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_wfi(vcpu);
  50
  51         return PSCI_RET_SUCCESS;
  52 }
  53
  54 static void kvm_psci_vcpu_off(struct kvm_vcpu *vcpu)
  55 {
  56         vcpu->arch.power_off = true;
  57         kvm_make_request(KVM_REQ_SLEEP, vcpu);
  58         kvm_vcpu_kick(vcpu);
  59 }
  60
  61 static inline bool kvm_psci_valid_affinity(struct kvm_vcpu *vcpu,
  62                                            unsigned long affinity)
  63 {
  64         return !(affinity & ~MPIDR_HWID_BITMASK);
  65 }
  66
  67 static unsigned long kvm_psci_vcpu_on(struct kvm_vcpu *source_vcpu)
  68 {
  69         struct vcpu_reset_state *reset_state;
  70         struct kvm *kvm = source_vcpu->kvm;
  71         struct kvm_vcpu *vcpu = NULL;
  72         unsigned long cpu_id;
  73
  74         cpu_id = smccc_get_arg1(source_vcpu);
  75         if (!kvm_psci_valid_affinity(source_vcpu, cpu_id))
  76                 return PSCI_RET_INVALID_PARAMS;
  77
  78         vcpu = kvm_mpidr_to_vcpu(kvm, cpu_id);
  79
  80         /*
  81          * Make sure the caller requested a valid CPU and that the CPU is
  82          * turned off.
  83          */
  84         if (!vcpu)
  85                 return PSCI_RET_INVALID_PARAMS;
  86         if (!vcpu->arch.power_off) {
  87                 if (kvm_psci_version(source_vcpu) != KVM_ARM_PSCI_0_1)
  88                         return PSCI_RET_ALREADY_ON;
  89                 else
  90                         return PSCI_RET_INVALID_PARAMS;
  91         }
  92
  93         reset_state = &vcpu->arch.reset_state;
  94
  95         reset_state->pc = smccc_get_arg2(source_vcpu);
  96
  97         /* Propagate caller endianness */
  98         reset_state->be = kvm_vcpu_is_be(source_vcpu);
  99
 100         /*
 101          * NOTE: We always update r0 (or x0) because for PSCI v0.1
 102          * the general purpose registers are undefined upon CPU_ON.
 103          */
 104         reset_state->r0 = smccc_get_arg3(source_vcpu);
 105
 106         WRITE_ONCE(reset_state->reset, true);
 107         kvm_make_request(KVM_REQ_VCPU_RESET, vcpu);
 108
 109         /*
 110          * Make sure the reset request is observed if the change to
 111          * power_off is observed.
 112          */
 113         smp_wmb();
 114
 115         vcpu->arch.power_off = false;
 116         kvm_vcpu_wake_up(vcpu);
 117
 118         return PSCI_RET_SUCCESS;
 119 }
 120
 121 static unsigned long kvm_psci_vcpu_affinity_info(struct kvm_vcpu *vcpu)
 122 {
 123         int matching_cpus = 0;
 124         unsigned long i, mpidr;
 125         unsigned long target_affinity;
 126         unsigned long target_affinity_mask;
 127         unsigned long lowest_affinity_level;
 128         struct kvm *kvm = vcpu->kvm;
 129         struct kvm_vcpu *tmp;
 130
 131         target_affinity = smccc_get_arg1(vcpu);
 132         lowest_affinity_level = smccc_get_arg2(vcpu);
 133
 134         if (!kvm_psci_valid_affinity(vcpu, target_affinity))
 135                 return PSCI_RET_INVALID_PARAMS;
 136
 137         /* Determine target affinity mask */
 138         target_affinity_mask = psci_affinity_mask(lowest_affinity_level);
 139         if (!target_affinity_mask)
 140                 return PSCI_RET_INVALID_PARAMS;
 141
 142         /* Ignore other bits of target affinity */
 143         target_affinity &= target_affinity_mask;
 144
 145         /*
 146          * If one or more VCPU matching target affinity are running
 147          * then ON else OFF
 148          */
 149         kvm_for_each_vcpu(i, tmp, kvm) {
 150                 mpidr = kvm_vcpu_get_mpidr_aff(tmp);
 151                 if ((mpidr & target_affinity_mask) == target_affinity) {
 152                         matching_cpus++;
 153                         if (!tmp->arch.power_off)
 154                                 return PSCI_0_2_AFFINITY_LEVEL_ON;
 155                 }
 156         }
 157
 158         if (!matching_cpus)
 159                 return PSCI_RET_INVALID_PARAMS;
 160
 161         return PSCI_0_2_AFFINITY_LEVEL_OFF;
 162 }
 163
 164 static void kvm_prepare_system_event(struct kvm_vcpu *vcpu, u32 type, u64 flags)
 165 {
 166         unsigned long i;
 167         struct kvm_vcpu *tmp;
 168
 169         /*
 170          * The KVM ABI specifies that a system event exit may call KVM_RUN
 171          * again and may perform shutdown/reboot at a later time that when the
 172          * actual request is made.  Since we are implementing PSCI and a
 173          * caller of PSCI reboot and shutdown expects that the system shuts
 174          * down or reboots immediately, let's make sure that VCPUs are not run
 175          * after this call is handled and before the VCPUs have been
 176          * re-initialized.
 177          */
 178         kvm_for_each_vcpu(i, tmp, vcpu->kvm)
 179                 tmp->arch.power_off = true;
 180         kvm_make_all_cpus_request(vcpu->kvm, KVM_REQ_SLEEP);
 181
 182         memset(&vcpu->run->system_event, 0, sizeof(vcpu->run->system_event));
 183         vcpu->run->system_event.type = type;
 184         vcpu->run->system_event.flags = flags;
 185         vcpu->run->exit_reason = KVM_EXIT_SYSTEM_EVENT;
 186 }
 187
 188 static void kvm_psci_system_off(struct kvm_vcpu *vcpu)
 189 {
 190         kvm_prepare_system_event(vcpu, KVM_SYSTEM_EVENT_SHUTDOWN, 0);
 191 }
 192
 193 static void kvm_psci_system_reset(struct kvm_vcpu *vcpu)
 194 {
 195         kvm_prepare_system_event(vcpu, KVM_SYSTEM_EVENT_RESET, 0);
 196 }
 197
 198 static void kvm_psci_system_reset2(struct kvm_vcpu *vcpu)
 199 {
 200         kvm_prepare_system_event(vcpu, KVM_SYSTEM_EVENT_RESET,
 201                                  KVM_SYSTEM_EVENT_RESET_FLAG_PSCI_RESET2);
 202 }
 203
 204 static void kvm_psci_narrow_to_32bit(struct kvm_vcpu *vcpu)
 205 {
 206         int i;
 207
 208         /*
 209          * Zero the input registers' upper 32 bits. They will be fully
 210          * zeroed on exit, so we're fine changing them in place.
 211          */
 212         for (i = 1; i < 4; i++)
 213                 vcpu_set_reg(vcpu, i, lower_32_bits(vcpu_get_reg(vcpu, i)));
 214 }
 215
 216 static unsigned long kvm_psci_check_allowed_function(struct kvm_vcpu *vcpu, u32 fn)
 217 {
 218         /*
 219          * Prevent 32 bit guests from calling 64 bit PSCI functions.
 220          */
 221         if ((fn & PSCI_0_2_64BIT) && vcpu_mode_is_32bit(vcpu))
 222                 return PSCI_RET_NOT_SUPPORTED;
 223
 224         return 0;
 225 }
 226
 227 static int kvm_psci_0_2_call(struct kvm_vcpu *vcpu)
 228 {
 229         struct kvm *kvm = vcpu->kvm;
 230         u32 psci_fn = smccc_get_function(vcpu);
 231         unsigned long val;
 232         int ret = 1;
 233
 234         switch (psci_fn) {
 235         case PSCI_0_2_FN_PSCI_VERSION:
 236                 /*
 237                  * Bits[31:16] = Major Version = 0
 238                  * Bits[15:0] = Minor Version = 2
 239                  */
 240                 val = KVM_ARM_PSCI_0_2;
 241                 break;
 242         case PSCI_0_2_FN_CPU_SUSPEND:
 243         case PSCI_0_2_FN64_CPU_SUSPEND:
 244                 val = kvm_psci_vcpu_suspend(vcpu);
 245                 break;
 246         case PSCI_0_2_FN_CPU_OFF:
 247                 kvm_psci_vcpu_off(vcpu);
 248                 val = PSCI_RET_SUCCESS;
 249                 break;
 250         case PSCI_0_2_FN_CPU_ON:
 251                 kvm_psci_narrow_to_32bit(vcpu);
 252                 fallthrough;
 253         case PSCI_0_2_FN64_CPU_ON:
 254                 mutex_lock(&kvm->lock);
 255                 val = kvm_psci_vcpu_on(vcpu);
 256                 mutex_unlock(&kvm->lock);
 257                 break;
 258         case PSCI_0_2_FN_AFFINITY_INFO:
 259                 kvm_psci_narrow_to_32bit(vcpu);
 260                 fallthrough;
 261         case PSCI_0_2_FN64_AFFINITY_INFO:
 262                 val = kvm_psci_vcpu_affinity_info(vcpu);
 263                 break;
 264         case PSCI_0_2_FN_MIGRATE_INFO_TYPE:
 265                 /*
 266                  * Trusted OS is MP hence does not require migration
 267                  * or
 268                  * Trusted OS is not present
 269                  */
 270                 val = PSCI_0_2_TOS_MP;
 271                 break;
 272         case PSCI_0_2_FN_SYSTEM_OFF:
 273                 kvm_psci_system_off(vcpu);
 274                 /*
 275                  * We shouldn't be going back to guest VCPU after
 276                  * receiving SYSTEM_OFF request.
 277                  *
 278                  * If user space accidentally/deliberately resumes
 279                  * guest VCPU after SYSTEM_OFF request then guest
 280                  * VCPU should see internal failure from PSCI return
 281                  * value. To achieve this, we preload r0 (or x0) with
 282                  * PSCI return value INTERNAL_FAILURE.
 283                  */
 284                 val = PSCI_RET_INTERNAL_FAILURE;
 285                 ret = 0;
 286                 break;
 287         case PSCI_0_2_FN_SYSTEM_RESET:
 288                 kvm_psci_system_reset(vcpu);
 289                 /*
 290                  * Same reason as SYSTEM_OFF for preloading r0 (or x0)
 291                  * with PSCI return value INTERNAL_FAILURE.
 292                  */
 293                 val = PSCI_RET_INTERNAL_FAILURE;
 294                 ret = 0;
 295                 break;
 296         default:
 297                 val = PSCI_RET_NOT_SUPPORTED;
 298                 break;
 299         }
 300
 301         smccc_set_retval(vcpu, val, 0, 0, 0);
 302         return ret;
 303 }
 304
 305 static int kvm_psci_1_x_call(struct kvm_vcpu *vcpu, u32 minor)
 306 {
 307         u32 psci_fn = smccc_get_function(vcpu);
 308         u32 arg;
 309         unsigned long val;
 310         int ret = 1;
 311
 312         switch(psci_fn) {
 313         case PSCI_0_2_FN_PSCI_VERSION:
 314                 val = minor == 0 ? KVM_ARM_PSCI_1_0 : KVM_ARM_PSCI_1_1;
 315                 break;
 316         case PSCI_1_0_FN_PSCI_FEATURES:
 317                 arg = smccc_get_arg1(vcpu);
 318                 val = kvm_psci_check_allowed_function(vcpu, arg);
 319                 if (val)
 320                         break;
 321
 322                 switch(arg) {
 323                 case PSCI_0_2_FN_PSCI_VERSION:
 324                 case PSCI_0_2_FN_CPU_SUSPEND:
 325                 case PSCI_0_2_FN64_CPU_SUSPEND:
 326                 case PSCI_0_2_FN_CPU_OFF:
 327                 case PSCI_0_2_FN_CPU_ON:
 328                 case PSCI_0_2_FN64_CPU_ON:
 329                 case PSCI_0_2_FN_AFFINITY_INFO:
 330                 case PSCI_0_2_FN64_AFFINITY_INFO:
 331                 case PSCI_0_2_FN_MIGRATE_INFO_TYPE:
 332                 case PSCI_0_2_FN_SYSTEM_OFF:
 333                 case PSCI_0_2_FN_SYSTEM_RESET:
 334                 case PSCI_1_0_FN_PSCI_FEATURES:
 335                 case ARM_SMCCC_VERSION_FUNC_ID:
 336                         val = 0;
 337                         break;
 338                 case PSCI_1_1_FN_SYSTEM_RESET2:
 339                 case PSCI_1_1_FN64_SYSTEM_RESET2:
 340                         if (minor >= 1) {
 341                                 val = 0;
 342                                 break;
 343                         }
 344                         fallthrough;
 345                 default:
 346                         val = PSCI_RET_NOT_SUPPORTED;
 347                         break;
 348                 }
 349                 break;
 350         case PSCI_1_1_FN_SYSTEM_RESET2:
 351                 kvm_psci_narrow_to_32bit(vcpu);
 352                 fallthrough;
 353         case PSCI_1_1_FN64_SYSTEM_RESET2:
 354                 if (minor >= 1) {
 355                         arg = smccc_get_arg1(vcpu);
 356
 357                         if (arg <= PSCI_1_1_RESET_TYPE_SYSTEM_WARM_RESET ||
 358                             arg >= PSCI_1_1_RESET_TYPE_VENDOR_START) {
 359                                 kvm_psci_system_reset2(vcpu);
 360                                 vcpu_set_reg(vcpu, 0, PSCI_RET_INTERNAL_FAILURE);
 361                                 return 0;
 362                         }
 363
 364                         val = PSCI_RET_INVALID_PARAMS;
 365                         break;
 366                 }
 367                 fallthrough;
 368         default:
 369                 return kvm_psci_0_2_call(vcpu);
 370         }
 371
 372         smccc_set_retval(vcpu, val, 0, 0, 0);
 373         return ret;
 374 }
 375
 376 static int kvm_psci_0_1_call(struct kvm_vcpu *vcpu)
 377 {
 378         struct kvm *kvm = vcpu->kvm;
 379         u32 psci_fn = smccc_get_function(vcpu);
 380         unsigned long val;
 381
 382         switch (psci_fn) {
 383         case KVM_PSCI_FN_CPU_OFF:
 384                 kvm_psci_vcpu_off(vcpu);
 385                 val = PSCI_RET_SUCCESS;
 386                 break;
 387         case KVM_PSCI_FN_CPU_ON:
 388                 mutex_lock(&kvm->lock);
 389                 val = kvm_psci_vcpu_on(vcpu);
 390                 mutex_unlock(&kvm->lock);
 391                 break;
 392         default:
 393                 val = PSCI_RET_NOT_SUPPORTED;
 394                 break;
 395         }
 396
 397         smccc_set_retval(vcpu, val, 0, 0, 0);
 398         return 1;
 399 }
 400
 401 /**
 402  * kvm_psci_call - handle PSCI call if r0 value is in range
 403  * @vcpu: Pointer to the VCPU struct
 404  *
 405  * Handle PSCI calls from guests through traps from HVC instructions.
 406  * The calling convention is similar to SMC calls to the secure world
 407  * where the function number is placed in r0.
 408  *
 409  * This function returns: > 0 (success), 0 (success but exit to user
 410  * space), and < 0 (errors)
 411  *
 412  * Errors:
 413  * -EINVAL: Unrecognized PSCI function
 414  */
 415 int kvm_psci_call(struct kvm_vcpu *vcpu)
 416 {
 417         u32 psci_fn = smccc_get_function(vcpu);
 418         unsigned long val;
 419
 420         val = kvm_psci_check_allowed_function(vcpu, psci_fn);
 421         if (val) {
 422                 smccc_set_retval(vcpu, val, 0, 0, 0);
 423                 return 1;
 424         }
 425
 426         switch (kvm_psci_version(vcpu)) {
 427         case KVM_ARM_PSCI_1_1:
 428                 return kvm_psci_1_x_call(vcpu, 1);
 429         case KVM_ARM_PSCI_1_0:
 430                 return kvm_psci_1_x_call(vcpu, 0);
 431         case KVM_ARM_PSCI_0_2:
 432                 return kvm_psci_0_2_call(vcpu);
 433         case KVM_ARM_PSCI_0_1:
 434                 return kvm_psci_0_1_call(vcpu);
 435         default:
 436                 return -EINVAL;
 437         }
 438 }
 439
 440 int kvm_arm_get_fw_num_regs(struct kvm_vcpu *vcpu)
 441 {
 442         return 4;               /* PSCI version and three workaround registers */
 443 }
 444
 445 int kvm_arm_copy_fw_reg_indices(struct kvm_vcpu *vcpu, u64 __user *uindices)
 446 {
 447         if (put_user(KVM_REG_ARM_PSCI_VERSION, uindices++))
 448                 return -EFAULT;
 449
 450         if (put_user(KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_1, uindices++))
 451                 return -EFAULT;
 452
 453         if (put_user(KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2, uindices++))
 454                 return -EFAULT;
 455
 456         if (put_user(KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_3, uindices++))
 457                 return -EFAULT;
 458
 459         return 0;
 460 }
 461
 462 #define KVM_REG_FEATURE_LEVEL_WIDTH     4
 463 #define KVM_REG_FEATURE_LEVEL_MASK      (BIT(KVM_REG_FEATURE_LEVEL_WIDTH) - 1)
 464
 465 /*
 466  * Convert the workaround level into an easy-to-compare number, where higher
 467  * values mean better protection.
 468  */
 469 static int get_kernel_wa_level(u64 regid)
 470 {
 471         switch (regid) {
 472         case KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_1:
 473                 switch (arm64_get_spectre_v2_state()) {
 474                 case SPECTRE_VULNERABLE:
 475                         return KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_1_NOT_AVAIL;
 476                 case SPECTRE_MITIGATED:
 477                         return KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_1_AVAIL;
 478                 case SPECTRE_UNAFFECTED:
 479                         return KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_1_NOT_REQUIRED;
 480                 }
 481                 return KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_1_NOT_AVAIL;
 482         case KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2:
 483                 switch (arm64_get_spectre_v4_state()) {
 484                 case SPECTRE_MITIGATED:
 485                         /*
 486                          * As for the hypercall discovery, we pretend we
 487                          * don't have any FW mitigation if SSBS is there at
 488                          * all times.
