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[35.185.214.157]) by smtp.gmail.com with ESMTPSA id z22sm3645466pfe.93.2021.12.15.09.59.58 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 15 Dec 2021 09:59:58 -0800 (PST) Date: Wed, 15 Dec 2021 17:59:55 +0000 From: Sean Christopherson To: Vitaly Kuznetsov Cc: kvm@vger.kernel.org, Paolo Bonzini , Wanpeng Li , Jim Mattson , oliver.sang@intel.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH] KVM: selftests: Avoid KVM_SET_CPUID2 after KVM_RUN in vmx_pmu_msrs_test Message-ID: References: <20211215161617.246563-1-vkuznets@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20211215161617.246563-1-vkuznets@redhat.com> Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Wed, Dec 15, 2021, Vitaly Kuznetsov wrote: > Commit feb627e8d6f6 ("KVM: x86: Forbid KVM_SET_CPUID{,2} after KVM_RUN") > forbade chaning vCPU's CPUID data after the first KVM_RUN but > vmx_pmu_msrs_test does exactly that. Test VM needs to be re-created after > vcpu_run(). > > Reported-by: kernel test robot > Fixes: feb627e8d6f6 ("KVM: x86: Forbid KVM_SET_CPUID{,2} after KVM_RUN") > Signed-off-by: Vitaly Kuznetsov > --- > tools/testing/selftests/kvm/x86_64/vmx_pmu_msrs_test.c | 5 +++++ > 1 file changed, 5 insertions(+) > > diff --git a/tools/testing/selftests/kvm/x86_64/vmx_pmu_msrs_test.c b/tools/testing/selftests/kvm/x86_64/vmx_pmu_msrs_test.c > index 23051d84b907..17882f79deed 100644 > --- a/tools/testing/selftests/kvm/x86_64/vmx_pmu_msrs_test.c > +++ b/tools/testing/selftests/kvm/x86_64/vmx_pmu_msrs_test.c > @@ -99,6 +99,11 @@ int main(int argc, char *argv[]) > vcpu_run(vm, VCPU_ID); > ASSERT_EQ(vcpu_get_msr(vm, VCPU_ID, MSR_IA32_PERF_CAPABILITIES), PMU_CAP_FW_WRITES); > > + /* Re-create guest VM after KVM_RUN so CPUID can be changed */ > + kvm_vm_free(vm); > + vm = vm_create_default(VCPU_ID, 0, guest_code); > + vcpu_set_cpuid(vm, VCPU_ID, cpuid); Why is this test even setting CPUID for the below cases? Guest CPUID shouldn't affect host_initiated writes. This part in particular looks wrong: entry_1_0->ecx |= X86_FEATURE_PDCM; eax.split.version_id = 0; entry_1_0->ecx = eax.full; vcpu_set_cpuid(vm, VCPU_ID, cpuid); ret = _vcpu_set_msr(vm, 0, MSR_IA32_PERF_CAPABILITIES, PMU_CAP_FW_WRITES); TEST_ASSERT(ret == 0, "Bad PERF_CAPABILITIES didn't fail."); As does the KVM code. The WRMSR path for MSR_IA32_PERF_CAPABILITIES looks especially wrong, as rejects a bad write iff userspace set PDCM in guest CPUID. struct kvm_msr_entry msr_ent = {.index = msr, .data = 0}; if (!msr_info->host_initiated) return 1; if (guest_cpuid_has(vcpu, X86_FEATURE_PDCM) && kvm_get_msr_feature(&msr_ent)) <===== Huh? return 1; if (data & ~msr_ent.data) return 1; vcpu->arch.perf_capabilities = data; return 0; } So I think we should fix KVM and then clean up the test accordingly. diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 85127b3e3690..65e297875405 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -3424,7 +3424,7 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info) if (!msr_info->host_initiated) return 1; - if (guest_cpuid_has(vcpu, X86_FEATURE_PDCM) && kvm_get_msr_feature(&msr_ent)) + if (kvm_get_msr_feature(&msr_ent)) return 1; if (data & ~msr_ent.data) return 1; @@ -3779,14 +3779,12 @@ int kvm_get_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info) msr_info->data = vcpu->arch.microcode_version; break; case MSR_IA32_ARCH_CAPABILITIES: - if (!msr_info->host_initiated && - !guest_cpuid_has(vcpu, X86_FEATURE_ARCH_CAPABILITIES)) + if (!msr_info->host_initiated) return 1; msr_info->data = vcpu->arch.arch_capabilities; break; case MSR_IA32_PERF_CAPABILITIES: - if (!msr_info->host_initiated && - !guest_cpuid_has(vcpu, X86_FEATURE_PDCM)) + if (!msr_info->host_initiated) return 1; msr_info->data = vcpu->arch.perf_capabilities; break; > + > /* testcase 2, check valid LBR formats are accepted */ > vcpu_set_msr(vm, 0, MSR_IA32_PERF_CAPABILITIES, 0); > ASSERT_EQ(vcpu_get_msr(vm, VCPU_ID, MSR_IA32_PERF_CAPABILITIES), 0); > -- > 2.33.1 >