virt/kvm/arm/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 #include <asm/kvm_host.h>
  16
  17 #include <kvm/arm_psci.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 u32 smccc_get_function(struct kvm_vcpu *vcpu)
  27 {
  28         return vcpu_get_reg(vcpu, 0);
  29 }
  30
  31 static unsigned long smccc_get_arg1(struct kvm_vcpu *vcpu)
  32 {
  33         return vcpu_get_reg(vcpu, 1);
  34 }
  35
  36 static unsigned long smccc_get_arg2(struct kvm_vcpu *vcpu)
  37 {
  38         return vcpu_get_reg(vcpu, 2);
  39 }
  40
  41 static unsigned long smccc_get_arg3(struct kvm_vcpu *vcpu)
  42 {
  43         return vcpu_get_reg(vcpu, 3);
  44 }
  45
  46 static void smccc_set_retval(struct kvm_vcpu *vcpu,
  47                              unsigned long a0,
  48                              unsigned long a1,
  49                              unsigned long a2,
  50                              unsigned long a3)
  51 {
  52         vcpu_set_reg(vcpu, 0, a0);
  53         vcpu_set_reg(vcpu, 1, a1);
  54         vcpu_set_reg(vcpu, 2, a2);
  55         vcpu_set_reg(vcpu, 3, a3);
  56 }
  57
  58 static unsigned long psci_affinity_mask(unsigned long affinity_level)
  59 {
  60         if (affinity_level <= 3)
  61                 return MPIDR_HWID_BITMASK & AFFINITY_MASK(affinity_level);
  62
  63         return 0;
  64 }
  65
  66 static unsigned long kvm_psci_vcpu_suspend(struct kvm_vcpu *vcpu)
  67 {
  68         /*
  69          * NOTE: For simplicity, we make VCPU suspend emulation to be
  70          * same-as WFI (Wait-for-interrupt) emulation.
  71          *
  72          * This means for KVM the wakeup events are interrupts and
  73          * this is consistent with intended use of StateID as described
  74          * in section 5.4.1 of PSCI v0.2 specification (ARM DEN 0022A).
  75          *
  76          * Further, we also treat power-down request to be same as
  77          * stand-by request as-per section 5.4.2 clause 3 of PSCI v0.2
  78          * specification (ARM DEN 0022A). This means all suspend states
  79          * for KVM will preserve the register state.
  80          */
  81         kvm_vcpu_block(vcpu);
  82         kvm_clear_request(KVM_REQ_UNHALT, vcpu);
  83
  84         return PSCI_RET_SUCCESS;
  85 }
  86
  87 static void kvm_psci_vcpu_off(struct kvm_vcpu *vcpu)
  88 {
  89         vcpu->arch.power_off = true;
  90         kvm_make_request(KVM_REQ_SLEEP, vcpu);
  91         kvm_vcpu_kick(vcpu);
  92 }
  93
  94 static unsigned long kvm_psci_vcpu_on(struct kvm_vcpu *source_vcpu)
  95 {
  96         struct vcpu_reset_state *reset_state;
  97         struct kvm *kvm = source_vcpu->kvm;
  98         struct kvm_vcpu *vcpu = NULL;
  99         unsigned long cpu_id;
 100
 101         cpu_id = smccc_get_arg1(source_vcpu) & MPIDR_HWID_BITMASK;
 102         if (vcpu_mode_is_32bit(source_vcpu))
 103                 cpu_id &= ~((u32) 0);
 104
 105         vcpu = kvm_mpidr_to_vcpu(kvm, cpu_id);
 106
 107         /*
 108          * Make sure the caller requested a valid CPU and that the CPU is
 109          * turned off.
