3.16.63-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Dmitry Bilunov <kmeaw@xxxxxxxxxxxxxx> commit 0c2df2a1affd183ba9c114915f42a2d464b4f58f upstream. 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. Signed-off-by: Dmitry Bilunov <kmeaw@xxxxxxxxxxxxxx> Signed-off-by: Radim Krčmář <rkrcmar@xxxxxxxxxx> Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx> --- arch/x86/kvm/x86.c | 1 + 1 file changed, 1 insertion(+) --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -2461,6 +2461,7 @@ int kvm_get_msr_common(struct kvm_vcpu * case MSR_AMD64_NB_CFG: case MSR_FAM10H_MMIO_CONF_BASE: case MSR_AMD64_BU_CFG2: + case MSR_IA32_PERF_CTL: msr_info->data = 0; break; case MSR_P6_PERFCTR0:
