Re: [Qemu-devel] test-filter-mirror hangs

["Dr. David Alan Gilbert" <dgilbert@redhat.com>]

* Peter Maydell (peter.maydell@linaro.org) wrote:
> On Thu, 17 Jan 2019 at 09:46, Jason Wang <jasowang@redhat.com> wrote:
> >
> >
> > On 2019/1/15 上午12:33, Zhang Chen wrote:
> > >
> > >
> > > On Sat, Jan 12, 2019 at 12:15 AM Dr. David Alan Gilbert
> > > <dgilbert@redhat.com <mailto:dgilbert@redhat.com>> wrote:
> > >
> > >     * Peter Maydell (peter.maydell@linaro.org
> > >     <mailto:peter.maydell@linaro.org>) wrote:
> > >     > Recently I've noticed that test-filter-mirror has been hanging
> > >     > intermittently, typically when run on some other TCG architecture.
> > >     > In the instance I've just looked at, this was with s390x guest on
> > >     > x86-64 host, though I've also seen it on other host archs and
> > >     > perhaps with other guests.
> > >
> > >     Watch out to see if you really do see it for other guests;
> > >     it carefully avoids using virtio-net to avoid vhost; but on s390x it
> > >     uses virtio-net-ccw - could that hit the vhost it was trying to avoid?
> > >
> > >     > Below is a backtrace, though it seems to be pretty unhelpful.
> > >     > Anybody got any theories ? Does the mirror test rely on dirty
> > >     > memory bitmaps like the migration test (which also hangs
> > >     > occasionally with TCG due to some bug I'm sure we've investigated
> > >     > in the past) ?
> > >
> > >     I don't think it relies on the CPU at all.
> 
> > >  I have no idea about this currently, but Jason and I designed the
> > > test case.
> > > Add Jason: Have any comments about this ?
> >
> >
> > I can't reproduce this locally with s390x-softmmu. It looks to me the
> > test should be independent to any kinds of emulation. It should pass
> > when mainloop work.
> 
> I've just seen a hang with ppc64 guest on s390x host, so it is
> indeed not specific to s390x guest (and so not specific to
> virtio-net either, since the ppc64 guest setup uses e1000).

Hmph, there goes that idea.

I guess we need some tracing of the packet flow;  do you build with
tracing on and can we enable it for a test?

Dave

> thanks
> -- PMM
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK