arch/arm64/kvm/psci.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Copyright (C) 2012 - ARM Ltd
   4  * Author: Marc Zyngier <marc.zyngier@arm.com>
   5  */
   6
   7 #include <linux/arm-smccc.h>
   8 #include <linux/preempt.h>
   9 #include <linux/kvm_host.h>
  10 #include <linux/uaccess.h>
  11 #include <linux/wait.h>
  12
  13 #include <asm/cputype.h>
  14 #include <asm/kvm_emulate.h>
  15
  16 #include <kvm/arm_psci.h>
  17 #include <kvm/arm_hypercalls.h>
  18
  19 /*
  20  * This is an implementation of the Power State Coordination Interface
  21  * as described in ARM document number ARM DEN 0022A.
  22  */
  23
  24 #define AFFINITY_MASK(level)    ~((0x1UL << ((level) * MPIDR_LEVEL_BITS)) - 1)
  25
  26 static unsigned long psci_affinity_mask(unsigned long affinity_level)
  27 {
  28         if (affinity_level <= 3)
  29                 return MPIDR_HWID_BITMASK & AFFINITY_MASK(affinity_level);
  30
  31         return 0;
  32 }
  33
  34 static unsigned long kvm_psci_vcpu_suspend(struct kvm_vcpu *vcpu)
  35 {
  36         /*
  37          * NOTE: For simplicity, we make VCPU suspend emulation to be
  38          * same-as WFI (Wait-for-interrupt) emulation.
  39          *
  40          * This means for KVM the wakeup events are interrupts and
  41          * this is consistent with intended use of StateID as described
  42          * in section 5.4.1 of PSCI v0.2 specification (ARM DEN 0022A).
  43          *
  44          * Further, we also treat power-down request to be same as
  45          * stand-by request as-per section 5.4.2 clause 3 of PSCI v0.2
  46          * specification (ARM DEN 0022A). This means all suspend states
  47          * for KVM will preserve the register state.
  48          */
  49         kvm_vcpu_halt(vcpu);
  50         kvm_clear_request(KVM_REQ_UNHALT, vcpu);
  51
  52         return PSCI_RET_SUCCESS;
  53 }
  54
  55 static void kvm_psci_vcpu_off(struct kvm_vcpu *vcpu)
  56 {
  57         vcpu->arch.power_off = true;
  58         kvm_make_request(KVM_REQ_SLEEP, vcpu);
  59         kvm_vcpu_kick(vcpu);
  60 }
  61
  62 static inline bool kvm_psci_valid_affinity(struct kvm_vcpu *vcpu,
  63                                            unsigned long affinity)
  64 {
  65         return !(affinity & ~MPIDR_HWID_BITMASK);
  66 }
  67
  68 static unsigned long kvm_psci_vcpu_on(struct kvm_vcpu *source_vcpu)
  69 {
  70         struct vcpu_reset_state *reset_state;
  71         struct kvm *kvm = source_vcpu->kvm;
  72         struct kvm_vcpu *vcpu = NULL;
  73         unsigned long cpu_id;
  74
  75         cpu_id = smccc_get_arg1(source_vcpu);
  76         if (!kvm_psci_valid_affinity(source_vcpu, cpu_id))
  77                 return PSCI_RET_INVALID_PARAMS;
  78
  79         vcpu = kvm_mpidr_to_vcpu(kvm, cpu_id);
  80
  81         /*
  82          * Make sure the caller requested a valid CPU and that the CPU is
  83          * turned off.
  84          */
  85         if (!vcpu)
  86                 return PSCI_RET_INVALID_PARAMS;
  87         if (!vcpu->arch.power_off) {
  88                 if (kvm_psci_version(source_vcpu, kvm) != KVM_ARM_PSCI_0_1)
  89                         return PSCI_RET_ALREADY_ON;
  90                 else
  91                         return PSCI_RET_INVALID_PARAMS;
  92         }
  93
  94         reset_state = &vcpu->arch.reset_state;
  95
  96         reset_state->pc = smccc_get_arg2(source_vcpu);
  97
  98         /* Propagate caller endianness */
  99         reset_state->be = kvm_vcpu_is_be(source_vcpu);
 100
 101         /*
 102          * NOTE: We always update r0 (or x0) because for PSCI v0.1
 103          * the general purpose registers are undefined upon CPU_ON.
