Re: VT-d faults with Integrated Intel graphics on 4.6

[Andrew Cooper <andrew.cooper3@citrix.com>]

On 26/08/15 18:15, Konrad Rzeszutek Wilk wrote:
> On Wed, Aug 26, 2015 at 05:19:39PM +0100, Malcolm Crossley wrote:
>> On 25/08/15 15:43, Konrad Rzeszutek Wilk wrote:
>>> On Tue, Aug 25, 2015 at 02:55:31PM +0800, Chen, Tiejun wrote:
>>>> On 8/25/2015 8:19 AM, Tamas K Lengyel wrote:
>>>>> Hi everyone,
>>>>> I saw some people passingly mention this on the list before but just in
>>>>> case it has been missed, my serial is also being spammed with the following
>>>>> printouts with both Xen 4.6 RC1 and the latest staging build:
>>>>>
>>>>> ...
>>>>> (XEN) [VT-D]DMAR:[DMA Read] Request device [0000:00:02.0] fault addr
>>>>> 33487d7000, iommu reg = ffff82c000201000
>>>>> (XEN) [VT-D]DMAR: reason 06 - PTE Read access is not set
>>>>> (XEN) [VT-D]DMAR:[DMA Read] Request device [0000:00:02.0] fault addr
>>>>> 33487d7000, iommu reg = ffff82c000201000
>>>>> (XEN) [VT-D]DMAR: reason 06 - PTE Read access is not set
>>>>> (XEN) [VT-D]DMAR:[DMA Read] Request device [0000:00:02.0] fault addr
>>>>> 33487d7000, iommu reg = ffff82c000201000
>>>>> (XEN) [VT-D]DMAR: reason 06 - PTE Read access is not set
>>>>> (XEN) [VT-D]DMAR:[DMA Read] Request device [0000:00:02.0] fault addr
>>>>> 33487d7000, iommu reg = ffff82c000201000
>>>>> (XEN) [VT-D]DMAR: reason 06 - PTE Read access is not set
>>>>> (XEN) [VT-D]DMAR:[DMA Read] Request device [0000:00:02.0] fault addr
>>>>> 2610742000, iommu reg = ffff82c000201000
>>>>> (XEN) [VT-D]DMAR: reason 07 - Next page table ptr is invalid
>>>>> ...
>>>>>
>> I think this problem is caused by missing IOMMU mappings for the RMRR regions
>> if the domain does not have shared EPT enabled. This includes PV Dom 0.
>>
>> I have posted a patch to fix the issue:
>>
>> http://lists.xen.org/archives/html/xen-devel/2015-08/msg02090.html
> No dice. Still seeing the same problem :-(

Does your BIOS provide suitable extra RMRR regions when AMT is in use? 
IIRC, AMT uses the on-chip GPU as part of its VNC handling.

~Andrew