xref: /openbmc/linux/arch/arm64/kvm/hyp/include/hyp/switch.h (revision 647d41d3) 
1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * Copyright (C) 2015 - ARM Ltd
4  * Author: Marc Zyngier <marc.zyngier@arm.com>
5  */
6 
7 #ifndef __ARM64_KVM_HYP_SWITCH_H__
8 #define __ARM64_KVM_HYP_SWITCH_H__
9 
10 #include <hyp/adjust_pc.h>
11 #include <hyp/fault.h>
12 
13 #include <linux/arm-smccc.h>
14 #include <linux/kvm_host.h>
15 #include <linux/types.h>
16 #include <linux/jump_label.h>
17 #include <uapi/linux/psci.h>
18 
19 #include <kvm/arm_psci.h>
20 
21 #include <asm/barrier.h>
22 #include <asm/cpufeature.h>
23 #include <asm/extable.h>
24 #include <asm/kprobes.h>
25 #include <asm/kvm_asm.h>
26 #include <asm/kvm_emulate.h>
27 #include <asm/kvm_hyp.h>
28 #include <asm/kvm_mmu.h>
29 #include <asm/fpsimd.h>
30 #include <asm/debug-monitors.h>
31 #include <asm/processor.h>
32 
33 struct kvm_exception_table_entry {
34 	int insn, fixup;
35 };
36 
37 extern struct kvm_exception_table_entry __start___kvm_ex_table;
38 extern struct kvm_exception_table_entry __stop___kvm_ex_table;
39 
40 /* Check whether the FP regs were dirtied while in the host-side run loop: */
41 static inline bool update_fp_enabled(struct kvm_vcpu *vcpu)
42 {
43 	/*
44 	 * When the system doesn't support FP/SIMD, we cannot rely on
45 	 * the _TIF_FOREIGN_FPSTATE flag. However, we always inject an
46 	 * abort on the very first access to FP and thus we should never
47 	 * see KVM_ARM64_FP_ENABLED. For added safety, make sure we always
48 	 * trap the accesses.
49 	 */
50 	if (!system_supports_fpsimd() ||
51 	    vcpu->arch.flags & KVM_ARM64_FP_FOREIGN_FPSTATE)
52 		vcpu->arch.flags &= ~(KVM_ARM64_FP_ENABLED |
53 				      KVM_ARM64_FP_HOST);
54 
55 	return !!(vcpu->arch.flags & KVM_ARM64_FP_ENABLED);
56 }
57 
58 /* Save the 32-bit only FPSIMD system register state */
59 static inline void __fpsimd_save_fpexc32(struct kvm_vcpu *vcpu)
60 {
61 	if (!vcpu_el1_is_32bit(vcpu))
62 		return;
63 
64 	__vcpu_sys_reg(vcpu, FPEXC32_EL2) = read_sysreg(fpexc32_el2);
65 }
66 
67 static inline void __activate_traps_fpsimd32(struct kvm_vcpu *vcpu)
68 {
69 	/*
70 	 * We are about to set CPTR_EL2.TFP to trap all floating point
71 	 * register accesses to EL2, however, the ARM ARM clearly states that
72 	 * traps are only taken to EL2 if the operation would not otherwise
73 	 * trap to EL1.  Therefore, always make sure that for 32-bit guests,
74 	 * we set FPEXC.EN to prevent traps to EL1, when setting the TFP bit.
75 	 * If FP/ASIMD is not implemented, FPEXC is UNDEFINED and any access to
76 	 * it will cause an exception.
77 	 */
78 	if (vcpu_el1_is_32bit(vcpu) && system_supports_fpsimd()) {
79 		write_sysreg(1 << 30, fpexc32_el2);
80 		isb();
81 	}
82 }
83 
84 static inline void __activate_traps_common(struct kvm_vcpu *vcpu)
85 {
86 	/* Trap on AArch32 cp15 c15 (impdef sysregs) accesses (EL1 or EL0) */
87 	write_sysreg(1 << 15, hstr_el2);
88 
89 	/*
90 	 * Make sure we trap PMU access from EL0 to EL2. Also sanitize
91 	 * PMSELR_EL0 to make sure it never contains the cycle
92 	 * counter, which could make a PMXEVCNTR_EL0 access UNDEF at
93 	 * EL1 instead of being trapped to EL2.