 104          */
 105         reset_state->r0 = smccc_get_arg3(source_vcpu);
 106
 107         WRITE_ONCE(reset_state->reset, true);
 108         kvm_make_request(KVM_REQ_VCPU_RESET, vcpu);
 109
 110         /*
 111          * Make sure the reset request is observed if the change to
 112          * power_off is observed.
 113          */
 114         smp_wmb();
 115
 116         vcpu->arch.power_off = false;
 117         kvm_vcpu_wake_up(vcpu);
 118
 119         return PSCI_RET_SUCCESS;
 120 }
 121
 122 static unsigned long kvm_psci_vcpu_affinity_info(struct kvm_vcpu *vcpu)
 123 {
 124         int matching_cpus = 0;
 125         unsigned long i, mpidr;
 126         unsigned long target_affinity;
 127         unsigned long target_affinity_mask;
 128         unsigned long lowest_affinity_level;
 129         struct kvm *kvm = vcpu->kvm;
 130         struct kvm_vcpu *tmp;
 131
 132         target_affinity = smccc_get_arg1(vcpu);
 133         lowest_affinity_level = smccc_get_arg2(vcpu);
 134
 135         if (!kvm_psci_valid_affinity(vcpu, target_affinity))
 136                 return PSCI_RET_INVALID_PARAMS;
 137
 138         /* Determine target affinity mask */
 139         target_affinity_mask = psci_affinity_mask(lowest_affinity_level);
 140         if (!target_affinity_mask)
 141                 return PSCI_RET_INVALID_PARAMS;
 142
 143         /* Ignore other bits of target affinity */
 144         target_affinity &= target_affinity_mask;
 145
 146         /*
 147          * If one or more VCPU matching target affinity are running
 148          * then ON else OFF
 149          */
 150         kvm_for_each_vcpu(i, tmp, kvm) {
 151                 mpidr = kvm_vcpu_get_mpidr_aff(tmp);
 152                 if ((mpidr & target_affinity_mask) == target_affinity) {
 153                         matching_cpus++;
 154                         if (!tmp->arch.power_off)
 155                                 return PSCI_0_2_AFFINITY_LEVEL_ON;
 156                 }
 157         }
 158
 159         if (!matching_cpus)
 160                 return PSCI_RET_INVALID_PARAMS;
 161
 162         return PSCI_0_2_AFFINITY_LEVEL_OFF;
 163 }
 164
 165 static void kvm_prepare_system_event(struct kvm_vcpu *vcpu, u32 type, u64 flags)
 166 {
 167         unsigned long i;
 168         struct kvm_vcpu *tmp;
 169
 170         /*
 171          * The KVM ABI specifies that a system event exit may call KVM_RUN
 172          * again and may perform shutdown/reboot at a later time that when the
 173          * actual request is made.  Since we are implementing PSCI and a
 174          * caller of PSCI reboot and shutdown expects that the system shuts
 175          * down or reboots immediately, let's make sure that VCPUs are not run
 176          * after this call is handled and before the VCPUs have been
 177          * re-initialized.
 178          */
 179         kvm_for_each_vcpu(i, tmp, vcpu->kvm)
 180                 tmp->arch.power_off = true;
 181         kvm_make_all_cpus_request(vcpu->kvm, KVM_REQ_SLEEP);
 182
 183         memset(&vcpu->run->system_event, 0, sizeof(vcpu->run->system_event));
 184         vcpu->run->system_event.type = type;
 185         vcpu->run->system_event.flags = flags;
 186         vcpu->run->exit_reason = KVM_EXIT_SYSTEM_EVENT;
 187 }
 188
 189 static void kvm_psci_system_off(struct kvm_vcpu *vcpu)
 190 {
 191         kvm_prepare_system_event(vcpu, KVM_SYSTEM_EVENT_SHUTDOWN, 0);
 192 }
 193
 194 static void kvm_psci_system_reset(struct kvm_vcpu *vcpu)
 195 {
 196         kvm_prepare_system_event(vcpu, KVM_SYSTEM_EVENT_RESET, 0);
 197 }
 198
 199 static void kvm_psci_system_reset2(struct kvm_vcpu *vcpu)
 200 {
 201         kvm_prepare_system_event(vcpu, KVM_SYSTEM_EVENT_RESET,
 202                                  KVM_SYSTEM_EVENT_RESET_FLAG_PSCI_RESET2);
 203 }
 204
 205 static void kvm_psci_narrow_to_32bit(struct kvm_vcpu *vcpu)
 206 {
 207         int i;
 208
 209         /*
 210          * Zero the input registers' upper 32 bits. They will be fully
 211          * zeroed on exit, so we're fine changing them in place.
