arch/x86/kernel/cpu/bugs.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  *  Copyright (C) 1994  Linus Torvalds
   4  *
   5  *  Cyrix stuff, June 1998 by:
   6  *      - Rafael R. Reilova (moved everything from head.S),
   7  *        <rreilova@ececs.uc.edu>
   8  *      - Channing Corn (tests & fixes),
   9  *      - Andrew D. Balsa (code cleanup).
  10  */
  11 #include <linux/init.h>
  12 #include <linux/utsname.h>
  13 #include <linux/cpu.h>
  14 #include <linux/module.h>
  15 #include <linux/nospec.h>
  16 #include <linux/prctl.h>
  17 #include <linux/sched/smt.h>
  18
  19 #include <asm/spec-ctrl.h>
  20 #include <asm/cmdline.h>
  21 #include <asm/bugs.h>
  22 #include <asm/processor.h>
  23 #include <asm/processor-flags.h>
  24 #include <asm/fpu/internal.h>
  25 #include <asm/msr.h>
  26 #include <asm/vmx.h>
  27 #include <asm/paravirt.h>
  28 #include <asm/alternative.h>
  29 #include <asm/pgtable.h>
  30 #include <asm/set_memory.h>
  31 #include <asm/intel-family.h>
  32 #include <asm/e820/api.h>
  33 #include <asm/hypervisor.h>
  34
  35 #include "cpu.h"
  36
  37 static void __init spectre_v2_select_mitigation(void);
  38 static void __init ssb_select_mitigation(void);
  39 static void __init l1tf_select_mitigation(void);
  40 static void __init mds_select_mitigation(void);
  41
  42 /* The base value of the SPEC_CTRL MSR that always has to be preserved. */
  43 u64 x86_spec_ctrl_base;
  44 EXPORT_SYMBOL_GPL(x86_spec_ctrl_base);
  45 static DEFINE_MUTEX(spec_ctrl_mutex);
  46
  47 /*
  48  * The vendor and possibly platform specific bits which can be modified in
  49  * x86_spec_ctrl_base.
  50  */
  51 static u64 __ro_after_init x86_spec_ctrl_mask = SPEC_CTRL_IBRS;
  52
  53 /*
  54  * AMD specific MSR info for Speculative Store Bypass control.
  55  * x86_amd_ls_cfg_ssbd_mask is initialized in identify_boot_cpu().
  56  */
  57 u64 __ro_after_init x86_amd_ls_cfg_base;
  58 u64 __ro_after_init x86_amd_ls_cfg_ssbd_mask;
  59
  60 /* Control conditional STIBP in switch_to() */
  61 DEFINE_STATIC_KEY_FALSE(switch_to_cond_stibp);
  62 /* Control conditional IBPB in switch_mm() */
  63 DEFINE_STATIC_KEY_FALSE(switch_mm_cond_ibpb);
  64 /* Control unconditional IBPB in switch_mm() */
  65 DEFINE_STATIC_KEY_FALSE(switch_mm_always_ibpb);
  66
  67 /* Control MDS CPU buffer clear before returning to user space */
  68 DEFINE_STATIC_KEY_FALSE(mds_user_clear);
  69 EXPORT_SYMBOL_GPL(mds_user_clear);
  70 /* Control MDS CPU buffer clear before idling (halt, mwait) */
  71 DEFINE_STATIC_KEY_FALSE(mds_idle_clear);
  72 EXPORT_SYMBOL_GPL(mds_idle_clear);
  73
  74 void __init check_bugs(void)
  75 {
  76         identify_boot_cpu();
  77
  78         /*
  79          * identify_boot_cpu() initialized SMT support information, let the
  80          * core code know.
  81          */
  82         cpu_smt_check_topology();
  83
  84         if (!IS_ENABLED(CONFIG_SMP)) {
  85                 pr_info("CPU: ");
  86                 print_cpu_info(&boot_cpu_data);
  87         }
  88
  89         /*
  90          * Read the SPEC_CTRL MSR to account for reserved bits which may
  91          * have unknown values. AMD64_LS_CFG MSR is cached in the early AMD
  92          * init code as it is not enumerated and depends on the family.
  93          */
  94         if (boot_cpu_has(X86_FEATURE_MSR_SPEC_CTRL))
  95                 rdmsrl(MSR_IA32_SPEC_CTRL, x86_spec_ctrl_base);
  96
  97         /* Allow STIBP in MSR_SPEC_CTRL if supported */
  98         if (boot_cpu_has(X86_FEATURE_STIBP))
  99                 x86_spec_ctrl_mask |= SPEC_CTRL_STIBP;
 100
 101         /* Select the proper spectre mitigation before patching alternatives */
 102         spectre_v2_select_mitigation();
 103
 104         /*
 105          * Select proper mitigation for any exposure to the Speculative Store
 106          * Bypass vulnerability.
 107          */
 108         ssb_select_mitigation();
 109
 110         l1tf_select_mitigation();
 111
 112         mds_select_mitigation();
 113
 114         arch_smt_update();
 115
 116 #ifdef CONFIG_X86_32
 117         /*
 118          * Check whether we are able to run this kernel safely on SMP.
 119          *
 120          * - i386 is no longer supported.
 121          * - In order to run on anything without a TSC, we need to be
 122          *   compiled for a i486.
 123          */
 124         if (boot_cpu_data.x86 < 4)
 125                 panic("Kernel requires i486+ for 'invlpg' and other features");
 126
 127         init_utsname()->machine[1] =
 128                 '0' + (boot_cpu_data.x86 > 6 ? 6 : boot_cpu_data.x86);
 129         alternative_instructions();
 130
 131         fpu__init_check_bugs();
 132 #else /* CONFIG_X86_64 */
 133         alternative_instructions();
 134
 135         /*
 136          * Make sure the first 2MB area is not mapped by huge pages
 137          * There are typically fixed size MTRRs in there and overlapping
 138          * MTRRs into large pages causes slow downs.
 139          *
 140          * Right now we don't do that with gbpages because there seems
 141          * very little benefit for that case.
 142          */
 143         if (!direct_gbpages)
 144                 set_memory_4k((unsigned long)__va(0), 1);
 145 #endif
 146 }
 147
 148 void
 149 x86_virt_spec_ctrl(u64 guest_spec_ctrl, u64 guest_virt_spec_ctrl, bool setguest)
 150 {
 151         u64 msrval, guestval, hostval = x86_spec_ctrl_base;
 152         struct thread_info *ti = current_thread_info();
 153
 154         /* Is MSR_SPEC_CTRL implemented ? */
 155         if (static_cpu_has(X86_FEATURE_MSR_SPEC_CTRL)) {
 156                 /*
 157                  * Restrict guest_spec_ctrl to supported values. Clear the
 158                  * modifiable bits in the host base value and or the
 159                  * modifiable bits from the guest value.
 160                  */
 161                 guestval = hostval & ~x86_spec_ctrl_mask;
 162                 guestval |= guest_spec_ctrl & x86_spec_ctrl_mask;
 163
 164                 /* SSBD controlled in MSR_SPEC_CTRL */
 165                 if (static_cpu_has(X86_FEATURE_SPEC_CTRL_SSBD) ||
 166                     static_cpu_has(X86_FEATURE_AMD_SSBD))
 167                         hostval |= ssbd_tif_to_spec_ctrl(ti->flags);
 168
 169                 /* Conditional STIBP enabled? */
 170                 if (static_branch_unlikely(&switch_to_cond_stibp))
 171                         hostval |= stibp_tif_to_spec_ctrl(ti->flags);
 172
 173                 if (hostval != guestval) {
 174                         msrval = setguest ? guestval : hostval;
 175                         wrmsrl(MSR_IA32_SPEC_CTRL, msrval);
 176                 }
 177         }
 178
 179         /*
 180          * If SSBD is not handled in MSR_SPEC_CTRL on AMD, update
 181          * MSR_AMD64_L2_CFG or MSR_VIRT_SPEC_CTRL if supported.
