amd-iommu: can't boot with amdgpu, AMD-Vi: Completion-Wait loop timed out

[Nath, Arindam]

>-----Original Message-----
>From: Deucher, Alexander
>Sent: Tuesday, March 14, 2017 1:31 AM
>To: 'Daniel Drake'; joro at 8bytes.org; Suthikulpanit, Suravee; Nath, Arindam
>Cc: Chris Chiu; iommu at lists.linux-foundation.org; Linux Upstreaming Team;
>amd-gfx at lists.freedesktop.org
>Subject: RE: amd-iommu: can't boot with amdgpu, AMD-Vi: Completion-Wait
>loop timed out
>
>> -----Original Message-----
>> From: amd-gfx [mailto:amd-gfx-bounces at lists.freedesktop.org] On Behalf
>> Of Daniel Drake
>> Sent: Monday, March 13, 2017 3:50 PM
>> To: joro at 8bytes.org
>> Cc: Chris Chiu; iommu at lists.linux-foundation.org; Linux Upstreaming Team;
>> amd-gfx at lists.freedesktop.org
>> Subject: amd-iommu: can't boot with amdgpu, AMD-Vi: Completion-Wait
>> loop timed out
>>
>> Hi,
>>
>> We are unable to boot Acer Aspire E5-553G (AMD FX-9800P RADEON R7) nor
>> Acer Aspire E5-523 with standard configurations because during boot
>> the screen is flooded with the following error message over and over:
>>
>>   AMD-Vi: Completion-Wait loop timed out
>>
>> We have left the system for quite a while but the message spam does
>> not stop and the system doesn't complete the boot sequence.
>>
>> We have reproduced on Linux 4.8 and Linux 4.10.
>>
>> To avoid this, we can boot with iommu=soft or just disable the amdgpu
>> display driver.
>>
>> Looks like this may also affect HP 15-ba012no :
>> https://bugzilla.redhat.com/show_bug.cgi?id=1409201
>>
>> Earlier during boot the iommu is detected as:
>>
>> [    1.274518] AMD-Vi: Found IOMMU at 0000:00:00.2 cap 0x40
>> [    1.274519] AMD-Vi: Extended features (0x37ef22294ada):
>> [    1.274519]  PPR NX GT IA GA PC GA_vAPIC
>> [    1.274523] AMD-Vi: Interrupt remapping enabled
>> [    1.274523] AMD-Vi: virtual APIC enabled
>> [    1.275144] AMD-Vi: Lazy IO/TLB flushing enabled
>> [    1.276498] perf: AMD NB counters detected
>> [    1.278096] LVT offset 0 assigned for vector 0x400
>> [    1.278963] perf: AMD IBS detected (0x000007ff)
>> [    1.278977] perf: amd_iommu: Detected. (0 banks, 0 counters/bank)
>>
>> Any suggestions for how we can fix this, or get more useful debug info?
>
>+Suravee and Arindam
>
>We ran into similar issues and bisected it to commit
>b1516a14657acf81a587e9a6e733a881625eee53.  I'm not too familiar with the
>IOMMU hardware to know if this is an iommu or display driver issue yet.

Like Alex mentioned, we have not yet been able to root cause the issue. But another way to work-around the issue without disabling graphics driver or IOMMU is to use amd_iommu=fullflush kernel boot param.

Thanks,
Arindam

>
>Alex
>
>>
>> Thanks
>> Daniel
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