Dne 19. 11. 19 v 16:45 Greg Kurz napsal(a): > 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 :-\ > >> ppc64/pseries to do that, and there it becomes a little bit complicated >> for a so small piece of code. >> >> So I think the best to do is to revert Greg's patch. >> > > I'm okay with that since this patch doesn't bring much for the moment. > > But soon, ie. linux-5.5 hopefully, KVM will allow to configure the number > of presenters in the XIVE and XICS-on-XIVE devices on POWER9. Combined > with this patch, it will allow to drastically reduce the consumption of > resources in the XIVE HW, which currently limits the number of VMs that > can run concurrently with an in-kernel irqchip. So I hope the 'make check' > you're willing to fix is worth it :-), and BTW you didn't answer David's > question about the test setup. > Hello Greg, guys, it is P8 machine using RHEL7 host with a stock kernel-3.10.0-XXXX. If you're interested in the whole setup, then: ./configure --enable-kvm --block-drv-rw-whitelist=vmdk,null-aio,quorum,null-co,blkverify,file,nbd,raw,blkdebug,host_device,qed,nbd,iscsi,gluster,rbd,qcow2,throttle,copy-on-read make -j 13 SPEED=slow make check Regards, Lukáš > Cheers, > > -- > Greg > >> Thanks, >> Laurent >> >