 212          */
 213         for (i = 1; i < 4; i++)
 214                 vcpu_set_reg(vcpu, i, lower_32_bits(vcpu_get_reg(vcpu, i)));
 215 }
 216
 217 static unsigned long kvm_psci_check_allowed_function(struct kvm_vcpu *vcpu, u32 fn)
 218 {
 219         switch(fn) {
 220         case PSCI_0_2_FN64_CPU_SUSPEND:
 221         case PSCI_0_2_FN64_CPU_ON:
 222         case PSCI_0_2_FN64_AFFINITY_INFO:
 223                 /* Disallow these functions for 32bit guests */
 224                 if (vcpu_mode_is_32bit(vcpu))
 225                         return PSCI_RET_NOT_SUPPORTED;
 226                 break;
 227         }
 228
 229         return 0;
 230 }
 231
 232 static int kvm_psci_0_2_call(struct kvm_vcpu *vcpu)
 233 {
 234         struct kvm *kvm = vcpu->kvm;
 235         u32 psci_fn = smccc_get_function(vcpu);
 236         unsigned long val;
 237         int ret = 1;
 238
 239         val = kvm_psci_check_allowed_function(vcpu, psci_fn);
 240         if (val)
 241                 goto out;
 242
 243         switch (psci_fn) {
 244         case PSCI_0_2_FN_PSCI_VERSION:
 245                 /*
 246                  * Bits[31:16] = Major Version = 0
 247                  * Bits[15:0] = Minor Version = 2
 248                  */
 249                 val = KVM_ARM_PSCI_0_2;
 250                 break;
 251         case PSCI_0_2_FN_CPU_SUSPEND:
 252         case PSCI_0_2_FN64_CPU_SUSPEND:
 253                 val = kvm_psci_vcpu_suspend(vcpu);
 254                 break;
 255         case PSCI_0_2_FN_CPU_OFF:
 256                 kvm_psci_vcpu_off(vcpu);
 257                 val = PSCI_RET_SUCCESS;
 258                 break;
 259         case PSCI_0_2_FN_CPU_ON:
 260                 kvm_psci_narrow_to_32bit(vcpu);
 261                 fallthrough;
 262         case PSCI_0_2_FN64_CPU_ON:
 263                 mutex_lock(&kvm->lock);
 264                 val = kvm_psci_vcpu_on(vcpu);
 265                 mutex_unlock(&kvm->lock);
 266                 break;
 267         case PSCI_0_2_FN_AFFINITY_INFO:
 268                 kvm_psci_narrow_to_32bit(vcpu);
 269                 fallthrough;
 270         case PSCI_0_2_FN64_AFFINITY_INFO:
 271                 val = kvm_psci_vcpu_affinity_info(vcpu);
 272                 break;
 273         case PSCI_0_2_FN_MIGRATE_INFO_TYPE:
 274                 /*
 275                  * Trusted OS is MP hence does not require migration
 276                  * or
 277                  * Trusted OS is not present
 278                  */
 279                 val = PSCI_0_2_TOS_MP;
 280                 break;
 281         case PSCI_0_2_FN_SYSTEM_OFF:
 282                 kvm_psci_system_off(vcpu);
 283                 /*
 284                  * We shouldn't be going back to guest VCPU after
 285                  * receiving SYSTEM_OFF request.
 286                  *
 287                  * If user space accidentally/deliberately resumes
 288                  * guest VCPU after SYSTEM_OFF request then guest
 289                  * VCPU should see internal failure from PSCI return
 290                  * value. To achieve this, we preload r0 (or x0) with
 291                  * PSCI return value INTERNAL_FAILURE.
