Subject: Re: bad DMAR interaction with iwlagn and SATA
From: Johannes Berg <johannes@sipsolutions.net>
To: Muli Ben-Yehuda <muli@il.ibm.com>
Cc: Jeff Garzik <jeff@garzik.org>, Andres Freund <andres@anarazel.de>,
	linux-kernel@vger.kernel.org,
	linux-wireless <linux-wireless@vger.kernel.org>,
	Tomas Winkler <tomasw@gmail.com>
In-Reply-To: <20080926144708.GD9118@il.ibm.com>
References: <200809251511.20132.andres@anarazel.de>
	 <48DC44D4.8000103@garzik.org> <200809260419.07713.andres@anarazel.de>
	 <48DC4BC0.7090203@garzik.org>  <20080926144708.GD9118@il.ibm.com>
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Date: Fri, 26 Sep 2008 17:12:35 +0200
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On Fri, 2008-09-26 at 17:47 +0300, Muli Ben-Yehuda wrote:

> The way to debug this is to figure out why device 00:1f.2 is trying to
> read from DMA address fffbf000 and does not have permission to do
> so. This could be indicative of a driver bug where it is programming
> the device to read from some buffer that has not been allocated
> through the DMA API and thus does not have a valid IOMMU mapping, or a
> hardware quirk where the device tries to read from memory without host
> involvement. The former is much more likely.

The same is probably true for the iwlagn case which was

> [ 4184.617392] DMAR:[DMA Read] Request device [03:00.0] fault addr fa9460=
00=20
> [ 4184.617393] DMAR:[fault reason 06] PTE Read access is not set
> [ 4184.644081] iwlagn: Microcode HW error detected.  Restarting.

and indeed matches experience from myself and Marcel that DMA bugs seem
to lurk.

johannes

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