treewide: refresh kmalloc_obj() conversionsgrafted

This is another run of the Coccinelle script for converting kmalloc()
family of allocations to kmalloc_obj() via the existing rules in
scripts/coccinelle/api/kmalloc_objs.cocci

This catches both the set of kmalloc() uses added since the first
kmalloc_obj() conversions in v7.0 and adds a large group missed in the
first pass due to Coccinelle not interacting well with the cleanup.h
scoped_...() family of macros[1]. I worked around this with spatch's
"--macro-file" argument to a file with all the scoped_...() macros mapped
to Coccinelle's YACFE_ITERATOR[2] as that was the closest viable control
flow indicator I could find.

Build tested allmodconfig on x86, arm64, arm, loongarch, mips, powerpc,
riscv, and s390 with no new warnings.

Link: https://lore.kernel.org/lkml/202609021314.8A9C0B8@keescook/ [1]
Link: https://github.com/coccinelle/coccinelle/blob/master/standard.h [2]
Signed-off-by: Kees Cook <kees+treewide@kernel.org>

1 files changed, 1786 insertions, 0 deletions

diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c
new file mode 100644
index 000000000..0c4da3208
--- /dev/null
+++ b/arch/x86/mm/tlb.c
@@ -0,0 +1,1786 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#include <linux/init.h>
+
+#include <linux/mm.h>
+#include <linux/spinlock.h>
+#include <linux/smp.h>
+#include <linux/interrupt.h>
+#include <linux/export.h>
+#include <linux/cpu.h>
+#include <linux/debugfs.h>
+#include <linux/sched/smt.h>
+#include <linux/task_work.h>
+#include <linux/mmu_notifier.h>
+#include <linux/mmu_context.h>
+#include <linux/kvm_types.h>
+
+#include <asm/tlbflush.h>
+#include <asm/mmu_context.h>
+#include <asm/nospec-branch.h>
+#include <asm/cache.h>
+#include <asm/cacheflush.h>
+#include <asm/apic.h>
+#include <asm/msr.h>
+#include <asm/perf_event.h>
+#include <asm/tlb.h>
+
+#include "mm_internal.h"
+
+#ifdef CONFIG_PARAVIRT
+# define STATIC_NOPV
+#else
+# define STATIC_NOPV			static
+# define __flush_tlb_local		native_flush_tlb_local
+# define __flush_tlb_global		native_flush_tlb_global
+# define __flush_tlb_one_user(addr)	native_flush_tlb_one_user(addr)
+# define __flush_tlb_multi(msk, info)	native_flush_tlb_multi(msk, info)
+#endif
+
+/*
+ *	TLB flushing, formerly SMP-only
+ *		c/o Linus Torvalds.
+ *
+ *	These mean you can really definitely utterly forget about
+ *	writing to user space from interrupts. (Its not allowed anyway).
+ *
+ *	Optimizations Manfred Spraul <manfred@colorfullife.com>
+ *
+ *	More scalable flush, from Andi Kleen
+ *
+ *	Implement flush IPI by CALL_FUNCTION_VECTOR, Alex Shi
+ */
+
+/*
+ * Bits to mangle the TIF_SPEC_* state into the mm pointer which is
+ * stored in cpu_tlb_state.last_user_mm_spec.
+ */
+#define LAST_USER_MM_IBPB	0x1UL
+#define LAST_USER_MM_L1D_FLUSH	0x2UL
+#define LAST_USER_MM_SPEC_MASK	(LAST_USER_MM_IBPB | LAST_USER_MM_L1D_FLUSH)
+
+/* Bits to set when tlbstate and flush is (re)initialized */
+#define LAST_USER_MM_INIT	LAST_USER_MM_IBPB
+
+/*
+ * The x86 feature is called PCID (Process Context IDentifier). It is similar
+ * to what is traditionally called ASID on the RISC processors.
+ *
+ * We don't use the traditional ASID implementation, where each process/mm gets
+ * its own ASID and flush/restart when we run out of ASID space.
+ *
+ * Instead we have a small per-cpu array of ASIDs and cache the last few mm's
+ * that came by on this CPU, allowing cheaper switch_mm between processes on
+ * this CPU.
+ *
+ * We end up with different spaces for different things. To avoid confusion we
+ * use different names for each of them:
+ *
+ * ASID  - [0, TLB_NR_DYN_ASIDS-1]
+ *         the canonical identifier for an mm, dynamically allocated on each CPU
+ *         [TLB_NR_DYN_ASIDS, MAX_ASID_AVAILABLE-1]
+ *         the canonical, global identifier for an mm, identical across all CPUs
+ *
+ * kPCID - [1, MAX_ASID_AVAILABLE]
+ *         the value we write into the PCID part of CR3; corresponds to the
+ *         ASID+1, because PCID 0 is special.
+ *
+ * uPCID - [2048 + 1, 2048 + MAX_ASID_AVAILABLE]
+ *         for KPTI each mm has two address spaces and thus needs two
+ *         PCID values, but we can still do with a single ASID denomination
+ *         for each mm. Corresponds to kPCID + 2048.
+ *
+ */
+
+/*
+ * When enabled, MITIGATION_PAGE_TABLE_ISOLATION consumes a single bit for
+ * user/kernel switches
+ */
+#ifdef CONFIG_MITIGATION_PAGE_TABLE_ISOLATION
+# define PTI_CONSUMED_PCID_BITS	1
+#else
+# define PTI_CONSUMED_PCID_BITS	0
+#endif
+
+#define CR3_AVAIL_PCID_BITS (X86_CR3_PCID_BITS - PTI_CONSUMED_PCID_BITS)
+
+/*
+ * ASIDs are zero-based: 0->MAX_AVAIL_ASID are valid.  -1 below to account
+ * for them being zero-based.  Another -1 is because PCID 0 is reserved for
+ * use by non-PCID-aware users.
+ */
+#define MAX_ASID_AVAILABLE ((1 << CR3_AVAIL_PCID_BITS) - 2)
+
+/*
+ * Given @asid, compute kPCID
+ */
+static inline u16 kern_pcid(u16 asid)
+{
+	VM_WARN_ON_ONCE(asid > MAX_ASID_AVAILABLE);
+
+#ifdef CONFIG_MITIGATION_PAGE_TABLE_ISOLATION
+	/*
+	 * Make sure that the dynamic ASID space does not conflict with the
+	 * bit we are using to switch between user and kernel ASIDs.
+	 */
+	BUILD_BUG_ON(TLB_NR_DYN_ASIDS >= (1 << X86_CR3_PTI_PCID_USER_BIT));
+
+	/*
+	 * The ASID being passed in here should have respected the
+	 * MAX_ASID_AVAILABLE and thus never have the switch bit set.
+	 */
+	VM_WARN_ON_ONCE(asid & (1 << X86_CR3_PTI_PCID_USER_BIT));
+#endif
+	/*
+	 * The dynamically-assigned ASIDs that get passed in are small
+	 * (<TLB_NR_DYN_ASIDS).  They never have the high switch bit set,
+	 * so do not bother to clear it.
+	 *
+	 * If PCID is on, ASID-aware code paths put the ASID+1 into the
+	 * PCID bits.  This serves two purposes.  It prevents a nasty
+	 * situation in which PCID-unaware code saves CR3, loads some other
+	 * value (with PCID == 0), and then restores CR3, thus corrupting
+	 * the TLB for ASID 0 if the saved ASID was nonzero.  It also means
+	 * that any bugs involving loading a PCID-enabled CR3 with
+	 * CR4.PCIDE off will trigger deterministically.
