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         switch(fn) {
 219         case PSCI_0_2_FN64_CPU_SUSPEND:
 220         case PSCI_0_2_FN64_CPU_ON:
 221         case PSCI_0_2_FN64_AFFINITY_INFO:
 222                 /* Disallow these functions for 32bit guests */
 223                 if (vcpu_mode_is_32bit(vcpu))
 224                         return PSCI_RET_NOT_SUPPORTED;
 225                 break;
 226         }
 227
 228         return 0;
 229 }
 230
 231 static int kvm_psci_0_2_call(struct kvm_vcpu *vcpu)
 232 {
 233         struct kvm *kvm = vcpu->kvm;
 234         u32 psci_fn = smccc_get_function(vcpu);
 235         unsigned long val;
 236         int ret = 1;
 237
 238         val = kvm_psci_check_allowed_function(vcpu, psci_fn);
 239         if (val)
 240                 goto out;
 241
 242         switch (psci_fn) {
 243         case PSCI_0_2_FN_PSCI_VERSION:
 244                 /*
 245                  * Bits[31:16] = Major Version = 0
 246                  * Bits[15:0] = Minor Version = 2
 247                  */
 248                 val = KVM_ARM_PSCI_0_2;
 249                 break;
 250         case PSCI_0_2_FN_CPU_SUSPEND:
 251         case PSCI_0_2_FN64_CPU_SUSPEND:
 252                 val = kvm_psci_vcpu_suspend(vcpu);
 253                 break;
 254         case PSCI_0_2_FN_CPU_OFF:
 255                 kvm_psci_vcpu_off(vcpu);
 256                 val = PSCI_RET_SUCCESS;
 257                 break;
 258         case PSCI_0_2_FN_CPU_ON:
 259                 kvm_psci_narrow_to_32bit(vcpu);
 260                 fallthrough;
 261         case PSCI_0_2_FN64_CPU_ON:
 262                 mutex_lock(&kvm->lock);
 263                 val = kvm_psci_vcpu_on(vcpu);
 264                 mutex_unlock(&kvm->lock);
 265                 break;
 266         case PSCI_0_2_FN_AFFINITY_INFO:
 267                 kvm_psci_narrow_to_32bit(vcpu);
 268                 fallthrough;
 269         case PSCI_0_2_FN64_AFFINITY_INFO:
 270                 val = kvm_psci_vcpu_affinity_info(vcpu);
 271                 break;
 272         case PSCI_0_2_FN_MIGRATE_INFO_TYPE:
 273                 /*
 274                  * Trusted OS is MP hence does not require migration
 275                  * or
 276                  * Trusted OS is not present
 277                  */
 278                 val = PSCI_0_2_TOS_MP;
 279                 break;
 280         case PSCI_0_2_FN_SYSTEM_OFF:
 281                 kvm_psci_system_off(vcpu);
 282                 /*
 283                  * We shouldn't be going back to guest VCPU after
 284                  * receiving SYSTEM_OFF request.
 285                  *
 286                  * If user space accidentally/deliberately resumes
 287                  * guest VCPU after SYSTEM_OFF request then guest
 288                  * VCPU should see internal failure from PSCI return
 289                  * value. To achieve this, we preload r0 (or x0) with
 290                  * PSCI return value INTERNAL_FAILURE.
 291                  */
 292                 val = PSCI_RET_INTERNAL_FAILURE;
 293                 ret = 0;
 294                 break;
 295         case PSCI_0_2_FN_SYSTEM_RESET:
 296                 kvm_psci_system_reset(vcpu);
 297                 /*
 298                  * Same reason as SYSTEM_OFF for preloading r0 (or x0)
 299                  * with PSCI return value INTERNAL_FAILURE.
 300                  */
 301                 val = PSCI_RET_INTERNAL_FAILURE;
 302                 ret = 0;
 303                 break;
 304         default:
 305                 val = PSCI_RET_NOT_SUPPORTED;
 306                 break;
 307         }
 308
 309 out:
 310         smccc_set_retval(vcpu, val, 0, 0, 0);
 311         return ret;
 312 }
 313
 314 static int kvm_psci_1_x_call(struct kvm_vcpu *vcpu, u32 minor)
 315 {
 316         u32 psci_fn = smccc_get_function(vcpu);
 317         u32 arg;
 318         unsigned long val;
 319         int ret = 1;
 320
 321         if (minor > 1)
 322                 return -EINVAL;
 323
 324         switch(psci_fn) {
 325         case PSCI_0_2_FN_PSCI_VERSION:
 326                 val = minor == 0 ? KVM_ARM_PSCI_1_0 : KVM_ARM_PSCI_1_1;
 327                 break;
 328         case PSCI_1_0_FN_PSCI_FEATURES:
 329                 arg = smccc_get_arg1(vcpu);
 330                 val = kvm_psci_check_allowed_function(vcpu, arg);
 331                 if (val)
 332                         break;
 333
 334                 switch(arg) {
 335                 case PSCI_0_2_FN_PSCI_VERSION:
 336                 case PSCI_0_2_FN_CPU_SUSPEND:
 337                 case PSCI_0_2_FN64_CPU_SUSPEND:
 338                 case PSCI_0_2_FN_CPU_OFF:
 339                 case PSCI_0_2_FN_CPU_ON:
 340                 case PSCI_0_2_FN64_CPU_ON:
 341                 case PSCI_0_2_FN_AFFINITY_INFO:
 342                 case PSCI_0_2_FN64_AFFINITY_INFO:
 343                 case PSCI_0_2_FN_MIGRATE_INFO_TYPE:
 344                 case PSCI_0_2_FN_SYSTEM_OFF:
 345                 case PSCI_0_2_FN_SYSTEM_RESET:
 346                 case PSCI_1_0_FN_PSCI_FEATURES:
 347                 case ARM_SMCCC_VERSION_FUNC_ID:
 348                         val = 0;
 349                         break;
 350                 case PSCI_1_1_FN_SYSTEM_RESET2:
 351                 case PSCI_1_1_FN64_SYSTEM_RESET2:
 352                         if (minor >= 1) {
 353                                 val = 0;
 354                                 break;
 355                         }
 356                         fallthrough;
 357                 default:
 358                         val = PSCI_RET_NOT_SUPPORTED;
 359                         break;
 360                 }
 361                 break;
 362         case PSCI_1_1_FN_SYSTEM_RESET2:
 363                 kvm_psci_narrow_to_32bit(vcpu);
 364                 fallthrough;
 365         case PSCI_1_1_FN64_SYSTEM_RESET2:
 366                 if (minor >= 1) {
 367                         arg = smccc_get_arg1(vcpu);
 368
 369                         if (arg <= PSCI_1_1_RESET_TYPE_SYSTEM_WARM_RESET ||
 370                             arg >= PSCI_1_1_RESET_TYPE_VENDOR_START) {
 371                                 kvm_psci_system_reset2(vcpu);
 372                                 vcpu_set_reg(vcpu, 0, PSCI_RET_INTERNAL_FAILURE);
 373                                 return 0;
 374                         }
 375
 376                         val = PSCI_RET_INVALID_PARAMS;
 377                         break;
 378                 }
 379                 fallthrough;
 380         default:
 381                 return kvm_psci_0_2_call(vcpu);
 382         }
 383
 384         smccc_set_retval(vcpu, val, 0, 0, 0);
 385         return ret;
 386 }
 387
 388 static int kvm_psci_0_1_call(struct kvm_vcpu *vcpu)
 389 {
 390         struct kvm *kvm = vcpu->kvm;
 391         u32 psci_fn = smccc_get_function(vcpu);
 392         unsigned long val;
 393
 394         switch (psci_fn) {
 395         case KVM_PSCI_FN_CPU_OFF:
 396                 kvm_psci_vcpu_off(vcpu);
 397                 val = PSCI_RET_SUCCESS;
 398                 break;
 399         case KVM_PSCI_FN_CPU_ON:
 400                 mutex_lock(&kvm->lock);
 401                 val = kvm_psci_vcpu_on(vcpu);
 402                 mutex_unlock(&kvm->lock);
 403                 break;
 404         default:
 405                 val = PSCI_RET_NOT_SUPPORTED;
 406                 break;
 407         }
 408
 409         smccc_set_retval(vcpu, val, 0, 0, 0);
 410         return 1;
 411 }
 412
 413 /**
 414  * kvm_psci_call - handle PSCI call if r0 value is in range
 415  * @vcpu: Pointer to the VCPU struct
 416  *
 417  * Handle PSCI calls from guests through traps from HVC instructions.
