netdev - [PATCH net v4 0/2] sfc: Restrict PIO for 64bit arch in order to avoid data corruption

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Message-ID: <538D9D1E.3090608@solarflare.com>
Date:	Tue, 3 Jun 2014 11:02:06 +0100
From:	Shradha Shah <sshah@...arflare.com>
To:	David Miller <davem@...emloft.net>
CC:	<netdev@...r.kernel.org>, <linux-net-drivers@...arflare.com>
Subject: [PATCH net v4 0/2] sfc: Restrict PIO for 64bit arch in order to avoid
 data corruption

This patch series 
Fixes: ee45fd92c739("sfc: Use TX PIO for sufficiently small packets")

The linux net driver uses memcpy_toio() in order to copy into
the PIO buffers.
Even on a 64bit machine this causes 32bit accesses to a write-
combined memory region.
There are hardware limitations that mean that only
64bit naturally aligned accesses are safe in all cases. Due to being
write-combined memory region two 32bit accesses may be coalesced to
form a 64bit non 64bit aligned access.
Solution was to open-code the memory copy routines using pointers
and to only enable PIO for x86_64 machines.

This bug fix applies to v3.13 and v3.14 stable branches.

Jon Cooper (2):
  sfc: use 64-bit writes for PIO.
  sfc: Restrict PIO to 64-bit architectures

 drivers/net/ethernet/sfc/io.h |  8 ++++++++
 drivers/net/ethernet/sfc/tx.c | 24 +++++++++++++++++++-----
 2 files changed, 27 insertions(+), 5 deletions(-)

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