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 "svm_util.h"
 17#include "kselftest.h"
 18
 19/* L2 is scaled up (from L1's perspective) by this factor */
 20#define L2_SCALE_FACTOR 4ULL
 21
 22#define TSC_OFFSET_L2 ((uint64_t) -33125236320908)
 23#define TSC_MULTIPLIER_L2 (L2_SCALE_FACTOR << 48)
 24
 25#define L2_GUEST_STACK_SIZE 64
 26
 27enum { USLEEP, UCHECK_L1, UCHECK_L2 };
 28#define GUEST_SLEEP(sec)         ucall(UCALL_SYNC, 2, USLEEP, sec)
 29#define GUEST_CHECK(level, freq) ucall(UCALL_SYNC, 2, level, freq)
 30
 31
 32/*
 33 * This function checks whether the "actual" TSC frequency of a guest matches
 34 * its expected frequency. In order to account for delays in taking the TSC
 35 * measurements, a difference of 1% between the actual and the expected value
 36 * is tolerated.
 37 */
 38static void compare_tsc_freq(uint64_t actual, uint64_t expected)
 39{
 40	uint64_t tolerance, thresh_low, thresh_high;
 41
 42	tolerance = expected / 100;
 43	thresh_low = expected - tolerance;
 44	thresh_high = expected + tolerance;
 45
 46	TEST_ASSERT(thresh_low < actual,
 47		"TSC freq is expected to be between %"PRIu64" and %"PRIu64
 48		" but it actually is %"PRIu64,
 49		thresh_low, thresh_high, actual);
 50	TEST_ASSERT(thresh_high > actual,
 51		"TSC freq is expected to be between %"PRIu64" and %"PRIu64
 52		" but it actually is %"PRIu64,
 53		thresh_low, thresh_high, actual);
 54}
 55
 56static void check_tsc_freq(int level)
 57{
 58	uint64_t tsc_start, tsc_end, tsc_freq;
 59
 60	/*
 61	 * Reading the TSC twice with about a second's difference should give
 62	 * us an approximation of the TSC frequency from the guest's
 63	 * perspective. Now, this won't be completely accurate, but it should
 64	 * be good enough for the purposes of this test.
 65	 */
 66	tsc_start = rdmsr(MSR_IA32_TSC);
 67	GUEST_SLEEP(1);
 68	tsc_end = rdmsr(MSR_IA32_TSC);
 69
 70	tsc_freq = tsc_end - tsc_start;
 71
 72	GUEST_CHECK(level, tsc_freq);
 73}
 74
 75static void l2_guest_code(void)
 76{
 77	check_tsc_freq(UCHECK_L2);
 78
 79	/* exit to L1 */
 80	__asm__ __volatile__("vmcall");
 81}
 82
 83static void l1_svm_code(struct svm_test_data *svm)
 84{
 85	unsigned long l2_guest_stack[L2_GUEST_STACK_SIZE];
 86
 87	/* check that L1's frequency looks alright before launching L2 */
 88	check_tsc_freq(UCHECK_L1);
 89
 90	generic_svm_setup(svm, l2_guest_code,
 91			  &l2_guest_stack[L2_GUEST_STACK_SIZE]);
 92
 93	/* enable TSC scaling for L2 */
 94	wrmsr(MSR_AMD64_TSC_RATIO, L2_SCALE_FACTOR << 32);
 95
 96	/* launch L2 */
 97	run_guest(svm->vmcb, svm->vmcb_gpa);
 98	GUEST_ASSERT(svm->vmcb->control.exit_code == SVM_EXIT_VMMCALL);
 99
100	/* check that L1's frequency still looks good */
101	check_tsc_freq(UCHECK_L1);
102
103	GUEST_DONE();
104}
105
106static void l1_vmx_code(struct vmx_pages *vmx_pages)
107{
108	unsigned long l2_guest_stack[L2_GUEST_STACK_SIZE];
109	uint32_t control;
110
111	/* check that L1's frequency looks alright before launching L2 */
112	check_tsc_freq(UCHECK_L1);
113
114	GUEST_ASSERT(prepare_for_vmx_operation(vmx_pages));
115	GUEST_ASSERT(load_vmcs(vmx_pages));
116
117	/* prepare the VMCS for L2 execution */
118	prepare_vmcs(vmx_pages, l2_guest_code, &l2_guest_stack[L2_GUEST_STACK_SIZE]);
119
120	/* enable TSC offsetting and TSC scaling for L2 */
121	control = vmreadz(CPU_BASED_VM_EXEC_CONTROL);
