diff options
Diffstat (limited to 'tools/testing/selftests/kvm/x86_64/vmx_nested_tsc_scaling_test.c')
-rw-r--r-- | tools/testing/selftests/kvm/x86_64/vmx_nested_tsc_scaling_test.c | 223 |
1 files changed, 223 insertions, 0 deletions
diff --git a/tools/testing/selftests/kvm/x86_64/vmx_nested_tsc_scaling_test.c b/tools/testing/selftests/kvm/x86_64/vmx_nested_tsc_scaling_test.c new file mode 100644 index 0000000000..e710b6e7fb --- /dev/null +++ b/tools/testing/selftests/kvm/x86_64/vmx_nested_tsc_scaling_test.c @@ -0,0 +1,223 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * vmx_nested_tsc_scaling_test + * + * Copyright 2021 Amazon.com, Inc. or its affiliates. All Rights Reserved. + * + * This test case verifies that nested TSC scaling behaves as expected when + * both L1 and L2 are scaled using different ratios. For this test we scale + * L1 down and scale L2 up. + */ + +#include <time.h> + +#include "kvm_util.h" +#include "vmx.h" +#include "kselftest.h" + +/* L2 is scaled up (from L1's perspective) by this factor */ +#define L2_SCALE_FACTOR 4ULL + +#define TSC_OFFSET_L2 ((uint64_t) -33125236320908) +#define TSC_MULTIPLIER_L2 (L2_SCALE_FACTOR << 48) + +#define L2_GUEST_STACK_SIZE 64 + +enum { USLEEP, UCHECK_L1, UCHECK_L2 }; +#define GUEST_SLEEP(sec) ucall(UCALL_SYNC, 2, USLEEP, sec) +#define GUEST_CHECK(level, freq) ucall(UCALL_SYNC, 2, level, freq) + + +/* + * This function checks whether the "actual" TSC frequency of a guest matches + * its expected frequency. In order to account for delays in taking the TSC + * measurements, a difference of 1% between the actual and the expected value + * is tolerated. + */ +static void compare_tsc_freq(uint64_t actual, uint64_t expected) +{ + uint64_t tolerance, thresh_low, thresh_high; + + tolerance = expected / 100; + thresh_low = expected - tolerance; + thresh_high = expected + tolerance; + + TEST_ASSERT(thresh_low < actual, + "TSC freq is expected to be between %"PRIu64" and %"PRIu64 + " but it actually is %"PRIu64, + thresh_low, thresh_high, actual); + TEST_ASSERT(thresh_high > actual, + "TSC freq is expected to be between %"PRIu64" and %"PRIu64 + " but it actually is %"PRIu64, + thresh_low, thresh_high, actual); +} + +static void check_tsc_freq(int level) +{ + uint64_t tsc_start, tsc_end, tsc_freq; + + /* + * Reading the TSC twice with about a second's difference should give + * us an approximation of the TSC frequency from the guest's + * perspective. Now, this won't be completely accurate, but it should + * be good enough for the purposes of this test. + */ + tsc_start = rdmsr(MSR_IA32_TSC); + GUEST_SLEEP(1); + tsc_end = rdmsr(MSR_IA32_TSC); + + tsc_freq = tsc_end - tsc_start; + + GUEST_CHECK(level, tsc_freq); +} + +static void l2_guest_code(void) +{ + check_tsc_freq(UCHECK_L2); + + /* exit to L1 */ + __asm__ __volatile__("vmcall"); +} + +static void l1_guest_code(struct vmx_pages *vmx_pages) +{ + unsigned long l2_guest_stack[L2_GUEST_STACK_SIZE]; + uint32_t control; + + /* check that L1's frequency looks alright before launching L2 */ + check_tsc_freq(UCHECK_L1); + + GUEST_ASSERT(prepare_for_vmx_operation(vmx_pages)); + GUEST_ASSERT(load_vmcs(vmx_pages)); + + /* prepare the VMCS for L2 execution */ + prepare_vmcs(vmx_pages, l2_guest_code, &l2_guest_stack[L2_GUEST_STACK_SIZE]); + + /* enable