Re: [Qemu-devel] [PATCH] tests/postcopy: Use KVM on ppc64 only if it is KVM-HV

[Greg Kurz <groug@kaod.org>]

Hi Laurent,

On Thu, 17 Nov 2016 21:22:33 +0100
Laurent Vivier <lvivier@redhat.com> wrote:

> On 16/11/2016 15:17, Greg Kurz wrote:
> > On Wed, 16 Nov 2016 14:17:47 +0100
> > Thomas Huth <thuth@redhat.com> wrote:
> >   
> >> On 16.11.2016 13:37, Greg Kurz wrote:  
> >>> On Wed, 16 Nov 2016 12:24:50 +0000
> >>> "Dr. David Alan Gilbert" <dgilbert@redhat.com> wrote:
> >>>     
> >>>> * Greg Kurz (groug@kaod.org) wrote:    
> >>>>> On Wed, 16 Nov 2016 09:39:31 +0100
> >>>>> Thomas Huth <thuth@redhat.com> wrote:
> >>>>>       
> >>>>>> The ppc64 postcopy test does not work with KVM-PR, and it is also
> >>>>>> causing annoying warning messages when run on a x86 host. So let's
> >>>>>> use KVM here only if we know that we're running with KVM-HV (which
> >>>>>> automatically also means that we're running on a ppc64 host), and
> >>>>>> fall back to TCG otherwise.
> >>>>>>       
> [..]
> > The changes to the code look ok and I prefer to spend time chasing the
> > KVM PR issue rather than arguing on a comment...  
> 
> For the problem itself, it seems to appear only after a
> BOOK3S_INTERRUPT_SYSCALL interrupt for an KVM_EXIT_PAPR_HCALL
> (H_PUT_TERM_CHAR). In this case, KVM has to exit to QEMU to manage the
> output. The following interrupt is always an BOOK3S_INTERRUPT_PROGRAM
> with an emulation failure.
> 

Which specific problem are you referring to ? 

On my side, when running postcopy-test in a nested guest, I hit either one of the
three following issues (in decreasing order of probability of occurence):

1) "Memory content inconsistency at ..." like Stefan

2) "Unexpected 32 on dest_serial serial" accompanied by the following in dmesg

[131613.428616] Couldn't emulate instruction 0x00000000 (op 0 xop 0)
[131613.503515] kvmppc_handle_exit_pr: emulation at d8 failed (00000000)

3) hang because the destination QEMU is looping on:

ioctl(19, KVM_RUN, 0)       = 2 (RESUME_HOST)


Host runs OpenPower HostOS (kernel 4.9, QEMU 2.7) and guest runs fedora25.

Cheers.

--
Greg

> Laurent