xref: /openbmc/linux/arch/arm64/kvm/hyp/include/hyp/switch.h (revision 6417f031) 
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 
12 #include <linux/arm-smccc.h>
13 #include <linux/kvm_host.h>
14 #include <linux/types.h>
15 #include <linux/jump_label.h>
16 #include <uapi/linux/psci.h>
17 
18 #include <kvm/arm_psci.h>
19 
20 #include <asm/barrier.h>
21 #include <asm/cpufeature.h>
22 #include <asm/extable.h>
23 #include <asm/kprobes.h>
24 #include <asm/kvm_asm.h>
25 #include <asm/kvm_emulate.h>
26 #include <asm/kvm_hyp.h>
27 #include <asm/kvm_mmu.h>
28 #include <asm/fpsimd.h>
29 #include <asm/debug-monitors.h>
30 #include <asm/processor.h>
31 #include <asm/thread_info.h>
32 
33 extern const char __hyp_panic_string[];
34 
35 extern struct exception_table_entry __start___kvm_ex_table;
36 extern struct exception_table_entry __stop___kvm_ex_table;
37 
38 /* Check whether the FP regs were dirtied while in the host-side run loop: */
39 static inline bool update_fp_enabled(struct kvm_vcpu *vcpu)
40 {
41 	/*
42 	 * When the system doesn't support FP/SIMD, we cannot rely on
43 	 * the _TIF_FOREIGN_FPSTATE flag. However, we always inject an
44 	 * abort on the very first access to FP and thus we should never
45 	 * see KVM_ARM64_FP_ENABLED. For added safety, make sure we always
46 	 * trap the accesses.
47 	 */
48 	if (!system_supports_fpsimd() ||
49 	    vcpu->arch.host_thread_info->flags & _TIF_FOREIGN_FPSTATE)
50 		vcpu->arch.flags &= ~(KVM_ARM64_FP_ENABLED |
51 				      KVM_ARM64_FP_HOST);
52 
53 	return !!(vcpu->arch.flags & KVM_ARM64_FP_ENABLED);
54 }
55 
56 /* Save the 32-bit only FPSIMD system register state */
57 static inline void __fpsimd_save_fpexc32(struct kvm_vcpu *vcpu)
58 {
59 	if (!vcpu_el1_is_32bit(vcpu))
60 		return;
61 
62 	__vcpu_sys_reg(vcpu, FPEXC32_EL2) = read_sysreg(fpexc32_el2);
63 }
64 
65 static inline void __activate_traps_fpsimd32(struct kvm_vcpu *vcpu)
66 {
67 	/*
68 	 * We are about to set CPTR_EL2.TFP to trap all floating point
69 	 * register accesses to EL2, however, the ARM ARM clearly states that
70 	 * traps are only taken to EL2 if the operation would not otherwise
71 	 * trap to EL1.  Therefore, always make sure that for 32-bit guests,
72 	 * we set FPEXC.EN to prevent traps to EL1, when setting the TFP bit.
73 	 * If FP/ASIMD is not implemented, FPEXC is UNDEFINED and any access to
74 	 * it will cause an exception.
75 	 */
76 	if (vcpu_el1_is_32bit(vcpu) && system_supports_fpsimd()) {
77 		write_sysreg(1 << 30, fpexc32_el2);
78 		isb();
79 	}
80 }
81 
82 static inline void __activate_traps_common(struct kvm_vcpu *vcpu)
83 {
84 	/* Trap on AArch32 cp15 c15 (impdef sysregs) accesses (EL1 or EL0) */
85 	write_sysreg(1 << 15, hstr_el2);
86 
87 	/*
88 	 * Make sure we trap PMU access from EL0 to EL2. Also sanitize
89 	 * PMSELR_EL0 to make sure it never contains the cycle
90 	 * counter, which could make a PMXEVCNTR_EL0 access UNDEF at
91 	 * EL1 instead of being trapped to EL2.
