[PATCH v4 6/6] KVM: selftests: Add svm_pmu_host_guest_test for Host-Only/Guest-Only bits

Yosry Ahmed
2026-03-26T03:12:33Z

From: Jim Mattson <jmattson@google.com>

Add a selftest to verify KVM correctly virtualizes the AMD PMU Host-Only
(bit 41) and Guest-Only (bit 40) event selector bits across all relevant
SVM state transitions.

The test programs 4 PMCs simultaneously with all combinations of the
Host-Only and Guest-Only bits, then verifies correct counting behavior:
1. SVME=0: all counters count (Host-Only/Guest-Only bits ignored)
2. Set SVME=1: Host-Only and neither/both count; Guest-Only stops
3. VMRUN to L2: Guest-Only and neither/both count; Host-Only stops
4. VMEXIT to L1: Host-Only and neither/both count; Guest-Only stops
5. Clear SVME=0: all counters count (bits ignored again)

Signed-off-by: Jim Mattson <jmattson@google.com>
Signed-off-by: Yosry Ahmed <yosry@kernel.org>
---
tools/testing/selftests/kvm/Makefile.kvm | 1 +
tools/testing/selftests/kvm/include/x86/pmu.h | 6 +
.../selftests/kvm/include/x86/processor.h | 2 +
.../kvm/x86/svm_pmu_host_guest_test.c | 199 ++++++++++++++++++
4 files changed, 208 insertions(+)
create mode 100644 tools/testing/selftests/kvm/x86/svm_pmu_host_guest_test.c

diff --git a/tools/testing/selftests/kvm/Makefile.kvm b/tools/testing/selftests/kvm/Makefile.kvm
index 3d372d78a2756..9418c45291231 100644
--- a/tools/testing/selftests/kvm/Makefile.kvm
+++ b/tools/testing/selftests/kvm/Makefile.kvm
@@ -116,6 +116,7 @@ TEST_GEN_PROGS_x86 += x86/svm_nested_invalid_vmcb12_gpa
TEST_GEN_PROGS_x86 += x86/svm_nested_shutdown_test
TEST_GEN_PROGS_x86 += x86/svm_nested_soft_inject_test
TEST_GEN_PROGS_x86 += x86/svm_lbr_nested_state
+TEST_GEN_PROGS_x86 += x86/svm_pmu_host_guest_test
TEST_GEN_PROGS_x86 += x86/tsc_scaling_sync
TEST_GEN_PROGS_x86 += x86/sync_regs_test
TEST_GEN_PROGS_x86 += x86/ucna_injection_test
diff --git a/tools/testing/selftests/kvm/include/x86/pmu.h b/tools/testing/selftests/kvm/include/x86/pmu.h
index 72575eadb63a0..af9b279c78df4 100644
--- a/tools/testing/selftests/kvm/include/x86/pmu.h
+++ b/tools/testing/selftests/kvm/include/x86/pmu.h
@@ -38,6 +38,12 @@
#define ARCH_PERFMON_EVENTSEL_INV BIT_ULL(23)
#define ARCH_PERFMON_EVENTSEL_CMASK GENMASK_ULL(31, 24)

+/*
+ * These are AMD-specific bits.
+ */
+#define AMD64_EVENTSEL_GUESTONLY BIT_ULL(40)
+#define AMD64_EVENTSEL_HOSTONLY BIT_ULL(41)
+
/* RDPMC control flags, Intel only. */
#define INTEL_RDPMC_METRICS BIT_ULL(29)
#define INTEL_RDPMC_FIXED BIT_ULL(30)
diff --git a/tools/testing/selftests/kvm/include/x86/processor.h b/tools/testing/selftests/kvm/include/x86/processor.h
index d8634a760a609..4cc1ba8752347 100644
--- a/tools/testing/selftests/kvm/include/x86/processor.h
+++ b/tools/testing/selftests/kvm/include/x86/processor.h
@@ -19,6 +19,8 @@
#include "kvm_util.h"
#include "ucall_common.h"

