arch/arm64/kvm/handle_exit.c

   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_coproc.h>
  18 #include <asm/kvm_emulate.h>
  19 #include <asm/kvm_mmu.h>
  20 #include <asm/debug-monitors.h>
  21 #include <asm/traps.h>
  22
  23 #include <kvm/arm_hypercalls.h>
  24
  25 #define CREATE_TRACE_POINTS
  26 #include "trace.h"
  27
  28 typedef int (*exit_handle_fn)(struct kvm_vcpu *, struct kvm_run *);
  29
  30 static void kvm_handle_guest_serror(struct kvm_vcpu *vcpu, u32 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, struct kvm_run *run)
  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, struct kvm_run *run)
  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_skip_instr(vcpu, kvm_vcpu_trap_il_is32bit(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, struct kvm_run *run)
  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: Yield the CPU and come back to this vcpu when the scheduler
  85  * decides to.
  86  * WFI: Simply call kvm_vcpu_block(), 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  */
  90 static int kvm_handle_wfx(struct kvm_vcpu *vcpu, struct kvm_run *run)
  91 {
  92         if (kvm_vcpu_get_hsr(vcpu) & ESR_ELx_WFx_ISS_WFE) {
  93                 trace_kvm_wfx_arm64(*vcpu_pc(vcpu), true);
  94                 vcpu->stat.wfe_exit_stat++;
  95                 kvm_vcpu_on_spin(vcpu, vcpu_mode_priv(vcpu));
  96         } else {
  97                 trace_kvm_wfx_arm64(*vcpu_pc(vcpu), false);
  98                 vcpu->stat.wfi_exit_stat++;
  99                 kvm_vcpu_block(vcpu);
 100                 kvm_clear_request(KVM_REQ_UNHALT, vcpu);
 101         }
 102
 103         kvm_skip_instr(vcpu, kvm_vcpu_trap_il_is32bit(vcpu));
 104
 105         return 1;
 106 }
 107
 108 /**
 109  * kvm_handle_guest_debug - handle a debug exception instruction
 110  *
 111  * @vcpu:       the vcpu pointer
 112  * @run:        access to the kvm_run structure for results
 113  *
 114  * We route all debug exceptions through the same handler. If both the
 115  * guest and host are using the same debug facilities it will be up to
 116  * userspace to re-inject the correct exception for guest delivery.
 117  *
 118  * @return: 0 (while setting run->exit_reason), -1 for error
 119  */
 120 static int kvm_handle_guest_debug(struct kvm_vcpu *vcpu, struct kvm_run *run)
 121 {
 122         u32 hsr = kvm_vcpu_get_hsr(vcpu);
 123         int ret = 0;
 124
 125         run->exit_reason = KVM_EXIT_DEBUG;
 126         run->debug.arch.hsr = hsr;
 127
 128         switch (ESR_ELx_EC(hsr)) {
 129         case ESR_ELx_EC_WATCHPT_LOW:
 130                 run->debug.arch.far = vcpu->arch.fault.far_el2;
 131                 /* fall through */
 132         case ESR_ELx_EC_SOFTSTP_LOW:
 133         case ESR_ELx_EC_BREAKPT_LOW:
 134         case ESR_ELx_EC_BKPT32:
 135         case ESR_ELx_EC_BRK64:
 136                 break;
 137         default:
 138                 kvm_err("%s: un-handled case hsr: %#08x\n",
 139                         __func__, (unsigned int) hsr);
 140                 ret = -1;
 141                 break;
 142         }
 143
 144         return ret;
 145 }
 146
 147 static int kvm_handle_unknown_ec(struct kvm_vcpu *vcpu, struct kvm_run *run)
 148 {
 149         u32 hsr = kvm_vcpu_get_hsr(vcpu);
 150
 151         kvm_pr_unimpl("Unknown exception class: hsr: %#08x -- %s\n",
 152                       hsr, esr_get_class_string(hsr));
 153
 154         kvm_inject_undefined(vcpu);
 155         return 1;
 156 }
 157
 158 static int handle_sve(struct kvm_vcpu *vcpu, struct kvm_run *run)
 159 {
 160         /* Until SVE is supported for guests: */
 161         kvm_inject_undefined(vcpu);
 162         return 1;
 163 }
 164
 165 #define __ptrauth_save_key(regs, key)                                           \
 166 ({                                                                              \
 167         regs[key ## KEYLO_EL1] = read_sysreg_s(SYS_ ## key ## KEYLO_EL1);       \
 168         regs[key ## KEYHI_EL1] = read_sysreg_s(SYS_ ## key ## KEYHI_EL1);       \
 169 })
 170
 171 /*
 172  * Handle the guest trying to use a ptrauth instruction, or trying to access a
 173  * ptrauth register.
