Re: [PATCH v8 26/26] KVM: selftests: Extend PMU counters test to validate RDPMC after WRMSR
From: Jinrong Liang
Date: Mon Nov 13 2023 - 22:07:46 EST
Sean Christopherson <seanjc@xxxxxxxxxx> 于2023年11月13日周一 21:40写道：
>
> On Mon, Nov 13, 2023, Jinrong Liang wrote:
> > 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@xxxxxxxxxx>
> > > ---
> > > + /* 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);
>
> > 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'
>
> Argh, I didn't add a check to see if forced emulation is actually enabled (forced
> emulation uses a magic "prefix" to trigger a #UD, which KVM intercepts; if forced
> emulation isn't enabled, KVM ignores the magic prefix and reflects the #UD back
> into the guest).
>
> This fixes the test for me:
>
> ---
> .../selftests/kvm/x86_64/pmu_counters_test.c | 42 ++++++++++++-------
> 1 file changed, 26 insertions(+), 16 deletions(-)
>
> 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 248ebe8c0577..ae5f6042f1e8 100644
> --- a/tools/testing/selftests/kvm/x86_64/pmu_counters_test.c
> +++ b/tools/testing/selftests/kvm/x86_64/pmu_counters_test.c
> @@ -325,6 +325,26 @@ __GUEST_ASSERT(expect_gp ? vector == GP_VECTOR : !vector, \
> "Expected " #insn "(0x%x) to yield 0x%lx, got 0x%lx", \
> msr, expected_val, val);
>
> +static void guest_test_rdpmc(uint32_t rdpmc_idx, bool expect_success,
> + uint64_t expected_val)
> +{
> + uint8_t vector;
> + uint64_t val;
> +
> + 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);
> +
> + if (!is_forced_emulation_enabled)
> + return;
> +
> + 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);
> +}
> +
> static void guest_rd_wr_counters(uint32_t base_msr, uint8_t nr_possible_counters,
> uint8_t nr_counters, uint32_t or_mask)
> {
> @@ -367,20 +387,15 @@ 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);
>
> + /*
> + * Redo the read tests with RDPMC, which has different indexing
> + * semantics and additional capabilities.
> + */
> 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);
> + guest_test_rdpmc(rdpmc_idx, expect_success, expected_val);
>
> /*
> * KVM doesn't support non-architectural PMUs, i.e. it should
> @@ -389,12 +404,7 @@ static void guest_rd_wr_counters(uint32_t base_msr, uint8_t nr_possible_counters
> */
> 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);
> + guest_test_rdpmc(rdpmc_idx, false, -1ull);
>
> vector = wrmsr_safe(msr, 0);
> GUEST_ASSERT_PMC_MSR_ACCESS(WRMSR, msr, expect_gp, vector);
>
> base-commit: 743a1a6d106931691be32e081e929d9b3de5777f
> --
This fix worked perfectly, thanks.
>