92 	 */
93 	if (kvm_arm_support_pmu_v3()) {
94 		write_sysreg(0, pmselr_el0);
95 		write_sysreg(ARMV8_PMU_USERENR_MASK, pmuserenr_el0);
96 	}
97 	write_sysreg(vcpu->arch.mdcr_el2, mdcr_el2);
98 }
99 
100 static inline void __deactivate_traps_common(void)
101 {
102 	write_sysreg(0, hstr_el2);
103 	if (kvm_arm_support_pmu_v3())
104 		write_sysreg(0, pmuserenr_el0);
105 }
106 
107 static inline void ___activate_traps(struct kvm_vcpu *vcpu)
108 {
109 	u64 hcr = vcpu->arch.hcr_el2;
110 
111 	if (cpus_have_final_cap(ARM64_WORKAROUND_CAVIUM_TX2_219_TVM))
112 		hcr |= HCR_TVM;
113 
114 	write_sysreg(hcr, hcr_el2);
115 
116 	if (cpus_have_final_cap(ARM64_HAS_RAS_EXTN) && (hcr & HCR_VSE))
117 		write_sysreg_s(vcpu->arch.vsesr_el2, SYS_VSESR_EL2);
118 }
119 
120 static inline void ___deactivate_traps(struct kvm_vcpu *vcpu)
121 {
122 	/*
123 	 * If we pended a virtual abort, preserve it until it gets
124 	 * cleared. See D1.14.3 (Virtual Interrupts) for details, but
125 	 * the crucial bit is "On taking a vSError interrupt,
126 	 * HCR_EL2.VSE is cleared to 0."
127 	 */
128 	if (vcpu->arch.hcr_el2 & HCR_VSE) {
129 		vcpu->arch.hcr_el2 &= ~HCR_VSE;
130 		vcpu->arch.hcr_el2 |= read_sysreg(hcr_el2) & HCR_VSE;
131 	}
132 }
133 
134 static inline bool __translate_far_to_hpfar(u64 far, u64 *hpfar)
135 {
136 	u64 par, tmp;
137 
138 	/*
139 	 * Resolve the IPA the hard way using the guest VA.
140 	 *
141 	 * Stage-1 translation already validated the memory access
142 	 * rights. As such, we can use the EL1 translation regime, and
143 	 * don't have to distinguish between EL0 and EL1 access.
144 	 *
145 	 * We do need to save/restore PAR_EL1 though, as we haven't
146 	 * saved the guest context yet, and we may return early...
147 	 */
148 	par = read_sysreg_par();
149 	if (!__kvm_at("s1e1r", far))
150 		tmp = read_sysreg_par();
151 	else
152 		tmp = SYS_PAR_EL1_F; /* back to the guest */
153 	write_sysreg(par, par_el1);
154 
155 	if (unlikely(tmp & SYS_PAR_EL1_F))
156 		return false; /* Translation failed, back to guest */
157 
158 	/* Convert PAR to HPFAR format */
159 	*hpfar = PAR_TO_HPFAR(tmp);
160 	return true;
161 }
162 
163 static inline bool __populate_fault_info(struct kvm_vcpu *vcpu)
164 {
165 	u8 ec;
166 	u64 esr;
167 	u64 hpfar, far;
168 
169 	esr = vcpu->arch.fault.esr_el2;
170 	ec = ESR_ELx_EC(esr);
171 
172 	if (ec != ESR_ELx_EC_DABT_LOW && ec != ESR_ELx_EC_IABT_LOW)
173 		return true;
174 
175 	far = read_sysreg_el2(SYS_FAR);
176 
177 	/*
178 	 * The HPFAR can be invalid if the stage 2 fault did not
179 	 * happen during a stage 1 page table walk (the ESR_EL2.S1PTW
180 	 * bit is clear) and one of the two following cases are true:
181 	 *   1. The fault was due to a permission fault
182 	 *   2. The processor carries errata 834220
183 	 *
184 	 * Therefore, for all non S1PTW faults where we either have a
185 	 * permission fault or the errata workaround is enabled, we
186 	 * resolve the IPA using the AT instruction.
187 	 */
188 	if (!(esr & ESR_ELx_S1PTW) &&
189 	    (cpus_have_final_cap(ARM64_WORKAROUND_834220) ||
190 	     (esr & ESR_ELx_FSC_TYPE) == FSC_PERM)) {
191 		if (!__translate_far_to_hpfar(far, &hpfar))
192 			return false;
193 	} else {
194 		hpfar = read_sysreg(hpfar_el2);
195 	}
196 
197 	vcpu->arch.fault.far_el2 = far;
198 	vcpu->arch.fault.hpfar_el2 = hpfar;
199 	return true;
200 }
201 
202 /* Check for an FPSIMD/SVE trap and handle as appropriate */
203 static inline bool __hyp_handle_fpsimd(struct kvm_vcpu *vcpu)
204 {
205 	bool vhe, sve_guest, sve_host;
206 	u8 esr_ec;
207 
208 	if (!system_supports_fpsimd())
209 		return false;
210 
211 	/*
212 	 * Currently system_supports_sve() currently implies has_vhe(),
213 	 * so the check is redundant. However, has_vhe() can be determined
214 	 * statically and helps the compiler remove dead code.
