selftests: kvm/x86: Add test for KVM_SET_PMU_EVENT_FILTER

Verify that the PMU event filter works as expected.

Note that the virtual PMU doesn't work as expected on AMD Zen CPUs (an
intercepted rdmsr is counted as a retired branch instruction), but the
PMU event filter does work.
Signed-off-by: Jim Mattson <jmattson@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <20220115052431.447232-7-jmattson@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

tools/testing/selftests/kvm/.gitignore

@@ -22,6 +22,7 @@
 /x86_64/mmio_warning_test
 /x86_64/mmu_role_test
 /x86_64/platform_info_test
+/x86_64/pmu_event_filter_test
 /x86_64/set_boot_cpu_id
 /x86_64/set_sregs_test
 /x86_64/sev_migrate_tests

tools/testing/selftests/kvm/Makefile

@@ -56,6 +56,7 @@ TEST_GEN_PROGS_x86_64 += x86_64/kvm_pv_test
 TEST_GEN_PROGS_x86_64 += x86_64/mmio_warning_test
 TEST_GEN_PROGS_x86_64 += x86_64/mmu_role_test
 TEST_GEN_PROGS_x86_64 += x86_64/platform_info_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
 TEST_GEN_PROGS_x86_64 += x86_64/smm_test

tools/testing/selftests/kvm/x86_64/pmu_event_filter_test.c

+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Test for x86 KVM_SET_PMU_EVENT_FILTER.
+ *
+ * Copyright (C) 2022, Google LLC.
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2.
+ *
+ * Verifies the expected behavior of allow lists and deny lists for
+ * virtual PMU events.
+ */
+
+#define _GNU_SOURCE /* for program_invocation_short_name */
+#include "test_util.h"
+#include "kvm_util.h"
+#include "processor.h"
+
+/*
+ * In lieu of copying perf_event.h into tools...
+ */
+#define ARCH_PERFMON_EVENTSEL_OS			(1ULL << 17)
+#define ARCH_PERFMON_EVENTSEL_ENABLE			(1ULL << 22)
+
+union cpuid10_eax {
+	struct {
+		unsigned int version_id:8;
+		unsigned int num_counters:8;
+		unsigned int bit_width:8;
+		unsigned int mask_length:8;
+	} split;
+	unsigned int full;
+};
+
+union cpuid10_ebx {
+	struct {
+		unsigned int no_unhalted_core_cycles:1;
+		unsigned int no_instructions_retired:1;
+		unsigned int no_unhalted_reference_cycles:1;
+		unsigned int no_llc_reference:1;
+		unsigned int no_llc_misses:1;
+		unsigned int no_branch_instruction_retired:1;
+		unsigned int no_branch_misses_retired:1;
+	} split;
+	unsigned int full;
+};
+
+/* End of stuff taken from perf_event.h. */
+
+/* Oddly, this isn't in perf_event.h. */
+#define ARCH_PERFMON_BRANCHES_RETIRED		5
+
+#define VCPU_ID 0
+#define NUM_BRANCHES 42
+
+/*
+ * This is how the event selector and unit mask are stored in an AMD
+ * core performance event-select register. Intel's format is similar,
+ * but the event selector is only 8 bits.
+ */
+#define EVENT(select, umask) ((select & 0xf00UL) << 24 | (select & 0xff) | \
+			      (umask & 0xff) << 8)
+
+/*
+ * "Branch instructions retired", from the Intel SDM, volume 3,
+ * "Pre-defined Architectural Performance Events."
+ */
+
+#define INTEL_BR_RETIRED EVENT(0xc4, 0)
+
+/*
+ * "Retired branch instructions", from Processor Programming Reference
+ * (PPR) for AMD Family 17h Model 01h, Revision B1 Processors,
+ * Preliminary Processor Programming Reference (PPR) for AMD Family
+ * 17h Model 31h, Revision B0 Processors, and Preliminary Processor
+ * Programming Reference (PPR) for AMD Family 19h Model 01h, Revision
