linux-kernel - Re: [PATCH v3 08/11] KVM: selftests: Test consistency of PMU MSRs with Intel PMU version

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Message-ID: <ZN6rkW4DHFI1v1vL@google.com>
Date:   Thu, 17 Aug 2023 16:21:53 -0700
From:   Sean Christopherson <seanjc@...gle.com>
To:     Jinrong Liang <ljr.kernel@...il.com>
Cc:     Paolo Bonzini <pbonzini@...hat.com>, Like Xu <likexu@...cent.com>,
        David Matlack <dmatlack@...gle.com>,
        Aaron Lewis <aaronlewis@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jinrong Liang <cloudliang@...cent.com>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 08/11] KVM: selftests: Test consistency of PMU MSRs
 with Intel PMU version

On Mon, Aug 14, 2023, Jinrong Liang wrote:
> @@ -341,6 +347,66 @@ static void intel_test_fixed_counters(void)
>  	}
>  }
>  
> +static void intel_guest_check_pmu_version(uint8_t version)
> +{
> +	switch (version) {
> +	case 0:
> +		GUEST_SYNC(wrmsr_safe(MSR_INTEL_ARCH_PMU_GPCTR, 0xffffull));
> +	case 1:
> +		GUEST_SYNC(wrmsr_safe(MSR_CORE_PERF_GLOBAL_CTRL, 0x1ull));
> +	case 2:
> +		/*
> +		 * AnyThread Bit is only supported in version 3
> +		 *
> +		 * The strange thing is that when version=0, writing ANY-Any
> +		 * Thread bit (bit 21) in MSR_P6_EVNTSEL0 and MSR_P6_EVNTSEL1
> +		 * will not generate #GP. While writing ANY-Any Thread bit
> +		 * (bit 21) in MSR_P6_EVNTSEL0+x (MAX_GP_CTR_NUM > x > 2) to
> +		 * ANY-Any Thread bit (bit 21) will generate #GP.
> +		 */
> +		if (version == 0)
> +			break;
> +
> +		GUEST_SYNC(wrmsr_safe(MSR_P6_EVNTSEL0,
> +				      ARCH_PERFMON_EVENTSEL_ANY));
> +		break;
> +	default:
> +		/* KVM currently supports up to pmu version 2 */
> +		GUEST_SYNC(GP_VECTOR);

This seems largely pointless, but I suppose it doesn't hurt anything.

> +	}
> +
> +	GUEST_DONE();
> +}
> +
> +static void test_pmu_version_setup(struct kvm_vcpu *vcpu, uint8_t version,
> +				   uint64_t expected)
> +{
> +	uint64_t msr_val = 0;
> +
> +	vcpu_set_cpuid_property(vcpu, X86_PROPERTY_PMU_VERSION, version);
> +
> +	vcpu_args_set(vcpu, 1, version);
> +	while (run_vcpu(vcpu, &msr_val) != UCALL_DONE)
> +		TEST_ASSERT_EQ(expected, msr_val);
> +}
> +
> +static void intel_test_pmu_version(void)
> +{
> +	uint8_t unsupported_version = kvm_cpu_property(X86_PROPERTY_PMU_VERSION) + 1;
> +	struct kvm_vcpu *vcpu;
> +	struct kvm_vm *vm;
> +	uint8_t version;
> +
> +	TEST_REQUIRE(kvm_cpu_property(X86_PROPERTY_PMU_NR_FIXED_COUNTERS) > 2);
> +
> +	for (version = 0; version <= unsupported_version; version++) {
> +		vm = pmu_vm_create_with_one_vcpu(&vcpu,
> +						 intel_guest_check_pmu_version);
> +		test_pmu_version_setup(vcpu, version, GP_VECTOR);

Why pass GP_VECTOR?  It's the _only_ expected result, just have the guest assert
that it got a #GP...

> +		kvm_vm_free(vm);

Again, stop making half-baked helpers.

> +	}
> +}
> +
>  int main(int argc, char *argv[])
>  {
>  	TEST_REQUIRE(get_kvm_param_bool("enable_pmu"));
> @@ -353,6 +419,7 @@ int main(int argc, char *argv[])
>  	intel_test_arch_events();
>  	intel_test_counters_num();
>  	intel_test_fixed_counters();
> +	intel_test_pmu_version();
>  
>  	return 0;
>  }
> -- 
> 2.39.3
>