Messages in this thread | | | Date | Fri, 27 May 2016 17:28:46 +0200 | From | Radim Krčmář <> | Subject | Re: [PATCH] KVM: Handle MSR_IA32_PERF_CTL |
| |
2016-05-26 10:32+0300, kmeaw@yandex-team.ru: > From: Dmitry Bilunov <kmeaw@yandex-team.ru> > > Intel CPUs having Turbo Boost feature implement an MSR to provide a > control interface via rdmsr/wrmsr instructions. One could detect the > presence of this feature by issuing one of these instructions and > handling the #GP exception which is generated in case the referenced MSR > is not implemented by the CPU. > > KVM's vCPU model behaves exactly as a real CPU in this case by injecting > a fault when MSR_IA32_PERF_CTL is called (which KVM does not support). > However, some operating systems use this register during an early boot > stage in which their kernel is not capable of handling #GP correctly, > causing #DP and finally a triple fault effectively resetting the vCPU. > > This patch implements a dummy handler for MSR_IA32_PERF_CTL to avoid the > crashes. Most notably it fixes an issue with MacOS X 10.10 kernel. > > Signed-off-by: Dmitry Bilunov <kmeaw@yandex-team.ru> > --- > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > @@ -983,6 +983,7 @@ static u32 emulated_msrs[] = { > MSR_IA32_MCG_STATUS, > MSR_IA32_MCG_CTL, > MSR_IA32_SMBASE, > + MSR_IA32_PERF_CTL,
The MSR value is always 0, so there is no point in putting it here.
| |