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