 182          */
 183         if (!static_cpu_has(X86_FEATURE_LS_CFG_SSBD) &&
 184             !static_cpu_has(X86_FEATURE_VIRT_SSBD))
 185                 return;
 186
 187         /*
 188          * If the host has SSBD mitigation enabled, force it in the host's
 189          * virtual MSR value. If its not permanently enabled, evaluate
 190          * current's TIF_SSBD thread flag.
 191          */
 192         if (static_cpu_has(X86_FEATURE_SPEC_STORE_BYPASS_DISABLE))
 193                 hostval = SPEC_CTRL_SSBD;
 194         else
 195                 hostval = ssbd_tif_to_spec_ctrl(ti->flags);
 196
 197         /* Sanitize the guest value */
 198         guestval = guest_virt_spec_ctrl & SPEC_CTRL_SSBD;
 199
 200         if (hostval != guestval) {
 201                 unsigned long tif;
 202
 203                 tif = setguest ? ssbd_spec_ctrl_to_tif(guestval) :
 204                                  ssbd_spec_ctrl_to_tif(hostval);
 205
 206                 speculation_ctrl_update(tif);
 207         }
 208 }
 209 EXPORT_SYMBOL_GPL(x86_virt_spec_ctrl);
 210
 211 static void x86_amd_ssb_disable(void)
 212 {
 213         u64 msrval = x86_amd_ls_cfg_base | x86_amd_ls_cfg_ssbd_mask;
 214
 215         if (boot_cpu_has(X86_FEATURE_VIRT_SSBD))
 216                 wrmsrl(MSR_AMD64_VIRT_SPEC_CTRL, SPEC_CTRL_SSBD);
 217         else if (boot_cpu_has(X86_FEATURE_LS_CFG_SSBD))
 218                 wrmsrl(MSR_AMD64_LS_CFG, msrval);
 219 }
 220
 221 #undef pr_fmt
 222 #define pr_fmt(fmt)     "MDS: " fmt
 223
 224 /* Default mitigation for MDS-affected CPUs */
 225 static enum mds_mitigations mds_mitigation __ro_after_init = MDS_MITIGATION_FULL;
 226 static bool mds_nosmt __ro_after_init = false;
 227
 228 static const char * const mds_strings[] = {
 229         [MDS_MITIGATION_OFF]    = "Vulnerable",
 230         [MDS_MITIGATION_FULL]   = "Mitigation: Clear CPU buffers",
 231         [MDS_MITIGATION_VMWERV] = "Vulnerable: Clear CPU buffers attempted, no microcode",
 232 };
 233
 234 static void __init mds_select_mitigation(void)
 235 {
 236         if (!boot_cpu_has_bug(X86_BUG_MDS) || cpu_mitigations_off()) {
 237                 mds_mitigation = MDS_MITIGATION_OFF;
 238                 return;
 239         }
 240
 241         if (mds_mitigation == MDS_MITIGATION_FULL) {
 242                 if (!boot_cpu_has(X86_FEATURE_MD_CLEAR))
 243                         mds_mitigation = MDS_MITIGATION_VMWERV;
 244
 245                 static_branch_enable(&mds_user_clear);
 246
 247                 if (!boot_cpu_has(X86_BUG_MSBDS_ONLY) &&
 248                     (mds_nosmt || cpu_mitigations_auto_nosmt()))
 249                         cpu_smt_disable(false);
 250         }
 251
 252         pr_info("%s\n", mds_strings[mds_mitigation]);
 253 }
 254
 255 static int __init mds_cmdline(char *str)
 256 {
 257         if (!boot_cpu_has_bug(X86_BUG_MDS))
 258                 return 0;
 259
 260         if (!str)
 261                 return -EINVAL;
 262
 263         if (!strcmp(str, "off"))
 264                 mds_mitigation = MDS_MITIGATION_OFF;
 265         else if (!strcmp(str, "full"))
 266                 mds_mitigation = MDS_MITIGATION_FULL;
 267         else if (!strcmp(str, "full,nosmt")) {
 268                 mds_mitigation = MDS_MITIGATION_FULL;
 269                 mds_nosmt = true;
 270         }
 271
 272         return 0;
 273 }
 274 early_param("mds", mds_cmdline);
 275
 276 #undef pr_fmt
 277 #define pr_fmt(fmt)     "Spectre V2 : " fmt
 278
 279 static enum spectre_v2_mitigation spectre_v2_enabled __ro_after_init =
 280         SPECTRE_V2_NONE;
 281
 282 static enum spectre_v2_user_mitigation spectre_v2_user __ro_after_init =
 283         SPECTRE_V2_USER_NONE;
 284
 285 #ifdef CONFIG_RETPOLINE
 286 static bool spectre_v2_bad_module;
 287
 288 bool retpoline_module_ok(bool has_retpoline)
 289 {
 290         if (spectre_v2_enabled == SPECTRE_V2_NONE || has_retpoline)
 291                 return true;
 292
 293         pr_err("System may be vulnerable to spectre v2\n");
 294         spectre_v2_bad_module = true;
 295         return false;
 296 }
 297
 298 static inline const char *spectre_v2_module_string(void)
 299 {
 300         return spectre_v2_bad_module ? " - vulnerable module loaded" : "";
 301 }
 302 #else
 303 static inline const char *spectre_v2_module_string(void) { return ""; }
 304 #endif
 305
 306 static inline bool match_option(const char *arg, int arglen, const char *opt)
 307 {
 308         int len = strlen(opt);
 309
 310         return len == arglen && !strncmp(arg, opt, len);
 311 }
 312
 313 /* The kernel command line selection for spectre v2 */
 314 enum spectre_v2_mitigation_cmd {
 315         SPECTRE_V2_CMD_NONE,
 316         SPECTRE_V2_CMD_AUTO,
 317         SPECTRE_V2_CMD_FORCE,
 318         SPECTRE_V2_CMD_RETPOLINE,
 319         SPECTRE_V2_CMD_RETPOLINE_GENERIC,
 320         SPECTRE_V2_CMD_RETPOLINE_AMD,
 321 };
 322
 323 enum spectre_v2_user_cmd {
 324         SPECTRE_V2_USER_CMD_NONE,
 325         SPECTRE_V2_USER_CMD_AUTO,
 326         SPECTRE_V2_USER_CMD_FORCE,
 327         SPECTRE_V2_USER_CMD_PRCTL,
 328         SPECTRE_V2_USER_CMD_PRCTL_IBPB,
 329         SPECTRE_V2_USER_CMD_SECCOMP,
 330         SPECTRE_V2_USER_CMD_SECCOMP_IBPB,
 331 };
 332
 333 static const char * const spectre_v2_user_strings[] = {
 334         [SPECTRE_V2_USER_NONE]                  = "User space: Vulnerable",
 335         [SPECTRE_V2_USER_STRICT]                = "User space: Mitigation: STIBP protection",
 336         [SPECTRE_V2_USER_STRICT_PREFERRED]      = "User space: Mitigation: STIBP always-on protection",
 337         [SPECTRE_V2_USER_PRCTL]                 = "User space: Mitigation: STIBP via prctl",
