netdev - Re: tg3: not checking dma errors?

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Date:	Wed, 2 Dec 2009 09:13:59 -0800
From:	"Matt Carlson" <mcarlson@...adcom.com>
To:	"Johannes Berg" <johannes@...solutions.net>
cc:	netdev <netdev@...r.kernel.org>,
	"Matthew Carlson" <mcarlson@...adcom.com>,
	"Michael Chan" <mchan@...adcom.com>
Subject: Re: tg3: not checking dma errors?

On Wed, Dec 02, 2009 at 06:01:06AM -0800, Johannes Berg wrote:
> I'm having some trouble with tg3 under memory pressure when it's
> receiving lots of data, and so far this is the only thing I could find
> -- unfortunately I can't capture the debug information on the machine --
> netconsole obviously doesn't work, there's no serial and the output
> doesn't fit on the screen...
> 
> So I figured I'd look at the code, and now I think there could be a bug
> with mappings:
> 
> tg3_alloc_rx_skb:
> ...
>         mapping = pci_map_single(tp->pdev, skb->data, skb_size,
>                                  PCI_DMA_FROMDEVICE);
> 
>         map->skb = skb;
>         pci_unmap_addr_set(map, mapping, mapping);
> 
>         if (src_map != NULL)
>                 src_map->skb = NULL;
> 
>         desc->addr_hi = ((u64)mapping >> 32);
>         desc->addr_lo = ((u64)mapping & 0xffffffff);
> 
>         return skb_size;
> 
> 
> 
> Shouldn't that check that 'mapping' is != DMA_ERROR_CODE?
> 
> Similarly in tg3_run_loopback()?
> 
> johannes

Yes.  I submitted a patch to the net-next-2.6 tree addressing this exact
problem.  It will appear in the 2.6.33 kernel.  The patch is appended at
the bottom of this email.

What kind of trouble are you seeing?  What device are you working with?

=====

Subject: [PATCH 06/20] tg3: Add more PCI DMA map error checking

This patch adds code to check the status of pci_map_single() before
allowing rx buffers to be used.  It also converts the pci_map_single()
call in tg3_run_loopback() to use skb_dma_map() instead.

Signed-off-by: Matt Carlson <mcarlson@...adcom.com>
Signed-off-by: Michael Chan <mchan@...adcom.com>
Signed-off-by: Benjamin Li <benli@...adcom.com>
---
 drivers/net/tg3.c |   14 +++++++++++---
 1 files changed, 11 insertions(+), 3 deletions(-)

diff --git a/drivers/net/tg3.c b/drivers/net/tg3.c
index 53a193e..54dbe98 100644
--- a/drivers/net/tg3.c
+++ b/drivers/net/tg3.c
@@ -4426,6 +4426,10 @@ static int tg3_alloc_rx_skb(struct tg3_napi *tnapi, u32 opaque_key,
 
 	mapping = pci_map_single(tp->pdev, skb->data, skb_size,
 				 PCI_DMA_FROMDEVICE);
+	if (pci_dma_mapping_error(tp->pdev, mapping)) {
+		dev_kfree_skb(skb);
+		return -EIO;
+	}
 
 	map->skb = skb;
 	pci_unmap_addr_set(map, mapping, mapping);
@@ -10369,7 +10373,10 @@ static int tg3_run_loopback(struct tg3 *tp, int loopback_mode)
 	for (i = 14; i < tx_len; i++)
 		tx_data[i] = (u8) (i & 0xff);
 
-	map = pci_map_single(tp->pdev, skb->data, tx_len, PCI_DMA_TODEVICE);
+	if (skb_dma_map(&tp->pdev->dev, skb, DMA_TO_DEVICE)) {
+		dev_kfree_skb(skb);
+		return -EIO;
+	}
 
 	tw32_f(HOSTCC_MODE, tp->coalesce_mode | HOSTCC_MODE_ENABLE |
 	       rnapi->coal_now);
@@ -10380,7 +10387,8 @@ static int tg3_run_loopback(struct tg3 *tp, int loopback_mode)
 
 	num_pkts = 0;
 
-	tg3_set_txd(tnapi, tnapi->tx_prod, map, tx_len, 0, 1);
+	tg3_set_txd(tnapi, tnapi->tx_prod,
+		    skb_shinfo(skb)->dma_head, tx_len, 0, 1);
 
 	tnapi->tx_prod++;
 	num_pkts++;
@@ -10404,7 +10412,7 @@ static int tg3_run_loopback(struct tg3 *tp, int loopback_mode)
 			break;
 	}
 
-	pci_unmap_single(tp->pdev, map, tx_len, PCI_DMA_TODEVICE);
+	skb_dma_unmap(&tp->pdev->dev, skb, DMA_TO_DEVICE);
 	dev_kfree_skb(skb);
 
 	if (tx_idx != tnapi->tx_prod)
-- 
1.6.4.4



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