1// SPDX-License-Identifier: GPL-2.0-only
   2#include <linux/init.h>
   3
   4#include <linux/mm.h>
   5#include <linux/spinlock.h>
   6#include <linux/smp.h>
   7#include <linux/interrupt.h>
   8#include <linux/export.h>
   9#include <linux/cpu.h>
  10#include <linux/debugfs.h>
  11#include <linux/sched/smt.h>
  12#include <linux/task_work.h>
  13#include <linux/mmu_notifier.h>
  14
  15#include <asm/tlbflush.h>
  16#include <asm/mmu_context.h>
  17#include <asm/nospec-branch.h>
  18#include <asm/cache.h>
  19#include <asm/cacheflush.h>
  20#include <asm/apic.h>
  21#include <asm/perf_event.h>
  22
  23#include "mm_internal.h"
  24
  25#ifdef CONFIG_PARAVIRT
  26# define STATIC_NOPV
  27#else
  28# define STATIC_NOPV			static
  29# define __flush_tlb_local		native_flush_tlb_local
  30# define __flush_tlb_global		native_flush_tlb_global
  31# define __flush_tlb_one_user(addr)	native_flush_tlb_one_user(addr)
  32# define __flush_tlb_multi(msk, info)	native_flush_tlb_multi(msk, info)
  33#endif
  34
  35/*
  36 *	TLB flushing, formerly SMP-only
  37 *		c/o Linus Torvalds.
  38 *
  39 *	These mean you can really definitely utterly forget about
  40 *	writing to user space from interrupts. (Its not allowed anyway).
  41 *
  42 *	Optimizations Manfred Spraul <manfred@colorfullife.com>
  43 *
  44 *	More scalable flush, from Andi Kleen
  45 *
  46 *	Implement flush IPI by CALL_FUNCTION_VECTOR, Alex Shi
  47 */
  48
  49/*
  50 * Bits to mangle the TIF_SPEC_* state into the mm pointer which is
  51 * stored in cpu_tlb_state.last_user_mm_spec.
  52 */
  53#define LAST_USER_MM_IBPB	0x1UL
  54#define LAST_USER_MM_L1D_FLUSH	0x2UL
  55#define LAST_USER_MM_SPEC_MASK	(LAST_USER_MM_IBPB | LAST_USER_MM_L1D_FLUSH)
  56
  57/* Bits to set when tlbstate and flush is (re)initialized */
  58#define LAST_USER_MM_INIT	LAST_USER_MM_IBPB
  59
  60/*
  61 * The x86 feature is called PCID (Process Context IDentifier). It is similar
  62 * to what is traditionally called ASID on the RISC processors.
  63 *
  64 * We don't use the traditional ASID implementation, where each process/mm gets
  65 * its own ASID and flush/restart when we run out of ASID space.
  66 *
  67 * Instead we have a small per-cpu array of ASIDs and cache the last few mm's
  68 * that came by on this CPU, allowing cheaper switch_mm between processes on
  69 * this CPU.
  70 *
  71 * We end up with different spaces for different things. To avoid confusion we
  72 * use different names for each of them:
  73 *
  74 * ASID  - [0, TLB_NR_DYN_ASIDS-1]
  75 *         the canonical identifier for an mm
  76 *
  77 * kPCID - [1, TLB_NR_DYN_ASIDS]
  78 *         the value we write into the PCID part of CR3; corresponds to the
  79 *         ASID+1, because PCID 0 is special.
  80 *
  81 * uPCID - [2048 + 1, 2048 + TLB_NR_DYN_ASIDS]
  82 *         for KPTI each mm has two address spaces and thus needs two
  83 *         PCID values, but we can still do with a single ASID denomination
  84 *         for each mm. Corresponds to kPCID + 2048.
  85 *
  86 */
  87
  88/* There are 12 bits of space for ASIDS in CR3 */
  89#define CR3_HW_ASID_BITS		12
  90
  91/*
  92 * When enabled, PAGE_TABLE_ISOLATION consumes a single bit for
  93 * user/kernel switches
  94 */
  95#ifdef CONFIG_PAGE_TABLE_ISOLATION
  96# define PTI_CONSUMED_PCID_BITS	1
  97#else
  98# define PTI_CONSUMED_PCID_BITS	0
  99#endif
 100
 101#define CR3_AVAIL_PCID_BITS (X86_CR3_PCID_BITS - PTI_CONSUMED_PCID_BITS)
 102
 103/*
 104 * ASIDs are zero-based: 0->MAX_AVAIL_ASID are valid.  -1 below to account
 105 * for them being zero-based.  Another -1 is because PCID 0 is reserved for
 106 * use by non-PCID-aware users.
 107 */
 108#define MAX_ASID_AVAILABLE ((1 << CR3_AVAIL_PCID_BITS) - 2)
 109
 110/*
 111 * Given @asid, compute kPCID
 112 */
 113static inline u16 kern_pcid(u16 asid)
 114{
 115	VM_WARN_ON_ONCE(asid > MAX_ASID_AVAILABLE);
 116
 117#ifdef CONFIG_PAGE_TABLE_ISOLATION
 118	/*
 119	 * Make sure that the dynamic ASID space does not conflict with the
 120	 * bit we are using to switch between user and kernel ASIDs.
 121	 */
 122	BUILD_BUG_ON(TLB_NR_DYN_ASIDS >= (1 << X86_CR3_PTI_PCID_USER_BIT));
 123
 124	/*
 125	 * The ASID being passed in here should have respected the
 126	 * MAX_ASID_AVAILABLE and thus never have the switch bit set.
 127	 */
 128	VM_WARN_ON_ONCE(asid & (1 << X86_CR3_PTI_PCID_USER_BIT));
 129#endif
 130	/*
 131	 * The dynamically-assigned ASIDs that get passed in are small
 132	 * (<TLB_NR_DYN_ASIDS).  They never have the high switch bit set,
 133	 * so do not bother to clear it.
 134	 *
 135	 * If PCID is on, ASID-aware code paths put the ASID+1 into the
 136	 * PCID bits.  This serves two purposes.  It prevents a nasty
 137	 * situation in which PCID-unaware code saves CR3, loads some other
 138	 * value (with PCID == 0), and then restores CR3, thus corrupting
 139	 * the TLB for ASID 0 if the saved ASID was nonzero.  It also means
 140	 * that any bugs involving loading a PCID-enabled CR3 with
 141	 * CR4.PCIDE off will trigger deterministically.
 142	 */
 143	return asid + 1;
 144}
 145
 146/*
 147 * Given @asid, compute uPCID
 148 */
 149static inline u16 user_pcid(u16 asid)
 150{
 151	u16 ret = kern_pcid(asid);
 152#ifdef CONFIG_PAGE_TABLE_ISOLATION
 153	ret |= 1 << X86_CR3_PTI_PCID_USER_BIT;
 154#endif
 155	return ret;
 156}
 157
 158static inline unsigned long build_cr3(pgd_t *pgd, u16 asid, unsigned long lam)
 159{
 160	unsigned long cr3 = __sme_pa(pgd) | lam;
 161
 162	if (static_cpu_has(X86_FEATURE_PCID)) {
 163		VM_WARN_ON_ONCE(asid > MAX_ASID_AVAILABLE);
 164		cr3 |= kern_pcid(asid);
 165	} else {
 166		VM_WARN_ON_ONCE(asid != 0);
 
