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Message-ID: <CALMp9eSzhXR8RiUo9vdz77ZjBpaLSQGtVn47p2EuwoyKbmz9EQ@mail.gmail.com>
Date: Wed, 24 May 2023 15:59:31 -0700
From: Jim Mattson <jmattson@...gle.com>
To: Like Xu <like.xu.linux@...il.com>
Cc: Sean Christopherson <seanjc@...gle.com>,
Paolo Bonzini <pbonzini@...hat.com>,
Jinrong Liang <cloudliang@...cent.com>,
linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Subject: Re: [PATCH 1/7] KVM: selftests: Test Intel PMU architectural events
on gp counters
On Thu, Mar 23, 2023 at 12:27 AM Like Xu <like.xu.linux@...il.com> wrote:
>
> From: Like Xu <likexu@...cent.com>
>
> Add test cases to check if different Architectural events are available
> after it's marked as unavailable via CPUID. It covers vPMU event filtering
> logic based on Intel CPUID, which is a complement to pmu_event_filter.
>
> According to Intel SDM, the number of architectural events is reported
> through CPUID.0AH:EAX[31:24] and the architectural event x is
> supported if EBX[x]=0 && EAX[31:24]>x.
>
> Co-developed-by: Jinrong Liang <cloudliang@...cent.com>
> Signed-off-by: Jinrong Liang <cloudliang@...cent.com>
> Signed-off-by: Like Xu <likexu@...cent.com>
> ---
> tools/testing/selftests/kvm/Makefile | 1 +
> .../selftests/kvm/x86_64/pmu_cpuid_test.c | 202 ++++++++++++++++++
> 2 files changed, 203 insertions(+)
> create mode 100644 tools/testing/selftests/kvm/x86_64/pmu_cpuid_test.c
>
> diff --git a/tools/testing/selftests/kvm/Makefile b/tools/testing/selftests/kvm/Makefile
> index 84a627c43795..8aa63081b3e6 100644
> --- a/tools/testing/selftests/kvm/Makefile
> +++ b/tools/testing/selftests/kvm/Makefile
> @@ -78,6 +78,7 @@ TEST_GEN_PROGS_x86_64 += x86_64/mmio_warning_test
> TEST_GEN_PROGS_x86_64 += x86_64/monitor_mwait_test
> TEST_GEN_PROGS_x86_64 += x86_64/nested_exceptions_test
> TEST_GEN_PROGS_x86_64 += x86_64/platform_info_test
> +TEST_GEN_PROGS_x86_64 += x86_64/pmu_cpuid_test
> TEST_GEN_PROGS_x86_64 += x86_64/pmu_event_filter_test
> TEST_GEN_PROGS_x86_64 += x86_64/set_boot_cpu_id
> TEST_GEN_PROGS_x86_64 += x86_64/set_sregs_test
> diff --git a/tools/testing/selftests/kvm/x86_64/pmu_cpuid_test.c b/tools/testing/selftests/kvm/x86_64/pmu_cpuid_test.c
> new file mode 100644
> index 000000000000..faab0a91e191
> --- /dev/null
> +++ b/tools/testing/selftests/kvm/x86_64/pmu_cpuid_test.c
> @@ -0,0 +1,202 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Test the consistency of the PMU's CPUID and its features
> + *
> + * Copyright (C) 2023, Tencent, Inc.
> + *
> + * Check that the VM's PMU behaviour is consistent with the
> + * VM CPUID definition.
