1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * vmx_nested_tsc_scaling_test 4 * 5 * Copyright 2021 Amazon.com, Inc. or its affiliates. All Rights Reserved. 6 * 7 * This test case verifies that nested TSC scaling behaves as expected when 8 * both L1 and L2 are scaled using different ratios. For this test we scale 9 * L1 down and scale L2 up. 10 */ 11 12 #include <time.h> 13 14 #include "kvm_util.h" 15 #include "vmx.h" 16 #include "kselftest.h" 17 18 19 #define VCPU_ID 0 20 21 /* L2 is scaled up (from L1's perspective) by this factor */ 22 #define L2_SCALE_FACTOR 4ULL 23 24 #define TSC_OFFSET_L2 ((uint64_t) -33125236320908) 25 #define TSC_MULTIPLIER_L2 (L2_SCALE_FACTOR << 48) 26 27 #define L2_GUEST_STACK_SIZE 64 28 29 enum { USLEEP, UCHECK_L1, UCHECK_L2 }; 30 #define GUEST_SLEEP(sec) ucall(UCALL_SYNC, 2, USLEEP, sec) 31 #define GUEST_CHECK(level, freq) ucall(UCALL_SYNC, 2, level, freq) 32 33 34 /* 35 * This function checks whether the "actual" TSC frequency of a guest matches 36 * its expected frequency. In order to account for delays in taking the TSC 37 * measurements, a difference of 1% between the actual and the expected value 38 * is tolerated. 39 */ 40 static void compare_tsc_freq(uint64_t actual, uint64_t expected) 41 { 42 uint64_t tolerance, thresh_low, thresh_high; 43 44 tolerance = expected / 100; 45 thresh_low = expected - tolerance; 46 thresh_high = expected + tolerance; 47 48 TEST_ASSERT(thresh_low < actual, 49 "TSC freq is expected to be between %"PRIu64" and %"PRIu64 50 " but it actually is %"PRIu64, 51 thresh_low, thresh_high, actual); 52 TEST_ASSERT(thresh_high > actual, 53 "TSC freq is expected to be between %"PRIu64" and %"PRIu64 54 " but it actually is %"PRIu64, 55 thresh_low, thresh_high, actual); 56 } 57 58 static void check_tsc_freq(int level) 59 { 60 uint64_t tsc_start, tsc_end, tsc_freq; 61 62 /* 63 * Reading the TSC twice with about a second's difference should give 64 * us an approximation of the TSC frequency from the guest's 65 * perspective. Now, this won't be completely accurate, but it should 66 * be good enough for the purposes of this test. 67 */ 68 tsc_start = rdmsr(MSR_IA32_TSC); 69 GUEST_SLEEP(1); 70 tsc_end = rdmsr(MSR_IA32_TSC); 71 72 tsc_freq = tsc_end - tsc_start; 73 74 GUEST_CHECK(level, tsc_freq); 75 } 76 77 static void l2_guest_code(void) 78 { 79 check_tsc_freq(UCHECK_L2); 80 81 /* exit to L1 */ 82 __asm__ __volatile__("vmcall"); 83 } 84 85 static void l1_guest_code(struct vmx_pages *vmx_pages) 86 { 87 unsigned long l2_guest_stack[L2_GUEST_STACK_SIZE]; 88 uint32_t control; 89 90 /* check that L1's frequency looks alright before launching L2 */ 91 check_tsc_freq(UCHECK_L1); 92 93 GUEST_ASSERT(prepare_for_vmx_operation(vmx_pages)); 94 GUEST_ASSERT(load_vmcs(vmx_pages)); 95 96 /* prepare the VMCS for L2 execution */ 97 prepare_vmcs(vmx_pages, l2_guest_code, &l2_guest_stack[L2_GUEST_STACK_SIZE]); 98 99 /* enable TSC offsetting and TSC scaling for L2 */ 100 control = vmreadz(CPU_BASED_VM_EXEC_CONTROL); 101 control |= CPU_BASED_USE_MSR_BITMAPS | CPU_BASED_USE_TSC_OFFSETTING; 102 vmwrite(CPU_BASED_VM_EXEC_CONTROL, control); 103 104 control = vmreadz(SECONDARY_VM_EXEC_CONTROL); 105 control |= SECONDARY_EXEC_TSC_SCALING; 106 vmwrite(SECONDARY_VM_EXEC_CONTROL, control); 107 108 vmwrite(TSC_OFFSET, TSC_OFFSET_L2); 109 vmwrite(TSC_MULTIPLIER, TSC_MULTIPLIER_L2); 110 vmwrite(TSC_MULTIPLIER_HIGH, TSC_MULTIPLIER_L2 >> 32); 111 112 /* launch L2 */ 113 