From: Thomas Huth <email@example.com> To: Greg Kurz <firstname.lastname@example.org> Cc: "Cédric Le Goater" <email@example.com>, firstname.lastname@example.org, "David Gibson" <email@example.com> Subject: Re: [Qemu-devel] [PATCH for-3.1] tests/cpu-plug-test: check CPU hotplug on ppc64 with KVM Date: Fri, 27 Jul 2018 13:25:33 +0200 [thread overview] Message-ID: <firstname.lastname@example.org> (raw) In-Reply-To: <20180727110000.16f55218@bahia> On 07/27/2018 11:00 AM, Greg Kurz wrote: > On Fri, 27 Jul 2018 10:18:14 +0200 > Thomas Huth <email@example.com> wrote: > >> On 07/27/2018 09:54 AM, Greg Kurz wrote: >>> On Fri, 27 Jul 2018 15:27:24 +1000 >>> David Gibson <firstname.lastname@example.org> 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 <email@example.com> >>>> >>>> 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. >> >> For a "real" test, I think you'd need a guest OS that is reacting to the >> hot plug events. So maybe this should rather be done in the avocado >> framework instead? >> > > The intent isn't a "real" test actually, but just to exercise the XICS-KVM > paths in QEMU that get called during CPU hotplug. This cannot be achieved > with the qtest accelerator. > > This patch would have revealed the regression in b585395b655a right away, > with the simple 'make check' developers are expected to run before posting. OK, that's fair. I think what rather bugs me here is that you start QEMU with -S to work around something that sounds like real bug in SLOF ... any chance that you could fix that bug in SLOF instead of using -S here? Thomas
next prev parent reply other threads:[~2018-07-27 11:25 UTC|newest] Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top 2018-07-25 14:45 Greg Kurz 2018-07-27 5:27 ` David Gibson 2018-07-27 7:54 ` Greg Kurz 2018-07-27 8:18 ` Thomas Huth 2018-07-27 9:00 ` Greg Kurz 2018-07-27 11:25 ` Thomas Huth [this message] 2018-07-27 12:03 ` Greg Kurz 2018-07-30 5:57 ` David Gibson 2018-07-30 8:41 ` Greg Kurz 2018-07-30 9:59 ` Greg Kurz 2018-07-31 3:27 ` David Gibson 2018-08-01 13:35 ` Greg Kurz 2018-07-31 3:25 ` David Gibson 2018-08-01 13:24 ` Greg Kurz 2018-08-02 4:08 ` David Gibson 2018-08-02 9:36 ` Igor Mammedov 2018-08-02 10:52 ` Greg Kurz
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