TSC offsetting and TSC scaling for L2 */ + control = vmreadz(CPU_BASED_VM_EXEC_CONTROL); + control |= CPU_BASED_USE_MSR_BITMAPS | CPU_BASED_USE_TSC_OFFSETTING; + vmwrite(CPU_BASED_VM_EXEC_CONTROL, control); + + control = vmreadz(SECONDARY_VM_EXEC_CONTROL); + control |= SECONDARY_EXEC_TSC_SCALING; + vmwrite(SECONDARY_VM_EXEC_CONTROL, control); + + vmwrite(TSC_OFFSET, TSC_OFFSET_L2); + vmwrite(TSC_MULTIPLIER, TSC_MULTIPLIER_L2); + vmwrite(TSC_MULTIPLIER_HIGH, TSC_MULTIPLIER_L2 >> 32); + + /* launch L2 */ + GUEST_ASSERT(!vmlaunch()); + GUEST_ASSERT(vmreadz(VM_EXIT_REASON) == EXIT_REASON_VMCALL); + + /* check that L1's frequency still looks good */ + check_tsc_freq(UCHECK_L1); + + GUEST_DONE(); +} + +static bool system_has_stable_tsc(void) +{ + bool tsc_is_stable; + FILE *fp; + char buf[4]; + + fp = fopen("/sys/devices/system/clocksource/clocksource0/current_clocksource", "r"); + if (fp == NULL) + return false; + + tsc_is_stable = fgets(buf, sizeof(buf), fp) && + !strncmp(buf, "tsc", sizeof(buf)); + + fclose(fp); + return tsc_is_stable; +} + +int main(int argc, char *argv[]) +{ + struct kvm_vcpu *vcpu; + struct kvm_vm *vm; + vm_vaddr_t vmx_pages_gva; + + uint64_t tsc_start, tsc_end; + uint64_t tsc_khz; + uint64_t l1_scale_factor; + uint64_t l0_tsc_freq = 0; + uint64_t l1_tsc_freq = 0; + uint64_t l2_tsc_freq = 0; + + TEST_REQUIRE(kvm_cpu_has(X86_FEATURE_VMX)); + TEST_REQUIRE(kvm_has_cap(KVM_CAP_TSC_CONTROL)); + TEST_REQUIRE(system_has_stable_tsc()); + + /* + * We set L1's scale factor to be a random number from 2 to 10. + * Ideally we would do the same for L2's factor but that one is + * referenced by both main() and l1_guest_code() and using a global + * variable does not work. + */ + srand(time(NULL)); + l1_scale_factor = (rand() % 9) + 2; + printf("L1's scale down factor is: %"PRIu64"\n", l1_scale_factor); + printf("L2's scale up factor is: %llu\n", L2_SCALE_FACTOR); + + tsc_start = rdtsc(); + sleep(1); + tsc_end = rdtsc(); + + l0_tsc_freq = tsc_end - tsc_start; + printf("real TSC frequency is around: %"PRIu64"\n", l0_tsc_freq); + + vm = vm_create_with_one_vcpu(&vcpu, l1_guest_code); + vcpu_alloc_vmx(vm, &vmx_pages_gva); + vcpu_args_set(vcpu, 1, vmx_pages_gva); + + tsc_khz = __vcpu_ioctl(vcpu, KVM_GET_TSC_KHZ, NULL); + TEST_ASSERT(tsc_khz != -1, "vcpu ioctl KVM_GET_TSC_KHZ failed"); + + /* scale down L1's TSC frequency */ + vcpu_ioctl(vcpu, KVM_SET_TSC_KHZ, (void *) (tsc_khz / l1_scale_factor)); + + for (;;) { + struct ucall uc; + + vcpu_run(vcpu); + TEST_ASSERT_KVM_EXIT_REASON(vcpu, KVM_EXIT_IO); + + switch (get_ucall(vcpu, &uc)) { + case UCALL_ABORT: + REPORT_GUEST_ASSERT(uc); + case UCALL_SYNC: + switch (uc.args[0]) { + case USLEEP: + sleep(uc.args[1]); + break; + case UCHECK_L1: + l1_tsc_freq = uc.args[1]; + printf("L1's TSC frequency is around: %"PRIu64 + "\n", l1_tsc_freq); + + compare_tsc_freq(l1_tsc_freq, + l0_tsc_freq / l1_scale_factor); + break; + case UCHECK_L2: + l2_tsc_freq = uc.args[1]; + printf("L2's TSC frequency is around: %"PRIu64 + "\n", l2_tsc_freq); + + compare_tsc_freq(l2_tsc_freq, + l1_tsc_freq * L2_SCALE_FACTOR); + break; + } + break; + case UCALL_DONE: + goto done; + default: + TEST_FAIL("Unknown ucall %lu", uc.cmd); + } + } + +done: + kvm_vm_free(vm); + return 0; +} |