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
open_dev_msr(int cpu)30 static 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
read_dev_msr(int msr_fd,uint32_t msr)38 static 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
guest_read_aperf_mperf(void)49 static 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
l2_guest_code(void)59 static void l2_guest_code(void)
60 {
61 guest_read_aperf_mperf();
62 GUEST_DONE();
63 }
64
l1_svm_code(struct svm_test_data * svm)65 static 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
l1_vmx_code(struct vmx_pages * vmx)74 static 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
guest_code(void * nested_test_data)94 static 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
guest_no_aperfmperf(void)108 static 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
main(int argc,char * argv[])122 int 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");
208 done:
209 kvm_vm_free(vm);
210 close(msr_fd);
211
212 return 0;
213 }
214