94 	 */
95 	if (kvm_arm_support_pmu_v3()) {
96 		write_sysreg(0, pmselr_el0);
97 		write_sysreg(ARMV8_PMU_USERENR_MASK, pmuserenr_el0);
98 	}
99 
100 	vcpu->arch.mdcr_el2_host = read_sysreg(mdcr_el2);
101 	write_sysreg(vcpu->arch.mdcr_el2, mdcr_el2);
102 }
103 
104 static inline void __deactivate_traps_common(struct kvm_vcpu *vcpu)
105 {
106 	write_sysreg(vcpu->arch.mdcr_el2_host, mdcr_el2);
107 
108 	write_sysreg(0, hstr_el2);
109 	if (kvm_arm_support_pmu_v3())
110 		write_sysreg(0, pmuserenr_el0);
111 }
112 
113 static inline void ___activate_traps(struct kvm_vcpu *vcpu)
114 {
115 	u64 hcr = vcpu->arch.hcr_el2;
116 
117 	if (cpus_have_final_cap(ARM64_WORKAROUND_CAVIUM_TX2_219_TVM))
118 		hcr |= HCR_TVM;
119 
120 	write_sysreg(hcr, hcr_el2);
121 
122 	if (cpus_have_final_cap(ARM64_HAS_RAS_EXTN) && (hcr & HCR_VSE))
123 		write_sysreg_s(vcpu->arch.vsesr_el2, SYS_VSESR_EL2);
124 }
125 
126 static inline void ___deactivate_traps(struct kvm_vcpu *vcpu)
127 {
128 	/*
129 	 * If we pended a virtual abort, preserve it until it gets
130 	 * cleared. See D1.14.3 (Virtual Interrupts) for details, but
131 	 * the crucial bit is "On taking a vSError interrupt,
132 	 * HCR_EL2.VSE is cleared to 0."
133 	 */
134 	if (vcpu->arch.hcr_el2 & HCR_VSE) {
135 		vcpu->arch.hcr_el2 &= ~HCR_VSE;
136 		vcpu->arch.hcr_el2 |= read_sysreg(hcr_el2) & HCR_VSE;
137 	}
138 }
139 
140 static inline bool __populate_fault_info(struct kvm_vcpu *vcpu)
141 {
142 	return __get_fault_info(vcpu->arch.fault.esr_el2, &vcpu->arch.fault);
143 }
144 
145 static inline void __hyp_sve_restore_guest(struct kvm_vcpu *vcpu)
146 {
147 	sve_cond_update_zcr_vq(vcpu_sve_max_vq(vcpu) - 1, SYS_ZCR_EL2);
148 	__sve_restore_state(vcpu_sve_pffr(vcpu),
149 			    &vcpu->arch.ctxt.fp_regs.fpsr);
150 	write_sysreg_el1(__vcpu_sys_reg(vcpu, ZCR_EL1), SYS_ZCR);
151 }
152 
153 /*
154  * We trap the first access to the FP/SIMD to save the host context and
155  * restore the guest context lazily.
156  * If FP/SIMD is not implemented, handle the trap and inject an undefined
157  * instruction exception to the guest. Similarly for trapped SVE accesses.
