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

[Laurent Vivier]

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".

Laurent