linux-kernel - Re: Current git fails to boot with VT-D enabled due to flood of DMAR errors

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Date:	Sat, 19 Sep 2009 21:41:08 -0700
From:	David Woodhouse <dwmw2@...radead.org>
To:	Robert Hancock <hancockrwd@...il.com>
Cc:	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: Current git fails to boot with VT-D enabled due to flood of
 DMAR errors

On Sat, 2009-09-19 at 22:32 -0600, Robert Hancock wrote:
> On an Asus P7P55D Pro-based system (Lynnfield CPU), with Intel VT-d 
> enabled in the BIOS, on 2.6.30.5 (the previous version I tested) I get 
> these lines in dmesg:
> 
> DMAR:Host address width 36
> DMAR:DRHD (flags: 0x00000001)base: 0x00000000fed90000
> DMAR:RMRR base: 0x00000000000e4000 end: 0x00000000000e7fff
> DMAR:RMRR base: 0x00000000bf7ec000 end: 0x00000000bf7fffff
> Not all IO-APIC's listed under remapping hardware
> 
> In current -git, I get these lines as well, but then I get this:
> 
> DRHD: handling fault status reg ffffffff
> DMAR:[DMA Read] Request device [ff:1f.7] fault addr fffffffffffff000
> DMAR:[fault reason 255] Unknown
> 
> The last two lines repeat in a continuous flood and the system doesn't 
> boot. This happens even if I pass "intel_iommu=off" (which seems like 
> it's already the default).
> 
> Could be a kernel bug or a BIOS bug, but in the latter case we should 
> probably deal with it better. The registers all reading FF seems like 
> maybe the registers are disabled or something..

This ought to be 'fixed' in linux-next by this commit:
http://git.infradead.org/iommu-2.6.git/commitdiff/0815565ad

Please try linux-next or the iommu tree from
git://git.infradead.org/iommu-2.6.git

-- 
David Woodhouse                            Open Source Technology Centre
David.Woodhouse@...el.com                              Intel Corporation

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