158  */
159 static bool kvm_hyp_handle_fpsimd(struct kvm_vcpu *vcpu, u64 *exit_code)
160 {
161 	bool sve_guest;
162 	u8 esr_ec;
163 	u64 reg;
164 
165 	if (!system_supports_fpsimd())
166 		return false;
167 
168 	sve_guest = vcpu_has_sve(vcpu);
169 	esr_ec = kvm_vcpu_trap_get_class(vcpu);
170 
171 	/* Don't handle SVE traps for non-SVE vcpus here: */
172 	if (!sve_guest && esr_ec != ESR_ELx_EC_FP_ASIMD)
173 		return false;
174 
175 	/* Valid trap.  Switch the context: */
176 	if (has_vhe()) {
177 		reg = CPACR_EL1_FPEN;
178 		if (sve_guest)
179 			reg |= CPACR_EL1_ZEN;
180 
181 		sysreg_clear_set(cpacr_el1, 0, reg);
182 	} else {
183 		reg = CPTR_EL2_TFP;
184 		if (sve_guest)
185 			reg |= CPTR_EL2_TZ;
186 
187 		sysreg_clear_set(cptr_el2, reg, 0);
188 	}
189 	isb();
190 
191 	if (vcpu->arch.flags & KVM_ARM64_FP_HOST) {
192 		__fpsimd_save_state(vcpu->arch.host_fpsimd_state);
193 		vcpu->arch.flags &= ~KVM_ARM64_FP_HOST;
194 	}
195 
196 	if (sve_guest)
197 		__hyp_sve_restore_guest(vcpu);
198 	else
199 		__fpsimd_restore_state(&vcpu->arch.ctxt.fp_regs);
200 
201 	/* Skip restoring fpexc32 for AArch64 guests */
202 	if (!(read_sysreg(hcr_el2) & HCR_RW))
203 		write_sysreg(__vcpu_sys_reg(vcpu, FPEXC32_EL2), fpexc32_el2);
204 
205 	vcpu->arch.flags |= KVM_ARM64_FP_ENABLED;
206 
207 	return true;
208 }
209 
210 static inline bool handle_tx2_tvm(struct kvm_vcpu *vcpu)
211 {
212 	u32 sysreg = esr_sys64_to_sysreg(kvm_vcpu_get_esr(vcpu));
213 	int rt = kvm_vcpu_sys_get_rt(vcpu);
214 	u64 val = vcpu_get_reg(vcpu, rt);
215 
216 	/*
217 	 * The normal sysreg handling code expects to see the traps,
218 	 * let's not do anything here.
219 	 */
220 	if (vcpu->arch.hcr_el2 & HCR_TVM)
221 		return false;
222 
223 	switch (sysreg) {
224 	case SYS_SCTLR_EL1:
225 		write_sysreg_el1(val, SYS_SCTLR);
226 		break;
227 	case SYS_TTBR0_EL1:
228 		write_sysreg_el1(val, SYS_TTBR0);
229 		break;
230 	case SYS_TTBR1_EL1:
231 		write_sysreg_el1(val, SYS_TTBR1);
232 		break;
233 	case SYS_TCR_EL1:
234 		write_sysreg_el1(val, SYS_TCR);
235 		break;
236 	case SYS_ESR_EL1:
237 		write_sysreg_el1(val, SYS_ESR);
238 		break;
239 	case SYS_FAR_EL1:
240 		write_sysreg_el1(val, SYS_FAR);
241 		break;
242 	case SYS_AFSR0_EL1:
243 		write_sysreg_el1(val, SYS_AFSR0);
244 		break;
245 	case SYS_AFSR1_EL1:
246 		write_sysreg_el1(val, SYS_AFSR1);
247 		break;
248 	case SYS_MAIR_EL1:
249 		write_sysreg_el1(val, SYS_MAIR);
250 		break;
251 	case SYS_AMAIR_EL1:
252 		write_sysreg_el1(val, SYS_AMAIR);
253 		break;
254 	case SYS_CONTEXTIDR_EL1:
255 		write_sysreg_el1(val, SYS_CONTEXTIDR);
256 		break;
257 	default:
258 		return false;
259 	}
260 
261 	__kvm_skip_instr(vcpu);
262 	return true;
263 }
264 
265 static inline bool esr_is_ptrauth_trap(u32 esr)
266 {
267 	switch (esr_sys64_to_sysreg(esr)) {
268 	case SYS_APIAKEYLO_EL1:
269 	case SYS_APIAKEYHI_EL1:
270 	case SYS_APIBKEYLO_EL1:
271 	case SYS_APIBKEYHI_EL1:
272 	case SYS_APDAKEYLO_EL1:
273 	case SYS_APDAKEYHI_EL1:
274 	case SYS_APDBKEYLO_EL1:
275 	case SYS_APDBKEYHI_EL1:
276 	case SYS_APGAKEYLO_EL1:
277 	case SYS_APGAKEYHI_EL1:
278 		return true;
279 	}
280 
281 	return false;
282 }
283 
284 #define __ptrauth_save_key(ctxt, key)					\
285 	do {								\
286 	u64 __val;                                                      \
287 	__val = read_sysreg_s(SYS_ ## key ## KEYLO_EL1);                \
288 	ctxt_sys_reg(ctxt, key ## KEYLO_EL1) = __val;                   \
289 	__val = read_sysreg_s(SYS_ ## key ## KEYHI_EL1);                \
290 	ctxt_sys_reg(ctxt, key ## KEYHI_EL1) = __val;                   \
291 } while(0)
292 
293 DECLARE_PER_CPU(struct kvm_cpu_context, kvm_hyp_ctxt);
294 
295 static bool kvm_hyp_handle_ptrauth(struct kvm_vcpu *vcpu, u64 *exit_code)
296 {
297 	struct kvm_cpu_context *ctxt;
298 	u64 val;
299 
300 	if (!vcpu_has_ptrauth(vcpu))
301 		return false;
302 
303 	ctxt = this_cpu_ptr(&kvm_hyp_ctxt);
304 	__ptrauth_save_key(ctxt, APIA);
305 	__ptrauth_save_key(ctxt, APIB);
306 	__ptrauth_save_key(ctxt, APDA);
307 	__ptrauth_save_key(ctxt, APDB);
308 	__ptrauth_save_key(ctxt, APGA);
309 
310 	vcpu_ptrauth_enable(vcpu);
311 
312 	val = read_sysreg(hcr_el2);
313 	val |= (HCR_API | HCR_APK);
314 	write_sysreg(val, hcr_el2);
315 
316 	return true;
317 }
318 
319 static bool kvm_hyp_handle_sysreg(struct kvm_vcpu *vcpu, u64 *exit_code)
320 {
321 	if (cpus_have_final_cap(ARM64_WORKAROUND_CAVIUM_TX2_219_TVM) &&
322 	    handle_tx2_tvm(vcpu))
323 		return true;
324 
325 	if (static_branch_unlikely(&vgic_v3_cpuif_trap) &&
326 	    __vgic_v3_perform_cpuif_access(vcpu) == 1)
327 		return true;
328 
329 	if (esr_is_ptrauth_trap(kvm_vcpu_get_esr(vcpu)))
330 		return kvm_hyp_handle_ptrauth(vcpu, exit_code);
331 
332 	return false;
333 }
334 
335 static bool kvm_hyp_handle_cp15_32(struct kvm_vcpu *vcpu, u64 *exit_code)
336 {
337 	if (static_branch_unlikely(&vgic_v3_cpuif_trap) &&
338 	    __vgic_v3_perform_cpuif_access(vcpu) == 1)
339 		return true;
340 
341 	return false;
342 }
343 
344 static bool kvm_hyp_handle_iabt_low(struct kvm_vcpu *vcpu, u64 *exit_code)
345 {
346 	if (!__populate_fault_info(vcpu))
347 		return true;
348 
349 	return false;
350 }
351 
352 static bool kvm_hyp_handle_dabt_low(struct kvm_vcpu *vcpu, u64 *exit_code)
353 {
354 	if (!__populate_fault_info(vcpu))
355 		return true;
356 
357 	if (static_branch_unlikely(&vgic_v2_cpuif_trap)) {
358 		bool valid;
359 
360 		valid = kvm_vcpu_trap_get_fault_type(vcpu) == FSC_FAULT &&
361 			kvm_vcpu_dabt_isvalid(vcpu) &&
362 			!kvm_vcpu_abt_issea(vcpu) &&
363 			!kvm_vcpu_abt_iss1tw(vcpu);
364 
365 		if (valid) {
366 			int ret = __vgic_v2_perform_cpuif_access(vcpu);
367 
368 			if (ret == 1)
369 				return true;
370 
371 			/* Promote an illegal access to an SError.*/
372 			if (ret == -1)
373 				*exit_code = ARM_EXCEPTION_EL1_SERROR;
374 		}
375 	}
376 
377 	return false;
378 }
379 
380 typedef bool (*exit_handler_fn)(struct kvm_vcpu *, u64 *);
381 
382 static const exit_handler_fn *kvm_get_exit_handler_array(struct kvm_vcpu *vcpu);
383 
384 static void early_exit_filter(struct kvm_vcpu *vcpu, u64 *exit_code);
385 
386 /*
387  * Allow the hypervisor to handle the exit with an exit handler if it has one.
