Subject: Re: DMAR regression in 2.6.31 leads to ext4 corruption?
From: David Woodhouse <dwmw2@infradead.org>
To: Andy Isaacson <adi@hexapodia.org>
Cc: Chris Wright <chrisw@sous-sol.org>, iommu@lists.linux-foundation.org,
       linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org
In-Reply-To: <20091010014714.GG30557@hexapodia.org>
References: <20091009061729.GA31242@hexapodia.org>
	 <20091010000926.GA17547@sequoia.sous-sol.org>
	 <20091010014714.GG30557@hexapodia.org>
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Date: Wed, 14 Oct 2009 13:09:26 +0100
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On Fri, 2009-10-09 at 18:47 -0700, Andy Isaacson wrote:
> Well, we don't know for sure what happened on the previous boot where
> the filesystem corruption occurred.  I'm imagining a nightmare scenario
> where GPU erroneous writes cause DMAR faults and handling them somehow
> causes AHCI DMA requests to get lost.

Seems unlikely. The GPU faults happen whenever the GATT changes, because
it translates _every_ address in the GATT through the IOMMU right there
and then -- so if parts of the table are uninitialised, they'll cause
stray write faults. But no writes are actually _happening_.

> I'm going to go ahead on the theory that the BIOS needs an update.

I can't really imagine how that would help; how the BIOS would be
responsible for this. I'm more inclined to blame the drive. It's not an
SSD, is it?

-- 
dwmw2

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