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Message-ID: <20250530185239.2335185-4-jmattson@google.com>
Date: Fri, 30 May 2025 11:52:25 -0700
From: Jim Mattson <jmattson@...gle.com>
To: linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
Sean Christopherson <seanjc@...gle.com>, Paolo Bonzini <pbonzini@...hat.com>
Cc: Jim Mattson <jmattson@...gle.com>
Subject: [PATCH v4 3/3] KVM: selftests: Test behavior of KVM_X86_DISABLE_EXITS_APERFMPERF
For a VCPU thread pinned to a single LPU, verify that interleaved host
and guest reads of IA32_[AM]PERF return strictly increasing values when
APERFMPERF exiting is disabled.
Signed-off-by: Jim Mattson <jmattson@...gle.com>
---
tools/testing/selftests/kvm/Makefile.kvm | 1 +
.../testing/selftests/kvm/include/kvm_util.h | 2 +
tools/testing/selftests/kvm/lib/kvm_util.c | 17 +++
.../selftests/kvm/x86/aperfmperf_test.c | 132 ++++++++++++++++++
4 files changed, 152 insertions(+)
create mode 100644 tools/testing/selftests/kvm/x86/aperfmperf_test.c
diff --git a/tools/testing/selftests/kvm/Makefile.kvm b/tools/testing/selftests/kvm/Makefile.kvm
index 3e786080473d..8d42a3bd0dd8 100644
--- a/tools/testing/selftests/kvm/Makefile.kvm
+++ b/tools/testing/selftests/kvm/Makefile.kvm
@@ -131,6 +131,7 @@ TEST_GEN_PROGS_x86 += x86/amx_test
TEST_GEN_PROGS_x86 += x86/max_vcpuid_cap_test
TEST_GEN_PROGS_x86 += x86/triple_fault_event_test
TEST_GEN_PROGS_x86 += x86/recalc_apic_map_test
+TEST_GEN_PROGS_x86 += x86/aperfmperf_test
TEST_GEN_PROGS_x86 += access_tracking_perf_test
TEST_GEN_PROGS_x86 += coalesced_io_test
TEST_GEN_PROGS_x86 += dirty_log_perf_test
diff --git a/tools/testing/selftests/kvm/include/kvm_util.h b/tools/testing/selftests/kvm/include/kvm_util.h
index 93013564428b..43a1bef10ec0 100644
--- a/tools/testing/selftests/kvm/include/kvm_util.h
+++ b/tools/testing/selftests/kvm/include/kvm_util.h
@@ -1158,4 +1158,6 @@ bool vm_is_gpa_protected(struct kvm_vm *vm, vm_paddr_t paddr);
uint32_t guest_get_vcpuid(void);
+int pin_task_to_one_cpu(void);
+
#endif /* SELFTEST_KVM_UTIL_H */
diff --git a/tools/testing/selftests/kvm/lib/kvm_util.c b/tools/testing/selftests/kvm/lib/kvm_util.c
index 5649cf2f40e8..b6c707ab92d7 100644
--- a/tools/testing/selftests/kvm/lib/kvm_util.c
+++ b/tools/testing/selftests/kvm/lib/kvm_util.c
@@ -10,6 +10,7 @@
#include "ucall_common.h"
#include <assert.h>
+#include <pthread.h>
#include <sched.h>
#include <sys/mman.h>
#include <sys/resource.h>
@@ -2321,3 +2322,19 @@ bool vm_is_gpa_protected(struct kvm_vm *vm, vm_paddr_t paddr)
pg = paddr >> vm->page_shift;
return sparsebit_is_set(region->protected_phy_pages, pg);
}
+
+int pin_task_to_one_cpu(void)
+{
+ int cpu = sched_getcpu();
+ cpu_set_t cpuset;
+ int rc;
+
+ CPU_ZERO(&cpuset);
+ CPU_SET(cpu, &cpuset);
+
+ rc = pthread_setaffinity_np(pthread_self(), sizeof(cpuset), &cpuset);
+ TEST_ASSERT(rc == 0, "%s: Can't set thread affinity", __func__);
+
+ return cpu;
+}
+
diff --git a/tools/testing/selftests/kvm/x86/aperfmperf_test.c b/tools/testing/selftests/kvm/x86/aperfmperf_test.c
new file mode 100644
index 000000000000..64d976156693
--- /dev/null
+++ b/tools/testing/selftests/kvm/x86/aperfmperf_test.c
@@ -0,0 +1,132 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Test for KVM_X86_DISABLE_EXITS_APERFMPERF
+ *
+ * Copyright (C) 2025, Google LLC.