 418  * The calling convention is similar to SMC calls to the secure world
 419  * where the function number is placed in r0.
 420  *
 421  * This function returns: > 0 (success), 0 (success but exit to user
 422  * space), and < 0 (errors)
 423  *
 424  * Errors:
 425  * -EINVAL: Unrecognized PSCI function
 426  */
 427 int kvm_psci_call(struct kvm_vcpu *vcpu)
 428 {
 429         switch (kvm_psci_version(vcpu)) {
 430         case KVM_ARM_PSCI_1_1:
 431                 return kvm_psci_1_x_call(vcpu, 1);
 432         case KVM_ARM_PSCI_1_0:
 433                 return kvm_psci_1_x_call(vcpu, 0);
 434         case KVM_ARM_PSCI_0_2:
 435                 return kvm_psci_0_2_call(vcpu);
 436         case KVM_ARM_PSCI_0_1:
 437                 return kvm_psci_0_1_call(vcpu);
 438         default:
 439                 return -EINVAL;
 440         }
 441 }
 442
 443 int kvm_arm_get_fw_num_regs(struct kvm_vcpu *vcpu)
 444 {
 445         return 4;               /* PSCI version and three workaround registers */
 446 }
 447
 448 int kvm_arm_copy_fw_reg_indices(struct kvm_vcpu *vcpu, u64 __user *uindices)
 449 {
 450         if (put_user(KVM_REG_ARM_PSCI_VERSION, uindices++))
 451                 return -EFAULT;
 452
 453         if (put_user(KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_1, uindices++))
 454                 return -EFAULT;
 455
 456         if (put_user(KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2, uindices++))
 457                 return -EFAULT;
 458
 459         if (put_user(KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_3, uindices++))
 460                 return -EFAULT;
 461
 462         return 0;
 463 }
 464
 465 #define KVM_REG_FEATURE_LEVEL_WIDTH     4
 466 #define KVM_REG_FEATURE_LEVEL_MASK      (BIT(KVM_REG_FEATURE_LEVEL_WIDTH) - 1)
 467
 468 /*
 469  * Convert the workaround level into an easy-to-compare number, where higher
 470  * values mean better protection.
 471  */
 472 static int get_kernel_wa_level(u64 regid)
 473 {
 474         switch (regid) {
 475         case KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_1:
 476                 switch (arm64_get_spectre_v2_state()) {
 477                 case SPECTRE_VULNERABLE:
 478                         return KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_1_NOT_AVAIL;
 479                 case SPECTRE_MITIGATED:
 480                         return KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_1_AVAIL;
 481                 case SPECTRE_UNAFFECTED:
 482                         return KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_1_NOT_REQUIRED;
 483                 }
 484                 return KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_1_NOT_AVAIL;
 485         case KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2:
 486                 switch (arm64_get_spectre_v4_state()) {
 487                 case SPECTRE_MITIGATED:
 488                         /*
 489                          * As for the hypercall discovery, we pretend we
 490                          * don't have any FW mitigation if SSBS is there at
 491                          * all times.
