aperfmperf_test.c

  1// SPDX-License-Identifier: GPL-2.0-only
  2/*
  3 * Test for KVM_X86_DISABLE_EXITS_APERFMPERF
  4 *
  5 * Copyright (C) 2025, Google LLC.
  6 *
  7 * Test the ability to disable VM-exits for rdmsr of IA32_APERF and
  8 * IA32_MPERF. When these VM-exits are disabled, reads of these MSRs
  9 * return the host's values.
 10 *
 11 * Note: Requires read access to /dev/cpu/<lpu>/msr to read host MSRs.
 12 */
 13
 14#include <fcntl.h>
 15#include <limits.h>
 16#include <stdbool.h>
 17#include <stdio.h>
 18#include <stdint.h>
 19#include <unistd.h>
 20#include <asm/msr-index.h>
 21
 22#include "kvm_util.h"
 23#include "processor.h"
 24#include "svm_util.h"
 25#include "test_util.h"
 26#include "vmx.h"
 27
 28#define NUM_ITERATIONS 10000
 29
 30static int open_dev_msr(int cpu)
 31{
 32	char path[PATH_MAX];
 33
 34	snprintf(path, sizeof(path), "/dev/cpu/%d/msr", cpu);
 35	return open_path_or_exit(path, O_RDONLY);
 36}
 37
 38static uint64_t read_dev_msr(int msr_fd, uint32_t msr)
 39{
 40	uint64_t data;
 41	ssize_t rc;
 42
 43	rc = pread(msr_fd, &data, sizeof(data), msr);
 44	TEST_ASSERT(rc == sizeof(data), "Read of MSR 0x%x failed", msr);
 45
 46	return data;
 47}
 48
 49static void guest_read_aperf_mperf(void)
 50{
 51	int i;
 52
 53	for (i = 0; i < NUM_ITERATIONS; i++)
 54		GUEST_SYNC2(rdmsr(MSR_IA32_APERF), rdmsr(MSR_IA32_MPERF));
 55}
 56
 57#define L2_GUEST_STACK_SIZE	64
 58
 59static void l2_guest_code(void)
 60{
 61	guest_read_aperf_mperf();
 62	GUEST_DONE();
 63}
 64
 65static void l1_svm_code(struct svm_test_data *svm)
 66{
 67	unsigned long l2_guest_stack[L2_GUEST_STACK_SIZE];
 68	struct vmcb *vmcb = svm->vmcb;
 69
 70	generic_svm_setup(svm, l2_guest_code, &l2_guest_stack[L2_GUEST_STACK_SIZE]);
 71	run_guest(vmcb, svm->vmcb_gpa);
 72}
 73
 74static void l1_vmx_code(struct vmx_pages *vmx)
 75{
 76	unsigned long l2_guest_stack[L2_GUEST_STACK_SIZE];
 77
 78	GUEST_ASSERT_EQ(prepare_for_vmx_operation(vmx), true);
 79	GUEST_ASSERT_EQ(load_vmcs(vmx), true);
 80
 81	prepare_vmcs(vmx, NULL, &l2_guest_stack[L2_GUEST_STACK_SIZE]);
 82
 83	/*
 84	 * Enable MSR bitmaps (the bitmap itself is allocated, zeroed, and set
 85	 * in the VMCS by prepare_vmcs()), as MSR exiting mandatory on Intel.