 338         [SPECTRE_V2_USER_SECCOMP]               = "User space: Mitigation: STIBP via seccomp and prctl",
 339 };
 340
 341 static const struct {
 342         const char                      *option;
 343         enum spectre_v2_user_cmd        cmd;
 344         bool                            secure;
 345 } v2_user_options[] __initconst = {
 346         { "auto",               SPECTRE_V2_USER_CMD_AUTO,               false },
 347         { "off",                SPECTRE_V2_USER_CMD_NONE,               false },
 348         { "on",                 SPECTRE_V2_USER_CMD_FORCE,              true  },
 349         { "prctl",              SPECTRE_V2_USER_CMD_PRCTL,              false },
 350         { "prctl,ibpb",         SPECTRE_V2_USER_CMD_PRCTL_IBPB,         false },
 351         { "seccomp",            SPECTRE_V2_USER_CMD_SECCOMP,            false },
 352         { "seccomp,ibpb",       SPECTRE_V2_USER_CMD_SECCOMP_IBPB,       false },
 353 };
 354
 355 static void __init spec_v2_user_print_cond(const char *reason, bool secure)
 356 {
 357         if (boot_cpu_has_bug(X86_BUG_SPECTRE_V2) != secure)
 358                 pr_info("spectre_v2_user=%s forced on command line.\n", reason);
 359 }
 360
 361 static enum spectre_v2_user_cmd __init
 362 spectre_v2_parse_user_cmdline(enum spectre_v2_mitigation_cmd v2_cmd)
 363 {
 364         char arg[20];
 365         int ret, i;
 366
 367         switch (v2_cmd) {
 368         case SPECTRE_V2_CMD_NONE:
 369                 return SPECTRE_V2_USER_CMD_NONE;
 370         case SPECTRE_V2_CMD_FORCE:
 371                 return SPECTRE_V2_USER_CMD_FORCE;
 372         default:
 373                 break;
 374         }
 375
 376         ret = cmdline_find_option(boot_command_line, "spectre_v2_user",
 377                                   arg, sizeof(arg));
 378         if (ret < 0)
 379                 return SPECTRE_V2_USER_CMD_AUTO;
 380
 381         for (i = 0; i < ARRAY_SIZE(v2_user_options); i++) {
 382                 if (match_option(arg, ret, v2_user_options[i].option)) {
 383                         spec_v2_user_print_cond(v2_user_options[i].option,
 384                                                 v2_user_options[i].secure);
 385                         return v2_user_options[i].cmd;
 386                 }
 387         }
 388
 389         pr_err("Unknown user space protection option (%s). Switching to AUTO select\n", arg);
 390         return SPECTRE_V2_USER_CMD_AUTO;
 391 }
 392
 393 static void __init
 394 spectre_v2_user_select_mitigation(enum spectre_v2_mitigation_cmd v2_cmd)
 395 {
 396         enum spectre_v2_user_mitigation mode = SPECTRE_V2_USER_NONE;
 397         bool smt_possible = IS_ENABLED(CONFIG_SMP);
 398         enum spectre_v2_user_cmd cmd;
 399
 400         if (!boot_cpu_has(X86_FEATURE_IBPB) && !boot_cpu_has(X86_FEATURE_STIBP))
 401                 return;
 402
 403         if (cpu_smt_control == CPU_SMT_FORCE_DISABLED ||
 404             cpu_smt_control == CPU_SMT_NOT_SUPPORTED)
 405                 smt_possible = false;
 406
 407         cmd = spectre_v2_parse_user_cmdline(v2_cmd);
 408         switch (cmd) {
 409         case SPECTRE_V2_USER_CMD_NONE:
 410                 goto set_mode;
 411         case SPECTRE_V2_USER_CMD_FORCE:
 412                 mode = SPECTRE_V2_USER_STRICT;
 413                 break;
 414         case SPECTRE_V2_USER_CMD_PRCTL:
 415         case SPECTRE_V2_USER_CMD_PRCTL_IBPB:
 416                 mode = SPECTRE_V2_USER_PRCTL;
 417                 break;
 418         case SPECTRE_V2_USER_CMD_AUTO:
 419         case SPECTRE_V2_USER_CMD_SECCOMP:
 420         case SPECTRE_V2_USER_CMD_SECCOMP_IBPB:
 421                 if (IS_ENABLED(CONFIG_SECCOMP))
 422                         mode = SPECTRE_V2_USER_SECCOMP;
 423                 else
 424                         mode = SPECTRE_V2_USER_PRCTL;
 425                 break;
 426         }
 427
 428         /*
 429          * At this point, an STIBP mode other than "off" has been set.
 430          * If STIBP support is not being forced, check if STIBP always-on
 431          * is preferred.
 432          */
 433         if (mode != SPECTRE_V2_USER_STRICT &&
 434             boot_cpu_has(X86_FEATURE_AMD_STIBP_ALWAYS_ON))
 435                 mode = SPECTRE_V2_USER_STRICT_PREFERRED;
 436
 437         /* Initialize Indirect Branch Prediction Barrier */
 438         if (boot_cpu_has(X86_FEATURE_IBPB)) {
 439                 setup_force_cpu_cap(X86_FEATURE_USE_IBPB);
 440
 441                 switch (cmd) {
 442                 case SPECTRE_V2_USER_CMD_FORCE:
 443                 case SPECTRE_V2_USER_CMD_PRCTL_IBPB:
 444                 case SPECTRE_V2_USER_CMD_SECCOMP_IBPB:
 445                         static_branch_enable(&switch_mm_always_ibpb);
 446                         break;
 447                 case SPECTRE_V2_USER_CMD_PRCTL:
 448                 case SPECTRE_V2_USER_CMD_AUTO:
 449                 case SPECTRE_V2_USER_CMD_SECCOMP:
 450                         static_branch_enable(&switch_mm_cond_ibpb);
 451                         break;
 452                 default:
 453                         break;
 454                 }
 455
 456                 pr_info("mitigation: Enabling %s Indirect Branch Prediction Barrier\n",
 457                         static_key_enabled(&switch_mm_always_ibpb) ?
 458                         "always-on" : "conditional");
 459         }
 460
 461         /* If enhanced IBRS is enabled no STIBP required */
 462         if (spectre_v2_enabled == SPECTRE_V2_IBRS_ENHANCED)
 463                 return;
 464
 465         /*
 466          * If SMT is not possible or STIBP is not available clear the STIBP
 467          * mode.