 492                          */
 493                         if (cpus_have_final_cap(ARM64_SSBS))
 494                                 return KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_NOT_AVAIL;
 495                         fallthrough;
 496                 case SPECTRE_UNAFFECTED:
 497                         return KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_NOT_REQUIRED;
 498                 case SPECTRE_VULNERABLE:
 499                         return KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_NOT_AVAIL;
 500                 }
 501                 break;
 502         case KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_3:
 503                 switch (arm64_get_spectre_bhb_state()) {
 504                 case SPECTRE_VULNERABLE:
 505                         return KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_3_NOT_AVAIL;
 506                 case SPECTRE_MITIGATED:
 507                         return KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_3_AVAIL;
 508                 case SPECTRE_UNAFFECTED:
 509                         return KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_3_NOT_REQUIRED;
 510                 }
 511                 return KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_3_NOT_AVAIL;
 512         }
 513
 514         return -EINVAL;
 515 }
 516
 517 int kvm_arm_get_fw_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
 518 {
 519         void __user *uaddr = (void __user *)(long)reg->addr;
 520         u64 val;
 521
 522         switch (reg->id) {
 523         case KVM_REG_ARM_PSCI_VERSION:
 524                 val = kvm_psci_version(vcpu);
 525                 break;
 526         case KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_1:
 527         case KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2:
 528         case KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_3:
 529                 val = get_kernel_wa_level(reg->id) & KVM_REG_FEATURE_LEVEL_MASK;
 530                 break;
 531         default:
 532                 return -ENOENT;
 533         }
 534
 535         if (copy_to_user(uaddr, &val, KVM_REG_SIZE(reg->id)))
 536                 return -EFAULT;
 537
 538         return 0;
 539 }
 540
 541 int kvm_arm_set_fw_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
 542 {
 543         void __user *uaddr = (void __user *)(long)reg->addr;
 544         u64 val;
 545         int wa_level;
 546
 547         if (copy_from_user(&val, uaddr, KVM_REG_SIZE(reg->id)))
 548                 return -EFAULT;
 549
 550         switch (reg->id) {
 551         case KVM_REG_ARM_PSCI_VERSION:
 552         {
 553                 bool wants_02;
 554
 555                 wants_02 = test_bit(KVM_ARM_VCPU_PSCI_0_2, vcpu->arch.features);
 556
 557                 switch (val) {
 558                 case KVM_ARM_PSCI_0_1:
 559                         if (wants_02)
 560                                 return -EINVAL;
 561                         vcpu->kvm->arch.psci_version = val;
 562                         return 0;
 563                 case KVM_ARM_PSCI_0_2:
 564                 case KVM_ARM_PSCI_1_0:
 565                 case KVM_ARM_PSCI_1_1:
 566                         if (!wants_02)
 567                                 return -EINVAL;
 568                         vcpu->kvm->arch.psci_version = val;
 569                         return 0;
 570                 }
 571                 break;
 572         }
 573
 574         case KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_1:
 575         case KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_3:
 576                 if (val & ~KVM_REG_FEATURE_LEVEL_MASK)
 577                         return -EINVAL;
 578
 579                 if (get_kernel_wa_level(reg->id) < val)
 580                         return -EINVAL;
 581
 582                 return 0;
 583
 584         case KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2:
 585                 if (val & ~(KVM_REG_FEATURE_LEVEL_MASK |
 586                             KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_ENABLED))
 587                         return -EINVAL;
 588
 589                 /* The enabled bit must not be set unless the level is AVAIL. */
 590                 if ((val & KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_ENABLED) &&
 591                     (val & KVM_REG_FEATURE_LEVEL_MASK) != KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_AVAIL)
 592                         return -EINVAL;
 593
 594                 /*
 595                  * Map all the possible incoming states to the only two we
 596                  * really want to deal with.
 597                  */
 598                 switch (val & KVM_REG_FEATURE_LEVEL_MASK) {
 599                 case KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_NOT_AVAIL:
 600                 case KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_UNKNOWN:
 601                         wa_level = KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_NOT_AVAIL;
 602                         break;
 603                 case KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_AVAIL:
 604                 case KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_NOT_REQUIRED:
 605                         wa_level = KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_NOT_REQUIRED;
 606                         break;
 607                 default:
 608                         return -EINVAL;
 609                 }
 610
 611                 /*
 612                  * We can deal with NOT_AVAIL on NOT_REQUIRED, but not the
 613                  * other way around.
 614                  */
 615                 if (get_kernel_wa_level(reg->id) < wa_level)
 616                         return -EINVAL;
 617
 618                 return 0;
 619         default:
 620                 return -ENOENT;
 621         }
 622
 623         return -EINVAL;
 624 }