> + */
> +
> +#define _GNU_SOURCE /* for program_invocation_short_name */
> +#include <x86intrin.h>
> +
> +#include "processor.h"
> +
> +/* Guest payload for any performance counter counting */
> +#define NUM_BRANCHES 10
> +
> +#define EVENTSEL_OS BIT_ULL(17)
> +#define EVENTSEL_EN BIT_ULL(22)
> +#define PMU_CAP_FW_WRITES BIT_ULL(13)
> +#define EVENTS_MASK GENMASK_ULL(7, 0)
> +#define PMU_VERSION_MASK GENMASK_ULL(7, 0)
> +#define GP_CTR_NUM_OFS_BIT 8
> +#define GP_CTR_NUM_MASK GENMASK_ULL(15, GP_CTR_NUM_OFS_BIT)
> +#define EVT_LEN_OFS_BIT 24
> +#define EVT_LEN_MASK GENMASK_ULL(31, EVT_LEN_OFS_BIT)
> +
> +#define ARCH_EVENT(select, umask) (((select) & 0xff) | ((umask) & 0xff) << 8)
> +
> +/*
> + * Intel Pre-defined Architectural Performance Events. Note some events
> + * are skipped for testing due to difficulties in stable reproduction.
> + */
> +static const uint64_t arch_events[] = {
> + [0] = ARCH_EVENT(0x3c, 0x0),
> + [1] = ARCH_EVENT(0xc0, 0x0),
> + [2] = ARCH_EVENT(0x3c, 0x1),
> + [3] = ARCH_EVENT(0x2e, 0x4f), /* LLC Reference */
> + [4] = ARCH_EVENT(0x2e, 0x41), /* LLC Misses */
> + [5] = ARCH_EVENT(0xc4, 0x0),
> + [6] = ARCH_EVENT(0xc5, 0x0), /* Branch Misses Retired */
> + [7] = ARCH_EVENT(0xa4, 0x1), /* Topdown Slots */
> +};
> +
> +static struct kvm_vcpu *new_vcpu(void *guest_code)
> +{
> + struct kvm_vm *vm;
> + struct kvm_vcpu *vcpu;
> +
> + vm = vm_create_with_one_vcpu(&vcpu, guest_code);
> + vm_init_descriptor_tables(vm);
> + vcpu_init_descriptor_tables(vcpu);
> +
> + return vcpu;
> +}
> +
> +static void free_vcpu(struct kvm_vcpu *vcpu)
> +{
> + kvm_vm_free(vcpu->vm);
> +}
> +
> +static void run_vcpu(struct kvm_vcpu *vcpu, const char *msg,
> + bool (*check_ucall)(struct ucall *uc, void *data),
> + void *expect_args)
> +{
> + struct ucall uc;
> +
> + for (;;) {
> + vcpu_run(vcpu);
> + switch (get_ucall(vcpu, &uc)) {
> + case UCALL_SYNC:
> + TEST_ASSERT(check_ucall(&uc, expect_args), "%s", msg);
> + continue;
> + case UCALL_DONE:
> + break;
> + default:
> + TEST_ASSERT(false, "Unexpected exit: %s",
> + exit_reason_str(vcpu->run->exit_reason));
> + }
> + break;
> + }
> +}
> +
> +static bool first_uc_arg_non_zero(struct ucall *uc, void *data)
> +{
> + return uc->args[1];
> +}
> +
> +static void intel_guest_run_arch_event(uint8_t version, uint8_t max_gp_num,
> + bool supported, uint32_t ctr_base_msr,
> + uint64_t evt_code)
> +{
> + uint32_t global_msr = MSR_CORE_PERF_GLOBAL_CTRL;
> + unsigned int i;
> +
> + for (i = 0; i < max_gp_num; i++) {
> + wrmsr(ctr_base_msr + i, 0);
> + wrmsr(MSR_P6_EVNTSEL0 + i, EVENTSEL_OS | EVENTSEL_EN | evt_code);
> + if (version > 1)
> + wrmsr(global_msr, BIT_ULL(i));
> +
> + __asm__ __volatile__("loop ." : "+c"((int){NUM_BRANCHES}));
> +
> + if (version > 1)
> + wrmsr(global_msr, 0);
> +
> + GUEST_SYNC(supported == !!_rdpmc(i));
Just because the counter is non-zero doesn't mean that the event is
supported. "Supported" would imply that it actually works, doesn't
it?