 468          */
 469         if (!smt_possible || !boot_cpu_has(X86_FEATURE_STIBP))
 470                 mode = SPECTRE_V2_USER_NONE;
 471 set_mode:
 472         spectre_v2_user = mode;
 473         /* Only print the STIBP mode when SMT possible */
 474         if (smt_possible)
 475                 pr_info("%s\n", spectre_v2_user_strings[mode]);
 476 }
 477
 478 static const char * const spectre_v2_strings[] = {
 479         [SPECTRE_V2_NONE]                       = "Vulnerable",
 480         [SPECTRE_V2_RETPOLINE_GENERIC]          = "Mitigation: Full generic retpoline",
 481         [SPECTRE_V2_RETPOLINE_AMD]              = "Mitigation: Full AMD retpoline",
 482         [SPECTRE_V2_IBRS_ENHANCED]              = "Mitigation: Enhanced IBRS",
 483 };
 484
 485 static const struct {
 486         const char *option;
 487         enum spectre_v2_mitigation_cmd cmd;
 488         bool secure;
 489 } mitigation_options[] __initconst = {
 490         { "off",                SPECTRE_V2_CMD_NONE,              false },
 491         { "on",                 SPECTRE_V2_CMD_FORCE,             true  },
 492         { "retpoline",          SPECTRE_V2_CMD_RETPOLINE,         false },
 493         { "retpoline,amd",      SPECTRE_V2_CMD_RETPOLINE_AMD,     false },
 494         { "retpoline,generic",  SPECTRE_V2_CMD_RETPOLINE_GENERIC, false },
 495         { "auto",               SPECTRE_V2_CMD_AUTO,              false },
 496 };
 497
 498 static void __init spec_v2_print_cond(const char *reason, bool secure)
 499 {
 500         if (boot_cpu_has_bug(X86_BUG_SPECTRE_V2) != secure)
 501                 pr_info("%s selected on command line.\n", reason);
 502 }
 503
 504 static enum spectre_v2_mitigation_cmd __init spectre_v2_parse_cmdline(void)
 505 {
 506         enum spectre_v2_mitigation_cmd cmd = SPECTRE_V2_CMD_AUTO;
 507         char arg[20];
 508         int ret, i;
 509
 510         if (cmdline_find_option_bool(boot_command_line, "nospectre_v2") ||
 511             cpu_mitigations_off())
 512                 return SPECTRE_V2_CMD_NONE;
 513
 514         ret = cmdline_find_option(boot_command_line, "spectre_v2", arg, sizeof(arg));
 515         if (ret < 0)
 516                 return SPECTRE_V2_CMD_AUTO;
 517
 518         for (i = 0; i < ARRAY_SIZE(mitigation_options); i++) {
 519                 if (!match_option(arg, ret, mitigation_options[i].option))
 520                         continue;
 521                 cmd = mitigation_options[i].cmd;
 522                 break;
 523         }
 524
 525         if (i >= ARRAY_SIZE(mitigation_options)) {
 526                 pr_err("unknown option (%s). Switching to AUTO select\n", arg);
 527                 return SPECTRE_V2_CMD_AUTO;
 528         }
 529
 530         if ((cmd == SPECTRE_V2_CMD_RETPOLINE ||
 531              cmd == SPECTRE_V2_CMD_RETPOLINE_AMD ||
 532              cmd == SPECTRE_V2_CMD_RETPOLINE_GENERIC) &&
 533             !IS_ENABLED(CONFIG_RETPOLINE)) {
 534                 pr_err("%s selected but not compiled in. Switching to AUTO select\n", mitigation_options[i].option);
 535                 return SPECTRE_V2_CMD_AUTO;
 536         }
 537
 538         if (cmd == SPECTRE_V2_CMD_RETPOLINE_AMD &&
 539             boot_cpu_data.x86_vendor != X86_VENDOR_HYGON &&
 540             boot_cpu_data.x86_vendor != X86_VENDOR_AMD) {
 541                 pr_err("retpoline,amd selected but CPU is not AMD. Switching to AUTO select\n");
 542                 return SPECTRE_V2_CMD_AUTO;
 543         }
 544
 545         spec_v2_print_cond(mitigation_options[i].option,
 546                            mitigation_options[i].secure);
 547         return cmd;
 548 }
 549
 550 static void __init spectre_v2_select_mitigation(void)
 551 {
 552         enum spectre_v2_mitigation_cmd cmd = spectre_v2_parse_cmdline();
 553         enum spectre_v2_mitigation mode = SPECTRE_V2_NONE;
 554
 555         /*
 556          * If the CPU is not affected and the command line mode is NONE or AUTO
 557          * then nothing to do.
 558          */
 559         if (!boot_cpu_has_bug(X86_BUG_SPECTRE_V2) &&
 560             (cmd == SPECTRE_V2_CMD_NONE || cmd == SPECTRE_V2_CMD_AUTO))
 561                 return;
 562
 563         switch (cmd) {
 564         case SPECTRE_V2_CMD_NONE:
 565                 return;
 566
 567         case SPECTRE_V2_CMD_FORCE:
 568         case SPECTRE_V2_CMD_AUTO:
 569                 if (boot_cpu_has(X86_FEATURE_IBRS_ENHANCED)) {
 570                         mode = SPECTRE_V2_IBRS_ENHANCED;
 571                         /* Force it so VMEXIT will restore correctly */
 572                         x86_spec_ctrl_base |= SPEC_CTRL_IBRS;
 573                         wrmsrl(MSR_IA32_SPEC_CTRL, x86_spec_ctrl_base);
 574                         goto specv2_set_mode;
 575                 }
 576                 if (IS_ENABLED(CONFIG_RETPOLINE))
 577                         goto retpoline_auto;
 578                 break;
 579         case SPECTRE_V2_CMD_RETPOLINE_AMD:
 580                 if (IS_ENABLED(CONFIG_RETPOLINE))
 581                         goto retpoline_amd;
 582                 break;
 583         case SPECTRE_V2_CMD_RETPOLINE_GENERIC:
 584                 if (IS_ENABLED(CONFIG_RETPOLINE))
 585                         goto retpoline_generic;
 586                 break;
 587         case SPECTRE_V2_CMD_RETPOLINE:
 588                 if (IS_ENABLED(CONFIG_RETPOLINE))
 589                         goto retpoline_auto;
 590                 break;
 591         }
 592         pr_err("Spectre mitigation: kernel not compiled with retpoline; no mitigation available!");
 593         return;
 594
 595 retpoline_auto:
 596         if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD ||
 597             boot_cpu_data.x86_vendor == X86_VENDOR_HYGON) {
 598         retpoline_amd:
 599                 if (!boot_cpu_has(X86_FEATURE_LFENCE_RDTSC)) {
 600                         pr_err("Spectre mitigation: LFENCE not serializing, switching to generic retpoline\n");
 601                         goto retpoline_generic;
 602                 }
 603                 mode = SPECTRE_V2_RETPOLINE_AMD;
 604                 setup_force_cpu_cap(X86_FEATURE_RETPOLINE_AMD);
 605                 setup_force_cpu_cap(X86_FEATURE_RETPOLINE);
 606         } else {
 607         retpoline_generic:
 608                 mode = SPECTRE_V2_RETPOLINE_GENERIC;
 609                 setup_force_cpu_cap(X86_FEATURE_RETPOLINE);
 610         }
 611
 612 specv2_set_mode:
 613         spectre_v2_enabled = mode;
 614         pr_info("%s\n", spectre_v2_strings[mode]);
 615
 616         /*
 617          * If spectre v2 protection has been enabled, unconditionally fill
 618          * RSB during a context switch; this protects against two independent
 619          * issues:
 620          *
 621          *      - RSB underflow (and switch to BTB) on Skylake+
 622          *      - SpectreRSB variant of spectre v2 on X86_BUG_SPECTRE_V2 CPUs
 623          */
 624         setup_force_cpu_cap(X86_FEATURE_RSB_CTXSW);
 625         pr_info("Spectre v2 / SpectreRSB mitigation: Filling RSB on context switch\n");
 626
 627         /*
 628          * Retpoline means the kernel is safe because it has no indirect
 629          * branches. Enhanced IBRS protects firmware too, so, enable restricted
 630          * speculation around firmware calls only when Enhanced IBRS isn't
 631          * supported.
 632          *
 633          * Use "mode" to check Enhanced IBRS instead of boot_cpu_has(), because
 634          * the user might select retpoline on the kernel command line and if
 635          * the CPU supports Enhanced IBRS, kernel might un-intentionally not
 636          * enable IBRS around firmware calls.
 637          */
 638         if (boot_cpu_has(X86_FEATURE_IBRS) && mode != SPECTRE_V2_IBRS_ENHANCED) {
 639                 setup_force_cpu_cap(X86_FEATURE_USE_IBRS_FW);
 640                 pr_info("Enabling Restricted Speculation for firmware calls\n");
 641         }
 642
 643         /* Set up IBPB and STIBP depending on the general spectre V2 command */
 644         spectre_v2_user_select_mitigation(cmd);
 645 }
 646
 647 static void update_stibp_msr(void * __unused)
 648 {
 649         wrmsrl(MSR_IA32_SPEC_CTRL, x86_spec_ctrl_base);
 650 }
 651
 652 /* Update x86_spec_ctrl_base in case SMT state changed. */
 653 static void update_stibp_strict(void)
 654 {
 655         u64 mask = x86_spec_ctrl_base & ~SPEC_CTRL_STIBP;
 656
 657         if (sched_smt_active())
 658                 mask |= SPEC_CTRL_STIBP;
 659
 660         if (mask == x86_spec_ctrl_base)
 661                 return;
 662
 663         pr_info("Update user space SMT mitigation: STIBP %s\n",
 664                 mask & SPEC_CTRL_STIBP ? "always-on" : "off");
 665         x86_spec_ctrl_base = mask;
 666         on_each_cpu(update_stibp_msr, NULL, 1);
 667 }
 668
 669 /* Update the static key controlling the evaluation of TIF_SPEC_IB */
 670 static void update_indir_branch_cond(void)
 671 {
 672         if (sched_smt_active())
 673                 static_branch_enable(&switch_to_cond_stibp);
 674         else
 675                 static_branch_disable(&switch_to_cond_stibp);
 676 }
 677
 678 #undef pr_fmt
 679 #define pr_fmt(fmt) fmt
 680
 681 /* Update the static key controlling the MDS CPU buffer clear in idle */
 682 static void update_mds_branch_idle(void)
 683 {
 684         /*
 685          * Enable the idle clearing if SMT is active on CPUs which are
 686          * affected only by MSBDS and not any other MDS variant.
