From: David Miller <davem@davemloft.net>
To: jeffrey.t.kirsher@intel.com
Cc: netdev@vger.kernel.org, gospo@redhat.com, miltonm@bga.com,
anton@samba.org, donald.c.skidmore@intel.com
Subject: Re: [net-next-2.6 PATCH] ixgbe: prevent speculative processing of descriptors before ready
Date: Mon, 22 Feb 2010 15:49:13 -0800 (PST) [thread overview]
Message-ID: <20100222.154913.144379311.davem@davemloft.net> (raw)
In-Reply-To: <20100220034419.31030.5083.stgit@localhost.localdomain>
From: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Date: Fri, 19 Feb 2010 19:44:42 -0800
> From: Milton Miller <miltonm@bga.com>
>
> The PowerPC architecture does not require loads to independent bytes to be
> ordered without adding an explicit barrier.
>
> In ixgbe_clean_rx_irq we load the status bit then load the packet data.
> With packet split disabled if these loads go out of order we get a
> stale packet, but we will notice the bad sequence numbers and drop it.
>
> The problem occurs with packet split enabled where the TCP/IP header and data
> are in different descriptors. If the reads go out of order we may have data
> that doesn't match the TCP/IP header. Since we use hardware checksumming this
> bad data is never verified and it makes it all the way to the application.
>
> This bug was found during stress testing and adding this barrier has been shown
> to fix it.
>
> Signed-off-by: Milton Miller <miltonm@bga.com>
> Signed-off-by: Anton Blanchard <anton@samba.org>
> Acked-by: Don Skidmore <donald.c.skidmore@intel.com>
> Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Applied.
prev parent reply other threads:[~2010-02-22 23:48 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-02-20 3:44 [net-next-2.6 PATCH] ixgbe: prevent speculative processing of descriptors before ready Jeff Kirsher
2010-02-22 23:49 ` David Miller [this message]
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