From d8f992e9fde8dc23b6fe649fa1b0ed5c123738fe Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Fri, 10 Mar 2023 16:46:18 -0800 Subject: [PATCH] KVM: selftests: Verify LBRs are disabled if vPMU is disabled Verify that disabling the guest's vPMU via CPUID also disables LBRs. KVM has had at least one bug where LBRs would remain enabled even though the intent was to disable everything PMU related. Link: https://lore.kernel.org/r/20230311004618.920745-22-seanjc@google.com Signed-off-by: Sean Christopherson --- .../selftests/kvm/x86_64/vmx_pmu_caps_test.c | 29 +++++++++++++++++++ 1 file changed, 29 insertions(+) diff --git a/tools/testing/selftests/kvm/x86_64/vmx_pmu_caps_test.c b/tools/testing/selftests/kvm/x86_64/vmx_pmu_caps_test.c index 29aaa0419294a..3009b3e5254d7 100644 --- a/tools/testing/selftests/kvm/x86_64/vmx_pmu_caps_test.c +++ b/tools/testing/selftests/kvm/x86_64/vmx_pmu_caps_test.c @@ -204,6 +204,34 @@ static void test_immutable_perf_capabilities(union perf_capabilities host_cap) kvm_vm_free(vm); } +/* + * Test that LBR MSRs are writable when LBRs are enabled, and then verify that + * disabling the vPMU via CPUID also disables LBR support. Set bits 2:0 of + * LBR_TOS as those bits are writable across all uarch implementations (arch + * LBRs will need to poke a different MSR). + */ +static void test_lbr_perf_capabilities(union perf_capabilities host_cap) +{ + struct kvm_vcpu *vcpu; + struct kvm_vm *vm; + int r; + + if (!host_cap.lbr_format) + return; + + vm = vm_create_with_one_vcpu(&vcpu, NULL); + + vcpu_set_msr(vcpu, MSR_IA32_PERF_CAPABILITIES, host_cap.capabilities); + vcpu_set_msr(vcpu, MSR_LBR_TOS, 7); + + vcpu_clear_cpuid_entry(vcpu, X86_PROPERTY_PMU_VERSION.function); + + r = _vcpu_set_msr(vcpu, MSR_LBR_TOS, 7); + TEST_ASSERT(!r, "Writing LBR_TOS should fail after disabling vPMU"); + + kvm_vm_free(vm); +} + int main(int argc, char *argv[]) { union perf_capabilities host_cap; @@ -222,4 +250,5 @@ int main(int argc, char *argv[]) test_fungible_perf_capabilities(host_cap); test_immutable_perf_capabilities(host_cap); test_guest_wrmsr_perf_capabilities(host_cap); + test_lbr_perf_capabilities(host_cap); } -- 2.30.2