 167	}
 168
 169	return cr3;
 170}
 171
 172static inline unsigned long build_cr3_noflush(pgd_t *pgd, u16 asid,
 173					      unsigned long lam)
 174{
 
 175	/*
 176	 * Use boot_cpu_has() instead of this_cpu_has() as this function
 177	 * might be called during early boot. This should work even after
 178	 * boot because all CPU's the have same capabilities:
 179	 */
 180	VM_WARN_ON_ONCE(!boot_cpu_has(X86_FEATURE_PCID));
 181	return build_cr3(pgd, asid, lam) | CR3_NOFLUSH;
 182}
 183
 184/*
 185 * We get here when we do something requiring a TLB invalidation
 186 * but could not go invalidate all of the contexts.  We do the
 187 * necessary invalidation by clearing out the 'ctx_id' which
 188 * forces a TLB flush when the context is loaded.
 189 */
 190static void clear_asid_other(void)
 191{
 192	u16 asid;
 193
 194	/*
 195	 * This is only expected to be set if we have disabled
 196	 * kernel _PAGE_GLOBAL pages.
 197	 */
 198	if (!static_cpu_has(X86_FEATURE_PTI)) {
 199		WARN_ON_ONCE(1);
 200		return;
 201	}
 202
 203	for (asid = 0; asid < TLB_NR_DYN_ASIDS; asid++) {
 204		/* Do not need to flush the current asid */
 205		if (asid == this_cpu_read(cpu_tlbstate.loaded_mm_asid))
 206			continue;
 207		/*
 208		 * Make sure the next time we go to switch to
 209		 * this asid, we do a flush:
 210		 */
 211		this_cpu_write(cpu_tlbstate.ctxs[asid].ctx_id, 0);
 212	}
 213	this_cpu_write(cpu_tlbstate.invalidate_other, false);
 214}
 215
 216atomic64_t last_mm_ctx_id = ATOMIC64_INIT(1);
 217
 218
 219static void choose_new_asid(struct mm_struct *next, u64 next_tlb_gen,
 220			    u16 *new_asid, bool *need_flush)
 221{
 222	u16 asid;
 223
 224	if (!static_cpu_has(X86_FEATURE_PCID)) {
 225		*new_asid = 0;
 226		*need_flush = true;
 227		return;
 228	}
 229
 230	if (this_cpu_read(cpu_tlbstate.invalidate_other))
 231		clear_asid_other();
 232
 233	for (asid = 0; asid < TLB_NR_DYN_ASIDS; asid++) {
 234		if (this_cpu_read(cpu_tlbstate.ctxs[asid].ctx_id) !=
 235		    next->context.ctx_id)
 236			continue;
 237
 238		*new_asid = asid;
 239		*need_flush = (this_cpu_read(cpu_tlbstate.ctxs[asid].tlb_gen) <
 240			       next_tlb_gen);
 241		return;
 242	}
 243
 244	/*
 245	 * We don't currently own an ASID slot on this CPU.
 246	 * Allocate a slot.
 247	 */
 248	*new_asid = this_cpu_add_return(cpu_tlbstate.next_asid, 1) - 1;
 249	if (*new_asid >= TLB_NR_DYN_ASIDS) {
 250		*new_asid = 0;
 251		this_cpu_write(cpu_tlbstate.next_asid, 1);
 252	}
 253	*need_flush = true;
 254}
 255
 256/*
 257 * Given an ASID, flush the corresponding user ASID.  We can delay this
 258 * until the next time we switch to it.
 259 *
 260 * See SWITCH_TO_USER_CR3.
 261 */
 262static inline void invalidate_user_asid(u16 asid)
 263{
 264	/* There is no user ASID if address space separation is off */
 265	if (!IS_ENABLED(CONFIG_PAGE_TABLE_ISOLATION))
 266		return;
 267
 268	/*
 269	 * We only have a single ASID if PCID is off and the CR3
 270	 * write will have flushed it.
 271	 */
 272	if (!cpu_feature_enabled(X86_FEATURE_PCID))
 273		return;
 274
 275	if (!static_cpu_has(X86_FEATURE_PTI))
 276		return;
 277
 278	__set_bit(kern_pcid(asid),
 279		  (unsigned long *)this_cpu_ptr(&cpu_tlbstate.user_pcid_flush_mask));
 280}
 281
 282static void load_new_mm_cr3(pgd_t *pgdir, u16 new_asid, unsigned long lam,
 283			    bool need_flush)
 284{
 285	unsigned long new_mm_cr3;
 286
 287	if (need_flush) {
 288		invalidate_user_asid(new_asid);
 289		new_mm_cr3 = build_cr3(pgdir, new_asid, lam);
 290	} else {
 291		new_mm_cr3 = build_cr3_noflush(pgdir, new_asid, lam);
 292	}
 293
 294	/*
 295	 * Caution: many callers of this function expect
 296	 * that load_cr3() is serializing and orders TLB
 297	 * fills with respect to the mm_cpumask writes.
 298	 */
 299	write_cr3(new_mm_cr3);
 300}
 301
 302void leave_mm(int cpu)
 303{
 304	struct mm_struct *loaded_mm = this_cpu_read(cpu_tlbstate.loaded_mm);
 305
 306	/*
 307	 * It's plausible that we're in lazy TLB mode while our mm is init_mm.
 308	 * If so, our callers still expect us to flush the TLB, but there
 309	 * aren't any user TLB entries in init_mm to worry about.
 310	 *
 311	 * This needs to happen before any other sanity checks due to
 312	 * intel_idle's shenanigans.
 313	 */
 314	if (loaded_mm == &init_mm)
 315		return;
 316
 317	/* Warn if we're not lazy. */
 318	WARN_ON(!this_cpu_read(cpu_tlbstate_shared.is_lazy));
 319
 320	switch_mm(NULL, &init_mm, NULL);
 321}
 322EXPORT_SYMBOL_GPL(leave_mm);
 323
 324void switch_mm(struct mm_struct *prev, struct mm_struct *next,
 325	       struct task_struct *tsk)
 326{
 327	unsigned long flags;
 328
 329	local_irq_save(flags);
 330	switch_mm_irqs_off(prev, next, tsk);
 331	local_irq_restore(flags);
 332}
 333
 334/*
 335 * Invoked from return to user/guest by a task that opted-in to L1D
 336 * flushing but ended up running on an SMT enabled core due to wrong
 337 * affinity settings or CPU hotplug. This is part of the paranoid L1D flush
 338 * contract which this task requested.
 339 */
 340static void l1d_flush_force_sigbus(struct callback_head *ch)
 341{
 342	force_sig(SIGBUS);
 343}
 344
 345static void l1d_flush_evaluate(unsigned long prev_mm, unsigned long next_mm,
 346				struct task_struct *next)
 347{
 348	/* Flush L1D if the outgoing task requests it */
 349	if (prev_mm & LAST_USER_MM_L1D_FLUSH)
 350		wrmsrl(MSR_IA32_FLUSH_CMD, L1D_FLUSH);
 351
 352	/* Check whether the incoming task opted in for L1D flush */
 353	if (likely(!(next_mm & LAST_USER_MM_L1D_FLUSH)))
 354		return;
 355
 356	/*
 357	 * Validate that it is not running on an SMT sibling as this would
 358	 * make the exercise pointless because the siblings share L1D. If
 359	 * it runs on a SMT sibling, notify it with SIGBUS on return to
 360	 * user/guest
 361	 */
 362	if (this_cpu_read(cpu_info.smt_active)) {
 363		clear_ti_thread_flag(&next->thread_info, TIF_SPEC_L1D_FLUSH);
 364		next->l1d_flush_kill.func = l1d_flush_force_sigbus;
 365		task_work_add(next, &next->l1d_flush_kill, TWA_RESUME);
 366	}
 367}
 368
 369static unsigned long mm_mangle_tif_spec_bits(struct task_struct *next)
 370{
 371	unsigned long next_tif = read_task_thread_flags(next);
 372	unsigned long spec_bits = (next_tif >> TIF_SPEC_IB) & LAST_USER_MM_SPEC_MASK;
 373
 374	/*
 375	 * Ensure that the bit shift above works as expected and the two flags
 376	 * end up in bit 0 and 1.
 377	 */
 378	BUILD_BUG_ON(TIF_SPEC_L1D_FLUSH != TIF_SPEC_IB + 1);
 379
 380	return (unsigned long)next->mm | spec_bits;
 381}
 382
 383static void cond_mitigation(struct task_struct *next)
 384{
 385	unsigned long prev_mm, next_mm;
 386
 387	if (!next || !next->mm)
 388		return;
 389
 390	next_mm = mm_mangle_tif_spec_bits(next);
 391	prev_mm = this_cpu_read(cpu_tlbstate.last_user_mm_spec);
 392
 393	/*
 394	 * Avoid user/user BTB poisoning by flushing the branch predictor
 395	 * when switching between processes. This stops one process from
 396	 * doing Spectre-v2 attacks on another.
 397	 *
 398	 * Both, the conditional and the always IBPB mode use the mm
 399	 * pointer to avoid the IBPB when switching between tasks of the
 400	 * same process. Using the mm pointer instead of mm->context.ctx_id
 401	 * opens a hypothetical hole vs. mm_struct reuse, which is more or
 402	 * less impossible to control by an attacker. Aside of that it
 403	 * would only affect the first schedule so the theoretically
 404	 * exposed data is not really interesting.
 405	 */
 406	if (static_branch_likely(&switch_mm_cond_ibpb)) {
 
