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KVM: selftests: Add svm_pmu_host_guest_test for Host-Only/Guest-Only bits

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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
with EFER.SVME clear and set, as well as in host mode and guest mode.
The test also verifies that updating Host-Only / Guest-Only bits for a
PMC works as intended, and that event filtering is still respected.

Signed-off-by: Jim Mattson <jmattson@google.com>
Co-developed-by: Yosry Ahmed <yosry@kernel.org>
Signed-off-by: Yosry Ahmed <yosry@kernel.org>
Link: https://patch.msgid.link/20260610003030.2957261-6-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
This commit is contained in:
Jim Mattson 2026-06-09 17:30:30 -07:00 committed by Sean Christopherson
parent 0c277410f5
commit 70f4701c12
3 changed files with 222 additions and 0 deletions
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1
tools/testing/selftests/kvm/Makefile.kvm
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@ -120,6 +120,7 @@ TEST_GEN_PROGS_x86 += x86/svm_nested_soft_inject_test
TEST_GEN_PROGS_x86 += x86/svm_nested_vmcb12_gpa
TEST_GEN_PROGS_x86 += x86/svm_nested_pat_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

6
tools/testing/selftests/kvm/include/x86/pmu.h
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@ -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)

215
tools/testing/selftests/kvm/x86/svm_pmu_host_guest_test.c Normal file
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@ -0,0 +1,215 @@
// 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 with different
* combinations of EFER.SVME and host/guest mode -- as well as event filtering.
*/
#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 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_NONE 0 /* Neither bit set */
#define PMC_G 1 /* Guest-Only bit set */
#define PMC_H 2 /* Host-Only bit set */
#define PMC_HG 3 /* Both bits set */
#define NR_PMCS 4
#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);
}
}
static uint64_t l2_deltas[NR_PMCS];
static void l2_guest_code(void)
{
run_and_measure(l2_deltas);
vmmcall();
}
static void l1_guest_code(struct svm_test_data *svm)
{
struct vmcb *vmcb = svm->vmcb;
uint64_t deltas[NR_PMCS];
uint64_t eventsel;
int i;
/* 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_G)
eventsel |= AMD64_EVENTSEL_GUESTONLY;
if (i & PMC_H)
eventsel |= AMD64_EVENTSEL_HOSTONLY;
wrmsr(MSR_F15H_PERF_CTL + 2 * i, eventsel);
wrmsr(MSR_F15H_PERF_CTR + 2 * i, 0);
}
/* Step 1: SVME=0 - Only the counter with neither bits set counts */
wrmsr(MSR_EFER, rdmsr(MSR_EFER) & ~EFER_SVME);
run_and_measure(deltas);
assert_pmc_counts(deltas, BIT(PMC_NONE));
/* 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, BIT(PMC_NONE) | BIT(PMC_H) | BIT(PMC_HG));
/* Step 3: VMRUN to L2 - In "guest mode"; Host-Only stops */
generic_svm_setup(svm, l2_guest_code);
vmcb->control.intercept &= ~(1ULL << INTERCEPT_MSR_PROT);
run_guest(vmcb, svm->vmcb_gpa);
GUEST_ASSERT_EQ(vmcb->control.exit_code, SVM_EXIT_VMMCALL);
assert_pmc_counts(l2_deltas, BIT(PMC_NONE) | BIT(PMC_G) | BIT(PMC_HG));
/* Step 4: After VMEXIT to L1 - Back in "host mode"; Guest-Only stops */
run_and_measure(deltas);
assert_pmc_counts(deltas, BIT(PMC_NONE) | BIT(PMC_H) | BIT(PMC_HG));
/* Step 5: Set KVM_PMU_EVENT_DENY - all counters stop */
GUEST_SYNC(KVM_PMU_EVENT_DENY);
run_and_measure(deltas);
assert_pmc_counts(deltas, 0);
/* Step 6: Set KVM_PMU_EVENT_ALLOW - back to all except Guest-only */
GUEST_SYNC(KVM_PMU_EVENT_ALLOW);
run_and_measure(deltas);
assert_pmc_counts(deltas, BIT(PMC_NONE) | BIT(PMC_H) | BIT(PMC_HG));
/* Step 7: Clear Host-Only for PMC_HG - counter stops in "host mode" */
eventsel = rdmsr(MSR_F15H_PERF_CTL + 2 * PMC_HG);
wrmsr(MSR_F15H_PERF_CTL + 2 * PMC_HG, eventsel & ~AMD64_EVENTSEL_HOSTONLY);
run_and_measure(deltas);
assert_pmc_counts(deltas, BIT(PMC_NONE) | BIT(PMC_H));
/* Step 8: Restore Host-Only for PMC_HG - counter counts again */
wrmsr(MSR_F15H_PERF_CTL + 2 * PMC_HG, eventsel);
run_and_measure(deltas);
assert_pmc_counts(deltas, BIT(PMC_NONE) | BIT(PMC_H) | BIT(PMC_HG));
/* Step 9: Clear SVME - Only the counter with neither bits set counts */
wrmsr(MSR_EFER, rdmsr(MSR_EFER) & ~EFER_SVME);
run_and_measure(deltas);
assert_pmc_counts(deltas, BIT(PMC_NONE));
GUEST_DONE();
}
static struct kvm_pmu_event_filter *alloc_event_filter(u64 event)
{
struct kvm_pmu_event_filter *filter;
filter = malloc(sizeof(*filter) + sizeof(event));
TEST_ASSERT(filter != NULL, "Filter allocation failed");
memset(filter, 0, sizeof(*filter));
memcpy(filter->events, &event, sizeof(event));
filter->nevents = 1;
filter->action = KVM_PMU_EVENT_ALLOW;
return filter;
}
int main(int argc, char *argv[])
{
struct kvm_pmu_event_filter *filter;
struct kvm_vcpu *vcpu;
struct kvm_vm *vm;
struct ucall uc;
gva_t svm_gva;
TEST_REQUIRE(kvm_cpu_has(X86_FEATURE_SVM));
TEST_REQUIRE(kvm_is_pmu_enabled());
TEST_REQUIRE(kvm_is_mediated_pmu_enabled());
vm = vm_create_with_one_vcpu(&vcpu, l1_guest_code);
vcpu_alloc_svm(vm, &svm_gva);
vcpu_args_set(vcpu, 1, svm_gva);
filter = alloc_event_filter(AMD_ZEN_INSTRUCTIONS_RETIRED);
for (;;) {
vcpu_run(vcpu);
TEST_ASSERT_KVM_EXIT_REASON(vcpu, KVM_EXIT_IO);
switch (get_ucall(vcpu, &uc)) {
case UCALL_ABORT:
REPORT_GUEST_ASSERT(uc);
goto done;
case UCALL_DONE:
goto done;
case UCALL_SYNC:
filter->action = uc.args[1];
vm_ioctl(vm, KVM_SET_PMU_EVENT_FILTER, filter);
break;
default:
TEST_FAIL("Unknown ucall %lu", uc.cmd);
goto done;
}
}
done:
kvm_vm_free(vm);
return 0;
}