 292                  */
 293                 val = PSCI_RET_INTERNAL_FAILURE;
 294                 ret = 0;
 295                 break;
 296         case PSCI_0_2_FN_SYSTEM_RESET:
 297                 kvm_psci_system_reset(vcpu);
 298                 /*
 299                  * Same reason as SYSTEM_OFF for preloading r0 (or x0)
 300                  * with PSCI return value INTERNAL_FAILURE.
 301                  */
 302                 val = PSCI_RET_INTERNAL_FAILURE;
 303                 ret = 0;
 304                 break;
 305         default:
 306                 val = PSCI_RET_NOT_SUPPORTED;
 307                 break;
 308         }
 309
 310 out:
 311         smccc_set_retval(vcpu, val, 0, 0, 0);
 312         return ret;
 313 }
 314
 315 static int kvm_psci_1_x_call(struct kvm_vcpu *vcpu, u32 minor)
 316 {
 317         u32 psci_fn = smccc_get_function(vcpu);
 318         u32 arg;
 319         unsigned long val;
 320         int ret = 1;
 321
 322         if (minor > 1)
 323                 return -EINVAL;
 324
 325         switch(psci_fn) {
 326         case PSCI_0_2_FN_PSCI_VERSION:
 327                 val = minor == 0 ? KVM_ARM_PSCI_1_0 : KVM_ARM_PSCI_1_1;
 328                 break;
 329         case PSCI_1_0_FN_PSCI_FEATURES:
 330                 arg = smccc_get_arg1(vcpu);
 331                 val = kvm_psci_check_allowed_function(vcpu, arg);
 332                 if (val)
 333                         break;
 334
 335                 switch(arg) {
 336                 case PSCI_0_2_FN_PSCI_VERSION:
 337                 case PSCI_0_2_FN_CPU_SUSPEND:
 338                 case PSCI_0_2_FN64_CPU_SUSPEND:
 339                 case PSCI_0_2_FN_CPU_OFF:
 340                 case PSCI_0_2_FN_CPU_ON:
 341                 case PSCI_0_2_FN64_CPU_ON:
 342                 case PSCI_0_2_FN_AFFINITY_INFO:
 343                 case PSCI_0_2_FN64_AFFINITY_INFO:
 344                 case PSCI_0_2_FN_MIGRATE_INFO_TYPE:
 345                 case PSCI_0_2_FN_SYSTEM_OFF:
 346                 case PSCI_0_2_FN_SYSTEM_RESET:
 347                 case PSCI_1_0_FN_PSCI_FEATURES:
 348                 case ARM_SMCCC_VERSION_FUNC_ID:
 349                         val = 0;
 350                         break;
 351                 case PSCI_1_1_FN_SYSTEM_RESET2:
 352                 case PSCI_1_1_FN64_SYSTEM_RESET2:
 353                         if (minor >= 1) {
 354                                 val = 0;
 355                                 break;
 356                         }
 357                         fallthrough;
 358                 default:
 359                         val = PSCI_RET_NOT_SUPPORTED;
 360                         break;
 361                 }
 362                 break;
 363         case PSCI_1_1_FN_SYSTEM_RESET2:
 364                 kvm_psci_narrow_to_32bit(vcpu);
 365                 fallthrough;
 366         case PSCI_1_1_FN64_SYSTEM_RESET2:
 367                 if (minor >= 1) {
 368                         arg = smccc_get_arg1(vcpu);
 369
 370                         if (arg > PSCI_1_1_RESET_TYPE_SYSTEM_WARM_RESET &&
 371                             arg < PSCI_1_1_RESET_TYPE_VENDOR_START) {
 372                                 val = PSCI_RET_INVALID_PARAMS;
 373                         } else {
 374                                 kvm_psci_system_reset2(vcpu);
 375                                 val = PSCI_RET_INTERNAL_FAILURE;
 376                                 ret = 0;
 377                         }
 378                         break;
 379                 }
 380                 fallthrough;
 381         default:
 382                 return kvm_psci_0_2_call(vcpu);
 383         }
 384
 385         smccc_set_retval(vcpu, val, 0, 0, 0);
 386         return ret;
 387 }
 388
 389 static int kvm_psci_0_1_call(struct kvm_vcpu *vcpu)
 390 {
 391         struct kvm *kvm = vcpu->kvm;
 392         u32 psci_fn = smccc_get_function(vcpu);
 393         unsigned long val;
 394
 395         switch (psci_fn) {
 396         case KVM_PSCI_FN_CPU_OFF:
 397                 kvm_psci_vcpu_off(vcpu);
 398                 val = PSCI_RET_SUCCESS;
 399                 break;
 400         case KVM_PSCI_FN_CPU_ON:
 401                 mutex_lock(&kvm->lock);
 402                 val = kvm_psci_vcpu_on(vcpu);
 403                 mutex_unlock(&kvm->lock);
 404                 break;
 405         default:
 406                 val = PSCI_RET_NOT_SUPPORTED;
 407                 break;
 408         }
 409
 410         smccc_set_retval(vcpu, val, 0, 0, 0);
 411         return 1;
 412 }
 413
 414 /**
 415  * kvm_psci_call - handle PSCI call if r0 value is in range
 416  * @vcpu: Pointer to the VCPU struct
 417  *
 418  * Handle PSCI calls from guests through traps from HVC instructions.