+	 */
+	return asid + 1;
+}
+
+/*
+ * Given @asid, compute uPCID
+ */
+static inline u16 user_pcid(u16 asid)
+{
+	u16 ret = kern_pcid(asid);
+#ifdef CONFIG_MITIGATION_PAGE_TABLE_ISOLATION
+	ret |= 1 << X86_CR3_PTI_PCID_USER_BIT;
+#endif
+	return ret;
+}
+
+static inline unsigned long build_cr3(pgd_t *pgd, u16 asid, unsigned long lam)
+{
+	unsigned long cr3 = __sme_pa(pgd) | lam;
+
+	if (cpu_feature_enabled(X86_FEATURE_PCID)) {
+		cr3 |= kern_pcid(asid);
+	} else {
+		VM_WARN_ON_ONCE(asid != 0);
+	}
+
+	return cr3;
+}
+
+static inline unsigned long build_cr3_noflush(pgd_t *pgd, u16 asid,
+					      unsigned long lam)
+{
+	/*
+	 * Use boot_cpu_has() instead of this_cpu_has() as this function
+	 * might be called during early boot. This should work even after
+	 * boot because all CPU's the have same capabilities:
+	 */
+	VM_WARN_ON_ONCE(!boot_cpu_has(X86_FEATURE_PCID));
+	return build_cr3(pgd, asid, lam) | CR3_NOFLUSH;
+}
+
+/*
+ * We get here when we do something requiring a TLB invalidation
+ * but could not go invalidate all of the contexts.  We do the
+ * necessary invalidation by clearing out the 'ctx_id' which
+ * forces a TLB flush when the context is loaded.
+ */
+static void clear_asid_other(void)
+{
+	u16 asid;
+
+	/*
+	 * This is only expected to be set if we have disabled
+	 * kernel _PAGE_GLOBAL pages.
+	 */
+	if (!cpu_feature_enabled(X86_FEATURE_PTI)) {
+		WARN_ON_ONCE(1);
+		return;
+	}
+
+	for (asid = 0; asid < TLB_NR_DYN_ASIDS; asid++) {
+		/* Do not need to flush the current asid */
+		if (asid == this_cpu_read(cpu_tlbstate.loaded_mm_asid))
+			continue;
+		/*
+		 * Make sure the next time we go to switch to
+		 * this asid, we do a flush:
+		 */
+		this_cpu_write(cpu_tlbstate.ctxs[asid].ctx_id, 0);
+	}
+	this_cpu_write(cpu_tlbstate.invalidate_other, false);
+}
+
+atomic64_t last_mm_ctx_id = ATOMIC64_INIT(1);
+
+struct new_asid {
+	unsigned int asid	: 16;
+	unsigned int need_flush : 1;
+};
+
+static struct new_asid choose_new_asid(struct mm_struct *next, u64 next_tlb_gen)
+{
+	struct new_asid ns;
+	u16 asid;
+
+	if (!cpu_feature_enabled(X86_FEATURE_PCID)) {
+		ns.asid = 0;
+		ns.need_flush = 1;
+		return ns;
+	}
+
+	/*
+	 * TLB consistency for global ASIDs is maintained with hardware assisted
+	 * remote TLB flushing. Global ASIDs are always up to date.
+	 */
+	if (cpu_feature_enabled(X86_FEATURE_INVLPGB)) {
+		u16 global_asid = mm_global_asid(next);
+
+		if (global_asid) {
+			ns.asid = global_asid;
+			ns.need_flush = 0;
+			return ns;
+		}
+	}
+
+	if (this_cpu_read(cpu_tlbstate.invalidate_other))
+		clear_asid_other();
+
+	for (asid = 0; asid < TLB_NR_DYN_ASIDS; asid++) {
+		if (this_cpu_read(cpu_tlbstate.ctxs[asid].ctx_id) !=
+		    next->context.ctx_id)
+			continue;
+
+		ns.asid = asid;
+		ns.need_flush = (this_cpu_read(cpu_tlbstate.ctxs[asid].tlb_gen) < next_tlb_gen);
+		return ns;
+	}
+
+	/*
+	 * We don't currently own an ASID slot on this CPU.
+	 * Allocate a slot.
+	 */
+	ns.asid = this_cpu_add_return(cpu_tlbstate.next_asid, 1) - 1;
+	if (ns.asid >= TLB_NR_DYN_ASIDS) {
+		ns.asid = 0;
+		this_cpu_write(cpu_tlbstate.next_asid, 1);
+	}
+	ns.need_flush = true;
+
+	return ns;
+}
+
+/*
+ * Global ASIDs are allocated for multi-threaded processes that are
+ * active on multiple CPUs simultaneously, giving each of those
+ * processes the same PCID on every CPU, for use with hardware-assisted
+ * TLB shootdown on remote CPUs, like AMD INVLPGB or Intel RAR.
+ *
+ * These global ASIDs are held for the lifetime of the process.
+ */
+static DEFINE_RAW_SPINLOCK(global_asid_lock);
+static u16 last_global_asid = MAX_ASID_AVAILABLE;
+static DECLARE_BITMAP(global_asid_used, MAX_ASID_AVAILABLE);
+static DECLARE_BITMAP(global_asid_freed, MAX_ASID_AVAILABLE);
+static int global_asid_available = MAX_ASID_AVAILABLE - TLB_NR_DYN_ASIDS - 1;
+
+/*
+ * When the search for a free ASID in the global ASID space reaches
+ * MAX_ASID_AVAILABLE, a global TLB flush guarantees that previously
+ * freed global ASIDs are safe to re-use.
+ *
+ * This way the global flush only needs to happen at ASID rollover
+ * time, and not at ASID allocation time.
+ */
+static void reset_global_asid_space(void)
+{
+	lockdep_assert_held(&global_asid_lock);
+
+	invlpgb_flush_all_nonglobals();
+
+	/*
+	 * The TLB flush above makes it safe to re-use the previously
+	 * freed global ASIDs.
+	 */
+	bitmap_andnot(global_asid_used, global_asid_used,
+			global_asid_freed, MAX_ASID_AVAILABLE);
+	bitmap_clear(global_asid_freed, 0, MAX_ASID_AVAILABLE);
+
+	/* Restart the search from the start of global ASID space. */
+	last_global_asid = TLB_NR_DYN_ASIDS;
+}
+
+static u16 allocate_global_asid(void)
+{
+	u16 asid;
+
+	lockdep_assert_held(&global_asid_lock);
+
+	/* The previous allocation hit the edge of available address space */
+	if (last_global_asid >= MAX_ASID_AVAILABLE - 1)
+		reset_global_asid_space();
+
+	asid = find_next_zero_bit(global_asid_used, MAX_ASID_AVAILABLE, last_global_asid);
+
+	if (asid >= MAX_ASID_AVAILABLE && !global_asid_available) {
+		/* This should never happen. */
+		VM_WARN_ONCE(1, "Unable to allocate global ASID despite %d available\n",
+				global_asid_available);
+		return 0;
+	}
+
+	/* Claim this global ASID. */
+	__set_bit(asid, global_asid_used);
+	last_global_asid = asid;
+	global_asid_available--;
+	return asid;
+}
+
+/*
+ * Check whether a process is currently active on more than @threshold CPUs.
+ * This is a cheap estimation on whether or not it may make sense to assign
+ * a global ASID to this process, and use broadcast TLB invalidation.
+ */
+static bool mm_active_cpus_exceeds(struct mm_struct *mm, int threshold)
+{
+	int count = 0;
+	int cpu;
+
+	/* This quick check should eliminate most single threaded programs. */
+	if (cpumask_weight(mm_cpumask(mm)) <= threshold)
+		return false;
+
+	/* Slower check to make sure. */
+	for_each_cpu(cpu, mm_cpumask(mm)) {
+		/* Skip the CPUs that aren't really running this process. */
+		if (per_cpu(cpu_tlbstate.loaded_mm, cpu) != mm)
+			continue;
+
+		if (per_cpu(cpu_tlbstate_shared.is_lazy, cpu))
+			continue;
+
+		if (++count > threshold)
+			return true;
+	}
+	return false;
+}
+
+/*
+ * Assign a global ASID to the current process, protecting against
+ * races between multiple threads in the process.
+ */
+static void use_global_asid(struct mm_struct *mm)
+{
+	u16 asid;
+
+	guard(raw_spinlock_irqsave)(&global_asid_lock);
+
+	/* This process is already using broadcast TLB invalidation. */
+	if (mm_global_asid(mm))
+		return;
+
+	/*
+	 * The last global ASID was consumed while waiting for the lock.