+ * B1 Processors Volume 1 of 2.
+ */
+
+#define AMD_ZEN_BR_RETIRED EVENT(0xc2, 0)
+
+/*
+ * This event list comprises Intel's eight architectural events plus
+ * AMD's "retired branch instructions" for Zen[123] (and possibly
+ * other AMD CPUs).
+ */
+static const uint64_t event_list[] = {
+	EVENT(0x3c, 0),
+	EVENT(0xc0, 0),
+	EVENT(0x3c, 1),
+	EVENT(0x2e, 0x4f),
+	EVENT(0x2e, 0x41),
+	EVENT(0xc4, 0),
+	EVENT(0xc5, 0),
+	EVENT(0xa4, 1),
+	AMD_ZEN_BR_RETIRED,
+};
+
+/*
+ * If we encounter a #GP during the guest PMU sanity check, then the guest
+ * PMU is not functional. Inform the hypervisor via GUEST_SYNC(0).
+ */
+static void guest_gp_handler(struct ex_regs *regs)
+{
+	GUEST_SYNC(0);
+}
+
+/*
+ * Check that we can write a new value to the given MSR and read it back.
+ * The caller should provide a non-empty set of bits that are safe to flip.
+ *
+ * Return on success. GUEST_SYNC(0) on error.
+ */
+static void check_msr(uint32_t msr, uint64_t bits_to_flip)
+{
+	uint64_t v = rdmsr(msr) ^ bits_to_flip;
+
+	wrmsr(msr, v);
+	if (rdmsr(msr) != v)
+		GUEST_SYNC(0);
+
+	v ^= bits_to_flip;
+	wrmsr(msr, v);
+	if (rdmsr(msr) != v)
+		GUEST_SYNC(0);
+}
+
+static void intel_guest_code(void)
+{
+	check_msr(MSR_CORE_PERF_GLOBAL_CTRL, 1);
+	check_msr(MSR_P6_EVNTSEL0, 0xffff);
+	check_msr(MSR_IA32_PMC0, 0xffff);
+	GUEST_SYNC(1);
+
+	for (;;) {
+		uint64_t br0, br1;
+
+		wrmsr(MSR_CORE_PERF_GLOBAL_CTRL, 0);
+		wrmsr(MSR_P6_EVNTSEL0, ARCH_PERFMON_EVENTSEL_ENABLE |
+		      ARCH_PERFMON_EVENTSEL_OS | INTEL_BR_RETIRED);
+		wrmsr(MSR_CORE_PERF_GLOBAL_CTRL, 1);
+		br0 = rdmsr(MSR_IA32_PMC0);
+		__asm__ __volatile__("loop ." : "+c"((int){NUM_BRANCHES}));
+		br1 = rdmsr(MSR_IA32_PMC0);
+		GUEST_SYNC(br1 - br0);
+	}
+}
+
+/*
+ * To avoid needing a check for CPUID.80000001:ECX.PerfCtrExtCore[bit 23],
+ * this code uses the always-available, legacy K7 PMU MSRs, which alias to
+ * the first four of the six extended core PMU MSRs.
+ */
+static void amd_guest_code(void)
+{
+	check_msr(MSR_K7_EVNTSEL0, 0xffff);
+	check_msr(MSR_K7_PERFCTR0, 0xffff);
+	GUEST_SYNC(1);
+
+	for (;;) {
+		uint64_t br0, br1;
+
+		wrmsr(MSR_K7_EVNTSEL0, 0);
+		wrmsr(MSR_K7_EVNTSEL0, ARCH_PERFMON_EVENTSEL_ENABLE |
+		      ARCH_PERFMON_EVENTSEL_OS | AMD_ZEN_BR_RETIRED);
+		br0 = rdmsr(MSR_K7_PERFCTR0);
+		__asm__ __volatile__("loop ." : "+c"((int){NUM_BRANCHES}));
+		br1 = rdmsr(MSR_K7_PERFCTR0);
+		GUEST_SYNC(br1 - br0);
+	}
+}
+
+/*
+ * Run the VM to the next GUEST_SYNC(value), and return the value passed
+ * to the sync. Any other exit from the guest is fatal.
+ */
+static uint64_t run_vm_to_sync(struct kvm_vm *vm)
+{
+	struct kvm_run *run = vcpu_state(vm, VCPU_ID);
+	struct ucall uc;
+
+	vcpu_run(vm, VCPU_ID);
+	TEST_ASSERT(run->exit_reason == KVM_EXIT_IO,
+		    "Exit_reason other than KVM_EXIT_IO: %u (%s)\n",
+		    run->exit_reason,
+		    exit_reason_str(run->exit_reason));
+	get_ucall(vm, VCPU_ID, &uc);
+	TEST_ASSERT(uc.cmd == UCALL_SYNC,
+		    "Received ucall other than UCALL_SYNC: %lu", uc.cmd);
+	return uc.args[1];
+}
+
+/*
+ * In a nested environment or if the vPMU is disabled, the guest PMU
+ * might not work as architected (accessing the PMU MSRs may raise
