On Tue, Aug 09, 2016 at 11:17:04AM +0200, Thomas Huth wrote: > There is a regression with the "-cpu" parameter which has been > introduced by the spapr CPU hotplug code: We used to allow to specify > a "CPU family" name with the "-cpu" parameter when running on KVM so > that the user does not need to know the gory details of the exact > CPU version of the host CPU. For example, it was possible to > use "-cpu POWER8" on a POWER8E host CPU. This behavior does not > work anymore with the new hot-pluggable spapr-cpu-core types. > Since libvirt already heavily depends on the old behavior, this > is quite a severe regression in the QEMU parameter interface, thus > I think these patches should still go into 2.7 if possible, to avoid > that we break the "upper layers" with the final 2.7 release.
I believed that "-cpu POWER8" on POWER8E host was broken in a way as the guest CPUs were getting reported as POWER8E instead of POWER8 (/proc/cpuinfo of guest) cpu : POWER8E (raw), altivec supported I thought, the correct configuration should have been cpu : POWER8 (architected), altivec supported which is what you get when you use POWER8 in compat mode on POWER8E host like below: -cpu host -global driver=host-powerpc64-cpu,property=compat,value=power8 However as you note libvirt is dependent on supporting POWER8 and there have been discussions and conclusions on this earlier, I guess it is better now to have your patchset to restore the expectations of libvirt. Regards, Bharata.
