xref: /openbmc/linux/arch/arm64/kvm/handle_exit.c (revision c4a7b9b5) 
1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * Copyright (C) 2012,2013 - ARM Ltd
4  * Author: Marc Zyngier <marc.zyngier@arm.com>
5  *
6  * Derived from arch/arm/kvm/handle_exit.c:
7  * Copyright (C) 2012 - Virtual Open Systems and Columbia University
8  * Author: Christoffer Dall <c.dall@virtualopensystems.com>
9  */
10 
11 #include <linux/kvm.h>
12 #include <linux/kvm_host.h>
13 
14 #include <asm/esr.h>
15 #include <asm/exception.h>
16 #include <asm/kvm_asm.h>
17 #include <asm/kvm_emulate.h>
18 #include <asm/kvm_mmu.h>
19 #include <asm/debug-monitors.h>
20 #include <asm/stacktrace/nvhe.h>
21 #include <asm/traps.h>
22 
23 #include <kvm/arm_hypercalls.h>
24 
25 #define CREATE_TRACE_POINTS
26 #include "trace_handle_exit.h"
27 
28 typedef int (*exit_handle_fn)(struct kvm_vcpu *);
29 
30 static void kvm_handle_guest_serror(struct kvm_vcpu *vcpu, u64 esr)
31 {
32 	if (!arm64_is_ras_serror(esr) || arm64_is_fatal_ras_serror(NULL, esr))
33 		kvm_inject_vabt(vcpu);
34 }
35 
36 static int handle_hvc(struct kvm_vcpu *vcpu)
37 {
38 	int ret;
39 
40 	trace_kvm_hvc_arm64(*vcpu_pc(vcpu), vcpu_get_reg(vcpu, 0),
41 			    kvm_vcpu_hvc_get_imm(vcpu));
42 	vcpu->stat.hvc_exit_stat++;
43 
44 	ret = kvm_hvc_call_handler(vcpu);
45 	if (ret < 0) {
46 		vcpu_set_reg(vcpu, 0, ~0UL);
47 		return 1;
48 	}
49 
50 	return ret;
51 }
52 
53 static int handle_smc(struct kvm_vcpu *vcpu)
54 {
55 	/*
56 	 * "If an SMC instruction executed at Non-secure EL1 is
57 	 * trapped to EL2 because HCR_EL2.TSC is 1, the exception is a
58 	 * Trap exception, not a Secure Monitor Call exception [...]"
59 	 *
60 	 * We need to advance the PC after the trap, as it would
61 	 * otherwise return to the same address...
62 	 */
63 	vcpu_set_reg(vcpu, 0, ~0UL);
64 	kvm_incr_pc(vcpu);
65 	return 1;
66 }
67 
68 /*
69  * Guest access to FP/ASIMD registers are routed to this handler only
70  * when the system doesn't support FP/ASIMD.
71  */
72 static int handle_no_fpsimd(struct kvm_vcpu *vcpu)
73 {
74 	kvm_inject_undefined(vcpu);
75 	return 1;
76 }
77 
78 /**
79  * kvm_handle_wfx - handle a wait-for-interrupts or wait-for-event
80  *		    instruction executed by a guest
81  *
82  * @vcpu:	the vcpu pointer
83  *
84  * WFE[T]: Yield the CPU and come back to this vcpu when the scheduler
85  * decides to.
86  * WFI: Simply call kvm_vcpu_halt(), which will halt execution of
87  * world-switches and schedule other host processes until there is an
88  * incoming IRQ or FIQ to the VM.
89  * WFIT: Same as WFI, with a timed wakeup implemented as a background timer
90  *
91  * WF{I,E}T can immediately return if the deadline has already expired.
92  */
93 static int kvm_handle_wfx(struct kvm_vcpu *vcpu)
94 {
95 	u64 esr = kvm_vcpu_get_esr(vcpu);
96 
97 	if (esr & ESR_ELx_WFx_ISS_WFE) {
98 		trace_kvm_wfx_arm64(*vcpu_pc(vcpu), true);
99 		vcpu->stat.wfe_exit_stat++;
100 	} else {
101 		trace_kvm_wfx_arm64(*vcpu_pc(vcpu), false);
102 		vcpu->stat.wfi_exit_stat++;
103 	}
104 
105 	if (esr & ESR_ELx_WFx_ISS_WFxT) {
106 		if (esr & ESR_ELx_WFx_ISS_RV) {
107 			u64 val, now;
108 
109 			now = kvm_arm_timer_get_reg(vcpu, KVM_REG_ARM_TIMER_CNT);
110 			val = vcpu_get_reg(vcpu, kvm_vcpu_sys_get_rt(vcpu));
111 
112 			if (now >= val)
113 				goto out;
114 		} else {
115 			/* Treat WFxT as WFx if RN is invalid */
116 			esr &= ~ESR_ELx_WFx_ISS_WFxT;
117 		}
118 	}
119 
120 	if (esr & ESR_ELx_WFx_ISS_WFE) {
121 		kvm_vcpu_on_spin(vcpu, vcpu_mode_priv(vcpu));
122 	} else {
123 		if (esr & ESR_ELx_WFx_ISS_WFxT)
124 			vcpu_set_flag(vcpu, IN_WFIT);
125 
126 		kvm_vcpu_wfi(vcpu);
127 	}
128 out:
129 	kvm_incr_pc(vcpu);
130 
131 	return 1;
132 }
133 
134 /**
135  * kvm_handle_guest_debug - handle a debug exception instruction
136  *
137  * @vcpu:	the vcpu pointer
138  *
139  * We route all debug exceptions through the same handler. If both the
140  * guest and host are using the same debug facilities it will be up to
141  * userspace to re-inject the correct exception for guest delivery.
142  *
143  * @return: 0 (while setting vcpu->run->exit_reason)
144  */
145 static int kvm_handle_guest_debug(struct kvm_vcpu *vcpu)
146 {
147 	struct kvm_run *run = vcpu->run;
148 	u64 esr = kvm_vcpu_get_esr(vcpu);
149 
150 	run->exit_reason = KVM_EXIT_DEBUG;
151 	run->debug.arch.hsr = lower_32_bits(esr);
152 	run->debug.arch.hsr_high = upper_32_bits(esr);
153 	run->flags = KVM_DEBUG_ARCH_HSR_HIGH_VALID;
154 
155 	switch (ESR_ELx_EC(esr)) {
156 	case ESR_ELx_EC_WATCHPT_LOW:
157 		run->debug.arch.far = vcpu->arch.fault.far_el2;
158 		break;
159 	case ESR_ELx_EC_SOFTSTP_LOW:
160 		vcpu_clear_flag(vcpu, DBG_SS_ACTIVE_PENDING);
161 		break;
162 	}
163 
164 	return 0;
165 }
166 
167 static int kvm_handle_unknown_ec(struct kvm_vcpu *vcpu)
168 {
169 	u64 esr = kvm_vcpu_get_esr(vcpu);
170 
171 	kvm_pr_unimpl("Unknown exception class: esr: %#016llx -- %s\n",
172 		      esr, esr_get_class_string(esr));
173 
174 	kvm_inject_undefined(vcpu);
175 	return 1;
176 }
177 
178 /*
179  * Guest access to SVE registers should be routed to this handler only
180  * when the system doesn't support SVE.
181  */
182 static int handle_sve(struct kvm_vcpu *vcpu)
183 {
184 	kvm_inject_undefined(vcpu);
185 	return 1;
186 }
187 
188 /*
189  * Guest usage of a ptrauth instruction (which the guest EL1 did not turn into
190  * a NOP). If we get here, it is that we didn't fixup ptrauth on exit, and all
191  * that we can do is give the guest an UNDEF.
