On Wed, Jun 13, 2018 at 06:10:30PM +0000, Moger, Babu wrote: > > -----Original Message----- > > From: Eduardo Habkost [mailto:ehabkost@xxxxxxxxxx] > > Sent: Wednesday, June 13, 2018 12:18 PM > > To: Moger, Babu <Babu.Moger@xxxxxxx> > > Cc: mst@xxxxxxxxxx; marcel.apfelbaum@xxxxxxxxx; pbonzini@xxxxxxxxxx; > > rth@xxxxxxxxxxx; mtosatti@xxxxxxxxxx; qemu-devel@xxxxxxxxxx; > > kvm@xxxxxxxxxxxxxxx; kash@xxxxxxxxxxxxxx; geoff@xxxxxxxxxxxxxxx; Jiri > > Denemark <jdenemar@xxxxxxxxxx> > > Subject: Re: [PATCH v13 3/5] i386: Enable TOPOEXT feature on AMD EPYC > > CPU > > > > On Wed, Jun 13, 2018 at 04:52:18PM +0000, Moger, Babu wrote: > > [...] > > > > What do you think our options are here? > > > > > > Should we drop automatic topoext completely and move forward? > > > What are your thoughts? > > > > Let's drop automatic topoext by now, and see if we find solutions > > later. I don't want to hold the rest of the patches because of > > this. > > Ok. I will drop topoext. > > > > > I'm thinking we could simply make kvm_arch_get_supported_cpuid() > > always return TOPOEXT on AMD CPUs, because the feature flag don't > > really depend on any KVM code to work (is that correct?). > > Yes, that is correct. I don't see any dependent code on TOPOEXT in KVM driver. > > Ok. Let me add TOPOEXT flag for all the AMD cpus and see how it goes. Hmm, this could actually solve all of our problems, then: We can forget about auto-topoext: just add TOPOEXT in kvm_arch_get_supported_cpuid(), add TOPOEXT unconditionally to the CPU models where you are interested into (EPYC only?), and add topoext=off to pc-2.12 compat_props. Sorry for not noticing that before. I was incorrectly assuming that TOPOEXT was safe to enable only if it was returned by GET_SUPPORTED_CPUID. -- Eduardo