+#define __stack_aligned__ __aligned(16)
+
extern bool host_cpu_is_intel;
extern bool host_cpu_is_amd;
extern bool host_cpu_is_hygon;
diff --git a/tools/testing/selftests/kvm/x86/svm_pmu_host_guest_test.c b/tools/testing/selftests/kvm/x86/svm_pmu_host_guest_test.c
new file mode 100644
index 0000000000000..a08c03a40d4f6
--- /dev/null
+++ b/tools/testing/selftests/kvm/x86/svm_pmu_host_guest_test.c
@@ -0,0 +1,199 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * KVM nested SVM PMU Host-Only/Guest-Only test
+ *
+ * Copyright (C) 2026, Google LLC.
+ *
+ * Test that KVM correctly virtualizes the AMD PMU Host-Only (bit 41) and
+ * Guest-Only (bit 40) event selector bits across all SVM state
+ * transitions.
+ *
+ * Programs 4 PMCs simultaneously with all combinations of Host-Only and
+ * Guest-Only bits, then verifies correct counting behavior through:
+ * 1. SVME=0: all counters count (Host-Only/Guest-Only bits ignored)
+ * 2. Set SVME=1: Host-Only and neither/both count; Guest-Only stops
+ * 3. VMRUN to L2: Guest-Only and neither/both count; Host-Only stops
+ * 4. VMEXIT to L1: Host-Only and neither/both count; Guest-Only stops
+ * 5. Clear SVME=0: all counters count (bits ignored again)
+ */
+#include <fcntl.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "test_util.h"
+#include "kvm_util.h"
+#include "processor.h"
+#include "svm_util.h"
+#include "pmu.h"
+
+#define L2_GUEST_STACK_SIZE 255
+
+#define EVENTSEL_RETIRED_INSNS (ARCH_PERFMON_EVENTSEL_OS | \
+ ARCH_PERFMON_EVENTSEL_USR | \
+ ARCH_PERFMON_EVENTSEL_ENABLE | \
+ AMD_ZEN_INSTRUCTIONS_RETIRED)
+
+/* PMC configurations: index corresponds to Host-Only | Guest-Only bits */
+#define PMC_NEITHER 0 /* Neither bit set */
+#define PMC_GUESTONLY 1 /* Guest-Only bit set */
+#define PMC_HOSTONLY 2 /* Host-Only bit set */
+#define PMC_BOTH 3 /* Both bits set */
+#define NR_PMCS 4
+
+/* Bitmasks for which PMCs should be counting in each state */
+#define COUNTS_ALL (BIT(PMC_NEITHER) | BIT(PMC_GUESTONLY) | \
+ BIT(PMC_HOSTONLY) | BIT(PMC_BOTH))
+#define COUNTS_L1 (BIT(PMC_NEITHER) | BIT(PMC_HOSTONLY) | BIT(PMC_BOTH))
+#define COUNTS_L2 (BIT(PMC_NEITHER) | BIT(PMC_GUESTONLY) | BIT(PMC_BOTH))
+
+#define LOOP_INSNS 1000
+
+static __always_inline void run_instruction_loop(void)
+{
+ unsigned int i;
+
+ for (i = 0; i < LOOP_INSNS; i++)
+ __asm__ __volatile__("nop");
+}
+
+static __always_inline void read_counters(uint64_t *counts)
+{
+ int i;
+
+ for (i = 0; i < NR_PMCS; i++)
+ counts[i] = rdmsr(MSR_F15H_PERF_CTR + 2 * i);
+}
+
+static __always_inline void run_and_measure(uint64_t *deltas)
+{
+ uint64_t before[NR_PMCS], after[NR_PMCS];
+ int i;
+
+ read_counters(before);
+ run_instruction_loop();
+ read_counters(after);
+
+ for (i = 0; i < NR_PMCS; i++)
+ deltas[i] = after[i] - before[i];
+}
+
+static void assert_pmc_counts(uint64_t *deltas, unsigned int expected_counting)
+{
+ int i;
+
+ for (i = 0; i < NR_PMCS; i++) {
+ if (expected_counting & BIT(i))
+ GUEST_ASSERT_NE(deltas[i], 0);
