Re: [Xen-devel] FreeBSD Dom0 IOMMU issues

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 07.05.15 at 09:27, <royger@xxxxxxxxxxx> wrote:
> El 07/05/15 a les 8.36, Jan Beulich ha escrit:
>>>>> Michael Dexter <editor@xxxxxxxxxxxxxxxxxx> 05/06/15 6:29 PM >>>
>>> I have been working with Roger Pau Monnà to bring FreeBSD Dom0 support 
>>> to a production-ready state but we appear to have hit an IOMMU issue.
>>>
>>> Hardware: Lenovo ThinkPad T420 i7-2640M CPU @ 2.80GHz with 16GB RAM.
>>>
>>> I am attaching my console logs which first show my loader.conf file the 
>>> DomU .cfg file and then DomU boot with Xorg starting.
>>>
>>> In the end I get:
>>>
>>> (XEN) ****************************************
>>> (XEN) Panic on CPU 2:
>>> (XEN) queue invalidate wait descriptor was not executed
>>> (XEN) ****************************************
>> 
>> In the end this may be a secondary issue. Namely looking at the more 
> complete
>> log in your resent mail we see a DMA fault before even starting Dom0. 
> Interestingly
>> 
>> (XEN) [VT-D]dmar.c:807: found ACPI_DMAR_RMRR:
>> (XEN) [VT-D]dmar.c:383:  endpoint: 0000:00:1d.0
>> (XEN) [VT-D]dmar.c:383:  endpoint: 0000:00:1a.0
>> (XEN) [VT-D]dmar.c:676:   RMRR region: base_addr dacd5000 end_address 
> dacebfff
>> (XEN) [VT-D]dmar.c:807: found ACPI_DMAR_RMRR:
>> (XEN) [VT-D]dmar.c:383:  endpoint: 0000:00:02.0
>> (XEN) [VT-D]dmar.c:676:   RMRR region: base_addr db800000 end_address 
> df9fffff
>> ...
>> (XEN) [VT-D]iommu.c:859: iommu_fault_status: Fault Overflow
>> (XEN) [VT-D]iommu.c:861: iommu_fault_status: Primary Pending Fault
>> (XEN) [VT-D]iommu.c:839: DMAR:[DMA Read] Request device [0000:00:1a.0] fault 
> addr dae22000, iommu reg = ffff82c000203000
>> 
>> i.e. the fault address is pretty close the RMRRs, which suggests an issue 
> currently
>> being the subject of an in progress patch series by Elena (firmware failing 
> to specify
>> all exclusion regions via RMRRs).
> 
> I've also seen this faults before Dom0 is started, but at least in my
> case they seem to be benign. I think this is what
> 
> http://lists.xenproject.org/archives/html/xen-devel/2015-05/msg00117.html 
> 
> tries to fix?

Not sure - that depends on whether the fault gets raised already
before enabling the IOMMU (i.e. left in the fault log by the firmware),
or only afterwards (i.e. a device still accessing that memory). In
the former case it would be the series you refer to that aims at
addressing this. In the latter case you'd need - as said - Elena's
workaround.

Jan

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