macb *bp)
>  					   "Unable to allocate sk_buff\n");
>  				break;
>  			}
> -			bp->rx_skbuff[entry] = skb;
>  
>  			/* now fill corresponding descriptor entry */
>  			paddr = dma_map_single(&bp->pdev->dev, skb->data,
>  					       bp->rx_buffer_size, DMA_FROM_DEVICE);
> +			if (dma_mapping_error(&bp->pdev->dev, paddr)) {
> +				dev_kfree_skb(skb);
> +				break;
> +			}
> +
> +			bp->rx_skbuff[entry] = skb;
>  
>  			if (entry == RX_RING_SIZE - 1)
>  				paddr |= MACB_BIT(RX_WRAP);
> @@ -1036,11 +1041,15 @@ static int macb_start_xmit(struct sk_buff *skb, struct net_device *dev)
>  	}
>  
>  	entry = macb_tx_ring_wrap(bp->tx_head);
> -	bp->tx_head++;
>  	netdev_vdbg(bp->dev, "Allocated ring entry %u\n", entry);
>  	mapping = dma_map_single(&bp->pdev->dev, skb->data,
>  				 len, DMA_TO_DEVICE);
> +	if (dma_mapping_error(&bp->pdev->dev, mapping)) {
> +		kfree_skb(skb);
> +		goto unlock;
> +	}
>  
> +	bp->tx_head++;
>  	tx_skb = &bp->tx_skb[entry];
>  	tx_skb->skb = skb;
>  	tx_skb->mapping = mapping;
> @@ -1066,6 +1075,7 @@ static int macb_start_xmit(struct sk_buff *skb, struct net_device *dev)
>  	if (CIRC_SPACE(bp->tx_head, bp->tx_tail, TX_RING_SIZE) < 1)
>  		netif_stop_queue(dev);
>  
> +unlock:
>  	spin_unlock_irqrestore(&bp->lock, flags);
>  
>  	return NETDEV_TX_OK;

-- 
Ben Hutchings
For every complex problem
there is a solution that is simple, neat, and wrong.

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