192  */
193 static int kvm_handle_ptrauth(struct kvm_vcpu *vcpu)
194 {
195 	kvm_inject_undefined(vcpu);
196 	return 1;
197 }
198 
199 static exit_handle_fn arm_exit_handlers[] = {
200 	[0 ... ESR_ELx_EC_MAX]	= kvm_handle_unknown_ec,
201 	[ESR_ELx_EC_WFx]	= kvm_handle_wfx,
202 	[ESR_ELx_EC_CP15_32]	= kvm_handle_cp15_32,
203 	[ESR_ELx_EC_CP15_64]	= kvm_handle_cp15_64,
204 	[ESR_ELx_EC_CP14_MR]	= kvm_handle_cp14_32,
205 	[ESR_ELx_EC_CP14_LS]	= kvm_handle_cp14_load_store,
206 	[ESR_ELx_EC_CP10_ID]	= kvm_handle_cp10_id,
207 	[ESR_ELx_EC_CP14_64]	= kvm_handle_cp14_64,
208 	[ESR_ELx_EC_HVC32]	= handle_hvc,
209 	[ESR_ELx_EC_SMC32]	= handle_smc,
210 	[ESR_ELx_EC_HVC64]	= handle_hvc,
211 	[ESR_ELx_EC_SMC64]	= handle_smc,
212 	[ESR_ELx_EC_SYS64]	= kvm_handle_sys_reg,
213 	[ESR_ELx_EC_SVE]	= handle_sve,
214 	[ESR_ELx_EC_IABT_LOW]	= kvm_handle_guest_abort,
215 	[ESR_ELx_EC_DABT_LOW]	= kvm_handle_guest_abort,
216 	[ESR_ELx_EC_SOFTSTP_LOW]= kvm_handle_guest_debug,
217 	[ESR_ELx_EC_WATCHPT_LOW]= kvm_handle_guest_debug,
218 	[ESR_ELx_EC_BREAKPT_LOW]= kvm_handle_guest_debug,
219 	[ESR_ELx_EC_BKPT32]	= kvm_handle_guest_debug,
220 	[ESR_ELx_EC_BRK64]	= kvm_handle_guest_debug,
221 	[ESR_ELx_EC_FP_ASIMD]	= handle_no_fpsimd,
222 	[ESR_ELx_EC_PAC]	= kvm_handle_ptrauth,
223 };
224 
225 static exit_handle_fn kvm_get_exit_handler(struct kvm_vcpu *vcpu)
226 {
227 	u64 esr = kvm_vcpu_get_esr(vcpu);
228 	u8 esr_ec = ESR_ELx_EC(esr);
229 
230 	return arm_exit_handlers[esr_ec];
231 }
232 
233 /*
234  * We may be single-stepping an emulated instruction. If the emulation
235  * has been completed in the kernel, we can return to userspace with a
236  * KVM_EXIT_DEBUG, otherwise userspace needs to complete its
237  * emulation first.
238  */
239 static int handle_trap_exceptions(struct kvm_vcpu *vcpu)
240 {
241 	int handled;
242 
243 	/*
244 	 * See ARM ARM B1.14.1: "Hyp traps on instructions
245 	 * that fail their condition code check"
246 	 */
247 	if (!kvm_condition_valid(vcpu)) {
248 		kvm_incr_pc(vcpu);
249 		handled = 1;
250 	} else {
251 		exit_handle_fn exit_handler;
252 
253 		exit_handler = kvm_get_exit_handler(vcpu);
254 		handled = exit_handler(vcpu);
255 	}
256 
257 	return handled;
258 }
259 
260 /*
261  * Return > 0 to return to guest, < 0 on error, 0 (and set exit_reason) on
262  * proper exit to userspace.
263  */
264 int handle_exit(struct kvm_vcpu *vcpu, int exception_index)
265 {
266 	struct kvm_run *run = vcpu->run;
267 
268 	if (ARM_SERROR_PENDING(exception_index)) {
269 		/*
270 		 * The SError is handled by handle_exit_early(). If the guest
271 		 * survives it will re-execute the original instruction.
272 		 */
273 		return 1;
274 	}
275 
276 	exception_index = ARM_EXCEPTION_CODE(exception_index);
277 
278 	switch (exception_index) {
279 	case ARM_EXCEPTION_IRQ:
280 		return 1;
281 	case ARM_EXCEPTION_EL1_SERROR:
282 		return 1;
283 	case ARM_EXCEPTION_TRAP:
284 		return handle_trap_exceptions(vcpu);
285 	case ARM_EXCEPTION_HYP_GONE:
286 		/*
287 		 * EL2 has been reset to the hyp-stub. This happens when a guest
288 		 * is pre-emptied by kvm_reboot()'s shutdown call.
