Re: [Qemu-devel] [PATCH for-3.1] tests/cpu-plug-test: check CPU hotplug on ppc64 with KVM

[David Gibson]

On Fri, Jul 27, 2018 at 09:54:52AM +0200, Greg Kurz wrote:
> On Fri, 27 Jul 2018 15:27:24 +1000
> David Gibson <address@hidden> wrote:
> 
> > On Wed, Jul 25, 2018 at 04:45:26PM +0200, Greg Kurz wrote:
> > > Commit b585395b655 fixed a regression introduced by some recent changes
> > > in the XICS code, that was causing QEMU to crash instantly during CPU
> > > hotplug with KVM. This is typically the kind of bug we'd like our
> > > test suite to detect before it gets merged. Unfortunately, the current
> > > tests run with '-machine accel=qtest' and don't exercise KVM specific
> > > paths in QEMU.
> > > 
> > > This patch hence changes add_pseries_test_case() to launch QEMU with
> > > '-machine accel=kvm' if KVM is available.
> > > 
> > > A notable consequence is that the guest will execute SLOF, but for some
> > > reasons SLOF sometimes hits a program exception. This causes the guest
> > > to loop forever and the test to be stuck.  Since we don't need the guest
> > > to be truely running, let's pass -S to QEMU to avoid that.
> > > 
> > > Also disable machine capabilities that could be unavailable in KVM, eg,
> > > when using PR KVM.
> > > 
> > > Signed-off-by: Greg Kurz <address@hidden>  
> > 
> > I'm pretty sure trying to change the accelerator on a qtest test just
> > doesn't make sense.  We'd need a different approach for testing cpu
> > hotplug against kvm & tcg backends.
> > 
> 
> The test starts QEMU, triggers the CPU hotplug code with a QMP command
> and checks the command didn't fail (or QEMU didn't crash, as it would
> have before commit b585395b655a)... I really don't understand what
> is wrong with that... Please elaborate.

Well, ok, let me turn that around.  A test that doesn't rely on
controlling the guest side behaviour at all probably shouldn't be a
qtest based test, since that's what qtest is all about.

-- 
David Gibson                    | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au  | minimalist, thank you.  NOT _the_ _other_
                                | _way_ _around_!
http://www.ozlabs.org/~dgibson

signature.asc
Description: PGP signature