2016-05-26 10:32+0300, km...@yandex-team.ru: > From: Dmitry Bilunov <km...@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 <km...@yandex-team.ru> > --- > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > @@ -2050,6 +2051,7 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct > msr_data *msr_info) > case MSR_VM_HSAVE_PA: > case MSR_AMD64_PATCH_LOADER: > case MSR_AMD64_BU_CFG2: > + case MSR_IA32_PERF_CTL: > break;
Does MacOS X write it too? Thanks.