+	 *
+	 * If this fires, a more aggressive ASID reuse scheme might be
+	 * needed.
+	 */
+	if (!global_asid_available) {
+		VM_WARN_ONCE(1, "Ran out of global ASIDs\n");
+		return;
+	}
+
+	asid = allocate_global_asid();
+	if (!asid)
+		return;
+
+	mm_assign_global_asid(mm, asid);
+}
+
+#ifdef CONFIG_BROADCAST_TLB_FLUSH
+void mm_free_global_asid(struct mm_struct *mm)
+{
+	if (!cpu_feature_enabled(X86_FEATURE_INVLPGB))
+		return;
+
+	if (!mm_global_asid(mm))
+		return;
+
+	guard(raw_spinlock_irqsave)(&global_asid_lock);
+
+	/* The global ASID can be re-used only after flush at wrap-around. */
+	__set_bit(mm->context.global_asid, global_asid_freed);
+
+	mm->context.global_asid = 0;
+	global_asid_available++;
+}
+#endif
+
+/*
+ * Is the mm transitioning from a CPU-local ASID to a global ASID?
+ */
+static bool mm_needs_global_asid(struct mm_struct *mm, u16 asid)
+{
+	u16 global_asid = mm_global_asid(mm);
+
+	if (!cpu_feature_enabled(X86_FEATURE_INVLPGB))
+		return false;
+
+	/* Process is transitioning to a global ASID */
+	if (global_asid && asid != global_asid)
+		return true;
+
+	return false;
+}
+
+/*
+ * x86 has 4k ASIDs (2k when compiled with KPTI), but the largest x86
+ * systems have over 8k CPUs. Because of this potential ASID shortage,
+ * global ASIDs are handed out to processes that have frequent TLB
+ * flushes and are active on 4 or more CPUs simultaneously.
+ */
+static void consider_global_asid(struct mm_struct *mm)
+{
+	if (!cpu_feature_enabled(X86_FEATURE_INVLPGB))
+		return;
+
+	/* Check every once in a while. */
+	if ((current->pid & 0x1f) != (jiffies & 0x1f))
+		return;
+
+	/*
+	 * Assign a global ASID if the process is active on
+	 * 4 or more CPUs simultaneously.
+	 */
+	if (mm_active_cpus_exceeds(mm, 3))
+		use_global_asid(mm);
+}
+
+static void finish_asid_transition(struct flush_tlb_info *info)
+{
+	struct mm_struct *mm = info->mm;
+	int bc_asid = mm_global_asid(mm);
+	int cpu;
+
+	if (!mm_in_asid_transition(mm))
+		return;
+
+	for_each_cpu(cpu, mm_cpumask(mm)) {
+		/*
+		 * The remote CPU is context switching. Wait for that to
+		 * finish, to catch the unlikely case of it switching to
+		 * the target mm with an out of date ASID.
+		 */
+		while (READ_ONCE(per_cpu(cpu_tlbstate.loaded_mm, cpu)) == LOADED_MM_SWITCHING)
+			cpu_relax();
+
+		if (READ_ONCE(per_cpu(cpu_tlbstate.loaded_mm, cpu)) != mm)
+			continue;
+
+		/*
+		 * If at least one CPU is not using the global ASID yet,
+		 * send a TLB flush IPI. The IPI should cause stragglers
+		 * to transition soon.
+		 *
+		 * This can race with the CPU switching to another task;
+		 * that results in a (harmless) extra IPI.
+		 */
+		if (READ_ONCE(per_cpu(cpu_tlbstate.loaded_mm_asid, cpu)) != bc_asid) {
+			flush_tlb_multi(mm_cpumask(info->mm), info);
+			return;
+		}
+	}
+
+	/* All the CPUs running this process are using the global ASID. */
+	mm_clear_asid_transition(mm);
+}
+
+static void broadcast_tlb_flush(struct flush_tlb_info *info)
+{
+	bool pmd = info->stride_shift == PMD_SHIFT;
+	unsigned long asid = mm_global_asid(info->mm);
+	unsigned long addr = info->start;
+
+	/*
+	 * TLB flushes with INVLPGB are kicked off asynchronously.
+	 * The inc_mm_tlb_gen() guarantees page table updates are done
+	 * before these TLB flushes happen.
+	 */
+	if (info->end == TLB_FLUSH_ALL) {
+		invlpgb_flush_single_pcid_nosync(kern_pcid(asid));
+		/* Do any CPUs supporting INVLPGB need PTI? */
+		if (cpu_feature_enabled(X86_FEATURE_PTI))
+			invlpgb_flush_single_pcid_nosync(user_pcid(asid));
+	} else do {
+		unsigned long nr = 1;
+
+		if (info->stride_shift <= PMD_SHIFT) {
+			nr = (info->end - addr) >> info->stride_shift;
+			nr = clamp_val(nr, 1, invlpgb_count_max);
+		}
+
+		invlpgb_flush_user_nr_nosync(kern_pcid(asid), addr, nr, pmd);
+		if (cpu_feature_enabled(X86_FEATURE_PTI))
+			invlpgb_flush_user_nr_nosync(user_pcid(asid), addr, nr, pmd);
+
+		addr += nr << info->stride_shift;
+	} while (addr < info->end);
+
+	finish_asid_transition(info);
+
+	/* Wait for the INVLPGBs kicked off above to finish. */
+	__tlbsync();
+}
+
+/*
+ * Given an ASID, flush the corresponding user ASID.  We can delay this
+ * until the next time we switch to it.
+ *
+ * See SWITCH_TO_USER_CR3.
+ */
+static inline void invalidate_user_asid(u16 asid)
+{
+	/* There is no user ASID if address space separation is off */
+	if (!IS_ENABLED(CONFIG_MITIGATION_PAGE_TABLE_ISOLATION))
+		return;
+
+	/*
+	 * We only have a single ASID if PCID is off and the CR3
+	 * write will have flushed it.
+	 */
+	if (!cpu_feature_enabled(X86_FEATURE_PCID))
+		return;
+
+	if (!cpu_feature_enabled(X86_FEATURE_PTI))
+		return;
+
+	__set_bit(kern_pcid(asid),
+		  (unsigned long *)this_cpu_ptr(&cpu_tlbstate.user_pcid_flush_mask));
+}
+
+static void load_new_mm_cr3(pgd_t *pgdir, u16 new_asid, unsigned long lam,
+			    bool need_flush)
+{
+	unsigned long new_mm_cr3;
+
+	if (need_flush) {
+		invalidate_user_asid(new_asid);
+		new_mm_cr3 = build_cr3(pgdir, new_asid, lam);
+	} else {
+		new_mm_cr3 = build_cr3_noflush(pgdir, new_asid, lam);
+	}
+
+	/*
+	 * Caution: many callers of this function expect
+	 * that load_cr3() is serializing and orders TLB
+	 * fills with respect to the mm_cpumask writes.
+	 */
+	write_cr3(new_mm_cr3);
+}
+
+void leave_mm(void)
+{
+	struct mm_struct *loaded_mm = this_cpu_read(cpu_tlbstate.loaded_mm);
+
+	/*
+	 * It's plausible that we're in lazy TLB mode while our mm is init_mm.
+	 * If so, our callers still expect us to flush the TLB, but there
+	 * aren't any user TLB entries in init_mm to worry about.
+	 *
+	 * This needs to happen before any other sanity checks due to
+	 * intel_idle's shenanigans.
+	 */
+	if (loaded_mm == &init_mm)
+		return;
+
+	/* Warn if we're not lazy. */
+	WARN_ON(!this_cpu_read(cpu_tlbstate_shared.is_lazy));
+
+	switch_mm(NULL, &init_mm, NULL);
+}
+EXPORT_SYMBOL_GPL(leave_mm);
+
+void switch_mm(struct mm_struct *prev, struct mm_struct *next,
+	       struct task_struct *tsk)
+{
+	unsigned long flags;
+
+	local_irq_save(flags);
+	switch_mm_irqs_off(NULL, next, tsk);
+	local_irq_restore(flags);
+}
+
+/*
+ * Invoked from return to user/guest by a task that opted-in to L1D
+ * flushing but ended up running on an SMT enabled core due to wrong
+ * affinity settings or CPU hotplug. This is part of the paranoid L1D flush
+ * contract which this task requested.