 110          */
 111         if (!vcpu)
 112                 return PSCI_RET_INVALID_PARAMS;
 113         if (!vcpu->arch.power_off) {
 114                 if (kvm_psci_version(source_vcpu, kvm) != KVM_ARM_PSCI_0_1)
 115                         return PSCI_RET_ALREADY_ON;
 116                 else
 117                         return PSCI_RET_INVALID_PARAMS;
 118         }
 119
 120         reset_state = &vcpu->arch.reset_state;
 121
 122         reset_state->pc = smccc_get_arg2(source_vcpu);
 123
 124         /* Propagate caller endianness */
 125         reset_state->be = kvm_vcpu_is_be(source_vcpu);
 126
 127         /*
 128          * NOTE: We always update r0 (or x0) because for PSCI v0.1
 129          * the general puspose registers are undefined upon CPU_ON.
 130          */
 131         reset_state->r0 = smccc_get_arg3(source_vcpu);
 132
 133         WRITE_ONCE(reset_state->reset, true);
 134         kvm_make_request(KVM_REQ_VCPU_RESET, vcpu);
 135
 136         /*
 137          * Make sure the reset request is observed if the change to
 138          * power_state is observed.
 139          */
 140         smp_wmb();
 141
 142         vcpu->arch.power_off = false;
 143         kvm_vcpu_wake_up(vcpu);
 144
 145         return PSCI_RET_SUCCESS;
 146 }
 147
 148 static unsigned long kvm_psci_vcpu_affinity_info(struct kvm_vcpu *vcpu)
 149 {
 150         int i, matching_cpus = 0;
 151         unsigned long mpidr;
 152         unsigned long target_affinity;
 153         unsigned long target_affinity_mask;
 154         unsigned long lowest_affinity_level;
 155         struct kvm *kvm = vcpu->kvm;
 156         struct kvm_vcpu *tmp;
 157
 158         target_affinity = smccc_get_arg1(vcpu);
 159         lowest_affinity_level = smccc_get_arg2(vcpu);
 160
 161         /* Determine target affinity mask */
 162         target_affinity_mask = psci_affinity_mask(lowest_affinity_level);
 163         if (!target_affinity_mask)
 164                 return PSCI_RET_INVALID_PARAMS;
 165
 166         /* Ignore other bits of target affinity */
 167         target_affinity &= target_affinity_mask;
 168
 169         /*
 170          * If one or more VCPU matching target affinity are running
 171          * then ON else OFF
 172          */
 173         kvm_for_each_vcpu(i, tmp, kvm) {
 174                 mpidr = kvm_vcpu_get_mpidr_aff(tmp);
 175                 if ((mpidr & target_affinity_mask) == target_affinity) {
 176                         matching_cpus++;
 177                         if (!tmp->arch.power_off)
 178                                 return PSCI_0_2_AFFINITY_LEVEL_ON;
 179                 }
 180         }
 181
 182         if (!matching_cpus)
 183                 return PSCI_RET_INVALID_PARAMS;
 184
 185         return PSCI_0_2_AFFINITY_LEVEL_OFF;
 186 }
 187
 188 static void kvm_prepare_system_event(struct kvm_vcpu *vcpu, u32 type)
 189 {
 190         int i;
 191         struct kvm_vcpu *tmp;
 192
 193         /*
 194          * The KVM ABI specifies that a system event exit may call KVM_RUN
 195          * again and may perform shutdown/reboot at a later time that when the
 196          * actual request is made.  Since we are implementing PSCI and a
 197          * caller of PSCI reboot and shutdown expects that the system shuts
 198          * down or reboots immediately, let's make sure that VCPUs are not run
 199          * after this call is handled and before the VCPUs have been
 200          * re-initialized.