+ else
+ GUEST_ASSERT_EQ(deltas[i], 0);
+ }
+}
+
+struct test_data {
+ uint64_t l2_deltas[NR_PMCS];
+ bool l2_done;
+};
+
+static struct test_data *test_data;
+
+static void l2_guest_code(void)
+{
+ run_and_measure(test_data->l2_deltas);
+ test_data->l2_done = true;
+ vmmcall();
+}
+
+static void l1_guest_code(struct svm_test_data *svm, struct test_data *data)
+{
+ unsigned long l2_guest_stack[L2_GUEST_STACK_SIZE] __stack_aligned__;
+ struct vmcb *vmcb = svm->vmcb;
+ uint64_t deltas[NR_PMCS];
+ uint64_t eventsel;
+ int i;
+
+ test_data = data;
+
+ /* Program 4 PMCs with all combinations of Host-Only/Guest-Only bits */
+ for (i = 0; i < NR_PMCS; i++) {
+ eventsel = EVENTSEL_RETIRED_INSNS;
+ if (i & PMC_GUESTONLY)
+ eventsel |= AMD64_EVENTSEL_GUESTONLY;
+ if (i & PMC_HOSTONLY)
+ eventsel |= AMD64_EVENTSEL_HOSTONLY;
+ wrmsr(MSR_F15H_PERF_CTL + 2 * i, eventsel);
+ wrmsr(MSR_F15H_PERF_CTR + 2 * i, 0);
+ }
+
+ /* Step 1: SVME=0 - Host-Only/Guest-Only bits ignored; all count */
+ wrmsr(MSR_EFER, rdmsr(MSR_EFER) & ~EFER_SVME);
+ run_and_measure(deltas);
+ assert_pmc_counts(deltas, COUNTS_ALL);
+
+ /* Step 2: Set SVME=1 - In L1 "host mode"; Guest-Only stops */
+ wrmsr(MSR_EFER, rdmsr(MSR_EFER) | EFER_SVME);
+ run_and_measure(deltas);
+ assert_pmc_counts(deltas, COUNTS_L1);
+
+ /* Step 3: VMRUN to L2 - In "guest mode"; Host-Only stops */
+ generic_svm_setup(svm, l2_guest_code,
+ &l2_guest_stack[L2_GUEST_STACK_SIZE]);
+ vmcb->control.intercept &= ~(1ULL << INTERCEPT_MSR_PROT);
+
+ run_guest(vmcb, svm->vmcb_gpa);
+
+ GUEST_ASSERT_EQ(vmcb->control.exit_code, SVM_EXIT_VMMCALL);
+ GUEST_ASSERT(data->l2_done);
+ assert_pmc_counts(data->l2_deltas, COUNTS_L2);
+
+ /* Step 4: After VMEXIT to L1 - Back in "host mode"; Guest-Only stops */
+ run_and_measure(deltas);
+ assert_pmc_counts(deltas, COUNTS_L1);
+
+ /* Step 5: Clear SVME - Host-Only/Guest-Only bits ignored; all count */
+ wrmsr(MSR_EFER, rdmsr(MSR_EFER) & ~EFER_SVME);
+ run_and_measure(deltas);
+ assert_pmc_counts(deltas, COUNTS_ALL);
+
+ GUEST_DONE();
+}
+
+int main(int argc, char *argv[])
+{
+ vm_vaddr_t svm_gva, data_gva;
+ struct test_data *data_hva;
+ struct kvm_vcpu *vcpu;
+ struct kvm_vm *vm;
+ struct ucall uc;
+
+ TEST_REQUIRE(kvm_cpu_has(X86_FEATURE_SVM));
+ TEST_REQUIRE(kvm_is_pmu_enabled());
+ TEST_REQUIRE(get_kvm_amd_param_bool("enable_mediated_pmu"));
+ TEST_REQUIRE(host_cpu_is_amd && kvm_cpu_family() >= 0x17);
+
+ vm = vm_create_with_one_vcpu(&vcpu, l1_guest_code);
+
+ vcpu_alloc_svm(vm, &svm_gva);
+
+ data_gva = vm_vaddr_alloc_page(vm);
+ data_hva = addr_gva2hva(vm, data_gva);
+ memset(data_hva, 0, sizeof(*data_hva));
+
+ vcpu_args_set(vcpu, 2, svm_gva, data_gva);
+
+ vcpu_run(vcpu);
+ TEST_ASSERT_KVM_EXIT_REASON(vcpu, KVM_EXIT_IO);
+
+ switch (get_ucall(vcpu, &uc)) {
+ case UCALL_ABORT:
+ REPORT_GUEST_ASSERT(uc);
+ break;
+ case UCALL_DONE:
+ break;
+ default:
+ TEST_FAIL("Unknown ucall %lu", uc.cmd);
+ }
+
+ kvm_vm_free(vm);
+ return 0;
+}
--
2.53.0.1018.g2bb0e51243-goog