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

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Message-ID: <4AB5B395.80400@gmail.com>
Date:	Sat, 19 Sep 2009 22:46:13 -0600
From:	Robert Hancock <hancockrwd@...il.com>
To:	David Woodhouse <dwmw2@...radead.org>
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 09/19/2009 10:41 PM, David Woodhouse wrote:
> 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

Yeah, I just came across that patch. Is that going to get pushed for 
2.6.32? It seems like something caused us to start tripping over this by 
default when we didn't before. (Passing intel_iommu=on with 2.6.30.5 
does cause the same problem.)

I'll try and report the problem to Asus, obviously something's borked 
with VT-d in their BIOS currently..
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