 687          *
 688          * The other variants cannot be mitigated when SMT is enabled, so
 689          * clearing the buffers on idle just to prevent the Store Buffer
 690          * repartitioning leak would be a window dressing exercise.
 691          */
 692         if (!boot_cpu_has_bug(X86_BUG_MSBDS_ONLY))
 693                 return;
 694
 695         if (sched_smt_active())
 696                 static_branch_enable(&mds_idle_clear);
 697         else
 698                 static_branch_disable(&mds_idle_clear);
 699 }
 700
 701 #define MDS_MSG_SMT "MDS CPU bug present and SMT on, data leak possible. See https://www.kernel.org/doc/html/latest/admin-guide/hw-vuln/mds.html for more details.\n"
 702
 703 void arch_smt_update(void)
 704 {
 705         /* Enhanced IBRS implies STIBP. No update required. */
 706         if (spectre_v2_enabled == SPECTRE_V2_IBRS_ENHANCED)
 707                 return;
 708
 709         mutex_lock(&spec_ctrl_mutex);
 710
 711         switch (spectre_v2_user) {
 712         case SPECTRE_V2_USER_NONE:
 713                 break;
 714         case SPECTRE_V2_USER_STRICT:
 715         case SPECTRE_V2_USER_STRICT_PREFERRED:
 716                 update_stibp_strict();
 717                 break;
 718         case SPECTRE_V2_USER_PRCTL:
 719         case SPECTRE_V2_USER_SECCOMP:
 720                 update_indir_branch_cond();
 721                 break;
 722         }
 723
 724         switch (mds_mitigation) {
 725         case MDS_MITIGATION_FULL:
 726         case MDS_MITIGATION_VMWERV:
 727                 if (sched_smt_active() && !boot_cpu_has(X86_BUG_MSBDS_ONLY))
 728                         pr_warn_once(MDS_MSG_SMT);
 729                 update_mds_branch_idle();
 730                 break;
 731         case MDS_MITIGATION_OFF:
 732                 break;
 733         }
 734
 735         mutex_unlock(&spec_ctrl_mutex);
 736 }
 737
 738 #undef pr_fmt
 739 #define pr_fmt(fmt)     "Speculative Store Bypass: " fmt
 740
 741 static enum ssb_mitigation ssb_mode __ro_after_init = SPEC_STORE_BYPASS_NONE;
 742
 743 /* The kernel command line selection */
 744 enum ssb_mitigation_cmd {
 745         SPEC_STORE_BYPASS_CMD_NONE,
 746         SPEC_STORE_BYPASS_CMD_AUTO,
 747         SPEC_STORE_BYPASS_CMD_ON,
 748         SPEC_STORE_BYPASS_CMD_PRCTL,
 749         SPEC_STORE_BYPASS_CMD_SECCOMP,
 750 };
 751
 752 static const char * const ssb_strings[] = {
 753         [SPEC_STORE_BYPASS_NONE]        = "Vulnerable",
 754         [SPEC_STORE_BYPASS_DISABLE]     = "Mitigation: Speculative Store Bypass disabled",
 755         [SPEC_STORE_BYPASS_PRCTL]       = "Mitigation: Speculative Store Bypass disabled via prctl",
 756         [SPEC_STORE_BYPASS_SECCOMP]     = "Mitigation: Speculative Store Bypass disabled via prctl and seccomp",
 757 };
 758
 759 static const struct {
 760         const char *option;
 761         enum ssb_mitigation_cmd cmd;
 762 } ssb_mitigation_options[]  __initconst = {
 763         { "auto",       SPEC_STORE_BYPASS_CMD_AUTO },    /* Platform decides */
 764         { "on",         SPEC_STORE_BYPASS_CMD_ON },      /* Disable Speculative Store Bypass */
 765         { "off",        SPEC_STORE_BYPASS_CMD_NONE },    /* Don't touch Speculative Store Bypass */
 766         { "prctl",      SPEC_STORE_BYPASS_CMD_PRCTL },   /* Disable Speculative Store Bypass via prctl */
 767         { "seccomp",    SPEC_STORE_BYPASS_CMD_SECCOMP }, /* Disable Speculative Store Bypass via prctl and seccomp */
 768 };
 769
 770 static enum ssb_mitigation_cmd __init ssb_parse_cmdline(void)
 771 {
 772         enum ssb_mitigation_cmd cmd = SPEC_STORE_BYPASS_CMD_AUTO;
 773         char arg[20];
 774         int ret, i;
 775
 776         if (cmdline_find_option_bool(boot_command_line, "nospec_store_bypass_disable") ||
 777             cpu_mitigations_off()) {
 778                 return SPEC_STORE_BYPASS_CMD_NONE;
 779         } else {
 780                 ret = cmdline_find_option(boot_command_line, "spec_store_bypass_disable",
 781                                           arg, sizeof(arg));
 782                 if (ret < 0)
 783                         return SPEC_STORE_BYPASS_CMD_AUTO;
 784
 785                 for (i = 0; i < ARRAY_SIZE(ssb_mitigation_options); i++) {
 786                         if (!match_option(arg, ret, ssb_mitigation_options[i].option))
 787                                 continue;
 788
 789                         cmd = ssb_mitigation_options[i].cmd;
 790                         break;
 791                 }
 792
 793                 if (i >= ARRAY_SIZE(ssb_mitigation_options)) {
 794                         pr_err("unknown option (%s). Switching to AUTO select\n", arg);
 795                         return SPEC_STORE_BYPASS_CMD_AUTO;
 796                 }
 797         }
 798
 799         return cmd;
 800 }
 801
 802 static enum ssb_mitigation __init __ssb_select_mitigation(void)
 803 {
 804         enum ssb_mitigation mode = SPEC_STORE_BYPASS_NONE;
 805         enum ssb_mitigation_cmd cmd;
 806
 807         if (!boot_cpu_has(X86_FEATURE_SSBD))
 808                 return mode;
 809
 810         cmd = ssb_parse_cmdline();
 811         if (!boot_cpu_has_bug(X86_BUG_SPEC_STORE_BYPASS) &&
 812             (cmd == SPEC_STORE_BYPASS_CMD_NONE ||
 813              cmd == SPEC_STORE_BYPASS_CMD_AUTO))
 814                 return mode;
 815
 816         switch (cmd) {
 817         case SPEC_STORE_BYPASS_CMD_AUTO:
 818         case SPEC_STORE_BYPASS_CMD_SECCOMP:
 819                 /*
 820                  * Choose prctl+seccomp as the default mode if seccomp is
 821                  * enabled.
 822                  */
 823                 if (IS_ENABLED(CONFIG_SECCOMP))
 824                         mode = SPEC_STORE_BYPASS_SECCOMP;
 825                 else
 826                         mode = SPEC_STORE_BYPASS_PRCTL;
 827                 break;
 828         case SPEC_STORE_BYPASS_CMD_ON:
 829                 mode = SPEC_STORE_BYPASS_DISABLE;
 830                 break;
 831         case SPEC_STORE_BYPASS_CMD_PRCTL:
 832                 mode = SPEC_STORE_BYPASS_PRCTL;
 833                 break;
 834         case SPEC_STORE_BYPASS_CMD_NONE:
 835                 break;
 836         }
 837
 838         /*
 839          * If SSBD is controlled by the SPEC_CTRL MSR, then set the proper
 840          * bit in the mask to allow guests to use the mitigation even in the
 841          * case where the host does not enable it.