 
 407		/*
 408		 * This is a bit more complex than the always mode because
 409		 * it has to handle two cases:
 410		 *
 411		 * 1) Switch from a user space task (potential attacker)
 412		 *    which has TIF_SPEC_IB set to a user space task
 413		 *    (potential victim) which has TIF_SPEC_IB not set.
 414		 *
 415		 * 2) Switch from a user space task (potential attacker)
 416		 *    which has TIF_SPEC_IB not set to a user space task
 417		 *    (potential victim) which has TIF_SPEC_IB set.
 418		 *
 419		 * This could be done by unconditionally issuing IBPB when
 420		 * a task which has TIF_SPEC_IB set is either scheduled in
 421		 * or out. Though that results in two flushes when:
 422		 *
 423		 * - the same user space task is scheduled out and later
 424		 *   scheduled in again and only a kernel thread ran in
 425		 *   between.
 426		 *
 427		 * - a user space task belonging to the same process is
 428		 *   scheduled in after a kernel thread ran in between
 429		 *
 430		 * - a user space task belonging to the same process is
 431		 *   scheduled in immediately.
 432		 *
 433		 * Optimize this with reasonably small overhead for the
 434		 * above cases. Mangle the TIF_SPEC_IB bit into the mm
 435		 * pointer of the incoming task which is stored in
 436		 * cpu_tlbstate.last_user_mm_spec for comparison.
 437		 *
 
 
 
 
 438		 * Issue IBPB only if the mm's are different and one or
 439		 * both have the IBPB bit set.
 440		 */
 441		if (next_mm != prev_mm &&
 442		    (next_mm | prev_mm) & LAST_USER_MM_IBPB)
 443			indirect_branch_prediction_barrier();
 
 
 444	}
 445
 446	if (static_branch_unlikely(&switch_mm_always_ibpb)) {
 447		/*
 448		 * Only flush when switching to a user space task with a
 449		 * different context than the user space task which ran
 450		 * last on this CPU.
 451		 */
 452		if ((prev_mm & ~LAST_USER_MM_SPEC_MASK) !=
 453					(unsigned long)next->mm)
 454			indirect_branch_prediction_barrier();
 