 419  * The calling convention is similar to SMC calls to the secure world
 420  * where the function number is placed in r0.
 421  *
 422  * This function returns: > 0 (success), 0 (success but exit to user
 423  * space), and < 0 (errors)
 424  *
 425  * Errors:
 426  * -EINVAL: Unrecognized PSCI function
 427  */
 428 int kvm_psci_call(struct kvm_vcpu *vcpu)
 429 {
 430         switch (kvm_psci_version(vcpu, vcpu->kvm)) {
 431         case KVM_ARM_PSCI_1_1:
 432                 return kvm_psci_1_x_call(vcpu, 1);
 433         case KVM_ARM_PSCI_1_0:
 434                 return kvm_psci_1_x_call(vcpu, 0);
 435         case KVM_ARM_PSCI_0_2:
 436                 return kvm_psci_0_2_call(vcpu);
 437         case KVM_ARM_PSCI_0_1:
 438                 return kvm_psci_0_1_call(vcpu);
 439         default:
 440                 return -EINVAL;
 441         }
 442 }
 443
 444 int kvm_arm_get_fw_num_regs(struct kvm_vcpu *vcpu)
 445 {
 446         return 3;               /* PSCI version and two workaround registers */
 447 }
 448
 449 int kvm_arm_copy_fw_reg_indices(struct kvm_vcpu *vcpu, u64 __user *uindices)
 450 {
 451         if (put_user(KVM_REG_ARM_PSCI_VERSION, uindices++))
 452                 return -EFAULT;
 453
 454         if (put_user(KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_1, uindices++))
 455                 return -EFAULT;
 456
 457         if (put_user(KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2, uindices++))
 458                 return -EFAULT;
 459
 460         return 0;
 461 }
 462
 463 #define KVM_REG_FEATURE_LEVEL_WIDTH     4
 464 #define KVM_REG_FEATURE_LEVEL_MASK      (BIT(KVM_REG_FEATURE_LEVEL_WIDTH) - 1)
 465
 466 /*
 467  * Convert the workaround level into an easy-to-compare number, where higher
 468  * values mean better protection.
 469  */
 470 static int get_kernel_wa_level(u64 regid)
 471 {
 472         switch (regid) {
 473         case KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_1:
 474                 switch (arm64_get_spectre_v2_state()) {
 475                 case SPECTRE_VULNERABLE:
 476                         return KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_1_NOT_AVAIL;
 477                 case SPECTRE_MITIGATED:
 478                         return KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_1_AVAIL;
 479                 case SPECTRE_UNAFFECTED:
 480                         return KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_1_NOT_REQUIRED;
 481                 }
 482                 return KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_1_NOT_AVAIL;
 483         case KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2:
 484                 switch (arm64_get_spectre_v4_state()) {
 485                 case SPECTRE_MITIGATED:
 486                         /*
 487                          * As for the hypercall discovery, we pretend we
 488                          * don't have any FW mitigation if SSBS is there at
 489                          * all times.