+ */
+static void l1d_flush_force_sigbus(struct callback_head *ch)
+{
+	force_sig(SIGBUS);
+}
+
+static void l1d_flush_evaluate(unsigned long prev_mm, unsigned long next_mm,
+				struct task_struct *next)
+{
+	/* Flush L1D if the outgoing task requests it */
+	if (prev_mm & LAST_USER_MM_L1D_FLUSH)
+		wrmsrq(MSR_IA32_FLUSH_CMD, L1D_FLUSH);
+
+	/* Check whether the incoming task opted in for L1D flush */
+	if (likely(!(next_mm & LAST_USER_MM_L1D_FLUSH)))
+		return;
+
+	/*
+	 * Validate that it is not running on an SMT sibling as this would
+	 * make the exercise pointless because the siblings share L1D. If
+	 * it runs on a SMT sibling, notify it with SIGBUS on return to
+	 * user/guest
+	 */
+	if (this_cpu_read(cpu_info.smt_active)) {
+		clear_ti_thread_flag(&next->thread_info, TIF_SPEC_L1D_FLUSH);
+		next->l1d_flush_kill.func = l1d_flush_force_sigbus;
+		task_work_add(next, &next->l1d_flush_kill, TWA_RESUME);
+	}
+}
+
+static unsigned long mm_mangle_tif_spec_bits(struct task_struct *next)
+{
+	unsigned long next_tif = read_task_thread_flags(next);
+	unsigned long spec_bits = (next_tif >> TIF_SPEC_IB) & LAST_USER_MM_SPEC_MASK;
+
+	/*
+	 * Ensure that the bit shift above works as expected and the two flags
+	 * end up in bit 0 and 1.
+	 */
+	BUILD_BUG_ON(TIF_SPEC_L1D_FLUSH != TIF_SPEC_IB + 1);
+
+	return (unsigned long)next->mm | spec_bits;
+}
+
+static void cond_mitigation(struct task_struct *next)
+{
+	unsigned long prev_mm, next_mm;
+
+	if (!next || !next->mm)
+		return;
+
+	next_mm = mm_mangle_tif_spec_bits(next);
+	prev_mm = this_cpu_read(cpu_tlbstate.last_user_mm_spec);
+
+	/*
+	 * Avoid user->user BTB/RSB poisoning by flushing them when switching
+	 * between processes. This stops one process from doing Spectre-v2
+	 * attacks on another.
+	 *
+	 * Both, the conditional and the always IBPB mode use the mm
+	 * pointer to avoid the IBPB when switching between tasks of the
+	 * same process. Using the mm pointer instead of mm->context.ctx_id
+	 * opens a hypothetical hole vs. mm_struct reuse, which is more or
+	 * less impossible to control by an attacker. Aside of that it
+	 * would only affect the first schedule so the theoretically
+	 * exposed data is not really interesting.
+	 */
+	if (static_branch_likely(&switch_mm_cond_ibpb)) {
+		/*
+		 * This is a bit more complex than the always mode because
+		 * it has to handle two cases:
+		 *
+		 * 1) Switch from a user space task (potential attacker)
+		 *    which has TIF_SPEC_IB set to a user space task
+		 *    (potential victim) which has TIF_SPEC_IB not set.
+		 *
+		 * 2) Switch from a user space task (potential attacker)
+		 *    which has TIF_SPEC_IB not set to a user space task
+		 *    (potential victim) which has TIF_SPEC_IB set.
+		 *
+		 * This could be done by unconditionally issuing IBPB when
+		 * a task which has TIF_SPEC_IB set is either scheduled in
+		 * or out. Though that results in two flushes when:
+		 *
+		 * - the same user space task is scheduled out and later
+		 *   scheduled in again and only a kernel thread ran in
+		 *   between.
+		 *
+		 * - a user space task belonging to the same process is
+		 *   scheduled in after a kernel thread ran in between
+		 *
+		 * - a user space task belonging to the same process is
+		 *   scheduled in immediately.
+		 *
+		 * Optimize this with reasonably small overhead for the
+		 * above cases. Mangle the TIF_SPEC_IB bit into the mm
+		 * pointer of the incoming task which is stored in
+		 * cpu_tlbstate.last_user_mm_spec for comparison.
+		 *
+		 * Issue IBPB only if the mm's are different and one or
+		 * both have the IBPB bit set.
+		 */
+		if (next_mm != prev_mm &&
+		    (next_mm | prev_mm) & LAST_USER_MM_IBPB)
+			indirect_branch_prediction_barrier();
+	}
+
+	if (static_branch_unlikely(&switch_mm_always_ibpb)) {
+		/*
+		 * Only flush when switching to a user space task with a
+		 * different context than the user space task which ran
+		 * last on this CPU.
+		 */
+		if ((prev_mm & ~LAST_USER_MM_SPEC_MASK) != (unsigned long)next->mm)
+			indirect_branch_prediction_barrier();
+	}
+
+	if (static_branch_unlikely(&switch_mm_cond_l1d_flush)) {
+		/*
+		 * Flush L1D when the outgoing task requested it and/or
+		 * check whether the incoming task requested L1D flushing
+		 * and ended up on an SMT sibling.
+		 */
+		if (unlikely((prev_mm | next_mm) & LAST_USER_MM_L1D_FLUSH))
+			l1d_flush_evaluate(prev_mm, next_mm, next);
+	}
+
+	this_cpu_write(cpu_tlbstate.last_user_mm_spec, next_mm);
+}
+
+#ifdef CONFIG_PERF_EVENTS
+static inline void cr4_update_pce_mm(struct mm_struct *mm)
+{
+	if (static_branch_unlikely(&rdpmc_always_available_key) ||
+	    (!static_branch_unlikely(&rdpmc_never_available_key) &&
+	     atomic_read(&mm->context.perf_rdpmc_allowed))) {
+		/*
+		 * Clear the existing dirty counters to
+		 * prevent the leak for an RDPMC task.
+		 */
+		perf_clear_dirty_counters();
+		cr4_set_bits_irqsoff(X86_CR4_PCE);
+	} else
+		cr4_clear_bits_irqsoff(X86_CR4_PCE);
+}
+
+void cr4_update_pce(void *ignored)
+{
+	cr4_update_pce_mm(this_cpu_read(cpu_tlbstate.loaded_mm));
+}
+
+#else
+static inline void cr4_update_pce_mm(struct mm_struct *mm) { }
+#endif
+
+/*
+ * This optimizes when not actually switching mm's.  Some architectures use the
+ * 'unused' argument for this optimization, but x86 must use
+ * 'cpu_tlbstate.loaded_mm' instead because it does not always keep
+ * 'current->active_mm' up to date.
+ */
+void switch_mm_irqs_off(struct mm_struct *unused, struct mm_struct *next,
+			struct task_struct *tsk)
+{
+	struct mm_struct *prev = this_cpu_read(cpu_tlbstate.loaded_mm);
+	u16 prev_asid = this_cpu_read(cpu_tlbstate.loaded_mm_asid);
+	bool was_lazy = this_cpu_read(cpu_tlbstate_shared.is_lazy);
+	unsigned cpu = smp_processor_id();
+	unsigned long new_lam;
+	struct new_asid ns;
+	u64 next_tlb_gen;
+
+
+	/* We don't want flush_tlb_func() to run concurrently with us. */
+	if (IS_ENABLED(CONFIG_PROVE_LOCKING))
+		WARN_ON_ONCE(!irqs_disabled());
+
+	/*
+	 * Verify that CR3 is what we think it is.  This will catch
+	 * hypothetical buggy code that directly switches to swapper_pg_dir
+	 * without going through leave_mm() / switch_mm_irqs_off() or that
+	 * does something like write_cr3(read_cr3_pa()).