 
 455	}
 456
 457	if (static_branch_unlikely(&switch_mm_cond_l1d_flush)) {
 458		/*
 459		 * Flush L1D when the outgoing task requested it and/or
 460		 * check whether the incoming task requested L1D flushing
 461		 * and ended up on an SMT sibling.
 462		 */
 463		if (unlikely((prev_mm | next_mm) & LAST_USER_MM_L1D_FLUSH))
 464			l1d_flush_evaluate(prev_mm, next_mm, next);
 465	}
 466
 467	this_cpu_write(cpu_tlbstate.last_user_mm_spec, next_mm);
 468}
 469
 470#ifdef CONFIG_PERF_EVENTS
 471static inline void cr4_update_pce_mm(struct mm_struct *mm)
 472{
 473	if (static_branch_unlikely(&rdpmc_always_available_key) ||
 474	    (!static_branch_unlikely(&rdpmc_never_available_key) &&
 475	     atomic_read(&mm->context.perf_rdpmc_allowed))) {
 476		/*
 477		 * Clear the existing dirty counters to
 478		 * prevent the leak for an RDPMC task.
 479		 */
 480		perf_clear_dirty_counters();
 481		cr4_set_bits_irqsoff(X86_CR4_PCE);
 482	} else
 483		cr4_clear_bits_irqsoff(X86_CR4_PCE);
 484}
 485
 486void cr4_update_pce(void *ignored)
 487{
 488	cr4_update_pce_mm(this_cpu_read(cpu_tlbstate.loaded_mm));
 489}
 490
 491#else
 492static inline void cr4_update_pce_mm(struct mm_struct *mm) { }
 493#endif
 494
 495void switch_mm_irqs_off(struct mm_struct *prev, struct mm_struct *next,
 496			struct task_struct *tsk)
 497{
 498	struct mm_struct *real_prev = this_cpu_read(cpu_tlbstate.loaded_mm);
 499	u16 prev_asid = this_cpu_read(cpu_tlbstate.loaded_mm_asid);
 500	unsigned long new_lam = mm_lam_cr3_mask(next);
 501	bool was_lazy = this_cpu_read(cpu_tlbstate_shared.is_lazy);
 502	unsigned cpu = smp_processor_id();
 503	u64 next_tlb_gen;
 504	bool need_flush;
 505	u16 new_asid;
 506
 507	/*
 508	 * NB: The scheduler will call us with prev == next when switching
 509	 * from lazy TLB mode to normal mode if active_mm isn't changing.
 510	 * When this happens, we don't assume that CR3 (and hence
 511	 * cpu_tlbstate.loaded_mm) matches next.
 512	 *
 513	 * NB: leave_mm() calls us with prev == NULL and tsk == NULL.
 514	 */
 515
 516	/* We don't want flush_tlb_func() to run concurrently with us. */
 517	if (IS_ENABLED(CONFIG_PROVE_LOCKING))
 518		WARN_ON_ONCE(!irqs_disabled());
 519
 520	/*
 521	 * Verify that CR3 is what we think it is.  This will catch
 522	 * hypothetical buggy code that directly switches to swapper_pg_dir
 523	 * without going through leave_mm() / switch_mm_irqs_off() or that
 524	 * does something like write_cr3(read_cr3_pa()).
 525	 *
 526	 * Only do this check if CONFIG_DEBUG_VM=y because __read_cr3()
 527	 * isn't free.
 528	 */
 529#ifdef CONFIG_DEBUG_VM
 530	if (WARN_ON_ONCE(__read_cr3() != build_cr3(real_prev->pgd, prev_asid,
 531						   tlbstate_lam_cr3_mask()))) {
 532		/*
 533		 * If we were to BUG here, we'd be very likely to kill
 534		 * the system so hard that we don't see the call trace.
 535		 * Try to recover instead by ignoring the error and doing
 536		 * a global flush to minimize the chance of corruption.
 537		 *
 538		 * (This is far from being a fully correct recovery.
 539		 *  Architecturally, the CPU could prefetch something
 540		 *  back into an incorrect ASID slot and leave it there
 541		 *  to cause trouble down the road.  It's better than
 542		 *  nothing, though.)
 543		 */
 544		__flush_tlb_all();
 545	}
 546#endif
 547	if (was_lazy)
 548		this_cpu_write(cpu_tlbstate_shared.is_lazy, false);
 549
 550	/*
 551	 * The membarrier system call requires a full memory barrier and
 552	 * core serialization before returning to user-space, after
 553	 * storing to rq->curr, when changing mm.  This is because
 554	 * membarrier() sends IPIs to all CPUs that are in the target mm
 555	 * to make them issue memory barriers.  However, if another CPU
 556	 * switches to/from the target mm concurrently with
 557	 * membarrier(), it can cause that CPU not to receive an IPI
 558	 * when it really should issue a memory barrier.  Writing to CR3
 559	 * provides that full memory barrier and core serializing
 560	 * instruction.
 561	 */
 562	if (real_prev == next) {
 563		/* Not actually switching mm's */
 564		VM_WARN_ON(this_cpu_read(cpu_tlbstate.ctxs[prev_asid].ctx_id) !=
 565			   next->context.ctx_id);
 566
 567		/*
 568		 * If this races with another thread that enables lam, 'new_lam'
 569		 * might not match tlbstate_lam_cr3_mask().
 570		 */
 571
 572		/*
 573		 * Even in lazy TLB mode, the CPU should stay set in the
 574		 * mm_cpumask. The TLB shootdown code can figure out from
 575		 * cpu_tlbstate_shared.is_lazy whether or not to send an IPI.
 576		 */
 577		if (WARN_ON_ONCE(real_prev != &init_mm &&
 578				 !cpumask_test_cpu(cpu, mm_cpumask(next))))
 579			cpumask_set_cpu(cpu, mm_cpumask(next));
 580
 581		/*
 582		 * If the CPU is not in lazy TLB mode, we are just switching
 583		 * from one thread in a process to another thread in the same
 584		 * process. No TLB flush required.
 585		 */
 586		if (!was_lazy)
 587			return;
 588
 589		/*
 590		 * Read the tlb_gen to check whether a flush is needed.
 591		 * If the TLB is up to date, just use it.
 592		 * The barrier synchronizes with the tlb_gen increment in
 593		 * the TLB shootdown code.
 594		 */
 595		smp_mb();
 596		next_tlb_gen = atomic64_read(&next->context.tlb_gen);
 597		if (this_cpu_read(cpu_tlbstate.ctxs[prev_asid].tlb_gen) ==
 598				next_tlb_gen)
 599			return;
 600
 601		/*
 602		 * TLB contents went out of date while we were in lazy
 603		 * mode. Fall through to the TLB switching code below.
 604		 */
 605		new_asid = prev_asid;
 606		need_flush = true;
 607	} else {
 608		/*
 609		 * Apply process to process speculation vulnerability
 610		 * mitigations if applicable.
 
