linux-kernel - Re: DMAR:[fault reason 02] Present bit in context entry is clear (firewire-ohci)

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Date:	Sat, 22 May 2010 06:12:12 -0600
From:	Matthew Wilcox <matthew@....cx>
To:	Stefan Richter <stefanr@...6.in-berlin.de>
Cc:	linux-pci@...r.kernel.org, linux1394-devel@...ts.sourceforge.net,
	linux-kernel@...r.kernel.org, David Woodhouse <dwmw2@...radead.org>
Subject: Re: DMAR:[fault reason 02] Present bit in context entry is clear
	(firewire-ohci)

On Sat, May 22, 2010 at 12:26:15PM +0200, Stefan Richter wrote:
> Hi,
> 
> I came across a report of the subject message.  What does it mean; what
> type of bug should be look for?
> 
> https://bugzilla.redhat.com/show_bug.cgi?id=587178
> >>>
> firewire_ohci 0000:04:00.4: PCI INT C -> GSI 16 (level, low) -> IRQ 16
> firewire_ohci 0000:04:00.4: setting latency timer to 64
> firewire_ohci: Added fw-ohci device 0000:04:00.4, OHCI version 1.0
> DRHD: handling fault status reg 2
> DMAR:[DMA Read] Request device [04:00.0] fault addr fffff000
> DMAR:[fault reason 02] Present bit in context entry is clear
> DMAR:[DMA Read] Request device [04:00.0] fault addr fffff000
> DMAR:[fault reason 02] Present bit in context entry is clear
> DMAR:[DMA Read] Request device [04:00.0] fault addr fffff000
> DMAR:[fault reason 02] Present bit in context entry is clear
> <<<
> 
> The log sounds as if this happens during from-device DMA of 04:00.4 into
> a consistent buffer, yet the fault is logged for device 04:00.0.  The
> log is from a Dell M4500.  The devices are, according to a web search,
> 04:00.0 CardBus bridge [0607]: Ricoh Co Ltd Device [1180:e476] (rev 02)
> 04:00.4 FireWire (IEEE 1394) [0c00]: Ricoh Co Ltd Device [1180:e832]
> (rev 03) (prog-if 10)

I would guess that the DMAR can't distinguish between the different
devices behind the Cardbus bridge.  Adding Dave Woodhouse.

-- 
Matthew Wilcox				Intel Open Source Technology Centre
"Bill, look, we understand that you're interested in selling us this
operating system, but compare it to ours.  We can't possibly take such
a retrograde step."
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