GUEST_ASSERT(!vmlaunch()); 114 GUEST_ASSERT(vmreadz(VM_EXIT_REASON) == EXIT_REASON_VMCALL); 115 116 /* check that L1's frequency still looks good */ 117 check_tsc_freq(UCHECK_L1); 118 119 GUEST_DONE(); 120 } 121 122 static void tsc_scaling_check_supported(void) 123 { 124 if (!kvm_check_cap(KVM_CAP_TSC_CONTROL)) { 125 print_skip("TSC scaling not supported by the HW"); 126 exit(KSFT_SKIP); 127 } 128 } 129 130 static void stable_tsc_check_supported(void) 131 { 132 FILE *fp; 133 char buf[4]; 134 135 fp = fopen("/sys/devices/system/clocksource/clocksource0/current_clocksource", "r"); 136 if (fp == NULL) 137 goto skip_test; 138 139 if (fgets(buf, sizeof(buf), fp) == NULL) 140 goto skip_test; 141 142 if (strncmp(buf, "tsc", sizeof(buf))) 143 goto skip_test; 144 145 return; 146 skip_test: 147 print_skip("Kernel does not use TSC clocksource - assuming that host TSC is not stable"); 148 exit(KSFT_SKIP); 149 } 150 151 int main(int argc, char *argv[]) 152 { 153 struct kvm_vm *vm; 154 vm_vaddr_t vmx_pages_gva; 155 156 uint64_t tsc_start, tsc_end; 157 uint64_t tsc_khz; 158 uint64_t l1_scale_factor; 159 uint64_t l0_tsc_freq = 0; 160 uint64_t l1_tsc_freq = 0; 161 uint64_t l2_tsc_freq = 0; 162 163 nested_vmx_check_supported(); 164 tsc_scaling_check_supported(); 165 stable_tsc_check_supported(); 166 167 /* 168 * We set L1's scale factor to be a random number from 2 to 10. 169 * Ideally we would do the same for L2's factor but that one is 170 * referenced by both main() and l1_guest_code() and using a global 171 * variable does not work. 172 */ 173 srand(time(NULL)); 174 l1_scale_factor = (rand() % 9) + 2; 175 printf("L1's scale down factor is: %"PRIu64"\n", l1_scale_factor); 176 printf("L2's scale up factor is: %llu\n", L2_SCALE_FACTOR); 177 178 tsc_start = rdtsc(); 179 sleep(1); 180 tsc_end = rdtsc(); 181 182 l0_tsc_freq = tsc_end - tsc_start; 183 printf("real TSC frequency is around: %"PRIu64"\n", l0_tsc_freq); 184 185 vm = vm_create_default(VCPU_ID, 0, (void *) l1_guest_code); 186 vcpu_alloc_vmx(vm, &vmx_pages_gva); 187 vcpu_args_set(vm, VCPU_ID, 1, vmx_pages_gva); 188 189 tsc_khz = _vcpu_ioctl(vm, VCPU_ID, KVM_GET_TSC_KHZ, NULL); 190 TEST_ASSERT(tsc_khz != -1, "vcpu ioctl KVM_GET_TSC_KHZ failed"); 191 192 /* scale down L1's TSC frequency */ 193 vcpu_ioctl(vm, VCPU_ID, KVM_SET_TSC_KHZ, 194 (void *) (tsc_khz / l1_scale_factor)); 195 196 for (;;) { 197 volatile struct kvm_run *run = vcpu_state(vm, VCPU_ID); 198 struct ucall uc; 199 200 vcpu_run(vm, VCPU_ID); 201 TEST_ASSERT(run->exit_reason == KVM_EXIT_IO, 202 "Got exit_reason other than KVM_EXIT_IO: %u (%s)\n", 203 run->exit_reason, 204 exit_reason_str(run->exit_reason)); 205 206 switch (get_ucall(vm, VCPU_ID, &uc)) { 207 case UCALL_ABORT: 208 TEST_FAIL("%s", (const char *) uc.args[0]); 209 case UCALL_SYNC: 210 switch (uc.args[0]) { 211 case USLEEP: 212 sleep(uc.args[1]); 213 break; 214 case UCHECK_L1: 215 l1_tsc_freq = uc.args[1]; 216 printf("L1's TSC frequency is around: %"PRIu64 217 "\n", l1_tsc_freq); 218 219 compare_tsc_freq(l1_tsc_freq, 220 l0_tsc_freq / l1_scale_factor); 221 break; 222 case UCHECK_L2: 223 l2_tsc_freq = uc.args[1]; 224 printf("L2's TSC frequency is around: %"PRIu64 225 "\n", l2_tsc_freq); 226 227 compare_tsc_freq(l2_tsc_freq, 228 l1_tsc_freq * L2_SCALE_FACTOR); 229 break; 230 } 231 break; 232 case UCALL_DONE: 233 goto done; 234 default: 235 TEST_FAIL("Unknown ucall %lu", uc.cmd); 236 } 237 } 238 239 done: 240 kvm_vm_free(vm); 241 return 0; 242 } 243