 489                          */
 490                         if (cpus_have_final_cap(ARM64_SSBS))
 491                                 return KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_NOT_AVAIL;
 492                         fallthrough;
 493                 case SPECTRE_UNAFFECTED:
 494                         return KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_NOT_REQUIRED;
 495                 case SPECTRE_VULNERABLE:
 496                         return KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_NOT_AVAIL;
 497                 }
 498                 break;
 499         case KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_3:
 500                 switch (arm64_get_spectre_bhb_state()) {
 501                 case SPECTRE_VULNERABLE:
 502                         return KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_3_NOT_AVAIL;
 503                 case SPECTRE_MITIGATED:
 504                         return KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_3_AVAIL;
 505                 case SPECTRE_UNAFFECTED:
 506                         return KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_3_NOT_REQUIRED;
 507                 }
 508                 return KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_3_NOT_AVAIL;
 509         }
 510
 511         return -EINVAL;
 512 }
 513
 514 int kvm_arm_get_fw_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
 515 {
 516         void __user *uaddr = (void __user *)(long)reg->addr;
 517         u64 val;
 518
 519         switch (reg->id) {
 520         case KVM_REG_ARM_PSCI_VERSION:
 521                 val = kvm_psci_version(vcpu);
 522                 break;
 523         case KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_1:
 524         case KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2:
 525         case KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_3:
 526                 val = get_kernel_wa_level(reg->id) & KVM_REG_FEATURE_LEVEL_MASK;
 527                 break;
 528         default:
 529                 return -ENOENT;
 530         }
 531
 532         if (copy_to_user(uaddr, &val, KVM_REG_SIZE(reg->id)))
 533                 return -EFAULT;
 534
 535         return 0;
 536 }
 537
 538 int kvm_arm_set_fw_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
 539 {
 540         void __user *uaddr = (void __user *)(long)reg->addr;
 541         u64 val;
 542         int wa_level;
 543
 544         if (copy_from_user(&val, uaddr, KVM_REG_SIZE(reg->id)))
 545                 return -EFAULT;
 546
 547         switch (reg->id) {
 548         case KVM_REG_ARM_PSCI_VERSION:
 549         {
 550                 bool wants_02;
 551
 552                 wants_02 = test_bit(KVM_ARM_VCPU_PSCI_0_2, vcpu->arch.features);
 553
 554                 switch (val) {
 555                 case KVM_ARM_PSCI_0_1:
 556                         if (wants_02)
 557                                 return -EINVAL;
 558                         vcpu->kvm->arch.psci_version = val;
 559                         return 0;
 560                 case KVM_ARM_PSCI_0_2:
 561                 case KVM_ARM_PSCI_1_0:
 562                 case KVM_ARM_PSCI_1_1:
 563                         if (!wants_02)
 564                                 return -EINVAL;
 565                         vcpu->kvm->arch.psci_version = val;
 566                         return 0;
 567                 }
 568                 break;
 569         }
 570
 571         case KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_1:
 572         case KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_3:
 573                 if (val & ~KVM_REG_FEATURE_LEVEL_MASK)
 574                         return -EINVAL;
 575
 576                 if (get_kernel_wa_level(reg->id) < val)
 577                         return -EINVAL;
 578
 579                 return 0;
 580
 581         case KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2:
 582                 if (val & ~(KVM_REG_FEATURE_LEVEL_MASK |
 583                             KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_ENABLED))
 584                         return -EINVAL;
 585
 586                 /* The enabled bit must not be set unless the level is AVAIL. */
 587                 if ((val & KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_ENABLED) &&
 588                     (val & KVM_REG_FEATURE_LEVEL_MASK) != KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_AVAIL)
 589                         return -EINVAL;
 590
 591                 /*
 592                  * Map all the possible incoming states to the only two we
 593                  * really want to deal with.
 594                  */
 595                 switch (val & KVM_REG_FEATURE_LEVEL_MASK) {
 596                 case KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_NOT_AVAIL:
 597                 case KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_UNKNOWN:
 598                         wa_level = KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_NOT_AVAIL;
 599                         break;
 600                 case KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_AVAIL:
 601                 case KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_NOT_REQUIRED:
 602                         wa_level = KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_NOT_REQUIRED;
 603                         break;
 604                 default:
 605                         return -EINVAL;
 606                 }
 607
 608                 /*
 609                  * We can deal with NOT_AVAIL on NOT_REQUIRED, but not the
 610                  * other way around.
 611                  */
 612                 if (get_kernel_wa_level(reg->id) < wa_level)
 613                         return -EINVAL;
 614
 615                 return 0;
 616         default:
 617                 return -ENOENT;
 618         }
 619
 620         return -EINVAL;
 621 }