 201          */
 202         kvm_for_each_vcpu(i, tmp, vcpu->kvm)
 203                 tmp->arch.power_off = true;
 204         kvm_make_all_cpus_request(vcpu->kvm, KVM_REQ_SLEEP);
 205
 206         memset(&vcpu->run->system_event, 0, sizeof(vcpu->run->system_event));
 207         vcpu->run->system_event.type = type;
 208         vcpu->run->exit_reason = KVM_EXIT_SYSTEM_EVENT;
 209 }
 210
 211 static void kvm_psci_system_off(struct kvm_vcpu *vcpu)
 212 {
 213         kvm_prepare_system_event(vcpu, KVM_SYSTEM_EVENT_SHUTDOWN);
 214 }
 215
 216 static void kvm_psci_system_reset(struct kvm_vcpu *vcpu)
 217 {
 218         kvm_prepare_system_event(vcpu, KVM_SYSTEM_EVENT_RESET);
 219 }
 220
 221 static int kvm_psci_0_2_call(struct kvm_vcpu *vcpu)
 222 {
 223         struct kvm *kvm = vcpu->kvm;
 224         u32 psci_fn = smccc_get_function(vcpu);
 225         unsigned long val;
 226         int ret = 1;
 227
 228         switch (psci_fn) {
 229         case PSCI_0_2_FN_PSCI_VERSION:
 230                 /*
 231                  * Bits[31:16] = Major Version = 0
 232                  * Bits[15:0] = Minor Version = 2
 233                  */
 234                 val = KVM_ARM_PSCI_0_2;
 235                 break;
 236         case PSCI_0_2_FN_CPU_SUSPEND:
 237         case PSCI_0_2_FN64_CPU_SUSPEND:
 238                 val = kvm_psci_vcpu_suspend(vcpu);
 239                 break;
 240         case PSCI_0_2_FN_CPU_OFF:
 241                 kvm_psci_vcpu_off(vcpu);
 242                 val = PSCI_RET_SUCCESS;
 243                 break;
 244         case PSCI_0_2_FN_CPU_ON:
 245         case PSCI_0_2_FN64_CPU_ON:
 246                 mutex_lock(&kvm->lock);
 247                 val = kvm_psci_vcpu_on(vcpu);
 248                 mutex_unlock(&kvm->lock);
 249                 break;
 250         case PSCI_0_2_FN_AFFINITY_INFO:
 251         case PSCI_0_2_FN64_AFFINITY_INFO:
 252                 val = kvm_psci_vcpu_affinity_info(vcpu);
 253                 break;
 254         case PSCI_0_2_FN_MIGRATE_INFO_TYPE:
 255                 /*
 256                  * Trusted OS is MP hence does not require migration
 257                  * or
 258                  * Trusted OS is not present
 259                  */
 260                 val = PSCI_0_2_TOS_MP;
 261                 break;
 262         case PSCI_0_2_FN_SYSTEM_OFF:
 263                 kvm_psci_system_off(vcpu);
 264                 /*
 265                  * We should'nt be going back to guest VCPU after
 266                  * receiving SYSTEM_OFF request.
 267                  *
 268                  * If user space accidently/deliberately resumes
 269                  * guest VCPU after SYSTEM_OFF request then guest
 270                  * VCPU should see internal failure from PSCI return
 271                  * value. To achieve this, we preload r0 (or x0) with
 272                  * PSCI return value INTERNAL_FAILURE.
 273                  */
 274                 val = PSCI_RET_INTERNAL_FAILURE;
 275                 ret = 0;
 276                 break;
 277         case PSCI_0_2_FN_SYSTEM_RESET:
 278                 kvm_psci_system_reset(vcpu);
 279                 /*
 280                  * Same reason as SYSTEM_OFF for preloading r0 (or x0)
 281                  * with PSCI return value INTERNAL_FAILURE.
