On Sat, Mar 22, 2014 at 11:05:03AM +0100, Peter Wu wrote: > On Saturday 22 March 2014 10:50:45 Gleb Natapov wrote: > > On Fri, Mar 21, 2014 at 12:04:32PM -0700, Venkatesh Srinivas wrote: > > > On Fri, Mar 21, 2014 at 10:46 AM, Peter Wu <peter@xxxxxxxxxxxxx> wrote: > > [skip] > > > > > When -cpu host is used, qemu/kvm passed the host CPUID F/M/S to the > > > guest. intel_pmu_cpu_*() -> intel_pmu_lbr_reset() uses rdmsr() / > > > wrmsr(), rather than the safe variants; if KVM does not support the > > > particular MSRs in question, you will see a #GP(0) there. See > > > https://lkml.org/lkml/2014/3/13/453 for a similar bug other PMU code. > > > > > When kernel is compiled with guest support all rdmsr()/wrmsr() become _safe(), > > so the question for Peter is if his guest kernel has guest support enabled? > > Linux guest support (CONFIG_HYPERVISOR_GUEST) was not enabled, see > .config in the first mail[1]. Enabling that option does not change the > situation. > > With CONFIG_PARAVIRT and CONFIG_KVM_GUEST enabled, the PMU GPF is gone, Yeah, it should be PARAVIRT indeed since rdmsr()/wrmsr() is substituted by _safe() using paravirt calls. > but now I have a NULL dereference (in rapl_pmu_init). Previously, when > `-cpu SandyBridge` was passed to qemu, it would show this: > > [ 0.016995] Performance Events: unsupported p6 CPU model 42 no PMU driver, software events only. > > The same NULL pointer deref would be visible (slightly different > addresses, but the Code lines are equal). With `-host`, the NULL deref > with `-cpu host` contains: > > [ 0.016445] Performance Events: 16-deep LBR, IvyBridge events, Intel PMU driver. > > Full dmesg below. > I am confused. Do you see crash now with -cpu SandyBridge and -cpu host, or -cpu host only? -- Gleb. -- 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
