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Message-ID: <ZVInZkwjbanQ2rkx@google.com>
Date: Mon, 13 Nov 2023 05:40:54 -0800
From: Sean Christopherson <seanjc@...gle.com>
To: Jinrong Liang <ljr.kernel@...il.com>
Cc: Paolo Bonzini <pbonzini@...hat.com>, 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 <cloudliang@...cent.com>
Subject: Re: [PATCH v8 26/26] KVM: selftests: Extend PMU counters test to
validate RDPMC after WRMSR
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@...gle.com>
> > ---
> > + /* 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
--
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