 490                          */
 491                         if (cpus_have_final_cap(ARM64_SSBS))
 492                                 return KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_NOT_AVAIL;
 493                         fallthrough;
 494                 case SPECTRE_UNAFFECTED:
 495                         return KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_NOT_REQUIRED;
 496                 case SPECTRE_VULNERABLE:
 497                         return KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_NOT_AVAIL;
 498                 }
 499         }
 500
 501         return -EINVAL;
 502 }
 503
 504 int kvm_arm_get_fw_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
 505 {
 506         void __user *uaddr = (void __user *)(long)reg->addr;
 507         u64 val;
 508
 509         switch (reg->id) {
 510         case KVM_REG_ARM_PSCI_VERSION:
 511                 val = kvm_psci_version(vcpu, vcpu->kvm);
 512                 break;
 513         case KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_1:
 514         case KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2:
 515                 val = get_kernel_wa_level(reg->id) & KVM_REG_FEATURE_LEVEL_MASK;
 516                 break;
 517         default:
 518                 return -ENOENT;
 519         }
 520
 521         if (copy_to_user(uaddr, &val, KVM_REG_SIZE(reg->id)))
 522                 return -EFAULT;
 523
 524         return 0;
 525 }
 526
 527 int kvm_arm_set_fw_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
 528 {
 529         void __user *uaddr = (void __user *)(long)reg->addr;
 530         u64 val;
 531         int wa_level;
 532
 533         if (copy_from_user(&val, uaddr, KVM_REG_SIZE(reg->id)))
 534                 return -EFAULT;
 535
 536         switch (reg->id) {
 537         case KVM_REG_ARM_PSCI_VERSION:
 538         {
 539                 bool wants_02;
 540
 541                 wants_02 = test_bit(KVM_ARM_VCPU_PSCI_0_2, vcpu->arch.features);
 542
 543                 switch (val) {
 544                 case KVM_ARM_PSCI_0_1:
 545                         if (wants_02)
 546                                 return -EINVAL;
 547                         vcpu->kvm->arch.psci_version = val;
 548                         return 0;
 549                 case KVM_ARM_PSCI_0_2:
 550                 case KVM_ARM_PSCI_1_0:
 551                 case KVM_ARM_PSCI_1_1:
 552                         if (!wants_02)
 553                                 return -EINVAL;
 554                         vcpu->kvm->arch.psci_version = val;
 555                         return 0;
 556                 }
 557                 break;
 558         }
 559
 560         case KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_1:
 561                 if (val & ~KVM_REG_FEATURE_LEVEL_MASK)
 562                         return -EINVAL;
 563
 564                 if (get_kernel_wa_level(reg->id) < val)
 565                         return -EINVAL;
 566
 567                 return 0;
 568
 569         case KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2:
 570                 if (val & ~(KVM_REG_FEATURE_LEVEL_MASK |
 571                             KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_ENABLED))
 572                         return -EINVAL;
 573
 574                 /* The enabled bit must not be set unless the level is AVAIL. */
 575                 if ((val & KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_ENABLED) &&
 576                     (val & KVM_REG_FEATURE_LEVEL_MASK) != KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_AVAIL)
 577                         return -EINVAL;
 578
 579                 /*
 580                  * Map all the possible incoming states to the only two we
 581                  * really want to deal with.
 582                  */
 583                 switch (val & KVM_REG_FEATURE_LEVEL_MASK) {
 584                 case KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_NOT_AVAIL:
 585                 case KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_UNKNOWN:
 586                         wa_level = KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_NOT_AVAIL;
 587                         break;
 588                 case KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_AVAIL:
 589                 case KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_NOT_REQUIRED:
 590                         wa_level = KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_NOT_REQUIRED;
 591                         break;
 592                 default:
 593                         return -EINVAL;
 594                 }
 595
 596                 /*
 597                  * We can deal with NOT_AVAIL on NOT_REQUIRED, but not the
 598                  * other way around.
 599                  */
 600                 if (get_kernel_wa_level(reg->id) < wa_level)
 601                         return -EINVAL;
 602
 603                 return 0;
 604         default:
 605                 return -ENOENT;
 606         }
 607
 608         return -EINVAL;
 609 }