+	 *
+	 * Only do this check if CONFIG_DEBUG_VM=y because __read_cr3()
+	 * isn't free.
+	 */
+#ifdef CONFIG_DEBUG_VM
+	if (WARN_ON_ONCE(__read_cr3() != build_cr3(prev->pgd, prev_asid,
+						   tlbstate_lam_cr3_mask()))) {
+		/*
+		 * If we were to BUG here, we'd be very likely to kill
+		 * the system so hard that we don't see the call trace.
+		 * Try to recover instead by ignoring the error and doing
+		 * a global flush to minimize the chance of corruption.
+		 *
+		 * (This is far from being a fully correct recovery.
+		 *  Architecturally, the CPU could prefetch something
+		 *  back into an incorrect ASID slot and leave it there
+		 *  to cause trouble down the road.  It's better than
+		 *  nothing, though.)
+		 */
+		__flush_tlb_all();
+	}
+#endif
+	if (was_lazy)
+		this_cpu_write(cpu_tlbstate_shared.is_lazy, false);
+
+	/*
+	 * The membarrier system call requires a full memory barrier and
+	 * core serialization before returning to user-space, after
+	 * storing to rq->curr, when changing mm.  This is because
+	 * membarrier() sends IPIs to all CPUs that are in the target mm
+	 * to make them issue memory barriers.  However, if another CPU
+	 * switches to/from the target mm concurrently with
+	 * membarrier(), it can cause that CPU not to receive an IPI
+	 * when it really should issue a memory barrier.  Writing to CR3
+	 * provides that full memory barrier and core serializing
+	 * instruction.
+	 */
+	if (prev == next) {
+		/* Not actually switching mm's */
+		VM_WARN_ON(is_dyn_asid(prev_asid) &&
+			   this_cpu_read(cpu_tlbstate.ctxs[prev_asid].ctx_id) !=
+			   next->context.ctx_id);
+
+		/*
+		 * If this races with another thread that enables lam, 'new_lam'
+		 * might not match tlbstate_lam_cr3_mask().
+		 */
+
+		/*
+		 * Even in lazy TLB mode, the CPU should stay set in the
+		 * mm_cpumask. The TLB shootdown code can figure out from
+		 * cpu_tlbstate_shared.is_lazy whether or not to send an IPI.
+		 */
+		if (IS_ENABLED(CONFIG_DEBUG_VM) &&
+		    WARN_ON_ONCE(prev != &init_mm && !is_notrack_mm(prev) &&
+				 !cpumask_test_cpu(cpu, mm_cpumask(next))))
+			cpumask_set_cpu(cpu, mm_cpumask(next));
+
+		/* Check if the current mm is transitioning to a global ASID */
+		if (mm_needs_global_asid(next, prev_asid)) {
+			next_tlb_gen = atomic64_read(&next->context.tlb_gen);
+			ns = choose_new_asid(next, next_tlb_gen);
+			goto reload_tlb;
+		}
+
+		/*
+		 * Broadcast TLB invalidation keeps this ASID up to date
+		 * all the time.
+		 */
+		if (is_global_asid(prev_asid))
+			return;
+
+		/*
+		 * If the CPU is not in lazy TLB mode, we are just switching
+		 * from one thread in a process to another thread in the same
+		 * process. No TLB flush required.
+		 */
+		if (!was_lazy)
+			return;
+
+		/*
+		 * Read the tlb_gen to check whether a flush is needed.
+		 * If the TLB is up to date, just use it.
+		 * The barrier synchronizes with the tlb_gen increment in
+		 * the TLB shootdown code.
+		 */
+		smp_mb();
+		next_tlb_gen = atomic64_read(&next->context.tlb_gen);
+		if (this_cpu_read(cpu_tlbstate.ctxs[prev_asid].tlb_gen) ==
+				next_tlb_gen)
+			return;
+
+		/*
+		 * TLB contents went out of date while we were in lazy
+		 * mode. Fall through to the TLB switching code below.
+		 */
+		ns.asid = prev_asid;
+		ns.need_flush = true;
+	} else {
+		/*
+		 * Apply process to process speculation vulnerability
+		 * mitigations if applicable.
+		 */
+		cond_mitigation(tsk);
+
+		/*
+		 * Indicate that CR3 is about to change. nmi_uaccess_okay()
+		 * and others are sensitive to the window where mm_cpumask(),
+		 * CR3 and cpu_tlbstate.loaded_mm are not all in sync.
+		 */
+		this_cpu_write(cpu_tlbstate.loaded_mm, LOADED_MM_SWITCHING);
+
+		/*
+		 * Make sure this CPU is set in mm_cpumask() such that we'll
+		 * receive invalidation IPIs.
+		 *
+		 * Rely on the smp_mb() implied by cpumask_set_cpu()'s atomic
+		 * operation, or explicitly provide one. Such that:
+		 *
+		 * switch_mm_irqs_off()				flush_tlb_mm_range()
+		 *   smp_store_release(loaded_mm, SWITCHING);     atomic64_inc_return(tlb_gen)
+		 *   smp_mb(); // here                            // smp_mb() implied
+		 *   atomic64_read(tlb_gen);                      this_cpu_read(loaded_mm);
+		 *
+		 * we properly order against flush_tlb_mm_range(), where the
+		 * loaded_mm load can happen in mative_flush_tlb_multi() ->
+		 * should_flush_tlb().
+		 *
+		 * This way switch_mm() must see the new tlb_gen or
+		 * flush_tlb_mm_range() must see the new loaded_mm, or both.
+		 */
+		if (next != &init_mm && !cpumask_test_cpu(cpu, mm_cpumask(next)))
+			cpumask_set_cpu(cpu, mm_cpumask(next));
+		else
+			smp_mb();
+
+		next_tlb_gen = atomic64_read(&next->context.tlb_gen);
+
+		ns = choose_new_asid(next, next_tlb_gen);
+	}
+
+reload_tlb:
+	new_lam = mm_lam_cr3_mask(next);
+	if (ns.need_flush) {
+		VM_WARN_ON_ONCE(is_global_asid(ns.asid));
+		this_cpu_write(cpu_tlbstate.ctxs[ns.asid].ctx_id, next->context.ctx_id);
+		this_cpu_write(cpu_tlbstate.ctxs[ns.asid].tlb_gen, next_tlb_gen);
+		load_new_mm_cr3(next->pgd, ns.asid, new_lam, true);
+
+		trace_tlb_flush(TLB_FLUSH_ON_TASK_SWITCH, TLB_FLUSH_ALL);
+	} else {
+		/* The new ASID is already up to date. */
+		load_new_mm_cr3(next->pgd, ns.asid, new_lam, false);
+
+		trace_tlb_flush(TLB_FLUSH_ON_TASK_SWITCH, 0);
+	}
+
+	/* Make sure we write CR3 before loaded_mm. */
+	barrier();
+
+	this_cpu_write(cpu_tlbstate.loaded_mm, next);
+	this_cpu_write(cpu_tlbstate.loaded_mm_asid, ns.asid);
+	cpu_tlbstate_update_lam(new_lam, mm_untag_mask(next));
+
+	if (next != prev) {
+		cr4_update_pce_mm(next);
+		switch_ldt(prev, next);
+	}
+}
+
+/*
+ * Using a temporary mm allows to set temporary mappings that are not accessible
+ * by other CPUs. Such mappings are needed to perform sensitive memory writes
+ * that override the kernel memory protections (e.g., W^X), without exposing the
+ * temporary page-table mappings that are required for these write operations to
+ * other CPUs. Using a temporary mm also allows to avoid TLB shootdowns when the
+ * mapping is torn down.  Temporary mms can also be used for EFI runtime service
+ * calls or similar functionality.
+ *
+ * It is illegal to schedule while using a temporary mm -- the context switch
+ * code is unaware of the temporary mm and does not know how to context switch.
+ * Use a real (non-temporary) mm in a kernel thread if you need to sleep.
