RE: [net] e1000: Small packets may get corrupted during padding by HW

-----Original Message-----
From: Michał Mirosław [mailto:mirqus@gmail.com]
Sent: Saturday, September 15, 2012 1:45 PM
To: Kirsher, Jeffrey T
Cc: davem@davemloft.net; Dave, Tushar N; netdev@vger.kernel.org;
gospo@redhat.com; sassmann@redhat.com
Subject: Re: [net] e1000: Small packets may get corrupted during padding
by HW

2012/9/15 Jeff Kirsher [off-list ref]:

quoted

From: Tushar Dave <redacted>

On PCI/PCI-X HW, if packet size is less than ETH_ZLEN, packets may get
corrupted during padding by HW.
To WA this issue, pad all small packets manually.

Signed-off-by: Tushar Dave <redacted>
Tested-by: Aaron Brown <redacted>
Signed-off-by: Jeff Kirsher <redacted>
---
 drivers/net/ethernet/intel/e1000/e1000_main.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/drivers/net/ethernet/intel/e1000/e1000_main.c

b/drivers/net/ethernet/intel/e1000/e1000_main.c
index 3bfbb8d..bde337e 100644

--- a/drivers/net/ethernet/intel/e1000/e1000_main.c
+++ b/drivers/net/ethernet/intel/e1000/e1000_main.c

@@ -3149,6 +3149,17 @@ static netdev_tx_t e1000_xmit_frame(struct

sk_buff *skb,

quoted

                return NETDEV_TX_OK;
        }

+       /* On PCI/PCI-X HW, if packet size is less than ETH_ZLEN,
+        * packets may get corrupted during padding by HW.
+        * To WA this issue, pad all small packets manually.
+        */
+       if (skb->len < ETH_ZLEN) {
+               if (skb_pad(skb, ETH_ZLEN - skb->len))
+                       return NETDEV_TX_OK;
+               skb->len = ETH_ZLEN;
+               skb_set_tail_pointer(skb, ETH_ZLEN);
+       }
+

Isn't there a skb_padto() that does just this?

Skb_padto calls skb_pad(). Calling skb_pad directly saves some cycles.