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

[Greg Kurz <groug@kaod.org>]

On Tue, 15 Nov 2016 16:07:40 +0100
Laurent Vivier <lvivier@redhat.com> wrote:

> On 15/11/2016 16:03, Greg Kurz wrote:
> > On Tue, 15 Nov 2016 14:48:30 +0000
> > Stefan Hajnoczi <stefanha@gmail.com> 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 (stefanha@gmail.com) wrote:    
> >>>>> On Tue, Nov 15, 2016 at 10:09 AM, Greg Kurz <groug@kaod.org> wrote:    
> >>>>>> On Tue, 15 Nov 2016 10:53:35 +0100
> >>>>>> Laurent Vivier <lvivier@redhat.com> 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).
> 

You're talking about the '"kvm" accelerator not found' error ?

> But I think postcopy is typically something we should test with KVM, not
> TCG, as there are some kernel dependencies (USERFAULTFD).
> 

I agree it should be tested with KVM when applicable but I don't understand
the 'not TCG' since it is the only way to test when you don't have access
to specific hardware...

> It has been suggested a while to use an environment variable, like for
> kvm-unit-tests, something like QTEST_ACCEL="kvm".
> 

Yeah, I think it would be better than "-accel kvm:tcg"

> Laurent

Cheers.

--
Greg