netdev - Re: [RFC] Kernel unaligned access at __skb_flow

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Message-ID: <1454092810.7627.53.camel@edumazet-glaptop2.roam.corp.google.com>
Date:	Fri, 29 Jan 2016 10:40:10 -0800
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Sowmini Varadhan <sowmini.varadhan@...cle.com>
Cc:	netdev@...r.kernel.org
Subject: Re: [RFC] Kernel unaligned access at __skb_flow_dissect

On Fri, 2016-01-29 at 10:33 -0800, Eric Dumazet wrote:

> 
> Why ipv6 stack itself does not trigger the issue ?
> 
> Maybe the driver itself does not properly align IP headers on sparc ?
> 
> Make sure NET_IP_ALIGN is 2 on your build.
> 
> Note that x86 does not care, but a driver should always align Ethernet
> header to NET_IP_ALIGN, so that IP headers are aligned to 4 bytes
> boundaries.
> 

I would try following ixgbe fix (sorry, totally untested, but you get
the idea...)

diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
index c4003a88bbf6..7ba64ed463a6 100644
--- a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
+++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
@@ -1525,7 +1525,7 @@ static bool ixgbe_alloc_mapped_page(struct ixgbe_ring *rx_ring,
 
 	bi->dma = dma;
 	bi->page = page;
-	bi->page_offset = 0;
+	bi->page_offset = NET_IP_ALIGN;
 
 	return true;
 }