 611		 */
 612		cond_mitigation(tsk);
 613
 614		/*
 615		 * Stop remote flushes for the previous mm.
 616		 * Skip kernel threads; we never send init_mm TLB flushing IPIs,
 617		 * but the bitmap manipulation can cause cache line contention.
 618		 */
 619		if (real_prev != &init_mm) {
 620			VM_WARN_ON_ONCE(!cpumask_test_cpu(cpu,
 621						mm_cpumask(real_prev)));
 622			cpumask_clear_cpu(cpu, mm_cpumask(real_prev));
 623		}
 624
 625		/*
 626		 * Start remote flushes and then read tlb_gen.
 627		 */
 628		if (next != &init_mm)
 629			cpumask_set_cpu(cpu, mm_cpumask(next));
 630		next_tlb_gen = atomic64_read(&next->context.tlb_gen);
 631
 632		choose_new_asid(next, next_tlb_gen, &new_asid, &need_flush);
 633
 634		/* Let nmi_uaccess_okay() know that we're changing CR3. */
 635		this_cpu_write(cpu_tlbstate.loaded_mm, LOADED_MM_SWITCHING);
 636		barrier();
 637	}
 638
 639	set_tlbstate_lam_mode(next);
 640	if (need_flush) {
 641		this_cpu_write(cpu_tlbstate.ctxs[new_asid].ctx_id, next->context.ctx_id);
 642		this_cpu_write(cpu_tlbstate.ctxs[new_asid].tlb_gen, next_tlb_gen);
 643		load_new_mm_cr3(next->pgd, new_asid, new_lam, true);
 644
 645		trace_tlb_flush(TLB_FLUSH_ON_TASK_SWITCH, TLB_FLUSH_ALL);
 646	} else {
 647		/* The new ASID is already up to date. */
 648		load_new_mm_cr3(next->pgd, new_asid, new_lam, false);
 649
 650		trace_tlb_flush(TLB_FLUSH_ON_TASK_SWITCH, 0);
 651	}
 652
 653	/* Make sure we write CR3 before loaded_mm. */
 654	barrier();
 655
 656	this_cpu_write(cpu_tlbstate.loaded_mm, next);
 657	this_cpu_write(cpu_tlbstate.loaded_mm_asid, new_asid);
 658
 659	if (next != real_prev) {
 660		cr4_update_pce_mm(next);
 661		switch_ldt(real_prev, next);
 662	}
 663}
 664
 665/*
 666 * Please ignore the name of this function.  It should be called
 667 * switch_to_kernel_thread().
 668 *
 669 * enter_lazy_tlb() is a hint from the scheduler that we are entering a
 670 * kernel thread or other context without an mm.  Acceptable implementations
 671 * include doing nothing whatsoever, switching to init_mm, or various clever
 672 * lazy tricks to try to minimize TLB flushes.
 673 *
 674 * The scheduler reserves the right to call enter_lazy_tlb() several times
 675 * in a row.  It will notify us that we're going back to a real mm by
 676 * calling switch_mm_irqs_off().
 677 */
 678void enter_lazy_tlb(struct mm_struct *mm, struct task_struct *tsk)
 679{
 680	if (this_cpu_read(cpu_tlbstate.loaded_mm) == &init_mm)
 681		return;
 682
 683	this_cpu_write(cpu_tlbstate_shared.is_lazy, true);
 684}
 685
 686/*
 687 * Call this when reinitializing a CPU.  It fixes the following potential
 688 * problems:
 689 *
 690 * - The ASID changed from what cpu_tlbstate thinks it is (most likely
 691 *   because the CPU was taken down and came back up with CR3's PCID
 692 *   bits clear.  CPU hotplug can do this.
 693 *
 694 * - The TLB contains junk in slots corresponding to inactive ASIDs.
 695 *
 696 * - The CPU went so far out to lunch that it may have missed a TLB
 697 *   flush.
 698 */
 699void initialize_tlbstate_and_flush(void)
 700{
 701	int i;
 702	struct mm_struct *mm = this_cpu_read(cpu_tlbstate.loaded_mm);
 703	u64 tlb_gen = atomic64_read(&init_mm.context.tlb_gen);
 704	unsigned long cr3 = __read_cr3();
 705
 706	/* Assert that CR3 already references the right mm. */
 707	WARN_ON((cr3 & CR3_ADDR_MASK) != __pa(mm->pgd));
 708
 709	/* LAM expected to be disabled */
 710	WARN_ON(cr3 & (X86_CR3_LAM_U48 | X86_CR3_LAM_U57));
 711	WARN_ON(mm_lam_cr3_mask(mm));
 712
 713	/*
 714	 * Assert that CR4.PCIDE is set if needed.  (CR4.PCIDE initialization
 715	 * doesn't work like other CR4 bits because it can only be set from
 716	 * long mode.)
 717	 */
 718	WARN_ON(boot_cpu_has(X86_FEATURE_PCID) &&
 719		!(cr4_read_shadow() & X86_CR4_PCIDE));
 720
 721	/* Disable LAM, force ASID 0 and force a TLB flush. */
 722	write_cr3(build_cr3(mm->pgd, 0, 0));
 723
 724	/* Reinitialize tlbstate. */
 725	this_cpu_write(cpu_tlbstate.last_user_mm_spec, LAST_USER_MM_INIT);
 726	this_cpu_write(cpu_tlbstate.loaded_mm_asid, 0);
 727	this_cpu_write(cpu_tlbstate.next_asid, 1);
 728	this_cpu_write(cpu_tlbstate.ctxs[0].ctx_id, mm->context.ctx_id);
 729	this_cpu_write(cpu_tlbstate.ctxs[0].tlb_gen, tlb_gen);
 730	set_tlbstate_lam_mode(mm);
 731
 732	for (i = 1; i < TLB_NR_DYN_ASIDS; i++)
 733		this_cpu_write(cpu_tlbstate.ctxs[i].ctx_id, 0);
 734}
 735
 736/*
 737 * flush_tlb_func()'s memory ordering requirement is that any
 738 * TLB fills that happen after we flush the TLB are ordered after we
 739 * read active_mm's tlb_gen.  We don't need any explicit barriers
 740 * because all x86 flush operations are serializing and the
 741 * atomic64_read operation won't be reordered by the compiler.
 742 */
 743static void flush_tlb_func(void *info)
 
 744{
 745	/*
 746	 * We have three different tlb_gen values in here.  They are:
 747	 *
 748	 * - mm_tlb_gen:     the latest generation.
 749	 * - local_tlb_gen:  the generation that this CPU has already caught
 750	 *                   up to.
 751	 * - f->new_tlb_gen: the generation that the requester of the flush
 752	 *                   wants us to catch up to.
 753	 */
 754	const struct flush_tlb_info *f = info;
 755	struct mm_struct *loaded_mm = this_cpu_read(cpu_tlbstate.loaded_mm);
 756	u32 loaded_mm_asid = this_cpu_read(cpu_tlbstate.loaded_mm_asid);
 
 757	u64 local_tlb_gen = this_cpu_read(cpu_tlbstate.ctxs[loaded_mm_asid].tlb_gen);
 758	bool local = smp_processor_id() == f->initiating_cpu;
 759	unsigned long nr_invalidate = 0;
 760	u64 mm_tlb_gen;
 761
 762	/* This code cannot presently handle being reentered. */
 763	VM_WARN_ON(!irqs_disabled());
 764
 765	if (!local) {
 766		inc_irq_stat(irq_tlb_count);
 767		count_vm_tlb_event(NR_TLB_REMOTE_FLUSH_RECEIVED);
 768
 769		/* Can only happen on remote CPUs */
 770		if (f->mm && f->mm != loaded_mm)
 771			return;
 772	}
 773
 774	if (unlikely(loaded_mm == &init_mm))
 775		return;
 776
 777	VM_WARN_ON(this_cpu_read(cpu_tlbstate.ctxs[loaded_mm_asid].ctx_id) !=
 778		   loaded_mm->context.ctx_id);
 779
 780	if (this_cpu_read(cpu_tlbstate_shared.is_lazy)) {
 781		/*
 782		 * We're in lazy mode.  We need to at least flush our
 783		 * paging-structure cache to avoid speculatively reading
 784		 * garbage into our TLB.  Since switching to init_mm is barely
 785		 * slower than a minimal flush, just switch to init_mm.
 786		 *
 787		 * This should be rare, with native_flush_tlb_multi() skipping
 788		 * IPIs to lazy TLB mode CPUs.
 789		 */
 790		switch_mm_irqs_off(NULL, &init_mm, NULL);
 791		return;
 792	}
 793
 794	if (unlikely(f->new_tlb_gen != TLB_GENERATION_INVALID &&
 795		     f->new_tlb_gen <= local_tlb_gen)) {
 796		/*
 797		 * The TLB is already up to date in respect to f->new_tlb_gen.
 798		 * While the core might be still behind mm_tlb_gen, checking
 799		 * mm_tlb_gen unnecessarily would have negative caching effects
 800		 * so avoid it.
 801		 */
 802		return;
 803	}
 804
 805	/*
 806	 * Defer mm_tlb_gen reading as long as possible to avoid cache
 807	 * contention.
 808	 */
 809	mm_tlb_gen = atomic64_read(&loaded_mm->context.tlb_gen);
 810
 811	if (unlikely(local_tlb_gen == mm_tlb_gen)) {
 812		/*
 813		 * There's nothing to do: we're already up to date.  This can
 814		 * happen if two concurrent flushes happen -- the first flush to
 815		 * be handled can catch us all the way up, leaving no work for
 816		 * the second flush.
 817		 */
 818		goto done;
 