+ * #GP, or writes could simply be discarded). In those situations,
+ * there is no point in running these tests. The guest code will perform
+ * a sanity check and then GUEST_SYNC(success). In the case of failure,
+ * the behavior of the guest on resumption is undefined.
+ */
+static bool sanity_check_pmu(struct kvm_vm *vm)
+{
+	bool success;
+
+	vm_install_exception_handler(vm, GP_VECTOR, guest_gp_handler);
+	success = run_vm_to_sync(vm);
+	vm_install_exception_handler(vm, GP_VECTOR, NULL);
+
+	return success;
+}
+
+static struct kvm_pmu_event_filter *make_pmu_event_filter(uint32_t nevents)
+{
+	struct kvm_pmu_event_filter *f;
+	int size = sizeof(*f) + nevents * sizeof(f->events[0]);
+
+	f = malloc(size);
+	TEST_ASSERT(f, "Out of memory");
+	memset(f, 0, size);
+	f->nevents = nevents;
+	return f;
+}
+
+static struct kvm_pmu_event_filter *event_filter(uint32_t action)
+{
+	struct kvm_pmu_event_filter *f;
+	int i;
+
+	f = make_pmu_event_filter(ARRAY_SIZE(event_list));
+	f->action = action;
+	for (i = 0; i < ARRAY_SIZE(event_list); i++)
+		f->events[i] = event_list[i];
+
+	return f;
+}
+
+/*
+ * Remove the first occurrence of 'event' (if any) from the filter's
+ * event list.
+ */
+static struct kvm_pmu_event_filter *remove_event(struct kvm_pmu_event_filter *f,
+						 uint64_t event)
+{
+	bool found = false;
+	int i;
+
+	for (i = 0; i < f->nevents; i++) {
+		if (found)
+			f->events[i - 1] = f->events[i];
+		else
+			found = f->events[i] == event;
+	}
+	if (found)
+		f->nevents--;
+	return f;
+}
+
+static void test_without_filter(struct kvm_vm *vm)
+{
+	uint64_t count = run_vm_to_sync(vm);
+
+	if (count != NUM_BRANCHES)
+		pr_info("%s: Branch instructions retired = %lu (expected %u)\n",
+			__func__, count, NUM_BRANCHES);
+	TEST_ASSERT(count, "Allowed PMU event is not counting");
+}
+
+static uint64_t test_with_filter(struct kvm_vm *vm,
+				 struct kvm_pmu_event_filter *f)
+{
+	vm_ioctl(vm, KVM_SET_PMU_EVENT_FILTER, (void *)f);
+	return run_vm_to_sync(vm);
+}
+
+static void test_member_deny_list(struct kvm_vm *vm)
+{
+	struct kvm_pmu_event_filter *f = event_filter(KVM_PMU_EVENT_DENY);
+	uint64_t count = test_with_filter(vm, f);
+
+	free(f);
+	if (count)
+		pr_info("%s: Branch instructions retired = %lu (expected 0)\n",
+			__func__, count);
+	TEST_ASSERT(!count, "Disallowed PMU Event is counting");
+}
+
+static void test_member_allow_list(struct kvm_vm *vm)
+{
+	struct kvm_pmu_event_filter *f = event_filter(KVM_PMU_EVENT_ALLOW);
+	uint64_t count = test_with_filter(vm, f);
+
+	free(f);
+	if (count != NUM_BRANCHES)
+		pr_info("%s: Branch instructions retired = %lu (expected %u)\n",
+			__func__, count, NUM_BRANCHES);
+	TEST_ASSERT(count, "Allowed PMU event is not counting");
+}
+
+static void test_not_member_deny_list(struct kvm_vm *vm)
+{
+	struct kvm_pmu_event_filter *f = event_filter(KVM_PMU_EVENT_DENY);
+	uint64_t count;
+
+	remove_event(f, INTEL_BR_RETIRED);
+	remove_event(f, AMD_ZEN_BR_RETIRED);
+	count = test_with_filter(vm, f);
+	free(f);
+	if (count != NUM_BRANCHES)
+		pr_info("%s: Branch instructions retired = %lu (expected %u)\n",
+			__func__, count, NUM_BRANCHES);
+	TEST_ASSERT(count, "Allowed PMU event is not counting");
+}
+
+static void test_not_member_allow_list(struct kvm_vm *vm)