 282                  */
 283                 val = PSCI_RET_INTERNAL_FAILURE;
 284                 ret = 0;
 285                 break;
 286         default:
 287                 val = PSCI_RET_NOT_SUPPORTED;
 288                 break;
 289         }
 290
 291         smccc_set_retval(vcpu, val, 0, 0, 0);
 292         return ret;
 293 }
 294
 295 static int kvm_psci_1_0_call(struct kvm_vcpu *vcpu)
 296 {
 297         u32 psci_fn = smccc_get_function(vcpu);
 298         u32 feature;
 299         unsigned long val;
 300         int ret = 1;
 301
 302         switch(psci_fn) {
 303         case PSCI_0_2_FN_PSCI_VERSION:
 304                 val = KVM_ARM_PSCI_1_0;
 305                 break;
 306         case PSCI_1_0_FN_PSCI_FEATURES:
 307                 feature = smccc_get_arg1(vcpu);
 308                 switch(feature) {
 309                 case PSCI_0_2_FN_PSCI_VERSION:
 310                 case PSCI_0_2_FN_CPU_SUSPEND:
 311                 case PSCI_0_2_FN64_CPU_SUSPEND:
 312                 case PSCI_0_2_FN_CPU_OFF:
 313                 case PSCI_0_2_FN_CPU_ON:
 314                 case PSCI_0_2_FN64_CPU_ON:
 315                 case PSCI_0_2_FN_AFFINITY_INFO:
 316                 case PSCI_0_2_FN64_AFFINITY_INFO:
 317                 case PSCI_0_2_FN_MIGRATE_INFO_TYPE:
 318                 case PSCI_0_2_FN_SYSTEM_OFF:
 319                 case PSCI_0_2_FN_SYSTEM_RESET:
 320                 case PSCI_1_0_FN_PSCI_FEATURES:
 321                 case ARM_SMCCC_VERSION_FUNC_ID:
 322                         val = 0;
 323                         break;
 324                 default:
 325                         val = PSCI_RET_NOT_SUPPORTED;
 326                         break;
 327                 }
 328                 break;
 329         default:
 330                 return kvm_psci_0_2_call(vcpu);
 331         }
 332
 333         smccc_set_retval(vcpu, val, 0, 0, 0);
 334         return ret;
 335 }
 336
 337 static int kvm_psci_0_1_call(struct kvm_vcpu *vcpu)
 338 {
 339         struct kvm *kvm = vcpu->kvm;
 340         u32 psci_fn = smccc_get_function(vcpu);
 341         unsigned long val;
 342
 343         switch (psci_fn) {
 344         case KVM_PSCI_FN_CPU_OFF:
 345                 kvm_psci_vcpu_off(vcpu);
 346                 val = PSCI_RET_SUCCESS;
 347                 break;
 348         case KVM_PSCI_FN_CPU_ON:
 349                 mutex_lock(&kvm->lock);
 350                 val = kvm_psci_vcpu_on(vcpu);
 351                 mutex_unlock(&kvm->lock);
 352                 break;
 353         default:
 354                 val = PSCI_RET_NOT_SUPPORTED;
 355                 break;
 356         }
 357
 358         smccc_set_retval(vcpu, val, 0, 0, 0);
 359         return 1;
 360 }
 361
 362 /**
 363  * kvm_psci_call - handle PSCI call if r0 value is in range
 364  * @vcpu: Pointer to the VCPU struct
 365  *
 366  * Handle PSCI calls from guests through traps from HVC instructions.
 367  * The calling convention is similar to SMC calls to the secure world
 368  * where the function number is placed in r0.
 369  *
 370  * This function returns: > 0 (success), 0 (success but exit to user
 371  * space), and < 0 (errors)
 372  *
 373  * Errors:
 374  * -EINVAL: Unrecognized PSCI function
 375  */
 376 static int kvm_psci_call(struct kvm_vcpu *vcpu)
 377 {
 378         switch (kvm_psci_version(vcpu, vcpu->kvm)) {
 379         case KVM_ARM_PSCI_1_0:
 380                 return kvm_psci_1_0_call(vcpu);
 381         case KVM_ARM_PSCI_0_2:
 382                 return kvm_psci_0_2_call(vcpu);
 383         case KVM_ARM_PSCI_0_1:
 384                 return kvm_psci_0_1_call(vcpu);
 385         default:
 386                 return -EINVAL;
 387         };
 388 }
 389
 390 int kvm_hvc_call_handler(struct kvm_vcpu *vcpu)
 391 {
 392         u32 func_id = smccc_get_function(vcpu);
 393         u32 val = SMCCC_RET_NOT_SUPPORTED;
 394         u32 feature;
 395
 396         switch (func_id) {
 397         case ARM_SMCCC_VERSION_FUNC_ID:
 398                 val = ARM_SMCCC_VERSION_1_1;
 399                 break;
 400         case ARM_SMCCC_ARCH_FEATURES_FUNC_ID:
 401                 feature = smccc_get_arg1(vcpu);
 402                 switch(feature) {
 403                 case ARM_SMCCC_ARCH_WORKAROUND_1:
 404                         switch (kvm_arm_harden_branch_predictor()) {