 819	}
 820
 821	WARN_ON_ONCE(local_tlb_gen > mm_tlb_gen);
 822	WARN_ON_ONCE(f->new_tlb_gen > mm_tlb_gen);
 823
 824	/*
 825	 * If we get to this point, we know that our TLB is out of date.
 826	 * This does not strictly imply that we need to flush (it's
 827	 * possible that f->new_tlb_gen <= local_tlb_gen), but we're
 828	 * going to need to flush in the very near future, so we might
 829	 * as well get it over with.
 830	 *
 831	 * The only question is whether to do a full or partial flush.
 832	 *
 833	 * We do a partial flush if requested and two extra conditions
 834	 * are met:
 835	 *
 836	 * 1. f->new_tlb_gen == local_tlb_gen + 1.  We have an invariant that
 837	 *    we've always done all needed flushes to catch up to
 838	 *    local_tlb_gen.  If, for example, local_tlb_gen == 2 and
 839	 *    f->new_tlb_gen == 3, then we know that the flush needed to bring
 840	 *    us up to date for tlb_gen 3 is the partial flush we're
 841	 *    processing.
 842	 *
 843	 *    As an example of why this check is needed, suppose that there
 844	 *    are two concurrent flushes.  The first is a full flush that
 845	 *    changes context.tlb_gen from 1 to 2.  The second is a partial
 846	 *    flush that changes context.tlb_gen from 2 to 3.  If they get
 847	 *    processed on this CPU in reverse order, we'll see
 848	 *     local_tlb_gen == 1, mm_tlb_gen == 3, and end != TLB_FLUSH_ALL.
 849	 *    If we were to use __flush_tlb_one_user() and set local_tlb_gen to
 850	 *    3, we'd be break the invariant: we'd update local_tlb_gen above
 851	 *    1 without the full flush that's needed for tlb_gen 2.
 852	 *
 853	 * 2. f->new_tlb_gen == mm_tlb_gen.  This is purely an optimization.
 854	 *    Partial TLB flushes are not all that much cheaper than full TLB
 855	 *    flushes, so it seems unlikely that it would be a performance win
 856	 *    to do a partial flush if that won't bring our TLB fully up to
 857	 *    date.  By doing a full flush instead, we can increase
 858	 *    local_tlb_gen all the way to mm_tlb_gen and we can probably
 859	 *    avoid another flush in the very near future.
 860	 */
 861	if (f->end != TLB_FLUSH_ALL &&
 862	    f->new_tlb_gen == local_tlb_gen + 1 &&
 863	    f->new_tlb_gen == mm_tlb_gen) {
 864		/* Partial flush */
 
 865		unsigned long addr = f->start;
 866
 867		/* Partial flush cannot have invalid generations */
 868		VM_WARN_ON(f->new_tlb_gen == TLB_GENERATION_INVALID);
 869
 870		/* Partial flush must have valid mm */
 871		VM_WARN_ON(f->mm == NULL);
 872
 873		nr_invalidate = (f->end - f->start) >> f->stride_shift;
 874
 875		while (addr < f->end) {
 876			flush_tlb_one_user(addr);
 877			addr += 1UL << f->stride_shift;
 878		}
 879		if (local)
 880			count_vm_tlb_events(NR_TLB_LOCAL_FLUSH_ONE, nr_invalidate);
 
 881	} else {
 882		/* Full flush. */
 883		nr_invalidate = TLB_FLUSH_ALL;
 884
 885		flush_tlb_local();
 886		if (local)
 887			count_vm_tlb_event(NR_TLB_LOCAL_FLUSH_ALL);
 
 888	}
 889
 890	/* Both paths above update our state to mm_tlb_gen. */
 891	this_cpu_write(cpu_tlbstate.ctxs[loaded_mm_asid].tlb_gen, mm_tlb_gen);
 
 892
 893	/* Tracing is done in a unified manner to reduce the code size */
 894done:
 895	trace_tlb_flush(!local ? TLB_REMOTE_SHOOTDOWN :
 896				(f->mm == NULL) ? TLB_LOCAL_SHOOTDOWN :
 897						  TLB_LOCAL_MM_SHOOTDOWN,
 898			nr_invalidate);
 899}
 900
 901static bool tlb_is_not_lazy(int cpu, void *data)
 902{
 903	return !per_cpu(cpu_tlbstate_shared.is_lazy, cpu);
 
 
 
 
 
 
 
 
 904}
 905
 906DEFINE_PER_CPU_SHARED_ALIGNED(struct tlb_state_shared, cpu_tlbstate_shared);
 907EXPORT_PER_CPU_SYMBOL(cpu_tlbstate_shared);
 
 
 908
 909STATIC_NOPV void native_flush_tlb_multi(const struct cpumask *cpumask,
 910					 const struct flush_tlb_info *info)
 911{
 912	/*
 913	 * Do accounting and tracing. Note that there are (and have always been)
 914	 * cases in which a remote TLB flush will be traced, but eventually
 915	 * would not happen.
 916	 */
 917	count_vm_tlb_event(NR_TLB_REMOTE_FLUSH);
 918	if (info->end == TLB_FLUSH_ALL)
 919		trace_tlb_flush(TLB_REMOTE_SEND_IPI, TLB_FLUSH_ALL);
 920	else
 921		trace_tlb_flush(TLB_REMOTE_SEND_IPI,
 922				(info->end - info->start) >> PAGE_SHIFT);
 923
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 924	/*
 925	 * If no page tables were freed, we can skip sending IPIs to
 926	 * CPUs in lazy TLB mode. They will flush the CPU themselves
 927	 * at the next context switch.
 928	 *
 929	 * However, if page tables are getting freed, we need to send the
 930	 * IPI everywhere, to prevent CPUs in lazy TLB mode from tripping
 931	 * up on the new contents of what used to be page tables, while
 932	 * doing a speculative memory access.
 933	 */
 934	if (info->freed_tables)
 935		on_each_cpu_mask(cpumask, flush_tlb_func, (void *)info, true);
 
