On 20/11/2019 10:00, Laurent Vivier wrote: > On 20/11/2019 05:36, David Gibson wrote: >> On Tue, Nov 19, 2019 at 04:45:26PM +0100, Greg Kurz wrote: >>> On Tue, 19 Nov 2019 15:06:51 +0100 >>> Laurent Vivier <lviv...@redhat.com> wrote: >>> >>>> On 19/11/2019 02:00, David Gibson wrote: >>>>> On Fri, Nov 08, 2019 at 05:47:59PM +0100, Greg Kurz wrote: >>>>>> On Fri, 8 Nov 2019 16:40:35 +0100 >>>>>> Laurent Vivier <lviv...@redhat.com> wrote: >>>>>> >>>>>>> Commit 29cb4187497d sets by default the VSMT to smp_threads, >>>>>>> but older kernels (< 4.13) don't support that. >>>>>>> >>>>>>> We can reasonably restore previous behavior with this kernel >>>>>>> to allow to run QEMU as before. >>>>>>> >>>>>>> If VSMT is not supported, VSMT will be set to MAX(8, smp_threads) >>>>>>> as it is done for previous machine types (< pseries-4.2) >>>>>>> >>>>>> >>>>>> It is usually _bad_ to base the machine behavior on host capabilities. >>>>>> What happens if we migrate between an older kernel and a recent one ? >>>>> >>>>> Right. We're really trying to remove instaces of such behaviour. I'd >>>>> prefer to completely revert Greg's original patch than to re-introduce >>>>> host configuration dependency into the guest configuration.. >>>>> >>>>>> I understand this is to fix tests/migration-test on older kernels. >>>>>> Couldn't this be achieved with migration-test doing some introspection >>>>>> and maybe pass vsmt=8 on the QEMU command line ? >>>>> >>>>> ..adjusting the test case like this might be a better idea, though. >>>>> >>>>> What's the test setup where we're using the old kernel? I really only >>>>> applied the original patch on the guess that we didn't really care >>>>> about kernels that old. The fact you've hit this in practice makes me >>>>> doubt that assumption. >>>>> >>>> >>>> The way to fix the tests is to add "-smp threads=8" on the command line >>>> (for all tests, so basically in qtest_init_without_qmp_handshake(), and >>>> it will impact all the machine types), and we have to check if it is >>> >>> Ohhh... it isn't possible to initialize Qtest with machine specific >>> properties ? That's a bit unfortunate :-\ >> >> Uhh... I don't see why we can't. Couldn't we just put either -machine >> vsmt=8 or -smp 8 into the cmd_src / cmd_dst printfs() in the >> strcmp(arch, "ppc64") case? > > Yes, but we need to do that to all other tests that fail. test-migration > is not the only one impacted by the problem (we have also pxe-test), so > it's why I thought to fix the problem in a generic place. > > But it seems there are only this couple of tests that are impacted so I > can modify both instead. I think only tests that really start CPU have > the problem. > > I'm going to send a patch to fix that.
And again, it's a little bit more complicated than expected: setting vsmt to 8 works only with kvm_hv, but breaks in case of TCG or kvm_pr. So the test must check what is in use... Thanks, Laurent
