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. Thanks, Laurent