388  *
389  * Returns true if the hypervisor handled the exit, and control should go back
390  * to the guest, or false if it hasn't.
391  */
392 static inline bool kvm_hyp_handle_exit(struct kvm_vcpu *vcpu, u64 *exit_code)
393 {
394 	const exit_handler_fn *handlers = kvm_get_exit_handler_array(vcpu);
395 	exit_handler_fn fn;
396 
397 	fn = handlers[kvm_vcpu_trap_get_class(vcpu)];
398 
399 	if (fn)
400 		return fn(vcpu, exit_code);
401 
402 	return false;
403 }
404 
405 /*
406  * Return true when we were able to fixup the guest exit and should return to
407  * the guest, false when we should restore the host state and return to the
408  * main run loop.
409  */
410 static inline bool fixup_guest_exit(struct kvm_vcpu *vcpu, u64 *exit_code)
411 {
412 	/*
413 	 * Save PSTATE early so that we can evaluate the vcpu mode
414 	 * early on.
415 	 */
416 	vcpu->arch.ctxt.regs.pstate = read_sysreg_el2(SYS_SPSR);
417 
418 	/*
419 	 * Check whether we want to repaint the state one way or
420 	 * another.
421 	 */
422 	early_exit_filter(vcpu, exit_code);
423 
424 	if (ARM_EXCEPTION_CODE(*exit_code) != ARM_EXCEPTION_IRQ)
425 		vcpu->arch.fault.esr_el2 = read_sysreg_el2(SYS_ESR);
426 
427 	if (ARM_SERROR_PENDING(*exit_code)) {
428 		u8 esr_ec = kvm_vcpu_trap_get_class(vcpu);
429 
430 		/*
431 		 * HVC already have an adjusted PC, which we need to
432 		 * correct in order to return to after having injected
433 		 * the SError.
434 		 *
435 		 * SMC, on the other hand, is *trapped*, meaning its
436 		 * preferred return address is the SMC itself.
437 		 */
438 		if (esr_ec == ESR_ELx_EC_HVC32 || esr_ec == ESR_ELx_EC_HVC64)
439 			write_sysreg_el2(read_sysreg_el2(SYS_ELR) - 4, SYS_ELR);
440 	}
441 
442 	/*
443 	 * We're using the raw exception code in order to only process
444 	 * the trap if no SError is pending. We will come back to the
445 	 * same PC once the SError has been injected, and replay the
446 	 * trapping instruction.
447 	 */
448 	if (*exit_code != ARM_EXCEPTION_TRAP)
449 		goto exit;
450 
451 	/* Check if there's an exit handler and allow it to handle the exit. */
452 	if (kvm_hyp_handle_exit(vcpu, exit_code))
453 		goto guest;
454 exit:
455 	/* Return to the host kernel and handle the exit */
456 	return false;
457 
458 guest:
459 	/* Re-enter the guest */
460 	asm(ALTERNATIVE("nop", "dmb sy", ARM64_WORKAROUND_1508412));
461 	return true;
462 }
463 
464 static inline void __kvm_unexpected_el2_exception(void)
465 {
466 	extern char __guest_exit_panic[];
467 	unsigned long addr, fixup;
468 	struct kvm_exception_table_entry *entry, *end;
469 	unsigned long elr_el2 = read_sysreg(elr_el2);
470 
471 	entry = &__start___kvm_ex_table;
472 	end = &__stop___kvm_ex_table;
473 
474 	while (entry < end) {
475 		addr = (unsigned long)&entry->insn + entry->insn;
476 		fixup = (unsigned long)&entry->fixup + entry->fixup;
477 
478 		if (addr != elr_el2) {
479 			entry++;
480 			continue;
481 		}
482 
483 		write_sysreg(fixup, elr_el2);
484 		return;
485 	}
486 
487 	/* Trigger a panic after restoring the hyp context. */
488 	write_sysreg(__guest_exit_panic, elr_el2);
489 }
490 
491 #endif /* __ARM64_KVM_HYP_SWITCH_H__ */
492