215 	 */
216 	if (has_vhe() && system_supports_sve()) {
217 		sve_guest = vcpu_has_sve(vcpu);
218 		sve_host = vcpu->arch.flags & KVM_ARM64_HOST_SVE_IN_USE;
219 		vhe = true;
220 	} else {
221 		sve_guest = false;
222 		sve_host = false;
223 		vhe = has_vhe();
224 	}
225 
226 	esr_ec = kvm_vcpu_trap_get_class(vcpu);
227 	if (esr_ec != ESR_ELx_EC_FP_ASIMD &&
228 	    esr_ec != ESR_ELx_EC_SVE)
229 		return false;
230 
231 	/* Don't handle SVE traps for non-SVE vcpus here: */
232 	if (!sve_guest)
233 		if (esr_ec != ESR_ELx_EC_FP_ASIMD)
234 			return false;
235 
236 	/* Valid trap.  Switch the context: */
237 
238 	if (vhe) {
239 		u64 reg = read_sysreg(cpacr_el1) | CPACR_EL1_FPEN;
240 
241 		if (sve_guest)
242 			reg |= CPACR_EL1_ZEN;
243 
244 		write_sysreg(reg, cpacr_el1);
245 	} else {
246 		write_sysreg(read_sysreg(cptr_el2) & ~(u64)CPTR_EL2_TFP,
247 			     cptr_el2);
248 	}
249 
250 	isb();
251 
252 	if (vcpu->arch.flags & KVM_ARM64_FP_HOST) {
253 		/*
254 		 * In the SVE case, VHE is assumed: it is enforced by
255 		 * Kconfig and kvm_arch_init().
256 		 */
257 		if (sve_host) {
258 			struct thread_struct *thread = container_of(
259 				vcpu->arch.host_fpsimd_state,
260 				struct thread_struct, uw.fpsimd_state);
261 
262 			sve_save_state(sve_pffr(thread),
263 				       &vcpu->arch.host_fpsimd_state->fpsr);
264 		} else {
265 			__fpsimd_save_state(vcpu->arch.host_fpsimd_state);
266 		}
267 
268 		vcpu->arch.flags &= ~KVM_ARM64_FP_HOST;
269 	}
270 
271 	if (sve_guest) {
272 		sve_load_state(vcpu_sve_pffr(vcpu),
273 			       &vcpu->arch.ctxt.fp_regs.fpsr,
274 			       sve_vq_from_vl(vcpu->arch.sve_max_vl) - 1);
275 		write_sysreg_s(__vcpu_sys_reg(vcpu, ZCR_EL1), SYS_ZCR_EL12);
276 	} else {
277 		__fpsimd_restore_state(&vcpu->arch.ctxt.fp_regs);
278 	}
279 
280 	/* Skip restoring fpexc32 for AArch64 guests */
281 	if (!(read_sysreg(hcr_el2) & HCR_RW))
282 		write_sysreg(__vcpu_sys_reg(vcpu, FPEXC32_EL2), fpexc32_el2);
283 
284 	vcpu->arch.flags |= KVM_ARM64_FP_ENABLED;
285 
286 	return true;
287 }
288 
289 static inline bool handle_tx2_tvm(struct kvm_vcpu *vcpu)
290 {
291 	u32 sysreg = esr_sys64_to_sysreg(kvm_vcpu_get_esr(vcpu));
292 	int rt = kvm_vcpu_sys_get_rt(vcpu);
293 	u64 val = vcpu_get_reg(vcpu, rt);
294 
295 	/*
296 	 * The normal sysreg handling code expects to see the traps,
297 	 * let's not do anything here.
