From: Kan Liang <kan.liang@xxxxxxxxx> With -cpu host KVM reports LBR and extra_regs support, so the perf driver may accesses the LBR and extra_regs MSRs. However, there is no LBR and extra_regs virtualization support yet. This could causes guest to crash. As a workaround, KVM just simply ignore the LBR and extra_regs MSRs to lie the guest. For reproducing the issue, please build the kernel with CONFIG_KVM_INTEL = y (for host kernel). And CONFIG_PARAVIRT = n and CONFIG_KVM_GUEST = n (for guest kernel). Start the guest with -cpu host. Run perf record with --branch-any or --branch-filter in guest to trigger LBR Run perf stat offcore events (E.g. LLC-loads/LLC-load-misses ...) in guest to trigger offcore_rsp #GP Signed-off-by: Andi Kleen <ak@xxxxxxxxxxxxxxx> Signed-off-by: Kan Liang <kan.liang@xxxxxxxxx> --- V3: add MSR_LBR_TOS V4: add MSR_LBR_SELECT and MSR_PEBS_LD_LAT_THRESHOLD V5: set_msr should return 0 to lie the guest arch/x86/kvm/pmu.c | 38 ++++++++++++++++++++++++++++++++++++++ 1 file changed, 38 insertions(+) diff --git a/arch/x86/kvm/pmu.c b/arch/x86/kvm/pmu.c index cbecaa9..5fd5b44 100644 --- a/arch/x86/kvm/pmu.c +++ b/arch/x86/kvm/pmu.c @@ -331,6 +331,18 @@ bool kvm_pmu_msr(struct kvm_vcpu *vcpu, u32 msr) case MSR_CORE_PERF_GLOBAL_OVF_CTRL: ret = pmu->version > 1; break; + case MSR_OFFCORE_RSP_0: + case MSR_OFFCORE_RSP_1: + case MSR_LBR_SELECT: + case MSR_PEBS_LD_LAT_THRESHOLD: + case MSR_LBR_TOS: + /* At most 8-deep LBR for core and atom */ + case MSR_LBR_CORE_FROM ... MSR_LBR_CORE_FROM + 7: + case MSR_LBR_CORE_TO ... MSR_LBR_CORE_TO + 7: + /* 16-deep LBR for core i3/i5/i7 series processors */ + case MSR_LBR_NHM_FROM ... MSR_LBR_NHM_FROM + 15: + case MSR_LBR_NHM_TO ... MSR_LBR_NHM_TO + 15: + return 1; /* to avoid crashes */ default: ret = get_gp_pmc(pmu, msr, MSR_IA32_PERFCTR0) || get_gp_pmc(pmu, msr, MSR_P6_EVNTSEL0) @@ -358,6 +370,19 @@ int kvm_pmu_get_msr(struct kvm_vcpu *vcpu, u32 index, u64 *data) case MSR_CORE_PERF_GLOBAL_OVF_CTRL: *data = pmu->global_ovf_ctrl; return 0; + case MSR_OFFCORE_RSP_0: + case MSR_OFFCORE_RSP_1: + case MSR_LBR_SELECT: + case MSR_PEBS_LD_LAT_THRESHOLD: + case MSR_LBR_TOS: + /* At most 8-deep LBR for core and atom */ + case MSR_LBR_CORE_FROM ... MSR_LBR_CORE_FROM + 7: + case MSR_LBR_CORE_TO ... MSR_LBR_CORE_TO + 7: + /* 16-deep LBR for core i3/i5/i7 series processors */ + case MSR_LBR_NHM_FROM ... MSR_LBR_NHM_FROM + 15: + case MSR_LBR_NHM_TO ... MSR_LBR_NHM_TO + 15: + *data = 0; + return 0; default: if ((pmc = get_gp_pmc(pmu, index, MSR_IA32_PERFCTR0)) || (pmc = get_fixed_pmc(pmu, index))) { @@ -409,6 +434,19 @@ int kvm_pmu_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info) return 0; } break; + case MSR_OFFCORE_RSP_0: + case MSR_OFFCORE_RSP_1: + case MSR_LBR_SELECT: + case MSR_PEBS_LD_LAT_THRESHOLD: + case MSR_LBR_TOS: + /* At most 8-deep LBR for core and atom */ + case MSR_LBR_CORE_FROM ... MSR_LBR_CORE_FROM + 7: + case MSR_LBR_CORE_TO ... MSR_LBR_CORE_TO + 7: + /* 16-deep LBR for core i3/i5/i7 series processors */ + case MSR_LBR_NHM_FROM ... MSR_LBR_NHM_FROM + 15: + case MSR_LBR_NHM_TO ... MSR_LBR_NHM_TO + 15: + /* dummy for now */ + return 0; default: if ((pmc = get_gp_pmc(pmu, index, MSR_IA32_PERFCTR0)) || (pmc = get_fixed_pmc(pmu, index))) { -- 1.8.3.1 -- 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