1 // SPDX-License-Identifier: GPL-2.0-only
2 #define _GNU_SOURCE /* for program_invocation_short_name */
3 
4 #include "test_util.h"
5 #include "kvm_util.h"
6 #include "processor.h"
7 #include "vmx.h"
8 #include "svm_util.h"
9 
10 #define L2_GUEST_STACK_SIZE 256
11 
12 /*
13  * Arbitrary, never shoved into KVM/hardware, just need to avoid conflict with
14  * the "real" exceptions used, #SS/#GP/#DF (12/13/8).
15  */
16 #define FAKE_TRIPLE_FAULT_VECTOR	0xaa
17 
18 /* Arbitrary 32-bit error code injected by this test. */
19 #define SS_ERROR_CODE 0xdeadbeef
20 
21 /*
22  * Bit '0' is set on Intel if the exception occurs while delivering a previous
23  * event/exception.  AMD's wording is ambiguous, but presumably the bit is set
24  * if the exception occurs while delivering an external event, e.g. NMI or INTR,
25  * but not for exceptions that occur when delivering other exceptions or
26  * software interrupts.
27  *
28  * Note, Intel's name for it, "External event", is misleading and much more
29  * aligned with AMD's behavior, but the SDM is quite clear on its behavior.
30  */
31 #define ERROR_CODE_EXT_FLAG	BIT(0)
32 
33 /*
34  * Bit '1' is set if the fault occurred when looking up a descriptor in the
35  * IDT, which is the case here as the IDT is empty/NULL.
36  */
37 #define ERROR_CODE_IDT_FLAG	BIT(1)
38 
39 /*
40  * The #GP that occurs when vectoring #SS should show the index into the IDT
41  * for #SS, plus have the "IDT flag" set.
42  */
43 #define GP_ERROR_CODE_AMD ((SS_VECTOR * 8) | ERROR_CODE_IDT_FLAG)
44 #define GP_ERROR_CODE_INTEL ((SS_VECTOR * 8) | ERROR_CODE_IDT_FLAG | ERROR_CODE_EXT_FLAG)
45 
46 /*
47  * Intel and AMD both shove '0' into the error code on #DF, regardless of what
48  * led to the double fault.
49  */
50 #define DF_ERROR_CODE 0
51 
52 #define INTERCEPT_SS		(BIT_ULL(SS_VECTOR))
53 #define INTERCEPT_SS_DF		(INTERCEPT_SS | BIT_ULL(DF_VECTOR))
54 #define INTERCEPT_SS_GP_DF	(INTERCEPT_SS_DF | BIT_ULL(GP_VECTOR))
55 
56 static void l2_ss_pending_test(void)
57 {
58 	GUEST_SYNC(SS_VECTOR);
59 }
60 
61 static void l2_ss_injected_gp_test(void)
62 {
63 	GUEST_SYNC(GP_VECTOR);
64 }
65 
66 static void l2_ss_injected_df_test(void)
67 {
68 	GUEST_SYNC(DF_VECTOR);
69 }
70 
71 static void l2_ss_injected_tf_test(void)
72 {
73 	GUEST_SYNC(FAKE_TRIPLE_FAULT_VECTOR);
74 }
75 
76 static void svm_run_l2(struct svm_test_data *svm, void *l2_code, int vector,
77 		       uint32_t error_code)
78 {
79 	struct vmcb *vmcb = svm->vmcb;
80 	struct vmcb_control_area *ctrl = &vmcb->control;
81 
82 	vmcb->save.rip = (u64)l2_code;
83 	run_guest(vmcb, svm->vmcb_gpa);
84 
85 	if (vector == FAKE_TRIPLE_FAULT_VECTOR)
86 		return;
87 
88 	GUEST_ASSERT_EQ(ctrl->exit_code, (SVM_EXIT_EXCP_BASE + vector));
89 	GUEST_ASSERT_EQ(ctrl->exit_info_1, error_code);
90 }
91 
92 static void l1_svm_code(struct svm_test_data *svm)
93 {
94 	struct vmcb_control_area *ctrl = &svm->vmcb->control;
95 	unsigned long l2_guest_stack[L2_GUEST_STACK_SIZE];
96 
97 	generic_svm_setup(svm, NULL, &l2_guest_stack[L2_GUEST_STACK_SIZE]);
98 	svm->vmcb->save.idtr.limit = 0;
99 	ctrl->intercept |= BIT_ULL(INTERCEPT_SHUTDOWN);
100 
101 	ctrl->intercept_exceptions = INTERCEPT_SS_GP_DF;
102 	svm_run_l2(svm, l2_ss_pending_test, SS_VECTOR, SS_ERROR_CODE);
103 	svm_run_l2(svm, l2_ss_injected_gp_test, GP_VECTOR, GP_ERROR_CODE_AMD);
104 
105 	ctrl->intercept_exceptions = INTERCEPT_SS_DF;
106 	svm_run_l2(svm, l2_ss_injected_df_test, DF_VECTOR, DF_ERROR_CODE);
107 
108 	ctrl->intercept_exceptions = INTERCEPT_SS;
109 	svm_run_l2(svm, l2_ss_injected_tf_test, FAKE_TRIPLE_FAULT_VECTOR, 0);
110 	GUEST_ASSERT_EQ(ctrl->exit_code, SVM_EXIT_SHUTDOWN);
111 
112 	GUEST_DONE();
