On 08/21/2012 01:35 PM, Peter Zijlstra wrote: > On Tue, 2012-08-21 at 11:34 +0300, Avi Kivity wrote: >> On 08/21/2012 10:11 AM, Peter Zijlstra wrote: >> > On Sun, 2012-08-19 at 12:55 +0300, Avi Kivity wrote: >> >> > I think Avi prefers the method where KVM 'fakes' the MSRs and we have to >> >> > detect if the MSRs actually work or not. >> >> >> >> s/we have/we don't have/. >> > >> > So for the 'normal' PMU we actually do check to see if the MSRs are >> > being faked and bail if they are. >> >> That was because earlier versions of kvm did not virtualize the pmu. >> >> The approaches are not mutually exclusive. We can check in the guest, >> and fake it in the host. > > This is actually what I proposed. Ah, I misunderstood you. > >> The problem with faking it in the host is if someone actually relies on >> the pmu for something, not just instrumentation. We do that for the >> watchdog, but I don't see it happening with the uncore pmu. > > Agreed, although from a usability POV its nicer to refuse the > device/events than to pretend it works while it doesn't. If/when we virtualize this pmu we can expose a flag that says "the pmu actually works even though this is a virtual machine". > Anyway, for now I've taken Zheng Yan's cpu_has_hypervisor patch, we can > always revisit this. Yup. -- error compiling committee.c: too many arguments to function -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
