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

   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 }