 936	else
 937		on_each_cpu_cond_mask(tlb_is_not_lazy, flush_tlb_func,
 938				(void *)info, 1, cpumask);
 939}
 940
 941void flush_tlb_multi(const struct cpumask *cpumask,
 942		      const struct flush_tlb_info *info)
 943{
 944	__flush_tlb_multi(cpumask, info);
 945}
 946
 947/*
 948 * See Documentation/arch/x86/tlb.rst for details.  We choose 33
 949 * because it is large enough to cover the vast majority (at
 950 * least 95%) of allocations, and is small enough that we are
 951 * confident it will not cause too much overhead.  Each single
 952 * flush is about 100 ns, so this caps the maximum overhead at
 953 * _about_ 3,000 ns.
 954 *
 955 * This is in units of pages.
 956 */
 957unsigned long tlb_single_page_flush_ceiling __read_mostly = 33;
 958
 959static DEFINE_PER_CPU_SHARED_ALIGNED(struct flush_tlb_info, flush_tlb_info);
 960
 961#ifdef CONFIG_DEBUG_VM
 962static DEFINE_PER_CPU(unsigned int, flush_tlb_info_idx);
 963#endif
 964
 965static struct flush_tlb_info *get_flush_tlb_info(struct mm_struct *mm,
 966			unsigned long start, unsigned long end,
 967			unsigned int stride_shift, bool freed_tables,
 968			u64 new_tlb_gen)
 969{
 970	struct flush_tlb_info *info = this_cpu_ptr(&flush_tlb_info);
 971
 972#ifdef CONFIG_DEBUG_VM
 973	/*
 974	 * Ensure that the following code is non-reentrant and flush_tlb_info
 975	 * is not overwritten. This means no TLB flushing is initiated by
 976	 * interrupt handlers and machine-check exception handlers.
 977	 */
 978	BUG_ON(this_cpu_inc_return(flush_tlb_info_idx) != 1);
 979#endif
 980
 981	info->start		= start;
 982	info->end		= end;
 983	info->mm		= mm;
 984	info->stride_shift	= stride_shift;
 985	info->freed_tables	= freed_tables;
 986	info->new_tlb_gen	= new_tlb_gen;
 987	info->initiating_cpu	= smp_processor_id();
 988
 989	return info;
 990}
 991
 992static void put_flush_tlb_info(void)
 993{
 994#ifdef CONFIG_DEBUG_VM
 995	/* Complete reentrancy prevention checks */
 996	barrier();
 997	this_cpu_dec(flush_tlb_info_idx);
 998#endif
 999}
1000
1001void flush_tlb_mm_range(struct mm_struct *mm, unsigned long start,
1002				unsigned long end, unsigned int stride_shift,
1003				bool freed_tables)
1004{
1005	struct flush_tlb_info *info;
1006	u64 new_tlb_gen;
1007	int cpu;
1008
1009	cpu = get_cpu();
1010
1011	/* Should we flush just the requested range? */
1012	if ((end == TLB_FLUSH_ALL) ||
1013	    ((end - start) >> stride_shift) > tlb_single_page_flush_ceiling) {
1014		start = 0;
1015		end = TLB_FLUSH_ALL;
1016	}
1017
1018	/* This is also a barrier that synchronizes with switch_mm(). */
1019	new_tlb_gen = inc_mm_tlb_gen(mm);
1020
1021	info = get_flush_tlb_info(mm, start, end, stride_shift, freed_tables,
1022				  new_tlb_gen);
1023
1024	/*
1025	 * flush_tlb_multi() is not optimized for the common case in which only
1026	 * a local TLB flush is needed. Optimize this use-case by calling
1027	 * flush_tlb_func_local() directly in this case.
1028	 */
1029	if (cpumask_any_but(mm_cpumask(mm), cpu) < nr_cpu_ids) {
1030		flush_tlb_multi(mm_cpumask(mm), info);
1031	} else if (mm == this_cpu_read(cpu_tlbstate.loaded_mm)) {
1032		lockdep_assert_irqs_enabled();
1033		local_irq_disable();
1034		flush_tlb_func(info);
1035		local_irq_enable();
1036	}
1037
 
 
 
1038	put_flush_tlb_info();
1039	put_cpu();
1040	mmu_notifier_arch_invalidate_secondary_tlbs(mm, start, end);
1041}
1042
1043
1044static void do_flush_tlb_all(void *info)
1045{
1046	count_vm_tlb_event(NR_TLB_REMOTE_FLUSH_RECEIVED);
1047	__flush_tlb_all();
1048}
1049
1050void flush_tlb_all(void)
1051{
1052	count_vm_tlb_event(NR_TLB_REMOTE_FLUSH);
1053	on_each_cpu(do_flush_tlb_all, NULL, 1);
1054}
1055
1056static void do_kernel_range_flush(void *info)
1057{
1058	struct flush_tlb_info *f = info;
1059	unsigned long addr;
1060
1061	/* flush range by one by one 'invlpg' */
1062	for (addr = f->start; addr < f->end; addr += PAGE_SIZE)
1063		flush_tlb_one_kernel(addr);
1064}
1065
1066void flush_tlb_kernel_range(unsigned long start, unsigned long end)
1067{
1068	/* Balance as user space task's flush, a bit conservative */
1069	if (end == TLB_FLUSH_ALL ||
1070	    (end - start) > tlb_single_page_flush_ceiling << PAGE_SHIFT) {
1071		on_each_cpu(do_flush_tlb_all, NULL, 1);
1072	} else {
1073		struct flush_tlb_info *info;
1074
1075		preempt_disable();
1076		info = get_flush_tlb_info(NULL, start, end, 0, false,
1077					  TLB_GENERATION_INVALID);
1078
1079		on_each_cpu(do_kernel_range_flush, info, 1);
1080
1081		put_flush_tlb_info();
1082		preempt_enable();
1083	}
1084}
1085
1086/*
1087 * This can be used from process context to figure out what the value of
1088 * CR3 is without needing to do a (slow) __read_cr3().
1089 *
1090 * It's intended to be used for code like KVM that sneakily changes CR3
1091 * and needs to restore it.  It needs to be used very carefully.
1092 */
1093unsigned long __get_current_cr3_fast(void)
1094{
1095	unsigned long cr3 =
1096		build_cr3(this_cpu_read(cpu_tlbstate.loaded_mm)->pgd,
1097			  this_cpu_read(cpu_tlbstate.loaded_mm_asid),
1098			  tlbstate_lam_cr3_mask());
1099
1100	/* For now, be very restrictive about when this can be called. */
1101	VM_WARN_ON(in_nmi() || preemptible());
1102
1103	VM_BUG_ON(cr3 != __read_cr3());
1104	return cr3;
1105}
1106EXPORT_SYMBOL_GPL(__get_current_cr3_fast);
1107
1108/*
1109 * Flush one page in the kernel mapping
1110 */
1111void flush_tlb_one_kernel(unsigned long addr)
1112{
1113	count_vm_tlb_event(NR_TLB_LOCAL_FLUSH_ONE);
1114
1115	/*
1116	 * If PTI is off, then __flush_tlb_one_user() is just INVLPG or its
1117	 * paravirt equivalent.  Even with PCID, this is sufficient: we only
1118	 * use PCID if we also use global PTEs for the kernel mapping, and
1119	 * INVLPG flushes global translations across all address spaces.
1120	 *
1121	 * If PTI is on, then the kernel is mapped with non-global PTEs, and
1122	 * __flush_tlb_one_user() will flush the given address for the current
1123	 * kernel address space and for its usermode counterpart, but it does
1124	 * not flush it for other address spaces.
1125	 */
1126	flush_tlb_one_user(addr);
1127
1128	if (!static_cpu_has(X86_FEATURE_PTI))
1129		return;
1130
1131	/*
1132	 * See above.  We need to propagate the flush to all other address
1133	 * spaces.  In principle, we only need to propagate it to kernelmode
1134	 * address spaces, but the extra bookkeeping we would need is not
1135	 * worth it.
1136	 */
1137	this_cpu_write(cpu_tlbstate.invalidate_other, true);
1138}
1139
1140/*
1141 * Flush one page in the user mapping
1142 */
1143STATIC_NOPV void native_flush_tlb_one_user(unsigned long addr)
1144{
1145	u32 loaded_mm_asid;
1146	bool cpu_pcide;
1147
1148	/* Flush 'addr' from the kernel PCID: */
1149	asm volatile("invlpg (%0)" ::"r" (addr) : "memory");
1150
1151	/* If PTI is off there is no user PCID and nothing to flush. */
1152	if (!static_cpu_has(X86_FEATURE_PTI))
1153		return;
1154
1155	loaded_mm_asid = this_cpu_read(cpu_tlbstate.loaded_mm_asid);
1156	cpu_pcide      = this_cpu_read(cpu_tlbstate.cr4) & X86_CR4_PCIDE;
1157
1158	/*
1159	 * invpcid_flush_one(pcid>0) will #GP if CR4.PCIDE==0.  Check
1160	 * 'cpu_pcide' to ensure that *this* CPU will not trigger those
1161	 * #GP's even if called before CR4.PCIDE has been initialized.
1162	 */
1163	if (boot_cpu_has(X86_FEATURE_INVPCID) && cpu_pcide)
1164		invpcid_flush_one(user_pcid(loaded_mm_asid), addr);
1165	else
1166		invalidate_user_asid(loaded_mm_asid);
 
