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. -- 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