 842          */
 843         if (static_cpu_has(X86_FEATURE_SPEC_CTRL_SSBD) ||
 844             static_cpu_has(X86_FEATURE_AMD_SSBD)) {
 845                 x86_spec_ctrl_mask |= SPEC_CTRL_SSBD;
 846         }
 847
 848         /*
 849          * We have three CPU feature flags that are in play here:
 850          *  - X86_BUG_SPEC_STORE_BYPASS - CPU is susceptible.
 851          *  - X86_FEATURE_SSBD - CPU is able to turn off speculative store bypass
 852          *  - X86_FEATURE_SPEC_STORE_BYPASS_DISABLE - engage the mitigation
 853          */
 854         if (mode == SPEC_STORE_BYPASS_DISABLE) {
 855                 setup_force_cpu_cap(X86_FEATURE_SPEC_STORE_BYPASS_DISABLE);
 856                 /*
 857                  * Intel uses the SPEC CTRL MSR Bit(2) for this, while AMD may
 858                  * use a completely different MSR and bit dependent on family.
 859                  */
 860                 if (!static_cpu_has(X86_FEATURE_SPEC_CTRL_SSBD) &&
 861                     !static_cpu_has(X86_FEATURE_AMD_SSBD)) {
 862                         x86_amd_ssb_disable();
 863                 } else {
 864                         x86_spec_ctrl_base |= SPEC_CTRL_SSBD;
 865                         wrmsrl(MSR_IA32_SPEC_CTRL, x86_spec_ctrl_base);
 866                 }
 867         }
 868
 869         return mode;
 870 }
 871
 872 static void ssb_select_mitigation(void)
 873 {
 874         ssb_mode = __ssb_select_mitigation();
 875
 876         if (boot_cpu_has_bug(X86_BUG_SPEC_STORE_BYPASS))
 877                 pr_info("%s\n", ssb_strings[ssb_mode]);
 878 }
 879
 880 #undef pr_fmt
 881 #define pr_fmt(fmt)     "Speculation prctl: " fmt
 882
 883 static void task_update_spec_tif(struct task_struct *tsk)
 884 {
 885         /* Force the update of the real TIF bits */
 886         set_tsk_thread_flag(tsk, TIF_SPEC_FORCE_UPDATE);
 887
 888         /*
 889          * Immediately update the speculation control MSRs for the current
 890          * task, but for a non-current task delay setting the CPU
 891          * mitigation until it is scheduled next.
 892          *
 893          * This can only happen for SECCOMP mitigation. For PRCTL it's
 894          * always the current task.
 895          */
 896         if (tsk == current)
 897                 speculation_ctrl_update_current();
 898 }
 899
 900 static int ssb_prctl_set(struct task_struct *task, unsigned long ctrl)
 901 {
 902         if (ssb_mode != SPEC_STORE_BYPASS_PRCTL &&
 903             ssb_mode != SPEC_STORE_BYPASS_SECCOMP)
 904                 return -ENXIO;
 905
 906         switch (ctrl) {
 907         case PR_SPEC_ENABLE:
 908                 /* If speculation is force disabled, enable is not allowed */
 909                 if (task_spec_ssb_force_disable(task))
 910                         return -EPERM;
 911                 task_clear_spec_ssb_disable(task);
 912                 task_clear_spec_ssb_noexec(task);
 913                 task_update_spec_tif(task);
 914                 break;
 915         case PR_SPEC_DISABLE:
 916                 task_set_spec_ssb_disable(task);
 917                 task_clear_spec_ssb_noexec(task);
 918                 task_update_spec_tif(task);
 919                 break;
 920         case PR_SPEC_FORCE_DISABLE:
 921                 task_set_spec_ssb_disable(task);
 922                 task_set_spec_ssb_force_disable(task);
 923                 task_clear_spec_ssb_noexec(task);
 924                 task_update_spec_tif(task);
 925                 break;
 926         case PR_SPEC_DISABLE_NOEXEC:
 927                 if (task_spec_ssb_force_disable(task))
 928                         return -EPERM;
 929                 task_set_spec_ssb_disable(task);
 930                 task_set_spec_ssb_noexec(task);
 931                 task_update_spec_tif(task);
 932                 break;
 933         default:
 934                 return -ERANGE;
 935         }
 936         return 0;
 937 }
 938
 939 static int ib_prctl_set(struct task_struct *task, unsigned long ctrl)
 940 {
 941         switch (ctrl) {
 942         case PR_SPEC_ENABLE:
 943                 if (spectre_v2_user == SPECTRE_V2_USER_NONE)
 944                         return 0;
 945                 /*
 946                  * Indirect branch speculation is always disabled in strict
 947                  * mode.
 948                  */
 949                 if (spectre_v2_user == SPECTRE_V2_USER_STRICT ||
 950                     spectre_v2_user == SPECTRE_V2_USER_STRICT_PREFERRED)
 951                         return -EPERM;
 952                 task_clear_spec_ib_disable(task);
 953                 task_update_spec_tif(task);
 954                 break;
 955         case PR_SPEC_DISABLE:
 956         case PR_SPEC_FORCE_DISABLE:
 957                 /*
 958                  * Indirect branch speculation is always allowed when
 959                  * mitigation is force disabled.
 960                  */
 961                 if (spectre_v2_user == SPECTRE_V2_USER_NONE)
 962                         return -EPERM;
 963                 if (spectre_v2_user == SPECTRE_V2_USER_STRICT ||
 964                     spectre_v2_user == SPECTRE_V2_USER_STRICT_PREFERRED)
 965                         return 0;
 966                 task_set_spec_ib_disable(task);
 967                 if (ctrl == PR_SPEC_FORCE_DISABLE)
 968                         task_set_spec_ib_force_disable(task);
 969                 task_update_spec_tif(task);
 970                 break;
 971         default:
 972                 return -ERANGE;
 973         }
 974         return 0;
 975 }
 976
 977 int arch_prctl_spec_ctrl_set(struct task_struct *task, unsigned long which,
 978                              unsigned long ctrl)
 979 {
 980         switch (which) {
 981         case PR_SPEC_STORE_BYPASS:
 982                 return ssb_prctl_set(task, ctrl);
 983         case PR_SPEC_INDIRECT_BRANCH:
 984                 return ib_prctl_set(task, ctrl);
 985         default:
 986                 return -ENODEV;
 987         }
 988 }
 989
 990 #ifdef CONFIG_SECCOMP
 991 void arch_seccomp_spec_mitigate(struct task_struct *task)
 992 {
 993         if (ssb_mode == SPEC_STORE_BYPASS_SECCOMP)
 994                 ssb_prctl_set(task, PR_SPEC_FORCE_DISABLE);
 995         if (spectre_v2_user == SPECTRE_V2_USER_SECCOMP)
 996                 ib_prctl_set(task, PR_SPEC_FORCE_DISABLE);
 997 }
 998 #endif
 999
1000 static int ssb_prctl_get(struct task_struct *task)
1001 {
1002         switch (ssb_mode) {
1003         case SPEC_STORE_BYPASS_DISABLE:
1004                 return PR_SPEC_DISABLE;
1005         case SPEC_STORE_BYPASS_SECCOMP:
1006         case SPEC_STORE_BYPASS_PRCTL:
1007                 if (task_spec_ssb_force_disable(task))
1008                         return PR_SPEC_PRCTL | PR_SPEC_FORCE_DISABLE;