 
1167}
1168
1169void flush_tlb_one_user(unsigned long addr)
1170{
1171	__flush_tlb_one_user(addr);
1172}
1173
1174/*
1175 * Flush everything
1176 */
1177STATIC_NOPV void native_flush_tlb_global(void)
1178{
1179	unsigned long flags;
1180
1181	if (static_cpu_has(X86_FEATURE_INVPCID)) {
1182		/*
1183		 * Using INVPCID is considerably faster than a pair of writes
1184		 * to CR4 sandwiched inside an IRQ flag save/restore.
1185		 *
1186		 * Note, this works with CR4.PCIDE=0 or 1.
1187		 */
1188		invpcid_flush_all();
1189		return;
1190	}
1191
1192	/*
1193	 * Read-modify-write to CR4 - protect it from preemption and
1194	 * from interrupts. (Use the raw variant because this code can
1195	 * be called from deep inside debugging code.)
1196	 */
1197	raw_local_irq_save(flags);
1198
1199	__native_tlb_flush_global(this_cpu_read(cpu_tlbstate.cr4));
 
 
 
 
1200
1201	raw_local_irq_restore(flags);
1202}
1203
1204/*
1205 * Flush the entire current user mapping
1206 */
1207STATIC_NOPV void native_flush_tlb_local(void)
1208{
1209	/*
1210	 * Preemption or interrupts must be disabled to protect the access
1211	 * to the per CPU variable and to prevent being preempted between
1212	 * read_cr3() and write_cr3().
1213	 */
1214	WARN_ON_ONCE(preemptible());
1215
1216	invalidate_user_asid(this_cpu_read(cpu_tlbstate.loaded_mm_asid));
1217
1218	/* If current->mm == NULL then the read_cr3() "borrows" an mm */
1219	native_write_cr3(__native_read_cr3());
1220}
1221
1222void flush_tlb_local(void)
1223{
1224	__flush_tlb_local();
1225}
1226
1227/*
1228 * Flush everything
1229 */
1230void __flush_tlb_all(void)
1231{
1232	/*
1233	 * This is to catch users with enabled preemption and the PGE feature
1234	 * and don't trigger the warning in __native_flush_tlb().
1235	 */
1236	VM_WARN_ON_ONCE(preemptible());
1237
1238	if (cpu_feature_enabled(X86_FEATURE_PGE)) {
1239		__flush_tlb_global();
1240	} else {
1241		/*
1242		 * !PGE -> !PCID (setup_pcid()), thus every flush is total.
1243		 */
1244		flush_tlb_local();
1245	}
1246}
1247EXPORT_SYMBOL_GPL(__flush_tlb_all);
1248
 
 
 
 
 
 
 
 
 
 
 
 
1249void arch_tlbbatch_flush(struct arch_tlbflush_unmap_batch *batch)
1250{
1251	struct flush_tlb_info *info;
1252
1253	int cpu = get_cpu();
1254
1255	info = get_flush_tlb_info(NULL, 0, TLB_FLUSH_ALL, 0, false,
1256				  TLB_GENERATION_INVALID);
1257	/*
1258	 * flush_tlb_multi() is not optimized for the common case in which only
1259	 * a local TLB flush is needed. Optimize this use-case by calling
1260	 * flush_tlb_func_local() directly in this case.
1261	 */
1262	if (cpumask_any_but(&batch->cpumask, cpu) < nr_cpu_ids) {
1263		flush_tlb_multi(&batch->cpumask, info);
1264	} else if (cpumask_test_cpu(cpu, &batch->cpumask)) {
1265		lockdep_assert_irqs_enabled();
1266		local_irq_disable();
1267		flush_tlb_func(info);
1268		local_irq_enable();
1269	}
1270
 
 
 
1271	cpumask_clear(&batch->cpumask);
1272
1273	put_flush_tlb_info();
1274	put_cpu();
1275}
1276
1277/*
1278 * Blindly accessing user memory from NMI context can be dangerous
1279 * if we're in the middle of switching the current user task or
1280 * switching the loaded mm.  It can also be dangerous if we
1281 * interrupted some kernel code that was temporarily using a
1282 * different mm.
1283 */
1284bool nmi_uaccess_okay(void)
1285{
1286	struct mm_struct *loaded_mm = this_cpu_read(cpu_tlbstate.loaded_mm);
1287	struct mm_struct *current_mm = current->mm;
1288
1289	VM_WARN_ON_ONCE(!loaded_mm);
1290
1291	/*
1292	 * The condition we want to check is
1293	 * current_mm->pgd == __va(read_cr3_pa()).  This may be slow, though,
1294	 * if we're running in a VM with shadow paging, and nmi_uaccess_okay()
1295	 * is supposed to be reasonably fast.
1296	 *
1297	 * Instead, we check the almost equivalent but somewhat conservative
1298	 * condition below, and we rely on the fact that switch_mm_irqs_off()
1299	 * sets loaded_mm to LOADED_MM_SWITCHING before writing to CR3.
1300	 */
1301	if (loaded_mm != current_mm)
1302		return false;
1303
1304	VM_WARN_ON_ONCE(current_mm->pgd != __va(read_cr3_pa()));
1305
1306	return true;
1307}
1308
1309static ssize_t tlbflush_read_file(struct file *file, char __user *user_buf,
1310			     size_t count, loff_t *ppos)
1311{
1312	char buf[32];
1313	unsigned int len;
1314
1315	len = sprintf(buf, "%ld\n", tlb_single_page_flush_ceiling);
1316	return simple_read_from_buffer(user_buf, count, ppos, buf, len);
1317}
1318
1319static ssize_t tlbflush_write_file(struct file *file,
1320		 const char __user *user_buf, size_t count, loff_t *ppos)
1321{
1322	char buf[32];
1323	ssize_t len;
1324	int ceiling;
1325
1326	len = min(count, sizeof(buf) - 1);
1327	if (copy_from_user(buf, user_buf, len))
1328		return -EFAULT;
1329
1330	buf[len] = '\0';
1331	if (kstrtoint(buf, 0, &ceiling))
1332		return -EINVAL;
1333
1334	if (ceiling < 0)
1335		return -EINVAL;
1336
1337	tlb_single_page_flush_ceiling = ceiling;
1338	return count;
1339}
1340
1341static const struct file_operations fops_tlbflush = {
1342	.read = tlbflush_read_file,
1343	.write = tlbflush_write_file,
1344	.llseek = default_llseek,
1345};
1346
1347static int __init create_tlb_single_page_flush_ceiling(void)
1348{
1349	debugfs_create_file("tlb_single_page_flush_ceiling", S_IRUSR | S_IWUSR,
1350			    arch_debugfs_dir, NULL, &fops_tlbflush);
1351	return 0;
1352}
1353late_initcall(create_tlb_single_page_flush_ceiling);