Re: [Qemu-devel] QEMU postcopy-test failing on ppc64

[Laurent Vivier]

On 15/11/2016 16:08, Dr. David Alan Gilbert wrote:
> * Laurent Vivier (address@hidden) wrote:
>>
>>
>> On 15/11/2016 16:03, Greg Kurz wrote:
>>> On Tue, 15 Nov 2016 14:48:30 +0000
>>> Stefan Hajnoczi <address@hidden> wrote:
>>>
>>>> On Tue, Nov 15, 2016 at 01:58:38PM +0100, Laurent Vivier wrote:
>>>>>
>>>>>
>>>>> On 15/11/2016 13:20, Dr. David Alan Gilbert wrote:  
>>>>>> * Stefan Hajnoczi (address@hidden) wrote:  
>>>>>>> On Tue, Nov 15, 2016 at 10:09 AM, Greg Kurz <address@hidden> wrote:  
>>>>>>>> On Tue, 15 Nov 2016 10:53:35 +0100
>>>>>>>> Laurent Vivier <address@hidden> wrote:
>>>>>>>>  
>>>>>>>>> On 14/11/2016 21:52, Stefan Hajnoczi wrote:  
>>>>>>>>>> I hit a failure running "make check" on ppc64 for the first time.  
>>>>>>>>>> Ideas?
>>>>>>>>>>
>>>>>>>>>> Stefan
>>>>>>>>>>
>>>>>>>>>> commit 682df581c65ed2c1b9e77093e332214ecaa1ee93
>>>>>>>>>>
>>>>>>>>>>   GTESTER check-qtest-ppc64
>>>>>>>>>> Memory content inconsistency at 5af4000 first_byte = 1b last_byte = 
>>>>>>>>>> 1a
>>>>>>>>>> current = 7c hit_edge = 1
>>>>>>>>>> Memory content inconsistency at 5af5000 first_byte = 1b last_byte = 
>>>>>>>>>> 7c
>>>>>>>>>> current = 1b hit_edge = 1
>>>>>>>>>> Memory content inconsistency at 5e59000 first_byte = 1b last_byte = 
>>>>>>>>>> 1b
>>>>>>>>>> current = 1a hit_edge = 1
>>>>>>>>>> **
>>>>>>>>>> ERROR:tests/postcopy-test.c:345:check_guests_ram: 'bad' should be 
>>>>>>>>>> FALSE
>>>>>>>>>> GTester: last random seed: R02S9d79166a1ca7e21940a0f4b0b1255d5b
>>>>>>>>>>  
>>>>>>>>>
>>>>>>>>> Are you using KVM PR?
>>>>>>>>>
>>>>>>>>> it  was working fine with TCG and KVM HV.
>>>>>>>>>
>>>>>>>>> Apparently, USERFAULTFD doesn't work with KVM PR.
>>>>>>>>>
>>>>>>>>> I've already seen this kind of error with nested KVM on Power:
>>>>>>>>> guest in guest with KVM PR in host.
>>>>>>>>>
>>>>>>>>> This problem was reported on IRC by Greg if I remember correctly (CC:)
>>>>>>>>>  
>>>>>>>>
>>>>>>>> Yeah I hit this when running make check in a PPC64 BE guest which
>>>>>>>> has kvm_pr loaded. I did not find time to investigate though... I've
>>>>>>>> switched to run make check on bare metal POWER7 instead.  
>>>>>>>
>>>>>>> Right, it's POWER7 PPC64 BE with kvm_pr.
>>>>>>>
>>>>>>> If this should be fixed for QEMU 2.8 please add it to
>>>>>>> http://qemu-project.org/Planning/2.8 and I'll track it (i.e. won't
>>>>>>> release before it's resolved).
>>>>>>>
>>>>>>> If this is a known issue that will be in QEMU 2.8 please add it to
>>>>>>> http://qemu-project.org/ChangeLog/2.8#Known_issues.  
>>>>>>
>>>>>> I don't think it's new with 2.8 (Laurent?) and I think it's actually
>>>>>> a kernel issue that needs fixing.  
>>>>>
>>>>> I's not a regression and I think it's a kernel issue.
>>>>>
>>>>> As it has never worked with KVM PR and can't be fixed at QEMU level, we
>>>>> can't solve it for 2.8 (no tracking).
>>>>>
>>>>> I'm going to update the know issues for 2.8.
>>>>> [and I'm going to try to understand what really happens]  
>>>>
>>>> Should the test be skipped on KVM PR?
>>>>
>>>> It's a shame that make check fails.
>>>>
>>>
>>> Yeah I agree this is lame but KVM PR isn't very cherished these days...
>>>
>>> Since postcopy-test runs QEMU with -accel kvm:tcg, a possible workaround is
>>> to kick KVM out of the environment you're running make check in.
>>
>> Moreover, using "-accel kvm:tcg" induces an error when the test is
>> running in cross-arch case (ppc on intel, or intel on ppc).
>>
>> But I think postcopy is typically something we should test with KVM, not
>> TCG, as there are some kernel dependencies (USERFAULTFD).
>>
>> It has been suggested a while to use an environment variable, like for
>> kvm-unit-tests, something like QTEST_ACCEL="kvm".
> 
> Can we detect kvm_pr at runtime in the test and just make it skip?

There was a discussion on the subject: tests must be run in a predictive
way, so always with the same parametes and conditions.
[I think it was said by danpb or Drew +CC]

Laurent