 174  */
 175 void kvm_arm_vcpu_ptrauth_trap(struct kvm_vcpu *vcpu)
 176 {
 177         struct kvm_cpu_context *ctxt;
 178
 179         if (vcpu_has_ptrauth(vcpu)) {
 180                 vcpu_ptrauth_enable(vcpu);
 181                 ctxt = vcpu->arch.host_cpu_context;
 182                 __ptrauth_save_key(ctxt->sys_regs, APIA);
 183                 __ptrauth_save_key(ctxt->sys_regs, APIB);
 184                 __ptrauth_save_key(ctxt->sys_regs, APDA);
 185                 __ptrauth_save_key(ctxt->sys_regs, APDB);
 186                 __ptrauth_save_key(ctxt->sys_regs, APGA);
 187         } else {
 188                 kvm_inject_undefined(vcpu);
 189         }
 190 }
 191
 192 /*
 193  * Guest usage of a ptrauth instruction (which the guest EL1 did not turn into
 194  * a NOP).
 195  */
 196 static int kvm_handle_ptrauth(struct kvm_vcpu *vcpu, struct kvm_run *run)
 197 {
 198         kvm_arm_vcpu_ptrauth_trap(vcpu);
 199         return 1;
 200 }
 201
 202 static exit_handle_fn arm_exit_handlers[] = {
 203         [0 ... ESR_ELx_EC_MAX]  = kvm_handle_unknown_ec,
 204         [ESR_ELx_EC_WFx]        = kvm_handle_wfx,
 205         [ESR_ELx_EC_CP15_32]    = kvm_handle_cp15_32,
 206         [ESR_ELx_EC_CP15_64]    = kvm_handle_cp15_64,
 207         [ESR_ELx_EC_CP14_MR]    = kvm_handle_cp14_32,
 208         [ESR_ELx_EC_CP14_LS]    = kvm_handle_cp14_load_store,
 209         [ESR_ELx_EC_CP14_64]    = kvm_handle_cp14_64,
 210         [ESR_ELx_EC_HVC32]      = handle_hvc,
 211         [ESR_ELx_EC_SMC32]      = handle_smc,
 212         [ESR_ELx_EC_HVC64]      = handle_hvc,
 213         [ESR_ELx_EC_SMC64]      = handle_smc,
 214         [ESR_ELx_EC_SYS64]      = kvm_handle_sys_reg,
 215         [ESR_ELx_EC_SVE]        = handle_sve,
 216         [ESR_ELx_EC_IABT_LOW]   = kvm_handle_guest_abort,
 217         [ESR_ELx_EC_DABT_LOW]   = kvm_handle_guest_abort,
 218         [ESR_ELx_EC_SOFTSTP_LOW]= kvm_handle_guest_debug,
 219         [ESR_ELx_EC_WATCHPT_LOW]= kvm_handle_guest_debug,
 220         [ESR_ELx_EC_BREAKPT_LOW]= kvm_handle_guest_debug,
 221         [ESR_ELx_EC_BKPT32]     = kvm_handle_guest_debug,
 222         [ESR_ELx_EC_BRK64]      = kvm_handle_guest_debug,
 223         [ESR_ELx_EC_FP_ASIMD]   = handle_no_fpsimd,
 224         [ESR_ELx_EC_PAC]        = kvm_handle_ptrauth,
 225 };
 226
 227 static exit_handle_fn kvm_get_exit_handler(struct kvm_vcpu *vcpu)
 228 {
 229         u32 hsr = kvm_vcpu_get_hsr(vcpu);
 230         u8 hsr_ec = ESR_ELx_EC(hsr);
 231
 232         return arm_exit_handlers[hsr_ec];
 233 }
 234
 235 /*
 236  * We may be single-stepping an emulated instruction. If the emulation
 237  * has been completed in the kernel, we can return to userspace with a
 238  * KVM_EXIT_DEBUG, otherwise userspace needs to complete its
 239  * emulation first.