> + }
> +
> + GUEST_DONE();
> +}
> +
> +static void test_arch_events_setup(struct kvm_vcpu *vcpu, uint8_t evt_vector,
> + uint8_t unavl_mask, uint8_t idx)
> +{
> + struct kvm_cpuid_entry2 *entry;
> + uint32_t ctr_msr = MSR_IA32_PERFCTR0;
> + bool is_supported;
> +
> + entry = vcpu_get_cpuid_entry(vcpu, 0xa);
> + entry->eax = (entry->eax & ~EVT_LEN_MASK) |
> + (evt_vector << EVT_LEN_OFS_BIT);
> + entry->ebx = (entry->ebx & ~EVENTS_MASK) | unavl_mask;
> + vcpu_set_cpuid(vcpu);
> +
> + if (vcpu_get_msr(vcpu, MSR_IA32_PERF_CAPABILITIES) & PMU_CAP_FW_WRITES)
> + ctr_msr = MSR_IA32_PMC0;
> +
> + /* Arch event x is supported if EBX[x]=0 && EAX[31:24]>x */
> + is_supported = !(entry->ebx & BIT_ULL(idx)) &&
> + (((entry->eax & EVT_LEN_MASK) >> EVT_LEN_OFS_BIT) > idx);
> +
> + vcpu_args_set(vcpu, 5, entry->eax & PMU_VERSION_MASK,
> + (entry->eax & GP_CTR_NUM_MASK) >> GP_CTR_NUM_OFS_BIT,
> + is_supported, ctr_msr, arch_events[idx]);
> +}
> +
> +static void intel_check_arch_event_is_unavl(uint8_t idx)
> +{
> + const char *msg = "Unavailable arch event is counting.";
> + uint8_t eax_evt_vec, ebx_unavl_mask, i, j;
> + struct kvm_vcpu *vcpu;
> +
> + /*
> + * A brute force iteration of all combinations of values is likely to
> + * exhaust the limit of the single-threaded thread fd nums, so it's
> + * tested here by iterating through all valid values on a single bit.
> + */
> + for (i = 0; i < ARRAY_SIZE(arch_events); i++) {
> + eax_evt_vec = BIT_ULL(i);
> + for (j = 0; j < ARRAY_SIZE(arch_events); j++) {
> + ebx_unavl_mask = BIT_ULL(j);
> +
> + vcpu = new_vcpu(intel_guest_run_arch_event);
> + test_arch_events_setup(vcpu, eax_evt_vec,
> + ebx_unavl_mask, idx);
> + run_vcpu(vcpu, msg, first_uc_arg_non_zero, NULL);
> + free_vcpu(vcpu);
> + }
> + }
> +}
> +
> +static void intel_test_arch_events(void)
> +{
> + uint8_t idx;
> +
> + for (idx = 0; idx < ARRAY_SIZE(arch_events); idx++) {
> + /*
> + * Given the stability of performance event recurrence,
> + * only these arch events are currently being tested:
> + * - Core cycle event (idx = 0)
> + * - Instruction retired event (idx = 1)
> + * - Reference cycles event (idx = 2)
Note that reference cycles is one event that actually cannot be
successfully virtualized.
> + * - Branch instruction retired event (idx = 5)
> + */
> + if (idx > 2 && idx != 5)
> + continue;
> +
> + intel_check_arch_event_is_unavl(idx);
> + }
> +}
> +
> +static void intel_test_pmu_cpuid(void)
> +{
> + intel_test_arch_events();
> +}
> +
> +int main(int argc, char *argv[])
> +{
> + TEST_REQUIRE(get_kvm_param_bool("enable_pmu"));
> +
> + if (host_cpu_is_intel) {
> + TEST_REQUIRE(kvm_cpu_has_p(X86_PROPERTY_PMU_VERSION));
> + TEST_REQUIRE(kvm_cpu_property(X86_PROPERTY_PMU_VERSION) > 0);
> + TEST_REQUIRE(kvm_cpu_has(X86_FEATURE_PDCM));
> +
> + intel_test_pmu_cpuid();
> + }
> +
> + return 0;
> +}
> --
> 2.40.0
>
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