122	control |= CPU_BASED_USE_MSR_BITMAPS | CPU_BASED_USE_TSC_OFFSETTING;
123	vmwrite(CPU_BASED_VM_EXEC_CONTROL, control);
124
125	control = vmreadz(SECONDARY_VM_EXEC_CONTROL);
126	control |= SECONDARY_EXEC_TSC_SCALING;
127	vmwrite(SECONDARY_VM_EXEC_CONTROL, control);
128
129	vmwrite(TSC_OFFSET, TSC_OFFSET_L2);
130	vmwrite(TSC_MULTIPLIER, TSC_MULTIPLIER_L2);
131	vmwrite(TSC_MULTIPLIER_HIGH, TSC_MULTIPLIER_L2 >> 32);
132
133	/* launch L2 */
134	GUEST_ASSERT(!vmlaunch());
135	GUEST_ASSERT(vmreadz(VM_EXIT_REASON) == EXIT_REASON_VMCALL);
136
137	/* check that L1's frequency still looks good */
138	check_tsc_freq(UCHECK_L1);
139
140	GUEST_DONE();
141}
142
143static void l1_guest_code(void *data)
144{
145	if (this_cpu_has(X86_FEATURE_VMX))
146		l1_vmx_code(data);
147	else
148		l1_svm_code(data);
149}
150
151int main(int argc, char *argv[])
152{
153	struct kvm_vcpu *vcpu;
154	struct kvm_vm *vm;
155	vm_vaddr_t guest_gva = 0;
156
157	uint64_t tsc_start, tsc_end;
158	uint64_t tsc_khz;
159	uint64_t l1_scale_factor;
160	uint64_t l0_tsc_freq = 0;
161	uint64_t l1_tsc_freq = 0;
162	uint64_t l2_tsc_freq = 0;
163
164	TEST_REQUIRE(kvm_cpu_has(X86_FEATURE_VMX) ||
165		     kvm_cpu_has(X86_FEATURE_SVM));
166	TEST_REQUIRE(kvm_has_cap(KVM_CAP_TSC_CONTROL));
167	TEST_REQUIRE(sys_clocksource_is_based_on_tsc());
168
169	/*
170	 * We set L1's scale factor to be a random number from 2 to 10.
171	 * Ideally we would do the same for L2's factor but that one is
172	 * referenced by both main() and l1_guest_code() and using a global
173	 * variable does not work.
174	 */
175	srand(time(NULL));
176	l1_scale_factor = (rand() % 9) + 2;
177	printf("L1's scale down factor is: %"PRIu64"\n", l1_scale_factor);
178	printf("L2's scale up factor is: %llu\n", L2_SCALE_FACTOR);
179
180	tsc_start = rdtsc();
181	sleep(1);
182	tsc_end = rdtsc();
183
184	l0_tsc_freq = tsc_end - tsc_start;
185	printf("real TSC frequency is around: %"PRIu64"\n", l0_tsc_freq);
186
187	vm = vm_create_with_one_vcpu(&vcpu, l1_guest_code);
188
189	if (kvm_cpu_has(X86_FEATURE_VMX))
190		vcpu_alloc_vmx(vm, &guest_gva);
191	else
192		vcpu_alloc_svm(vm, &guest_gva);
193
194	vcpu_args_set(vcpu, 1, guest_gva);
195
196	tsc_khz = __vcpu_ioctl(vcpu, KVM_GET_TSC_KHZ, NULL);
197	TEST_ASSERT(tsc_khz != -1, "vcpu ioctl KVM_GET_TSC_KHZ failed");
198
199	/* scale down L1's TSC frequency */
200	vcpu_ioctl(vcpu, KVM_SET_TSC_KHZ, (void *) (tsc_khz / l1_scale_factor));
201
202	for (;;) {
203		struct ucall uc;
204
205		vcpu_run(vcpu);
206		TEST_ASSERT_KVM_EXIT_REASON(vcpu, KVM_EXIT_IO);
207
208		switch (get_ucall(vcpu, &uc)) {
209		case UCALL_ABORT:
210			REPORT_GUEST_ASSERT(uc);
211		case UCALL_SYNC:
212			switch (uc.args[0]) {
213			case USLEEP:
214				sleep(uc.args[1]);
215				break;
216			case UCHECK_L1:
217				l1_tsc_freq = uc.args[1];
218				printf("L1's TSC frequency is around: %"PRIu64
219				       "\n", l1_tsc_freq);
220
221				compare_tsc_freq(l1_tsc_freq,
222						 l0_tsc_freq / l1_scale_factor);
223				break;
224			case UCHECK_L2:
225				l2_tsc_freq = uc.args[1];
226				printf("L2's TSC frequency is around: %"PRIu64
227				       "\n", l2_tsc_freq);
228
229				compare_tsc_freq(l2_tsc_freq,
230						 l1_tsc_freq * L2_SCALE_FACTOR);
231				break;
232			}
233			break;
234		case UCALL_DONE:
235			goto done;
236		default:
237			TEST_FAIL("Unknown ucall %lu", uc.cmd);
238		}
239	}
240
241done:
242	kvm_vm_free(vm);
243	return 0;
244}