+{
+	struct kvm_pmu_event_filter *f = event_filter(KVM_PMU_EVENT_ALLOW);
+	uint64_t count;
+
+	remove_event(f, INTEL_BR_RETIRED);
+	remove_event(f, AMD_ZEN_BR_RETIRED);
+	count = test_with_filter(vm, f);
+	free(f);
+	if (count)
+		pr_info("%s: Branch instructions retired = %lu (expected 0)\n",
+			__func__, count);
+	TEST_ASSERT(!count, "Disallowed PMU Event is counting");
+}
+
+/*
+ * Check for a non-zero PMU version, at least one general-purpose
+ * counter per logical processor, an EBX bit vector of length greater
+ * than 5, and EBX[5] clear.
+ */
+static bool check_intel_pmu_leaf(struct kvm_cpuid_entry2 *entry)
+{
+	union cpuid10_eax eax = { .full = entry->eax };
+	union cpuid10_ebx ebx = { .full = entry->ebx };
+
+	return eax.split.version_id && eax.split.num_counters > 0 &&
+		eax.split.mask_length > ARCH_PERFMON_BRANCHES_RETIRED &&
+		!ebx.split.no_branch_instruction_retired;
+}
+
+/*
+ * Note that CPUID leaf 0xa is Intel-specific. This leaf should be
+ * clear on AMD hardware.
+ */
+static bool use_intel_pmu(void)
+{
+	struct kvm_cpuid_entry2 *entry;
+	struct kvm_cpuid2 *cpuid;
+
+	cpuid = kvm_get_supported_cpuid();
+	entry = kvm_get_supported_cpuid_index(0xa, 0);
+	return is_intel_cpu() && entry && check_intel_pmu_leaf(entry);
+}
+
+static bool is_zen1(uint32_t eax)
+{
+	return x86_family(eax) == 0x17 && x86_model(eax) <= 0x0f;
+}
+
+static bool is_zen2(uint32_t eax)
+{
+	return x86_family(eax) == 0x17 &&
+		x86_model(eax) >= 0x30 && x86_model(eax) <= 0x3f;
+}
+
+static bool is_zen3(uint32_t eax)
+{
+	return x86_family(eax) == 0x19 && x86_model(eax) <= 0x0f;
+}
+
+/*
+ * Determining AMD support for a PMU event requires consulting the AMD
+ * PPR for the CPU or reference material derived therefrom. The AMD
+ * test code herein has been verified to work on Zen1, Zen2, and Zen3.
+ *
+ * Feel free to add more AMD CPUs that are documented to support event
+ * select 0xc2 umask 0 as "retired branch instructions."
+ */
+static bool use_amd_pmu(void)
+{
+	struct kvm_cpuid_entry2 *entry;
+	struct kvm_cpuid2 *cpuid;
+
+	cpuid = kvm_get_supported_cpuid();
+	entry = kvm_get_supported_cpuid_index(1, 0);
+	return is_amd_cpu() && entry &&
+		(is_zen1(entry->eax) ||
+		 is_zen2(entry->eax) ||
+		 is_zen3(entry->eax));
+}
+
+int main(int argc, char *argv[])
+{
+	void (*guest_code)(void) = NULL;
+	struct kvm_vm *vm;
+	int r;
+
+	/* Tell stdout not to buffer its content */
+	setbuf(stdout, NULL);
+
+	r = kvm_check_cap(KVM_CAP_PMU_EVENT_FILTER);
+	if (!r) {
+		print_skip("KVM_CAP_PMU_EVENT_FILTER not supported");
+		exit(KSFT_SKIP);
+	}
+
+	if (use_intel_pmu())
+		guest_code = intel_guest_code;
+	else if (use_amd_pmu())
+		guest_code = amd_guest_code;
+
+	if (!guest_code) {
+		print_skip("Don't know how to test this guest PMU");
+		exit(KSFT_SKIP);
+	}
+
+	vm = vm_create_default(VCPU_ID, 0, guest_code);
+
+	vm_init_descriptor_tables(vm);
+	vcpu_init_descriptor_tables(vm, VCPU_ID);
+
+	if (!sanity_check_pmu(vm)) {
+		print_skip("Guest PMU is not functional");
+		exit(KSFT_SKIP);
+	}
+
+	test_without_filter(vm);
+	test_member_deny_list(vm);
+	test_member_allow_list(vm);
+	test_not_member_deny_list(vm);
+	test_not_member_allow_list(vm);
+
+	kvm_vm_free(vm);
+
+	return 0;
+}