Re: FreeBSD Dom0 IOMMU issues

["Roger Pau Monné" <royger@FreeBSD.org>]

El 07/05/15 a les 8.36, Jan Beulich ha escrit:
>>>> Michael Dexter <editor@callfortesting.org> 05/06/15 6:29 PM >>>
>> I have been working with Roger Pau Monné 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?

> The faults during guest startup may - as Yang also said - indicate a deeper problem,
> due to the addresses being clearly out of range. Since you don't seem to be passing
> through 0000:00:02.0 (the graphics card), it ought to be Dom0 that mis-programs
> something, but oddly enough only when a guest is being started. The fact that the
> majority of the fault instances show the same offending address seems to support
> this (or something getting corrupted in the process of creating the guest).

Michael can probably elaborate on this, but if I'm not mistaken he can
use X on the Dom0 without problems, but when he launches a guest all
those IOMMU faults start showing up. Then if the guest is created
without X running everything works as expected (Michael please correct
me if I'm wrong).

Roger.


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