 86	 */
 87	vmwrite(CPU_BASED_VM_EXEC_CONTROL,
 88		vmreadz(CPU_BASED_VM_EXEC_CONTROL) | CPU_BASED_USE_MSR_BITMAPS);
 89
 90	GUEST_ASSERT(!vmwrite(GUEST_RIP, (u64)l2_guest_code));
 91	GUEST_ASSERT(!vmlaunch());
 92}
 93
 94static void guest_code(void *nested_test_data)
 95{
 96	guest_read_aperf_mperf();
 97
 98	if (this_cpu_has(X86_FEATURE_SVM))
 99		l1_svm_code(nested_test_data);
100	else if (this_cpu_has(X86_FEATURE_VMX))
101		l1_vmx_code(nested_test_data);
102	else
103		GUEST_DONE();
104
105	TEST_FAIL("L2 should have signaled 'done'");
106}
107
108static void guest_no_aperfmperf(void)
109{
110	uint64_t msr_val;
111	uint8_t vector;
112
113	vector = rdmsr_safe(MSR_IA32_APERF, &msr_val);
114	GUEST_ASSERT(vector == GP_VECTOR);
115
116	vector = rdmsr_safe(MSR_IA32_APERF, &msr_val);
117	GUEST_ASSERT(vector == GP_VECTOR);
118
119	GUEST_DONE();
120}
121
122int main(int argc, char *argv[])
123{
124	const bool has_nested = kvm_cpu_has(X86_FEATURE_SVM) || kvm_cpu_has(X86_FEATURE_VMX);
125	uint64_t host_aperf_before, host_mperf_before;
126	vm_vaddr_t nested_test_data_gva;
127	struct kvm_vcpu *vcpu;
128	struct kvm_vm *vm;
129	int msr_fd, cpu, i;
130
131	/* Sanity check that APERF/MPERF are unsupported by default. */
132	vm = vm_create_with_one_vcpu(&vcpu, guest_no_aperfmperf);
133	vcpu_run(vcpu);
134	TEST_ASSERT_EQ(get_ucall(vcpu, NULL), UCALL_DONE);
135	kvm_vm_free(vm);
136
137	cpu = pin_self_to_any_cpu();
138
139	msr_fd = open_dev_msr(cpu);
140
141	/*
142	 * This test requires a non-standard VM initialization, because
143	 * KVM_ENABLE_CAP cannot be used on a VM file descriptor after
144	 * a VCPU has been created.
145	 */
146	vm = vm_create(1);
147
148	TEST_REQUIRE(vm_check_cap(vm, KVM_CAP_X86_DISABLE_EXITS) &
149		     KVM_X86_DISABLE_EXITS_APERFMPERF);
150
151	vm_enable_cap(vm, KVM_CAP_X86_DISABLE_EXITS,
152		      KVM_X86_DISABLE_EXITS_APERFMPERF);
153
154	vcpu = vm_vcpu_add(vm, 0, guest_code);
155
156	if (!has_nested)
157		nested_test_data_gva = NONCANONICAL;
158	else if (kvm_cpu_has(X86_FEATURE_SVM))
159		vcpu_alloc_svm(vm, &nested_test_data_gva);
160	else
161		vcpu_alloc_vmx(vm, &nested_test_data_gva);
162
163	vcpu_args_set(vcpu, 1, nested_test_data_gva);
164
165	host_aperf_before = read_dev_msr(msr_fd, MSR_IA32_APERF);
166	host_mperf_before = read_dev_msr(msr_fd, MSR_IA32_MPERF);
167
168	for (i = 0; i <= NUM_ITERATIONS * (1 + has_nested); i++) {
169		uint64_t host_aperf_after, host_mperf_after;
170		uint64_t guest_aperf, guest_mperf;
171		struct ucall uc;
172
173		vcpu_run(vcpu);
174		TEST_ASSERT_KVM_EXIT_REASON(vcpu, KVM_EXIT_IO);
175
176		switch (get_ucall(vcpu, &uc)) {
177		case UCALL_DONE:
178			goto done;
179		case UCALL_ABORT:
180			REPORT_GUEST_ASSERT(uc);
181		case UCALL_SYNC:
182			guest_aperf = uc.args[0];
183			guest_mperf = uc.args[1];
184
185			host_aperf_after = read_dev_msr(msr_fd, MSR_IA32_APERF);
186			host_mperf_after = read_dev_msr(msr_fd, MSR_IA32_MPERF);
187
188			TEST_ASSERT(host_aperf_before < guest_aperf,
189				    "APERF: host_before (0x%" PRIx64 ") >= guest (0x%" PRIx64 ")",
190				    host_aperf_before, guest_aperf);
191			TEST_ASSERT(guest_aperf < host_aperf_after,
192				    "APERF: guest (0x%" PRIx64 ") >= host_after (0x%" PRIx64 ")",
193				    guest_aperf, host_aperf_after);
194			TEST_ASSERT(host_mperf_before < guest_mperf,
195				    "MPERF: host_before (0x%" PRIx64 ") >= guest (0x%" PRIx64 ")",
196				    host_mperf_before, guest_mperf);
197			TEST_ASSERT(guest_mperf < host_mperf_after,
198				    "MPERF: guest (0x%" PRIx64 ") >= host_after (0x%" PRIx64 ")",
199				    guest_mperf, host_mperf_after);
200
201			host_aperf_before = host_aperf_after;
202			host_mperf_before = host_mperf_after;
203
204			break;
205		}
206	}
207	TEST_FAIL("Didn't receive UCALL_DONE\n");
208done:
209	kvm_vm_free(vm);
210	close(msr_fd);
211
212	return 0;
213}