1009                 if (task_spec_ssb_noexec(task))
1010                         return PR_SPEC_PRCTL | PR_SPEC_DISABLE_NOEXEC;
1011                 if (task_spec_ssb_disable(task))
1012                         return PR_SPEC_PRCTL | PR_SPEC_DISABLE;
1013                 return PR_SPEC_PRCTL | PR_SPEC_ENABLE;
1014         default:
1015                 if (boot_cpu_has_bug(X86_BUG_SPEC_STORE_BYPASS))
1016                         return PR_SPEC_ENABLE;
1017                 return PR_SPEC_NOT_AFFECTED;
1018         }
1019 }
1020
1021 static int ib_prctl_get(struct task_struct *task)
1022 {
1023         if (!boot_cpu_has_bug(X86_BUG_SPECTRE_V2))
1024                 return PR_SPEC_NOT_AFFECTED;
1025
1026         switch (spectre_v2_user) {
1027         case SPECTRE_V2_USER_NONE:
1028                 return PR_SPEC_ENABLE;
1029         case SPECTRE_V2_USER_PRCTL:
1030         case SPECTRE_V2_USER_SECCOMP:
1031                 if (task_spec_ib_force_disable(task))
1032                         return PR_SPEC_PRCTL | PR_SPEC_FORCE_DISABLE;
1033                 if (task_spec_ib_disable(task))
1034                         return PR_SPEC_PRCTL | PR_SPEC_DISABLE;
1035                 return PR_SPEC_PRCTL | PR_SPEC_ENABLE;
1036         case SPECTRE_V2_USER_STRICT:
1037         case SPECTRE_V2_USER_STRICT_PREFERRED:
1038                 return PR_SPEC_DISABLE;
1039         default:
1040                 return PR_SPEC_NOT_AFFECTED;
1041         }
1042 }
1043
1044 int arch_prctl_spec_ctrl_get(struct task_struct *task, unsigned long which)
1045 {
1046         switch (which) {
1047         case PR_SPEC_STORE_BYPASS:
1048                 return ssb_prctl_get(task);
1049         case PR_SPEC_INDIRECT_BRANCH:
1050                 return ib_prctl_get(task);
1051         default:
1052                 return -ENODEV;
1053         }
1054 }
1055
1056 void x86_spec_ctrl_setup_ap(void)
1057 {
1058         if (boot_cpu_has(X86_FEATURE_MSR_SPEC_CTRL))
1059                 wrmsrl(MSR_IA32_SPEC_CTRL, x86_spec_ctrl_base);
1060
1061         if (ssb_mode == SPEC_STORE_BYPASS_DISABLE)
1062                 x86_amd_ssb_disable();
1063 }
1064
1065 #undef pr_fmt
1066 #define pr_fmt(fmt)     "L1TF: " fmt
1067
1068 /* Default mitigation for L1TF-affected CPUs */
1069 enum l1tf_mitigations l1tf_mitigation __ro_after_init = L1TF_MITIGATION_FLUSH;
1070 #if IS_ENABLED(CONFIG_KVM_INTEL)
1071 EXPORT_SYMBOL_GPL(l1tf_mitigation);
1072 #endif
1073 enum vmx_l1d_flush_state l1tf_vmx_mitigation = VMENTER_L1D_FLUSH_AUTO;
1074 EXPORT_SYMBOL_GPL(l1tf_vmx_mitigation);
1075
1076 /*
1077  * These CPUs all support 44bits physical address space internally in the
1078  * cache but CPUID can report a smaller number of physical address bits.
1079  *
1080  * The L1TF mitigation uses the top most address bit for the inversion of
1081  * non present PTEs. When the installed memory reaches into the top most
1082  * address bit due to memory holes, which has been observed on machines
1083  * which report 36bits physical address bits and have 32G RAM installed,
1084  * then the mitigation range check in l1tf_select_mitigation() triggers.
1085  * This is a false positive because the mitigation is still possible due to
1086  * the fact that the cache uses 44bit internally. Use the cache bits
1087  * instead of the reported physical bits and adjust them on the affected
1088  * machines to 44bit if the reported bits are less than 44.
1089  */
1090 static void override_cache_bits(struct cpuinfo_x86 *c)
1091 {
1092         if (c->x86 != 6)
1093                 return;
1094
1095         switch (c->x86_model) {
1096         case INTEL_FAM6_NEHALEM:
1097         case INTEL_FAM6_WESTMERE:
1098         case INTEL_FAM6_SANDYBRIDGE:
1099         case INTEL_FAM6_IVYBRIDGE:
1100         case INTEL_FAM6_HASWELL_CORE:
1101         case INTEL_FAM6_HASWELL_ULT:
1102         case INTEL_FAM6_HASWELL_GT3E:
1103         case INTEL_FAM6_BROADWELL_CORE:
1104         case INTEL_FAM6_BROADWELL_GT3E:
1105         case INTEL_FAM6_SKYLAKE_MOBILE:
1106         case INTEL_FAM6_SKYLAKE_DESKTOP:
1107         case INTEL_FAM6_KABYLAKE_MOBILE:
1108         case INTEL_FAM6_KABYLAKE_DESKTOP:
1109                 if (c->x86_cache_bits < 44)
1110                         c->x86_cache_bits = 44;
1111                 break;
1112         }
1113 }
1114
1115 static void __init l1tf_select_mitigation(void)
1116 {
1117         u64 half_pa;
1118
1119         if (!boot_cpu_has_bug(X86_BUG_L1TF))
1120                 return;
1121
1122         if (cpu_mitigations_off())
1123                 l1tf_mitigation = L1TF_MITIGATION_OFF;
1124         else if (cpu_mitigations_auto_nosmt())
1125                 l1tf_mitigation = L1TF_MITIGATION_FLUSH_NOSMT;
1126
1127         override_cache_bits(&boot_cpu_data);
1128
1129         switch (l1tf_mitigation) {
1130         case L1TF_MITIGATION_OFF:
1131         case L1TF_MITIGATION_FLUSH_NOWARN:
1132         case L1TF_MITIGATION_FLUSH:
1133                 break;
1134         case L1TF_MITIGATION_FLUSH_NOSMT:
1135         case L1TF_MITIGATION_FULL:
1136                 cpu_smt_disable(false);
1137                 break;
1138         case L1TF_MITIGATION_FULL_FORCE:
1139                 cpu_smt_disable(true);
1140                 break;
1141         }
1142
1143 #if CONFIG_PGTABLE_LEVELS == 2
1144         pr_warn("Kernel not compiled for PAE. No mitigation for L1TF\n");
1145         return;
1146 #endif
1147
1148         half_pa = (u64)l1tf_pfn_limit() << PAGE_SHIFT;
1149         if (l1tf_mitigation != L1TF_MITIGATION_OFF &&
1150                         e820__mapped_any(half_pa, ULLONG_MAX - half_pa, E820_TYPE_RAM)) {
1151                 pr_warn("System has more than MAX_PA/2 memory. L1TF mitigation not effective.\n");
1152                 pr_info("You may make it effective by booting the kernel with mem=%llu parameter.\n",
1153                                 half_pa);
1154                 pr_info("However, doing so will make a part of your RAM unusable.\n");
1155                 pr_info("Reading https://www.kernel.org/doc/html/latest/admin-guide/hw-vuln/l1tf.html might help you decide.\n");
1156                 return;
1157         }
1158
1159         setup_force_cpu_cap(X86_FEATURE_L1TF_PTEINV);
1160 }
1161
1162 static int __init l1tf_cmdline(char *str)
1163 {
1164         if (!boot_cpu_has_bug(X86_BUG_L1TF))
1165                 return 0;
1166
1167         if (!str)
1168                 return -EINVAL;
1169
1170         if (!strcmp(str, "off"))
1171                 l1tf_mitigation = L1TF_MITIGATION_OFF;
1172         else if (!strcmp(str, "flush,nowarn"))
1173                 l1tf_mitigation = L1TF_MITIGATION_FLUSH_NOWARN;
1174         else if (!strcmp(str, "flush"))
1175                 l1tf_mitigation = L1TF_MITIGATION_FLUSH;
1176         else if (!strcmp(str, "flush,nosmt"))