113 }
114 
115 static void vmx_run_l2(void *l2_code, int vector, uint32_t error_code)
116 {
117 	GUEST_ASSERT(!vmwrite(GUEST_RIP, (u64)l2_code));
118 
119 	GUEST_ASSERT_EQ(vector == SS_VECTOR ? vmlaunch() : vmresume(), 0);
120 
121 	if (vector == FAKE_TRIPLE_FAULT_VECTOR)
122 		return;
123 
124 	GUEST_ASSERT_EQ(vmreadz(VM_EXIT_REASON), EXIT_REASON_EXCEPTION_NMI);
125 	GUEST_ASSERT_EQ((vmreadz(VM_EXIT_INTR_INFO) & 0xff), vector);
126 	GUEST_ASSERT_EQ(vmreadz(VM_EXIT_INTR_ERROR_CODE), error_code);
127 }
128 
129 static void l1_vmx_code(struct vmx_pages *vmx)
130 {
131 	unsigned long l2_guest_stack[L2_GUEST_STACK_SIZE];
132 
133 	GUEST_ASSERT_EQ(prepare_for_vmx_operation(vmx), true);
134 
135 	GUEST_ASSERT_EQ(load_vmcs(vmx), true);
136 
137 	prepare_vmcs(vmx, NULL, &l2_guest_stack[L2_GUEST_STACK_SIZE]);
138 	GUEST_ASSERT_EQ(vmwrite(GUEST_IDTR_LIMIT, 0), 0);
139 
140 	/*
141 	 * VMX disallows injecting an exception with error_code[31:16] != 0,
142 	 * and hardware will never generate a VM-Exit with bits 31:16 set.
143 	 * KVM should likewise truncate the "bad" userspace value.
144 	 */
145 	GUEST_ASSERT_EQ(vmwrite(EXCEPTION_BITMAP, INTERCEPT_SS_GP_DF), 0);
146 	vmx_run_l2(l2_ss_pending_test, SS_VECTOR, (u16)SS_ERROR_CODE);
147 	vmx_run_l2(l2_ss_injected_gp_test, GP_VECTOR, GP_ERROR_CODE_INTEL);
148 
149 	GUEST_ASSERT_EQ(vmwrite(EXCEPTION_BITMAP, INTERCEPT_SS_DF), 0);
150 	vmx_run_l2(l2_ss_injected_df_test, DF_VECTOR, DF_ERROR_CODE);
151 
152 	GUEST_ASSERT_EQ(vmwrite(EXCEPTION_BITMAP, INTERCEPT_SS), 0);
153 	vmx_run_l2(l2_ss_injected_tf_test, FAKE_TRIPLE_FAULT_VECTOR, 0);
154 	GUEST_ASSERT_EQ(vmreadz(VM_EXIT_REASON), EXIT_REASON_TRIPLE_FAULT);
155 
156 	GUEST_DONE();
157 }
158 
159 static void __attribute__((__flatten__)) l1_guest_code(void *test_data)
160 {
161 	if (this_cpu_has(X86_FEATURE_SVM))
162 		l1_svm_code(test_data);
163 	else
164 		l1_vmx_code(test_data);
165 }
166 
167 static void assert_ucall_vector(struct kvm_vcpu *vcpu, int vector)
168 {
169 	struct ucall uc;
170 
171 	TEST_ASSERT_KVM_EXIT_REASON(vcpu, KVM_EXIT_IO);
172 
173 	switch (get_ucall(vcpu, &uc)) {
174 	case UCALL_SYNC:
175 		TEST_ASSERT(vector == uc.args[1],
176 			    "Expected L2 to ask for %d, got %ld", vector, uc.args[1]);
177 		break;
178 	case UCALL_DONE:
179 		TEST_ASSERT(vector == -1,
180 			    "Expected L2 to ask for %d, L2 says it's done", vector);
181 		break;
182 	case UCALL_ABORT:
183 		REPORT_GUEST_ASSERT(uc);
184 		break;
185 	default:
186 		TEST_FAIL("Expected L2 to ask for %d, got unexpected ucall %lu", vector, uc.cmd);
187 	}
188 }
189 
190 static void queue_ss_exception(struct kvm_vcpu *vcpu, bool inject)
191 {
192 	struct kvm_vcpu_events events;
193 
194 	vcpu_events_get(vcpu, &events);
195 
196 	TEST_ASSERT(!events.exception.pending,
197 		    "Vector %d unexpectedlt pending", events.exception.nr);
198 	TEST_ASSERT(!events.exception.injected,
199 		    "Vector %d unexpectedly injected", events.exception.nr);
200 
201 	events.flags = KVM_VCPUEVENT_VALID_PAYLOAD;
202 	events.exception.pending = !inject;
203 	events.exception.injected = inject;
204 	events.exception.nr = SS_VECTOR;
205 	events.exception.has_error_code = true;
206 	events.exception.error_code = SS_ERROR_CODE;
207 	vcpu_events_set(vcpu, &events);
208 }
209 
210 /*
211  * Verify KVM_{G,S}ET_EVENTS play nice with pending vs. injected exceptions
212  * when an exception is being queued for L2.  Specifically, verify that KVM
213  * honors L1 exception intercept controls when a #SS is pending/injected,
214  * triggers a #GP on vectoring the #SS, morphs to #DF if #GP isn't intercepted
215  * by L1, and finally causes (nested) SHUTDOWN if #DF isn't intercepted by L1.