+ *
+ * Test the ability to disable VM-exits for rdmsr of IA32_APERF and
+ * IA32_MPERF. When these VM-exits are disabled, reads of these MSRs
+ * return the host's values.
+ *
+ * Note: Requires read access to /dev/cpu/<lpu>/msr to read host MSRs.
+ */
+
+#include <fcntl.h>
+#include <limits.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdint.h>
+#include <unistd.h>
+#include <asm/msr-index.h>
+
+#include "kvm_util.h"
+#include "processor.h"
+#include "test_util.h"
+
+#define NUM_ITERATIONS 100
+
+static int open_dev_msr(int cpu)
+{
+ char path[PATH_MAX];
+
+ snprintf(path, sizeof(path), "/dev/cpu/%d/msr", cpu);
+ return open_path_or_exit(path, O_RDONLY);
+}
+
+static uint64_t read_dev_msr(int msr_fd, uint32_t msr)
+{
+ uint64_t data;
+ ssize_t rc;
+
+ rc = pread(msr_fd, &data, sizeof(data), msr);
+ TEST_ASSERT(rc == sizeof(data), "Read of MSR 0x%x failed", msr);
+
+ return data;
+}
+
+static void guest_code(void)
+{
+ int i;
+
+ for (i = 0; i < NUM_ITERATIONS; i++)
+ GUEST_SYNC2(rdmsr(MSR_IA32_APERF), rdmsr(MSR_IA32_MPERF));
+
+ GUEST_DONE();
+}
+
+int main(int argc, char *argv[])
+{
+ uint64_t host_aperf_before, host_mperf_before;
+ struct kvm_vcpu *vcpu;
+ struct kvm_vm *vm;
+ int msr_fd;
+ int cpu;
+ int i;
+
+ cpu = pin_task_to_one_cpu();
+
+ msr_fd = open_dev_msr(cpu);
+
+ /*
+ * This test requires a non-standard VM initialization, because
+ * KVM_ENABLE_CAP cannot be used on a VM file descriptor after
+ * a VCPU has been created.
+ */
+ vm = vm_create(1);
+
+ TEST_REQUIRE(vm_check_cap(vm, KVM_CAP_X86_DISABLE_EXITS) &
+ KVM_X86_DISABLE_EXITS_APERFMPERF);
+
+ vm_enable_cap(vm, KVM_CAP_X86_DISABLE_EXITS,
+ KVM_X86_DISABLE_EXITS_APERFMPERF);
+
+ vcpu = vm_vcpu_add(vm, 0, guest_code);
+
+ host_aperf_before = read_dev_msr(msr_fd, MSR_IA32_APERF);
+ host_mperf_before = read_dev_msr(msr_fd, MSR_IA32_MPERF);
+
+ for (i = 0; i < NUM_ITERATIONS; i++) {
+ uint64_t host_aperf_after, host_mperf_after;
+ uint64_t guest_aperf, guest_mperf;
+ struct ucall uc;
+
+ vcpu_run(vcpu);
+ TEST_ASSERT_KVM_EXIT_REASON(vcpu, KVM_EXIT_IO);
+
+ switch (get_ucall(vcpu, &uc)) {
+ case UCALL_DONE:
+ break;
+ case UCALL_ABORT:
+ REPORT_GUEST_ASSERT(uc);
+ case UCALL_SYNC:
+ guest_aperf = uc.args[0];
+ guest_mperf = uc.args[1];
+
+ host_aperf_after = read_dev_msr(msr_fd, MSR_IA32_APERF);
+ host_mperf_after = read_dev_msr(msr_fd, MSR_IA32_MPERF);
+
+ TEST_ASSERT(host_aperf_before < guest_aperf,
+ "APERF: host_before (0x%" PRIx64 ") >= guest (0x%" PRIx64 ")",
+ host_aperf_before, guest_aperf);
+ TEST_ASSERT(guest_aperf < host_aperf_after,
+ "APERF: guest (0x%" PRIx64 ") >= host_after (0x%" PRIx64 ")",
+ guest_aperf, host_aperf_after);
+ TEST_ASSERT(host_mperf_before < guest_mperf,
+ "MPERF: host_before (0x%" PRIx64 ") >= guest (0x%" PRIx64 ")",
+ host_mperf_before, guest_mperf);
+ TEST_ASSERT(guest_mperf < host_mperf_after,
+ "MPERF: guest (0x%" PRIx64 ") >= host_after (0x%" PRIx64 ")",
+ guest_mperf, host_mperf_after);
+
+ host_aperf_before = host_aperf_after;
+ host_mperf_before = host_mperf_after;
+
+ break;
+ }
+ }
+
+ kvm_vm_free(vm);
+ close(msr_fd);
+
+ return 0;
+}
--
2.49.0.1204.g71687c7c1d-goog
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