298 	 */
299 	if (vcpu->arch.hcr_el2 & HCR_TVM)
300 		return false;
301 
302 	switch (sysreg) {
303 	case SYS_SCTLR_EL1:
304 		write_sysreg_el1(val, SYS_SCTLR);
305 		break;
306 	case SYS_TTBR0_EL1:
307 		write_sysreg_el1(val, SYS_TTBR0);
308 		break;
309 	case SYS_TTBR1_EL1:
310 		write_sysreg_el1(val, SYS_TTBR1);
311 		break;
312 	case SYS_TCR_EL1:
313 		write_sysreg_el1(val, SYS_TCR);
314 		break;
315 	case SYS_ESR_EL1:
316 		write_sysreg_el1(val, SYS_ESR);
317 		break;
318 	case SYS_FAR_EL1:
319 		write_sysreg_el1(val, SYS_FAR);
320 		break;
321 	case SYS_AFSR0_EL1:
322 		write_sysreg_el1(val, SYS_AFSR0);
323 		break;
324 	case SYS_AFSR1_EL1:
325 		write_sysreg_el1(val, SYS_AFSR1);
326 		break;
327 	case SYS_MAIR_EL1:
328 		write_sysreg_el1(val, SYS_MAIR);
329 		break;
330 	case SYS_AMAIR_EL1:
331 		write_sysreg_el1(val, SYS_AMAIR);
332 		break;
333 	case SYS_CONTEXTIDR_EL1:
334 		write_sysreg_el1(val, SYS_CONTEXTIDR);
335 		break;
336 	default:
337 		return false;
338 	}
339 
340 	__kvm_skip_instr(vcpu);
341 	return true;
342 }
343 
344 static inline bool esr_is_ptrauth_trap(u32 esr)
345 {
346 	u32 ec = ESR_ELx_EC(esr);
347 
348 	if (ec == ESR_ELx_EC_PAC)
349 		return true;
350 
351 	if (ec != ESR_ELx_EC_SYS64)
352 		return false;
353 
354 	switch (esr_sys64_to_sysreg(esr)) {
355 	case SYS_APIAKEYLO_EL1:
356 	case SYS_APIAKEYHI_EL1:
357 	case SYS_APIBKEYLO_EL1:
358 	case SYS_APIBKEYHI_EL1:
359 	case SYS_APDAKEYLO_EL1:
360 	case SYS_APDAKEYHI_EL1:
361 	case SYS_APDBKEYLO_EL1:
362 	case SYS_APDBKEYHI_EL1:
363 	case SYS_APGAKEYLO_EL1:
364 	case SYS_APGAKEYHI_EL1:
365 		return true;
366 	}
367 
368 	return false;
369 }
370 
371 #define __ptrauth_save_key(ctxt, key)					\
372 	do {								\
373 	u64 __val;                                                      \
374 	__val = read_sysreg_s(SYS_ ## key ## KEYLO_EL1);                \
375 	ctxt_sys_reg(ctxt, key ## KEYLO_EL1) = __val;                   \
376 	__val = read_sysreg_s(SYS_ ## key ## KEYHI_EL1);                \
377 	ctxt_sys_reg(ctxt, key ## KEYHI_EL1) = __val;                   \
378 } while(0)
379 
380 DECLARE_PER_CPU(struct kvm_cpu_context, kvm_hyp_ctxt);
381 
382 static inline bool __hyp_handle_ptrauth(struct kvm_vcpu *vcpu)
383 {
384 	struct kvm_cpu_context *ctxt;
385 	u64 val;
386 
387 	if (!vcpu_has_ptrauth(vcpu) ||
388 	    !esr_is_ptrauth_trap(kvm_vcpu_get_esr(vcpu)))
389 		return false;
390 
391 	ctxt = this_cpu_ptr(&kvm_hyp_ctxt);
392 	__ptrauth_save_key(ctxt, APIA);
393 	__ptrauth_save_key(ctxt, APIB);
394 	__ptrauth_save_key(ctxt, APDA);
395 	__ptrauth_save_key(ctxt, APDB);
396 	__ptrauth_save_key(ctxt, APGA);
397 
398 	vcpu_ptrauth_enable(vcpu);
399 
400 	val = read_sysreg(hcr_el2);
401 	val |= (HCR_API | HCR_APK);
402 	write_sysreg(val, hcr_el2);
403 
404 	return true;
405 }
406 
407 /*
408  * Return true when we were able to fixup the guest exit and should return to
409  * the guest, false when we should restore the host state and return to the
410  * main run loop.
411  */
412 static inline bool fixup_guest_exit(struct kvm_vcpu *vcpu, u64 *exit_code)
413 {
414 	if (ARM_EXCEPTION_CODE(*exit_code) != ARM_EXCEPTION_IRQ)
415 		vcpu->arch.fault.esr_el2 = read_sysreg_el2(SYS_ESR);
416 
417 	if (ARM_SERROR_PENDING(*exit_code)) {
418 		u8 esr_ec = kvm_vcpu_trap_get_class(vcpu);
419 
420 		/*
421 		 * HVC already have an adjusted PC, which we need to
422 		 * correct in order to return to after having injected
423 		 * the SError.