+ *
+ * Note: For sensitive memory writes, the temporary mm needs to be used
+ *       exclusively by a single core, and IRQs should be disabled while the
+ *       temporary mm is loaded, thereby preventing interrupt handler bugs from
+ *       overriding the kernel memory protection.
+ */
+struct mm_struct *use_temporary_mm(struct mm_struct *temp_mm)
+{
+	struct mm_struct *prev_mm;
+
+	lockdep_assert_preemption_disabled();
+	guard(irqsave)();
+
+	/*
+	 * Make sure not to be in TLB lazy mode, as otherwise we'll end up
+	 * with a stale address space WITHOUT being in lazy mode after
+	 * restoring the previous mm.
+	 */
+	if (this_cpu_read(cpu_tlbstate_shared.is_lazy))
+		leave_mm();
+
+	prev_mm = this_cpu_read(cpu_tlbstate.loaded_mm);
+	switch_mm_irqs_off(NULL, temp_mm, current);
+
+	/*
+	 * If breakpoints are enabled, disable them while the temporary mm is
+	 * used. Userspace might set up watchpoints on addresses that are used
+	 * in the temporary mm, which would lead to wrong signals being sent or
+	 * crashes.
+	 *
+	 * Note that breakpoints are not disabled selectively, which also causes
+	 * kernel breakpoints (e.g., perf's) to be disabled. This might be
+	 * undesirable, but still seems reasonable as the code that runs in the
+	 * temporary mm should be short.
+	 */
+	if (hw_breakpoint_active())
+		hw_breakpoint_disable();
+
+	return prev_mm;
+}
+
+void unuse_temporary_mm(struct mm_struct *prev_mm)
+{
+	lockdep_assert_preemption_disabled();
+	guard(irqsave)();
+
+	/* Clear the cpumask, to indicate no TLB flushing is needed anywhere */
+	cpumask_clear_cpu(smp_processor_id(), mm_cpumask(this_cpu_read(cpu_tlbstate.loaded_mm)));
+
+	switch_mm_irqs_off(NULL, prev_mm, current);
+
+	/*
+	 * Restore the breakpoints if they were disabled before the temporary mm
+	 * was loaded.
+	 */
+	if (hw_breakpoint_active())
+		hw_breakpoint_restore();
+}
+
+/*
+ * Call this when reinitializing a CPU.  It fixes the following potential
+ * problems:
+ *
+ * - The ASID changed from what cpu_tlbstate thinks it is (most likely
+ *   because the CPU was taken down and came back up with CR3's PCID
+ *   bits clear.  CPU hotplug can do this.
+ *
+ * - The TLB contains junk in slots corresponding to inactive ASIDs.
+ *
+ * - The CPU went so far out to lunch that it may have missed a TLB
+ *   flush.
+ */
+void initialize_tlbstate_and_flush(void)
+{
+	int i;
+	struct mm_struct *mm = this_cpu_read(cpu_tlbstate.loaded_mm);
+	u64 tlb_gen = atomic64_read(&init_mm.context.tlb_gen);
+	unsigned long lam = mm_lam_cr3_mask(mm);
+	unsigned long cr3 = __read_cr3();
+
+	/* Assert that CR3 already references the right mm. */
+	WARN_ON((cr3 & CR3_ADDR_MASK) != __pa(mm->pgd));
+
+	/* LAM expected to be disabled */
+	WARN_ON(cr3 & (X86_CR3_LAM_U48 | X86_CR3_LAM_U57));
+	WARN_ON(lam);
+
+	/*
+	 * Assert that CR4.PCIDE is set if needed.  (CR4.PCIDE initialization
+	 * doesn't work like other CR4 bits because it can only be set from
+	 * long mode.)
+	 */
+	WARN_ON(boot_cpu_has(X86_FEATURE_PCID) &&
+		!(cr4_read_shadow() & X86_CR4_PCIDE));
+
+	/* Disable LAM, force ASID 0 and force a TLB flush. */
+	write_cr3(build_cr3(mm->pgd, 0, 0));
+
+	/* Reinitialize tlbstate. */
+	this_cpu_write(cpu_tlbstate.last_user_mm_spec, LAST_USER_MM_INIT);
+	this_cpu_write(cpu_tlbstate.loaded_mm_asid, 0);
+	this_cpu_write(cpu_tlbstate.next_asid, 1);
+	this_cpu_write(cpu_tlbstate.ctxs[0].ctx_id, mm->context.ctx_id);
+	this_cpu_write(cpu_tlbstate.ctxs[0].tlb_gen, tlb_gen);
+	cpu_tlbstate_update_lam(lam, mm_untag_mask(mm));
+
+	for (i = 1; i < TLB_NR_DYN_ASIDS; i++)
+		this_cpu_write(cpu_tlbstate.ctxs[i].ctx_id, 0);
+}
+
+/*
+ * flush_tlb_func()'s memory ordering requirement is that any
+ * TLB fills that happen after we flush the TLB are ordered after we
+ * read active_mm's tlb_gen.  We don't need any explicit barriers
+ * because all x86 flush operations are serializing and the
+ * atomic64_read operation won't be reordered by the compiler.
+ */
+static void flush_tlb_func(void *info)
+{
+	/*
+	 * We have three different tlb_gen values in here.  They are:
+	 *
+	 * - mm_tlb_gen:     the latest generation.
+	 * - local_tlb_gen:  the generation that this CPU has already caught
+	 *                   up to.
+	 * - f->new_tlb_gen: the generation that the requester of the flush
+	 *                   wants us to catch up to.
+	 */
+	const struct flush_tlb_info *f = info;
+	struct mm_struct *loaded_mm = this_cpu_read(cpu_tlbstate.loaded_mm);
+	u32 loaded_mm_asid = this_cpu_read(cpu_tlbstate.loaded_mm_asid);
+	u64 local_tlb_gen;
+	bool local = smp_processor_id() == f->initiating_cpu;
+	unsigned long nr_invalidate = 0;
+	u64 mm_tlb_gen;
+
+	/* This code cannot presently handle being reentered. */
+	VM_WARN_ON(!irqs_disabled());
+
+	if (!local) {
+		inc_irq_stat(TLB);
+		count_vm_tlb_event(NR_TLB_REMOTE_FLUSH_RECEIVED);
+	}
+
+	/* The CPU was left in the mm_cpumask of the target mm. Clear it. */
+	if (f->mm && f->mm != loaded_mm) {
+		cpumask_clear_cpu(raw_smp_processor_id(), mm_cpumask(f->mm));
+		trace_tlb_flush(TLB_REMOTE_WRONG_CPU, 0);
+		return;
+	}
+
+	if (unlikely(loaded_mm == &init_mm))
+		return;
+
+	/* Reload the ASID if transitioning into or out of a global ASID */
+	if (mm_needs_global_asid(loaded_mm, loaded_mm_asid)) {
+		switch_mm_irqs_off(NULL, loaded_mm, NULL);
+		loaded_mm_asid = this_cpu_read(cpu_tlbstate.loaded_mm_asid);
+	}
+
+	/* Broadcast ASIDs are always kept up to date with INVLPGB. */
+	if (is_global_asid(loaded_mm_asid))
+		return;
+
+	VM_WARN_ON(this_cpu_read(cpu_tlbstate.ctxs[loaded_mm_asid].ctx_id) !=
+		   loaded_mm->context.ctx_id);
+
+	if (this_cpu_read(cpu_tlbstate_shared.is_lazy)) {
+		/*
+		 * We're in lazy mode.  We need to at least flush our
+		 * paging-structure cache to avoid speculatively reading
+		 * garbage into our TLB.  Since switching to init_mm is barely
+		 * slower than a minimal flush, just switch to init_mm.
+		 *
+		 * This should be rare, with native_flush_tlb_multi() skipping
+		 * IPIs to lazy TLB mode CPUs.
+		 */
+		switch_mm_irqs_off(NULL, &init_mm, NULL);
+		return;
+	}
+
+	local_tlb_gen = this_cpu_read(cpu_tlbstate.ctxs[loaded_mm_asid].tlb_gen);
+
+	if (unlikely(f->new_tlb_gen != TLB_GENERATION_INVALID &&
+		     f->new_tlb_gen <= local_tlb_gen)) {
+		/*
+		 * The TLB is already up to date in respect to f->new_tlb_gen.
