linux-kernel - Re: [PATCH v8 26/26] KVM: selftests: Extend PMU counters test to validate RDPMC after WRMSR

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Date:   Mon, 13 Nov 2023 19:41:24 +0800
From:   Jinrong Liang <ljr.kernel@...il.com>
To:     Sean Christopherson <seanjc@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>
Cc:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        Kan Liang <kan.liang@...ux.intel.com>,
        Dapeng Mi <dapeng1.mi@...ux.intel.com>,
        Jim Mattson <jmattson@...gle.com>,
        Aaron Lewis <aaronlewis@...gle.com>,
        Like Xu <likexu@...cent.com>,
        Jinrong Liang <ljr.kernel@...il.com>,
        Jinrong Liang <cloudliang@...cent.com>
Subject: Re: [PATCH v8 26/26] KVM: selftests: Extend PMU counters test to
 validate RDPMC after WRMSR

在 2023/11/10 10:13, Sean Christopherson 写道:
> Extend the read/write PMU counters subtest to verify that RDPMC also reads
> back the written value.  Opportunsitically verify that attempting to use
> the "fast" mode of RDPMC fails, as the "fast" flag is only supported by
> non-architectural PMUs, which KVM doesn't virtualize.
> 
> Signed-off-by: Sean Christopherson <seanjc@...gle.com>
> ---
>   .../selftests/kvm/x86_64/pmu_counters_test.c  | 31 +++++++++++++++++++
>   1 file changed, 31 insertions(+)
> 
> diff --git a/tools/testing/selftests/kvm/x86_64/pmu_counters_test.c b/tools/testing/selftests/kvm/x86_64/pmu_counters_test.c
> index cb808ac827ba..248ebe8c0577 100644
> --- a/tools/testing/selftests/kvm/x86_64/pmu_counters_test.c
> +++ b/tools/testing/selftests/kvm/x86_64/pmu_counters_test.c
> @@ -328,6 +328,7 @@ __GUEST_ASSERT(expect_gp ? vector == GP_VECTOR : !vector,			\
>   static void guest_rd_wr_counters(uint32_t base_msr, uint8_t nr_possible_counters,
>   				 uint8_t nr_counters, uint32_t or_mask)
>   {
> +	const bool pmu_has_fast_mode = !guest_get_pmu_version();
>   	uint8_t i;
>   
>   	for (i = 0; i < nr_possible_counters; i++) {
> @@ -352,6 +353,7 @@ static void guest_rd_wr_counters(uint32_t base_msr, uint8_t nr_possible_counters
>   		const uint64_t expected_val = expect_success ? test_val : 0;
>   		const bool expect_gp = !expect_success && msr != MSR_P6_PERFCTR0 &&
>   				       msr != MSR_P6_PERFCTR1;
> +		uint32_t rdpmc_idx;
>   		uint8_t vector;
>   		uint64_t val;
>   
> @@ -365,6 +367,35 @@ static void guest_rd_wr_counters(uint32_t base_msr, uint8_t nr_possible_counters
>   		if (!expect_gp)
>   			GUEST_ASSERT_PMC_VALUE(RDMSR, msr, val, expected_val);
>   
> +		rdpmc_idx = i;
> +		if (base_msr == MSR_CORE_PERF_FIXED_CTR0)
> +			rdpmc_idx |= INTEL_RDPMC_FIXED;
> +
> +		/* Redo the read tests with RDPMC, and with forced emulation. */
> +		vector = rdpmc_safe(rdpmc_idx, &val);
> +		GUEST_ASSERT_PMC_MSR_ACCESS(RDPMC, rdpmc_idx, !expect_success, vector);
> +		if (expect_success)
> +			GUEST_ASSERT_PMC_VALUE(RDPMC, rdpmc_idx, val, expected_val);
> +
> +		vector = rdpmc_safe_fep(rdpmc_idx, &val);
> +		GUEST_ASSERT_PMC_MSR_ACCESS(RDPMC, rdpmc_idx, !expect_success, vector);
> +		if (expect_success)
> +			GUEST_ASSERT_PMC_VALUE(RDPMC, rdpmc_idx, val, expected_val);
> +
> +		/*
> +		 * KVM doesn't support non-architectural PMUs, i.e. it should
> +		 * impossible to have fast mode RDPMC.  Verify that attempting
> +		 * to use fast RDPMC always #GPs.
> +		 */
> +		GUEST_ASSERT(!expect_success || !pmu_has_fast_mode);
> +		rdpmc_idx |= INTEL_RDPMC_FAST;
> +
> +		vector = rdpmc_safe(rdpmc_idx, &val);
> +		GUEST_ASSERT_PMC_MSR_ACCESS(RDPMC, rdpmc_idx, true, vector);
> +
> +		vector = rdpmc_safe_fep(rdpmc_idx, &val);
> +		GUEST_ASSERT_PMC_MSR_ACCESS(RDPMC, rdpmc_idx, true, vector);
> +
>   		vector = wrmsr_safe(msr, 0);
>   		GUEST_ASSERT_PMC_MSR_ACCESS(WRMSR, msr, expect_gp, vector);
>   	}
> 

This test case failed on my Intel machine.

Error message：
Testing arch events, PMU version 0, perf_caps = 0
Testing GP counters, PMU version 0, perf_caps = 0
==== Test Assertion Failure ====
   lib/x86_64/processor.c:1100: Unhandled exception in guest
   pid=464480 tid=464480 errno=4 - Interrupted system call
      1	0x00000000004120e1: assert_on_unhandled_exception 于 
processor.c:1146
      2	0x00000000004062d9: _vcpu_run 于 kvm_util.c:1634
      3	0x00000000004062fa: vcpu_run 于 kvm_util.c:1645
      4	0x0000000000403697: run_vcpu 于 pmu_counters_test.c:56
      5	0x00000000004026fc: test_gp_counters 于 pmu_counters_test.c:434
      6	(已内连入)test_intel_counters 于 pmu_counters_test.c:580
      7	(已内连入)main 于 pmu_counters_test.c:604
      8	0x00007f7a2f03ad84: ?? ??:0
      9	0x00000000004028bd: _start 于 ??:?
   Unhandled exception '0x6' at guest RIP '0x402bab'