 240  */
 241 static int handle_trap_exceptions(struct kvm_vcpu *vcpu, struct kvm_run *run)
 242 {
 243         int handled;
 244
 245         /*
 246          * See ARM ARM B1.14.1: "Hyp traps on instructions
 247          * that fail their condition code check"
 248          */
 249         if (!kvm_condition_valid(vcpu)) {
 250                 kvm_skip_instr(vcpu, kvm_vcpu_trap_il_is32bit(vcpu));
 251                 handled = 1;
 252         } else {
 253                 exit_handle_fn exit_handler;
 254
 255                 exit_handler = kvm_get_exit_handler(vcpu);
 256                 handled = exit_handler(vcpu, run);
 257         }
 258
 259         return handled;
 260 }
 261
 262 /*
 263  * Return > 0 to return to guest, < 0 on error, 0 (and set exit_reason) on
 264  * proper exit to userspace.
 265  */
 266 int handle_exit(struct kvm_vcpu *vcpu, struct kvm_run *run,
 267                        int exception_index)
 268 {
 269         if (ARM_SERROR_PENDING(exception_index)) {
 270                 u8 hsr_ec = ESR_ELx_EC(kvm_vcpu_get_hsr(vcpu));
 271
 272                 /*
 273                  * HVC/SMC already have an adjusted PC, which we need
 274                  * to correct in order to return to after having
 275                  * injected the SError.
 276                  */
 277                 if (hsr_ec == ESR_ELx_EC_HVC32 || hsr_ec == ESR_ELx_EC_HVC64 ||
 278                     hsr_ec == ESR_ELx_EC_SMC32 || hsr_ec == ESR_ELx_EC_SMC64) {
 279                         u32 adj =  kvm_vcpu_trap_il_is32bit(vcpu) ? 4 : 2;
 280                         *vcpu_pc(vcpu) -= adj;
 281                 }
 282
 283                 return 1;
 284         }
 285
 286         exception_index = ARM_EXCEPTION_CODE(exception_index);
 287
 288         switch (exception_index) {
 289         case ARM_EXCEPTION_IRQ:
 290                 return 1;
 291         case ARM_EXCEPTION_EL1_SERROR:
 292                 return 1;
 293         case ARM_EXCEPTION_TRAP:
 294                 return handle_trap_exceptions(vcpu, run);
 295         case ARM_EXCEPTION_HYP_GONE:
 296                 /*
 297                  * EL2 has been reset to the hyp-stub. This happens when a guest
 298                  * is pre-empted by kvm_reboot()'s shutdown call.
 299                  */
 300                 run->exit_reason = KVM_EXIT_FAIL_ENTRY;
 301                 return 0;
 302         case ARM_EXCEPTION_IL:
 303                 /*
 304                  * We attempted an illegal exception return.  Guest state must
 305                  * have been corrupted somehow.  Give up.
 306                  */
 307                 run->exit_reason = KVM_EXIT_FAIL_ENTRY;
 308                 return -EINVAL;
 309         default:
 310                 kvm_pr_unimpl("Unsupported exception type: %d",
 311                               exception_index);
 312                 run->exit_reason = KVM_EXIT_INTERNAL_ERROR;
 313                 return 0;
 314         }
 315 }
 316
 317 /* For exit types that need handling before we can be preempted */
 318 void handle_exit_early(struct kvm_vcpu *vcpu, struct kvm_run *run,
 319                        int exception_index)
 320 {
 321         if (ARM_SERROR_PENDING(exception_index)) {
 322                 if (this_cpu_has_cap(ARM64_HAS_RAS_EXTN)) {
 323                         u64 disr = kvm_vcpu_get_disr(vcpu);
 324
 325                         kvm_handle_guest_serror(vcpu, disr_to_esr(disr));
 326                 } else {
 327                         kvm_inject_vabt(vcpu);
 328                 }
 329
 330                 return;
 331         }
 332
 333         exception_index = ARM_EXCEPTION_CODE(exception_index);
 334
 335         if (exception_index == ARM_EXCEPTION_EL1_SERROR)
 336                 kvm_handle_guest_serror(vcpu, kvm_vcpu_get_hsr(vcpu));
 337 }