216  */
217 int main(int argc, char *argv[])
218 {
219 	vm_vaddr_t nested_test_data_gva;
220 	struct kvm_vcpu_events events;
221 	struct kvm_vcpu *vcpu;
222 	struct kvm_vm *vm;
223 
224 	TEST_REQUIRE(kvm_has_cap(KVM_CAP_EXCEPTION_PAYLOAD));
225 	TEST_REQUIRE(kvm_cpu_has(X86_FEATURE_SVM) || kvm_cpu_has(X86_FEATURE_VMX));
226 
227 	vm = vm_create_with_one_vcpu(&vcpu, l1_guest_code);
228 	vm_enable_cap(vm, KVM_CAP_EXCEPTION_PAYLOAD, -2ul);
229 
230 	if (kvm_cpu_has(X86_FEATURE_SVM))
231 		vcpu_alloc_svm(vm, &nested_test_data_gva);
232 	else
233 		vcpu_alloc_vmx(vm, &nested_test_data_gva);
234 
235 	vcpu_args_set(vcpu, 1, nested_test_data_gva);
236 
237 	/* Run L1 => L2.  L2 should sync and request #SS. */
238 	vcpu_run(vcpu);
239 	assert_ucall_vector(vcpu, SS_VECTOR);
240 
241 	/* Pend #SS and request immediate exit.  #SS should still be pending. */
242 	queue_ss_exception(vcpu, false);
243 	vcpu->run->immediate_exit = true;
244 	vcpu_run_complete_io(vcpu);
245 
246 	/* Verify the pending events comes back out the same as it went in. */
247 	vcpu_events_get(vcpu, &events);
248 	TEST_ASSERT_EQ(events.flags & KVM_VCPUEVENT_VALID_PAYLOAD,
249 			KVM_VCPUEVENT_VALID_PAYLOAD);
250 	TEST_ASSERT_EQ(events.exception.pending, true);
251 	TEST_ASSERT_EQ(events.exception.nr, SS_VECTOR);
252 	TEST_ASSERT_EQ(events.exception.has_error_code, true);
253 	TEST_ASSERT_EQ(events.exception.error_code, SS_ERROR_CODE);
254 
255 	/*
256 	 * Run for real with the pending #SS, L1 should get a VM-Exit due to
257 	 * #SS interception and re-enter L2 to request #GP (via injected #SS).
258 	 */
259 	vcpu->run->immediate_exit = false;
260 	vcpu_run(vcpu);
261 	assert_ucall_vector(vcpu, GP_VECTOR);
262 
263 	/*
264 	 * Inject #SS, the #SS should bypass interception and cause #GP, which
265 	 * L1 should intercept before KVM morphs it to #DF.  L1 should then
266 	 * disable #GP interception and run L2 to request #DF (via #SS => #GP).
267 	 */
268 	queue_ss_exception(vcpu, true);
269 	vcpu_run(vcpu);
270 	assert_ucall_vector(vcpu, DF_VECTOR);
271 
272 	/*
273 	 * Inject #SS, the #SS should bypass interception and cause #GP, which
274 	 * L1 is no longer interception, and so should see a #DF VM-Exit.  L1
275 	 * should then signal that is done.
276 	 */
277 	queue_ss_exception(vcpu, true);
278 	vcpu_run(vcpu);
279 	assert_ucall_vector(vcpu, FAKE_TRIPLE_FAULT_VECTOR);
280 
281 	/*
282 	 * Inject #SS yet again.  L1 is not intercepting #GP or #DF, and so
283 	 * should see nested TRIPLE_FAULT / SHUTDOWN.
284 	 */
285 	queue_ss_exception(vcpu, true);
286 	vcpu_run(vcpu);
287 	assert_ucall_vector(vcpu, -1);
288 
289 	kvm_vm_free(vm);
290 }
291