+		 * While the core might be still behind mm_tlb_gen, checking
+		 * mm_tlb_gen unnecessarily would have negative caching effects
+		 * so avoid it.
+		 */
+		return;
+	}
+
+	/*
+	 * Defer mm_tlb_gen reading as long as possible to avoid cache
+	 * contention.
+	 */
+	mm_tlb_gen = atomic64_read(&loaded_mm->context.tlb_gen);
+
+	if (unlikely(local_tlb_gen == mm_tlb_gen)) {
+		/*
+		 * There's nothing to do: we're already up to date.  This can
+		 * happen if two concurrent flushes happen -- the first flush to
+		 * be handled can catch us all the way up, leaving no work for
+		 * the second flush.
+		 */
+		goto done;
+	}
+
+	WARN_ON_ONCE(local_tlb_gen > mm_tlb_gen);
+	WARN_ON_ONCE(f->new_tlb_gen > mm_tlb_gen);
+
+	/*
+	 * If we get to this point, we know that our TLB is out of date.
+	 * This does not strictly imply that we need to flush (it's
+	 * possible that f->new_tlb_gen <= local_tlb_gen), but we're
+	 * going to need to flush in the very near future, so we might
+	 * as well get it over with.
+	 *
+	 * The only question is whether to do a full or partial flush.
+	 *
+	 * We do a partial flush if requested and two extra conditions
+	 * are met:
+	 *
+	 * 1. f->new_tlb_gen == local_tlb_gen + 1.  We have an invariant that
+	 *    we've always done all needed flushes to catch up to
+	 *    local_tlb_gen.  If, for example, local_tlb_gen == 2 and
+	 *    f->new_tlb_gen == 3, then we know that the flush needed to bring
+	 *    us up to date for tlb_gen 3 is the partial flush we're
+	 *    processing.
+	 *
+	 *    As an example of why this check is needed, suppose that there
+	 *    are two concurrent flushes.  The first is a full flush that
+	 *    changes context.tlb_gen from 1 to 2.  The second is a partial
+	 *    flush that changes context.tlb_gen from 2 to 3.  If they get
+	 *    processed on this CPU in reverse order, we'll see
+	 *     local_tlb_gen == 1, mm_tlb_gen == 3, and end != TLB_FLUSH_ALL.
+	 *    If we were to use __flush_tlb_one_user() and set local_tlb_gen to
+	 *    3, we'd be break the invariant: we'd update local_tlb_gen above
+	 *    1 without the full flush that's needed for tlb_gen 2.
+	 *
+	 * 2. f->new_tlb_gen == mm_tlb_gen.  This is purely an optimization.
+	 *    Partial TLB flushes are not all that much cheaper than full TLB
+	 *    flushes, so it seems unlikely that it would be a performance win
+	 *    to do a partial flush if that won't bring our TLB fully up to
+	 *    date.  By doing a full flush instead, we can increase
+	 *    local_tlb_gen all the way to mm_tlb_gen and we can probably
+	 *    avoid another flush in the very near future.
+	 */
+	if (f->end != TLB_FLUSH_ALL &&
+	    f->new_tlb_gen == local_tlb_gen + 1 &&
+	    f->new_tlb_gen == mm_tlb_gen) {
+		/* Partial flush */
+		unsigned long addr = f->start;
+
+		/* Partial flush cannot have invalid generations */
+		VM_WARN_ON(f->new_tlb_gen == TLB_GENERATION_INVALID);
+
+		/* Partial flush must have valid mm */
+		VM_WARN_ON(f->mm == NULL);
+
+		nr_invalidate = (f->end - f->start) >> f->stride_shift;
+
+		while (addr < f->end) {
+			flush_tlb_one_user(addr);
+			addr += 1UL << f->stride_shift;
+		}
+		if (local)
+			count_vm_tlb_events(NR_TLB_LOCAL_FLUSH_ONE, nr_invalidate);
+	} else {
+		/* Full flush. */
+		nr_invalidate = TLB_FLUSH_ALL;
+
+		flush_tlb_local();
+		if (local)
+			count_vm_tlb_event(NR_TLB_LOCAL_FLUSH_ALL);
+	}
+
+	/* Both paths above update our state to mm_tlb_gen. */
+	this_cpu_write(cpu_tlbstate.ctxs[loaded_mm_asid].tlb_gen, mm_tlb_gen);
+
+	/* Tracing is done in a unified manner to reduce the code size */
+done:
+	trace_tlb_flush(!local ? TLB_REMOTE_SHOOTDOWN :
+				(f->mm == NULL) ? TLB_LOCAL_SHOOTDOWN :
+						  TLB_LOCAL_MM_SHOOTDOWN,
+			nr_invalidate);
+}
+
+static bool should_flush_tlb(int cpu, void *data)
+{
+	struct mm_struct *loaded_mm = per_cpu(cpu_tlbstate.loaded_mm, cpu);
+	struct flush_tlb_info *info = data;
+
+	/*
+	 * Order the 'loaded_mm' and 'is_lazy' against their
+	 * write ordering in switch_mm_irqs_off(). Ensure
+	 * 'is_lazy' is at least as new as 'loaded_mm'.
+	 */
+	smp_rmb();
+
+	/* Lazy TLB will get flushed at the next context switch. */
+	if (per_cpu(cpu_tlbstate_shared.is_lazy, cpu))
+		return false;
+
+	/* No mm means kernel memory flush. */
+	if (!info->mm)
+		return true;
+
+	/*
+	 * While switching, the remote CPU could have state from
+	 * either the prev or next mm. Assume the worst and flush.
+	 */
+	if (loaded_mm == LOADED_MM_SWITCHING)
+		return true;
+
+	/* The target mm is loaded, and the CPU is not lazy. */
+	if (loaded_mm == info->mm)
+		return true;
+
+	/* In cpumask, but not the loaded mm? Periodically remove by flushing. */
+	if (info->trim_cpumask)
+		return true;
+
+	return false;
+}
+
+static bool should_trim_cpumask(struct mm_struct *mm)
+{
+	if (time_after(jiffies, READ_ONCE(mm->context.next_trim_cpumask))) {
+		WRITE_ONCE(mm->context.next_trim_cpumask, jiffies + HZ);
+		return true;
+	}
+	return false;
+}
+
+DEFINE_PER_CPU_SHARED_ALIGNED(struct tlb_state_shared, cpu_tlbstate_shared);
+EXPORT_PER_CPU_SYMBOL(cpu_tlbstate_shared);
+
+STATIC_NOPV void native_flush_tlb_multi(const struct cpumask *cpumask,
+					 const struct flush_tlb_info *info)
+{
+	/*
+	 * Do accounting and tracing. Note that there are (and have always been)
+	 * cases in which a remote TLB flush will be traced, but eventually
+	 * would not happen.
+	 */
+	count_vm_tlb_event(NR_TLB_REMOTE_FLUSH);
+	if (info->end == TLB_FLUSH_ALL)
+		trace_tlb_flush(TLB_REMOTE_SEND_IPI, TLB_FLUSH_ALL);
+	else
+		trace_tlb_flush(TLB_REMOTE_SEND_IPI,
+				(info->end - info->start) >> PAGE_SHIFT);
+
+	/*
+	 * If no page tables were freed, we can skip sending IPIs to
+	 * CPUs in lazy TLB mode. They will flush the CPU themselves
+	 * at the next context switch.
+	 *
+	 * However, if page tables are getting freed, we need to send the
+	 * IPI everywhere, to prevent CPUs in lazy TLB mode from tripping
+	 * up on the new contents of what used to be page tables, while
+	 * doing a speculative memory access.
