On Wed, Nov 20, 2019 at 12:28:19PM +0100, Laurent Vivier wrote: > 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 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 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... Ugh, yeah, that's getting too ugly. I think the feasible options are either to revert the patch, or just say that upstream qemu no longer supports a RHEL7 host. -- 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