 405                         case KVM_BP_HARDEN_UNKNOWN:
 406                                 break;
 407                         case KVM_BP_HARDEN_WA_NEEDED:
 408                                 val = SMCCC_RET_SUCCESS;
 409                                 break;
 410                         case KVM_BP_HARDEN_NOT_REQUIRED:
 411                                 val = SMCCC_RET_NOT_REQUIRED;
 412                                 break;
 413                         }
 414                         break;
 415                 case ARM_SMCCC_ARCH_WORKAROUND_2:
 416                         switch (kvm_arm_have_ssbd()) {
 417                         case KVM_SSBD_FORCE_DISABLE:
 418                         case KVM_SSBD_UNKNOWN:
 419                                 break;
 420                         case KVM_SSBD_KERNEL:
 421                                 val = SMCCC_RET_SUCCESS;
 422                                 break;
 423                         case KVM_SSBD_FORCE_ENABLE:
 424                         case KVM_SSBD_MITIGATED:
 425                                 val = SMCCC_RET_NOT_REQUIRED;
 426                                 break;
 427                         }
 428                         break;
 429                 }
 430                 break;
 431         default:
 432                 return kvm_psci_call(vcpu);
 433         }
 434
 435         smccc_set_retval(vcpu, val, 0, 0, 0);
 436         return 1;
 437 }
 438
 439 int kvm_arm_get_fw_num_regs(struct kvm_vcpu *vcpu)
 440 {
 441         return 3;               /* PSCI version and two workaround registers */
 442 }
 443
 444 int kvm_arm_copy_fw_reg_indices(struct kvm_vcpu *vcpu, u64 __user *uindices)
 445 {
 446         if (put_user(KVM_REG_ARM_PSCI_VERSION, uindices++))
 447                 return -EFAULT;
 448
 449         if (put_user(KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_1, uindices++))
 450                 return -EFAULT;
 451
 452         if (put_user(KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2, uindices++))
 453                 return -EFAULT;
 454
 455         return 0;
 456 }
 457
 458 #define KVM_REG_FEATURE_LEVEL_WIDTH     4
 459 #define KVM_REG_FEATURE_LEVEL_MASK      (BIT(KVM_REG_FEATURE_LEVEL_WIDTH) - 1)
 460
 461 /*
 462  * Convert the workaround level into an easy-to-compare number, where higher
 463  * values mean better protection.
 464  */
 465 static int get_kernel_wa_level(u64 regid)
 466 {
 467         switch (regid) {
 468         case KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_1:
 469                 switch (kvm_arm_harden_branch_predictor()) {
 470                 case KVM_BP_HARDEN_UNKNOWN:
 471                         return KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_1_NOT_AVAIL;
 472                 case KVM_BP_HARDEN_WA_NEEDED:
 473                         return KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_1_AVAIL;
 474                 case KVM_BP_HARDEN_NOT_REQUIRED:
 475                         return KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_1_NOT_REQUIRED;
 476                 }
 477                 return KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_1_NOT_AVAIL;
 478         case KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2:
 479                 switch (kvm_arm_have_ssbd()) {
 480                 case KVM_SSBD_FORCE_DISABLE:
 481                         return KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_NOT_AVAIL;
 482                 case KVM_SSBD_KERNEL:
 483                         return KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_AVAIL;
 484                 case KVM_SSBD_FORCE_ENABLE:
 485                 case KVM_SSBD_MITIGATED:
 486                         return KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_NOT_REQUIRED;
 487                 case KVM_SSBD_UNKNOWN:
 488                 default:
 489                         return KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_UNKNOWN;
 490                 }
 491         }
 492
 493         return -EINVAL;
 494 }
 495
 496 int kvm_arm_get_fw_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
 497 {
 498         void __user *uaddr = (void __user *)(long)reg->addr;
 499         u64 val;
 500
 501         switch (reg->id) {
 502         case KVM_REG_ARM_PSCI_VERSION:
 503                 val = kvm_psci_version(vcpu, vcpu->kvm);
 504                 break;
 505         case KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_1:
 506                 val = get_kernel_wa_level(reg->id) & KVM_REG_FEATURE_LEVEL_MASK;
 507                 break;
 508         case KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2:
 509                 val = get_kernel_wa_level(reg->id) & KVM_REG_FEATURE_LEVEL_MASK;
 510
 511                 if (val == KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_AVAIL &&
 512                     kvm_arm_get_vcpu_workaround_2_flag(vcpu))
 513                         val |= KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_ENABLED;
 514                 break;
 515         default:
 516                 return -ENOENT;
 517         }
 518
 519         if (copy_to_user(uaddr, &val, KVM_REG_SIZE(reg->id)))
 520                 return -EFAULT;
 521
 522         return 0;
 523 }
 524
 525 int kvm_arm_set_fw_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
 526 {
 527         void __user *uaddr = (void __user *)(long)reg->addr;
 528         u64 val;
 529         int wa_level;
 530
 531         if (copy_from_user(&val, uaddr, KVM_REG_SIZE(reg->id)))
 532                 return -EFAULT;
 533
 534         switch (reg->id) {
 535         case KVM_REG_ARM_PSCI_VERSION:
 536         {
 537                 bool wants_02;
 538
 539                 wants_02 = test_bit(KVM_ARM_VCPU_PSCI_0_2, vcpu->arch.features);
 540
 541                 switch (val) {
 542                 case KVM_ARM_PSCI_0_1:
 543                         if (wants_02)
 544                                 return -EINVAL;
 545                         vcpu->kvm->arch.psci_version = val;
 546                         return 0;
 547                 case KVM_ARM_PSCI_0_2:
 548                 case KVM_ARM_PSCI_1_0:
 549                         if (!wants_02)
 550                                 return -EINVAL;
 551                         vcpu->kvm->arch.psci_version = val;
 552                         return 0;
 553                 }
 554                 break;
 555         }
 556
 557         case KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_1:
 558                 if (val & ~KVM_REG_FEATURE_LEVEL_MASK)
 559                         return -EINVAL;
 560
 561                 if (get_kernel_wa_level(reg->id) < val)
 562                         return -EINVAL;
 563
 564                 return 0;
 565
 566         case KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2:
 567                 if (val & ~(KVM_REG_FEATURE_LEVEL_MASK |
 568                             KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_ENABLED))
 569                         return -EINVAL;
 570
 571                 wa_level = val & KVM_REG_FEATURE_LEVEL_MASK;
 572
 573                 if (get_kernel_wa_level(reg->id) < wa_level)
 574                         return -EINVAL;
 575
 576                 /* The enabled bit must not be set unless the level is AVAIL. */
 577                 if (wa_level != KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_AVAIL &&
 578                     wa_level != val)
 579                         return -EINVAL;
 580
 581                 /* Are we finished or do we need to check the enable bit ? */
 582                 if (kvm_arm_have_ssbd() != KVM_SSBD_KERNEL)
 583                         return 0;
 584
 585                 /*
 586                  * If this kernel supports the workaround to be switched on
 587                  * or off, make sure it matches the requested setting.
 588                  */
 589                 switch (wa_level) {
 590                 case KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_AVAIL:
 591                         kvm_arm_set_vcpu_workaround_2_flag(vcpu,
 592                             val & KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_ENABLED);
 593                         break;
 594                 case KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_NOT_REQUIRED:
 595                         kvm_arm_set_vcpu_workaround_2_flag(vcpu, true);
 596                         break;
 597                 }
 598
 599                 return 0;
 600         default:
 601                 return -ENOENT;
 602         }
 603
 604         return -EINVAL;
 605 }