1177                 l1tf_mitigation = L1TF_MITIGATION_FLUSH_NOSMT;
1178         else if (!strcmp(str, "full"))
1179                 l1tf_mitigation = L1TF_MITIGATION_FULL;
1180         else if (!strcmp(str, "full,force"))
1181                 l1tf_mitigation = L1TF_MITIGATION_FULL_FORCE;
1182
1183         return 0;
1184 }
1185 early_param("l1tf", l1tf_cmdline);
1186
1187 #undef pr_fmt
1188 #define pr_fmt(fmt) fmt
1189
1190 #ifdef CONFIG_SYSFS
1191
1192 #define L1TF_DEFAULT_MSG "Mitigation: PTE Inversion"
1193
1194 #if IS_ENABLED(CONFIG_KVM_INTEL)
1195 static const char * const l1tf_vmx_states[] = {
1196         [VMENTER_L1D_FLUSH_AUTO]                = "auto",
1197         [VMENTER_L1D_FLUSH_NEVER]               = "vulnerable",
1198         [VMENTER_L1D_FLUSH_COND]                = "conditional cache flushes",
1199         [VMENTER_L1D_FLUSH_ALWAYS]              = "cache flushes",
1200         [VMENTER_L1D_FLUSH_EPT_DISABLED]        = "EPT disabled",
1201         [VMENTER_L1D_FLUSH_NOT_REQUIRED]        = "flush not necessary"
1202 };
1203
1204 static ssize_t l1tf_show_state(char *buf)
1205 {
1206         if (l1tf_vmx_mitigation == VMENTER_L1D_FLUSH_AUTO)
1207                 return sprintf(buf, "%s\n", L1TF_DEFAULT_MSG);
1208
1209         if (l1tf_vmx_mitigation == VMENTER_L1D_FLUSH_EPT_DISABLED ||
1210             (l1tf_vmx_mitigation == VMENTER_L1D_FLUSH_NEVER &&
1211              sched_smt_active())) {
1212                 return sprintf(buf, "%s; VMX: %s\n", L1TF_DEFAULT_MSG,
1213                                l1tf_vmx_states[l1tf_vmx_mitigation]);
1214         }
1215
1216         return sprintf(buf, "%s; VMX: %s, SMT %s\n", L1TF_DEFAULT_MSG,
1217                        l1tf_vmx_states[l1tf_vmx_mitigation],
1218                        sched_smt_active() ? "vulnerable" : "disabled");
1219 }
1220 #else
1221 static ssize_t l1tf_show_state(char *buf)
1222 {
1223         return sprintf(buf, "%s\n", L1TF_DEFAULT_MSG);
1224 }
1225 #endif
1226
1227 static ssize_t mds_show_state(char *buf)
1228 {
1229         if (!hypervisor_is_type(X86_HYPER_NATIVE)) {
1230                 return sprintf(buf, "%s; SMT Host state unknown\n",
1231                                mds_strings[mds_mitigation]);
1232         }
1233
1234         if (boot_cpu_has(X86_BUG_MSBDS_ONLY)) {
1235                 return sprintf(buf, "%s; SMT %s\n", mds_strings[mds_mitigation],
1236                                (mds_mitigation == MDS_MITIGATION_OFF ? "vulnerable" :
1237                                 sched_smt_active() ? "mitigated" : "disabled"));
1238         }
1239
1240         return sprintf(buf, "%s; SMT %s\n", mds_strings[mds_mitigation],
1241                        sched_smt_active() ? "vulnerable" : "disabled");
1242 }
1243
1244 static char *stibp_state(void)
1245 {
1246         if (spectre_v2_enabled == SPECTRE_V2_IBRS_ENHANCED)
1247                 return "";
1248
1249         switch (spectre_v2_user) {
1250         case SPECTRE_V2_USER_NONE:
1251                 return ", STIBP: disabled";
1252         case SPECTRE_V2_USER_STRICT:
1253                 return ", STIBP: forced";
1254         case SPECTRE_V2_USER_STRICT_PREFERRED:
1255                 return ", STIBP: always-on";
1256         case SPECTRE_V2_USER_PRCTL:
1257         case SPECTRE_V2_USER_SECCOMP:
1258                 if (static_key_enabled(&switch_to_cond_stibp))
1259                         return ", STIBP: conditional";
1260         }
1261         return "";
1262 }
1263
1264 static char *ibpb_state(void)
1265 {
1266         if (boot_cpu_has(X86_FEATURE_IBPB)) {
1267                 if (static_key_enabled(&switch_mm_always_ibpb))
1268                         return ", IBPB: always-on";
1269                 if (static_key_enabled(&switch_mm_cond_ibpb))
1270                         return ", IBPB: conditional";
1271                 return ", IBPB: disabled";
1272         }
1273         return "";
1274 }
1275
1276 static ssize_t cpu_show_common(struct device *dev, struct device_attribute *attr,
1277                                char *buf, unsigned int bug)
1278 {
1279         if (!boot_cpu_has_bug(bug))
1280                 return sprintf(buf, "Not affected\n");
1281
1282         switch (bug) {
1283         case X86_BUG_CPU_MELTDOWN:
1284                 if (boot_cpu_has(X86_FEATURE_PTI))
1285                         return sprintf(buf, "Mitigation: PTI\n");
1286
1287                 if (hypervisor_is_type(X86_HYPER_XEN_PV))
1288                         return sprintf(buf, "Unknown (XEN PV detected, hypervisor mitigation required)\n");
1289
1290                 break;
1291
1292         case X86_BUG_SPECTRE_V1:
1293                 return sprintf(buf, "Mitigation: __user pointer sanitization\n");
1294
1295         case X86_BUG_SPECTRE_V2:
1296                 return sprintf(buf, "%s%s%s%s%s%s\n", spectre_v2_strings[spectre_v2_enabled],
1297                                ibpb_state(),
1298                                boot_cpu_has(X86_FEATURE_USE_IBRS_FW) ? ", IBRS_FW" : "",
1299                                stibp_state(),
1300                                boot_cpu_has(X86_FEATURE_RSB_CTXSW) ? ", RSB filling" : "",
1301                                spectre_v2_module_string());
1302
1303         case X86_BUG_SPEC_STORE_BYPASS:
1304                 return sprintf(buf, "%s\n", ssb_strings[ssb_mode]);
1305
1306         case X86_BUG_L1TF:
1307                 if (boot_cpu_has(X86_FEATURE_L1TF_PTEINV))
1308                         return l1tf_show_state(buf);
1309                 break;
1310
1311         case X86_BUG_MDS:
1312                 return mds_show_state(buf);
1313
1314         default:
1315                 break;
1316         }
1317
1318         return sprintf(buf, "Vulnerable\n");
1319 }
1320
1321 ssize_t cpu_show_meltdown(struct device *dev, struct device_attribute *attr, char *buf)
1322 {
1323         return cpu_show_common(dev, attr, buf, X86_BUG_CPU_MELTDOWN);
1324 }
1325
1326 ssize_t cpu_show_spectre_v1(struct device *dev, struct device_attribute *attr, char *buf)
1327 {
1328         return cpu_show_common(dev, attr, buf, X86_BUG_SPECTRE_V1);
1329 }
1330
1331 ssize_t cpu_show_spectre_v2(struct device *dev, struct device_attribute *attr, char *buf)
1332 {
1333         return cpu_show_common(dev, attr, buf, X86_BUG_SPECTRE_V2);
1334 }
1335
1336 ssize_t cpu_show_spec_store_bypass(struct device *dev, struct device_attribute *attr, char *buf)
1337 {
1338         return cpu_show_common(dev, attr, buf, X86_BUG_SPEC_STORE_BYPASS);
1339 }
1340
1341 ssize_t cpu_show_l1tf(struct device *dev, struct device_attribute *attr, char *buf)
1342 {
1343         return cpu_show_common(dev, attr, buf, X86_BUG_L1TF);
1344 }
1345
1346 ssize_t cpu_show_mds(struct device *dev, struct device_attribute *attr, char *buf)
1347 {
1348         return cpu_show_common(dev, attr, buf, X86_BUG_MDS);
1349 }
1350 #endif