289 		 */
290 		run->exit_reason = KVM_EXIT_FAIL_ENTRY;
291 		return 0;
292 	case ARM_EXCEPTION_IL:
293 		/*
294 		 * We attempted an illegal exception return.  Guest state must
295 		 * have been corrupted somehow.  Give up.
296 		 */
297 		run->exit_reason = KVM_EXIT_FAIL_ENTRY;
298 		return -EINVAL;
299 	default:
300 		kvm_pr_unimpl("Unsupported exception type: %d",
301 			      exception_index);
302 		run->exit_reason = KVM_EXIT_INTERNAL_ERROR;
303 		return 0;
304 	}
305 }
306 
307 /* For exit types that need handling before we can be preempted */
308 void handle_exit_early(struct kvm_vcpu *vcpu, int exception_index)
309 {
310 	if (ARM_SERROR_PENDING(exception_index)) {
311 		if (this_cpu_has_cap(ARM64_HAS_RAS_EXTN)) {
312 			u64 disr = kvm_vcpu_get_disr(vcpu);
313 
314 			kvm_handle_guest_serror(vcpu, disr_to_esr(disr));
315 		} else {
316 			kvm_inject_vabt(vcpu);
317 		}
318 
319 		return;
320 	}
321 
322 	exception_index = ARM_EXCEPTION_CODE(exception_index);
323 
324 	if (exception_index == ARM_EXCEPTION_EL1_SERROR)
325 		kvm_handle_guest_serror(vcpu, kvm_vcpu_get_esr(vcpu));
326 }
327 
328 void __noreturn __cold nvhe_hyp_panic_handler(u64 esr, u64 spsr,
329 					      u64 elr_virt, u64 elr_phys,
330 					      u64 par, uintptr_t vcpu,
331 					      u64 far, u64 hpfar) {
332 	u64 elr_in_kimg = __phys_to_kimg(elr_phys);
333 	u64 hyp_offset = elr_in_kimg - kaslr_offset() - elr_virt;
334 	u64 mode = spsr & PSR_MODE_MASK;
335 	u64 panic_addr = elr_virt + hyp_offset;
336 
337 	if (mode != PSR_MODE_EL2t && mode != PSR_MODE_EL2h) {
338 		kvm_err("Invalid host exception to nVHE hyp!\n");
339 	} else if (ESR_ELx_EC(esr) == ESR_ELx_EC_BRK64 &&
340 		   (esr & ESR_ELx_BRK64_ISS_COMMENT_MASK) == BUG_BRK_IMM) {
341 		const char *file = NULL;
342 		unsigned int line = 0;
343 
344 		/* All hyp bugs, including warnings, are treated as fatal. */
345 		if (!is_protected_kvm_enabled() ||
346 		    IS_ENABLED(CONFIG_NVHE_EL2_DEBUG)) {
347 			struct bug_entry *bug = find_bug(elr_in_kimg);
348 
349 			if (bug)
350 				bug_get_file_line(bug, &file, &line);
351 		}
352 
353 		if (file)
354 			kvm_err("nVHE hyp BUG at: %s:%u!\n", file, line);
355 		else
356 			kvm_err("nVHE hyp BUG at: [<%016llx>] %pB!\n", panic_addr,
357 					(void *)(panic_addr + kaslr_offset()));
358 	} else {
359 		kvm_err("nVHE hyp panic at: [<%016llx>] %pB!\n", panic_addr,
360 				(void *)(panic_addr + kaslr_offset()));
361 	}
362 
363 	/* Dump the nVHE hypervisor backtrace */
364 	kvm_nvhe_dump_backtrace(hyp_offset);
365 
366 	/*
367 	 * Hyp has panicked and we're going to handle that by panicking the
368 	 * kernel. The kernel offset will be revealed in the panic so we're
369 	 * also safe to reveal the hyp offset as a debugging aid for translating
370 	 * hyp VAs to vmlinux addresses.
371 	 */
372 	kvm_err("Hyp Offset: 0x%llx\n", hyp_offset);
373 
374 	panic("HYP panic:\nPS:%08llx PC:%016llx ESR:%016llx\nFAR:%016llx HPFAR:%016llx PAR:%016llx\nVCPU:%016lx\n",
375 	      spsr, elr_virt, esr, far, hpfar, par, vcpu);
376 }
377