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[35.230.65.123]) by smtp.gmail.com with ESMTPSA id c11-20020a62f84b000000b0051844a64d3dsm2082312pfm.25.2022.06.16.11.34.58 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 16 Jun 2022 11:34:59 -0700 (PDT) Date: Thu, 16 Jun 2022 18:34:55 +0000 From: Sean Christopherson To: Yang Weijiang Cc: pbonzini@redhat.com, like.xu.linux@gmail.com, jmattson@google.com, kvm@vger.kernel.org Subject: Re: [kvm-unit-tests PATCH v2 2/3] x86: Skip running test when pmu is disabled Message-ID: References: <20220615084641.6977-1-weijiang.yang@intel.com> <20220615084641.6977-3-weijiang.yang@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220615084641.6977-3-weijiang.yang@intel.com> Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Wed, Jun 15, 2022, Yang Weijiang wrote: > Read MSR_IA32_PERF_CAPABILITIES triggers #GP when pmu is disabled > by enable_pmu=0 in KVM. Let's check whether pmu is available before > issue msr reading to avoid the #GP. Also check PDCM bit before read > the MSR. > > Signed-off-by: Yang Weijiang > --- > x86/pmu_lbr.c | 12 +++++++++++- > 1 file changed, 11 insertions(+), 1 deletion(-) > > diff --git a/x86/pmu_lbr.c b/x86/pmu_lbr.c > index 688634d..62614a0 100644 > --- a/x86/pmu_lbr.c > +++ b/x86/pmu_lbr.c > @@ -5,6 +5,7 @@ > #define N 1000000 > #define MAX_NUM_LBR_ENTRY 32 > #define DEBUGCTLMSR_LBR (1UL << 0) > +#define PDCM_ENABLED (1UL << 15) > #define PMU_CAP_LBR_FMT 0x3f > > #define MSR_LBR_NHM_FROM 0x00000680 > @@ -74,13 +75,22 @@ int main(int ac, char **av) > return 0; > } > > - perf_cap = rdmsr(MSR_IA32_PERF_CAPABILITIES); > eax.full = id.a; > > if (!eax.split.version_id) { > printf("No pmu is detected!\n"); > return report_summary(); > } > + > + id = cpuid(1); > + > + if (!(id.c & PDCM_ENABLED)) { Don't open code cpuid(), add and use X86_FEATURE_PDCM: #define X86_FEATURE_PDCM (CPUID(0x1, 0, ECX, 15)) if (!this_cpu_has(X86_FEATURE_PDCM)) ... > + printf("No PDCM is detected!\n"); If your going to bother printing a message, please make it useful. Every time I read PMU code I have to reread the kernel's cpufeatures.h to remember what PDCM stands for. printf("Perf/Debug Capabilities MSR isn't supported\n"); > + return report_summary(); > + } > + > + perf_cap = rdmsr(MSR_IA32_PERF_CAPABILITIES); > + > if (!(perf_cap & PMU_CAP_LBR_FMT)) { > printf("No LBR is detected!\n"); Similar complaint, printf("Architectural LBRs are not supported.\n"); > return report_summary(); > -- > 2.31.1 >