424 		 *
425 		 * SMC, on the other hand, is *trapped*, meaning its
426 		 * preferred return address is the SMC itself.
427 		 */
428 		if (esr_ec == ESR_ELx_EC_HVC32 || esr_ec == ESR_ELx_EC_HVC64)
429 			write_sysreg_el2(read_sysreg_el2(SYS_ELR) - 4, SYS_ELR);
430 	}
431 
432 	/*
433 	 * We're using the raw exception code in order to only process
434 	 * the trap if no SError is pending. We will come back to the
435 	 * same PC once the SError has been injected, and replay the
436 	 * trapping instruction.
437 	 */
438 	if (*exit_code != ARM_EXCEPTION_TRAP)
439 		goto exit;
440 
441 	if (cpus_have_final_cap(ARM64_WORKAROUND_CAVIUM_TX2_219_TVM) &&
442 	    kvm_vcpu_trap_get_class(vcpu) == ESR_ELx_EC_SYS64 &&
443 	    handle_tx2_tvm(vcpu))
444 		goto guest;
445 
446 	/*
447 	 * We trap the first access to the FP/SIMD to save the host context
448 	 * and restore the guest context lazily.
449 	 * If FP/SIMD is not implemented, handle the trap and inject an
450 	 * undefined instruction exception to the guest.
451 	 * Similarly for trapped SVE accesses.
452 	 */
453 	if (__hyp_handle_fpsimd(vcpu))
454 		goto guest;
455 
456 	if (__hyp_handle_ptrauth(vcpu))
457 		goto guest;
458 
459 	if (!__populate_fault_info(vcpu))
460 		goto guest;
461 
462 	if (static_branch_unlikely(&vgic_v2_cpuif_trap)) {
463 		bool valid;
464 
465 		valid = kvm_vcpu_trap_get_class(vcpu) == ESR_ELx_EC_DABT_LOW &&
466 			kvm_vcpu_trap_get_fault_type(vcpu) == FSC_FAULT &&
467 			kvm_vcpu_dabt_isvalid(vcpu) &&
468 			!kvm_vcpu_abt_issea(vcpu) &&
469 			!kvm_vcpu_abt_iss1tw(vcpu);
470 
471 		if (valid) {
472 			int ret = __vgic_v2_perform_cpuif_access(vcpu);
473 
474 			if (ret == 1)
475 				goto guest;
476 
477 			/* Promote an illegal access to an SError.*/
478 			if (ret == -1)
479 				*exit_code = ARM_EXCEPTION_EL1_SERROR;
480 
481 			goto exit;
482 		}
483 	}
484 
485 	if (static_branch_unlikely(&vgic_v3_cpuif_trap) &&
486 	    (kvm_vcpu_trap_get_class(vcpu) == ESR_ELx_EC_SYS64 ||
487 	     kvm_vcpu_trap_get_class(vcpu) == ESR_ELx_EC_CP15_32)) {
488 		int ret = __vgic_v3_perform_cpuif_access(vcpu);
489 
490 		if (ret == 1)
491 			goto guest;
492 	}
493 
494 exit:
495 	/* Return to the host kernel and handle the exit */
496 	return false;
497 
498 guest:
499 	/* Re-enter the guest */
500 	asm(ALTERNATIVE("nop", "dmb sy", ARM64_WORKAROUND_1508412));
501 	return true;
502 }
503 
504 static inline void __kvm_unexpected_el2_exception(void)
505 {
506 	extern char __guest_exit_panic[];
507 	unsigned long addr, fixup;
508 	struct exception_table_entry *entry, *end;
509 	unsigned long elr_el2 = read_sysreg(elr_el2);
510 
511 	entry = &__start___kvm_ex_table;
512 	end = &__stop___kvm_ex_table;
513 
514 	while (entry < end) {
515 		addr = (unsigned long)&entry->insn + entry->insn;
516 		fixup = (unsigned long)&entry->fixup + entry->fixup;
517 
518 		if (addr != elr_el2) {
519 			entry++;
520 			continue;
521 		}
522 
523 		write_sysreg(fixup, elr_el2);
524 		return;
525 	}
526 
527 	/* Trigger a panic after restoring the hyp context. */
528 	write_sysreg(__guest_exit_panic, elr_el2);
529 }
530 
531 #endif /* __ARM64_KVM_HYP_SWITCH_H__ */
532