+	 */
+	if (info->freed_tables || mm_in_asid_transition(info->mm))
+		on_each_cpu_mask(cpumask, flush_tlb_func, (void *)info, true);
+	else
+		on_each_cpu_cond_mask(should_flush_tlb, flush_tlb_func,
+				(void *)info, 1, cpumask);
+}
+
+void flush_tlb_multi(const struct cpumask *cpumask,
+		      const struct flush_tlb_info *info)
+{
+	__flush_tlb_multi(cpumask, info);
+}
+
+/*
+ * See Documentation/arch/x86/tlb.rst for details.  We choose 33
+ * because it is large enough to cover the vast majority (at
+ * least 95%) of allocations, and is small enough that we are
+ * confident it will not cause too much overhead.  Each single
+ * flush is about 100 ns, so this caps the maximum overhead at
+ * _about_ 3,000 ns.
+ *
+ * This is in units of pages.
+ */
+unsigned long tlb_single_page_flush_ceiling __read_mostly = 33;
+
+static void init_flush_tlb_info(struct flush_tlb_info *info,
+				struct mm_struct *mm,
+				unsigned long start, unsigned long end,
+				unsigned int stride_shift, bool freed_tables,
+				u64 new_tlb_gen)
+{
+	/*
+	 * If the number of flushes is so large that a full flush
+	 * would be faster, do a full flush.
+	 */
+	if ((end - start) >> stride_shift > tlb_single_page_flush_ceiling) {
+		start	= 0;
+		end	= TLB_FLUSH_ALL;
+	}
+
+	info->start		= start;
+	info->end		= end;
+	info->mm		= mm;
+	info->stride_shift	= stride_shift;
+	info->freed_tables	= freed_tables;
+	info->new_tlb_gen	= new_tlb_gen;
+	info->initiating_cpu	= smp_processor_id();
+	info->trim_cpumask	= 0;
+}
+
+void flush_tlb_mm_range(struct mm_struct *mm, unsigned long start,
+				unsigned long end, unsigned int stride_shift,
+				bool freed_tables)
+{
+	struct flush_tlb_info info;
+	bool remote_flush = false;
+	int cpu = get_cpu();
+	u64 new_tlb_gen;
+
+	/* This is also a barrier that synchronizes with switch_mm(). */
+	new_tlb_gen = inc_mm_tlb_gen(mm);
+
+	init_flush_tlb_info(&info, mm, start, end, stride_shift, freed_tables, new_tlb_gen);
+
+	/*
+	 * flush_tlb_multi() is not optimized for the common case in which only
+	 * a local TLB flush is needed. Optimize this use-case by calling
+	 * flush_tlb_func_local() directly in this case.
+	 */
+	if (mm_global_asid(mm)) {
+		broadcast_tlb_flush(&info);
+	} else if (cpumask_any_but(mm_cpumask(mm), cpu) < nr_cpu_ids) {
+		remote_flush = true;
+	} else if (mm == this_cpu_read(cpu_tlbstate.loaded_mm)) {
+		lockdep_assert_irqs_enabled();
+		local_irq_disable();
+		flush_tlb_func(&info);
+		local_irq_enable();
+	}
+
+	put_cpu();
+
+	if (remote_flush) {
+		info.trim_cpumask = should_trim_cpumask(mm);
+		flush_tlb_multi(mm_cpumask(mm), &info);
+		consider_global_asid(mm);
+	}
+
+	mmu_notifier_arch_invalidate_secondary_tlbs(mm, start, end);
+}
+
+static void do_flush_tlb_all(void *info)
+{
+	count_vm_tlb_event(NR_TLB_REMOTE_FLUSH_RECEIVED);
+	__flush_tlb_all();
+}
+
+void flush_tlb_all(void)
+{
+	count_vm_tlb_event(NR_TLB_REMOTE_FLUSH);
+
+	/* First try (faster) hardware-assisted TLB invalidation. */
+	if (cpu_feature_enabled(X86_FEATURE_INVLPGB))
+		invlpgb_flush_all();
+	else
+		/* Fall back to the IPI-based invalidation. */
+		on_each_cpu(do_flush_tlb_all, NULL, 1);
+}
+
+/* Flush an arbitrarily large range of memory with INVLPGB. */
+static void invlpgb_kernel_range_flush(struct flush_tlb_info *info)
+{
+	unsigned long addr, nr;
+
+	for (addr = info->start; addr < info->end; addr += nr << PAGE_SHIFT) {
+		nr = (info->end - addr) >> PAGE_SHIFT;
+
+		/*
+		 * INVLPGB has a limit on the size of ranges it can
+		 * flush. Break up large flushes.
+		 */
+		nr = clamp_val(nr, 1, invlpgb_count_max);
+
+		invlpgb_flush_addr_nosync(addr, nr);
+	}
+	__tlbsync();
+}
+
+static void do_kernel_range_flush(void *info)
+{
+	struct flush_tlb_info *f = info;
+	unsigned long addr;
+
+	/* flush range by one by one 'invlpg' */
+	for (addr = f->start; addr < f->end; addr += PAGE_SIZE)
+		flush_tlb_one_kernel(addr);
+}
+
+static void kernel_tlb_flush_all(struct flush_tlb_info *info)
+{
+	if (cpu_feature_enabled(X86_FEATURE_INVLPGB))
+		invlpgb_flush_all();
+	else
+		on_each_cpu(do_flush_tlb_all, NULL, 1);
+}
+
+static void kernel_tlb_flush_range(struct flush_tlb_info *info)
+{
+	if (cpu_feature_enabled(X86_FEATURE_INVLPGB))
+		invlpgb_kernel_range_flush(info);
+	else
+		on_each_cpu(do_kernel_range_flush, info, 1);
+}
+
+void flush_tlb_kernel_range(unsigned long start, unsigned long end)
+{
+	struct flush_tlb_info info;
+
+	guard(preempt)();
+	init_flush_tlb_info(&info, NULL, start, end, PAGE_SHIFT, false,
+			    TLB_GENERATION_INVALID);
+
+	if (info.end == TLB_FLUSH_ALL)
+		kernel_tlb_flush_all(&info);
+	else
+		kernel_tlb_flush_range(&info);
+}
+
+/*
+ * This can be used from process context to figure out what the value of
+ * CR3 is without needing to do a (slow) __read_cr3().
+ *
+ * It's intended to be used for code like KVM that sneakily changes CR3
+ * and needs to restore it.  It needs to be used very carefully.
+ */
+unsigned long __get_current_cr3_fast(void)
+{
+	unsigned long cr3 =
+		build_cr3(this_cpu_read(cpu_tlbstate.loaded_mm)->pgd,
+			  this_cpu_read(cpu_tlbstate.loaded_mm_asid),
+			  tlbstate_lam_cr3_mask());
+
+	/* For now, be very restrictive about when this can be called. */
+	VM_WARN_ON(in_nmi() || preemptible());
+
+	VM_BUG_ON(cr3 != __read_cr3());
+	return cr3;
+}
+EXPORT_SYMBOL_FOR_KVM(__get_current_cr3_fast);
+
+/*
+ * Flush one page in the kernel mapping
+ */
+void flush_tlb_one_kernel(unsigned long addr)
+{
+	count_vm_tlb_event(NR_TLB_LOCAL_FLUSH_ONE);
+
+	/*
+	 * If PTI is off, then __flush_tlb_one_user() is just INVLPG or its
+	 * paravirt equivalent.  Even with PCID, this is sufficient: we only
+	 * use PCID if we also use global PTEs for the kernel mapping, and
+	 * INVLPG flushes global translations across all address spaces.
+	 *
+	 * If PTI is on, then the kernel is mapped with non-global PTEs, and
+	 * __flush_tlb_one_user() will flush the given address for the current
+	 * kernel address space and for its usermode counterpart, but it does
+	 * not flush it for other address spaces.
+	 */
+	flush_tlb_one_user(addr);
+
+	if (!cpu_feature_enabled(X86_FEATURE_PTI))
+		return;
+
+	/*
+	 * See above.  We need to propagate the flush to all other address
+	 * spaces.  In principle, we only need to propagate it to kernelmode
+	 * address spaces, but the extra bookkeeping we would need is not
+	 * worth it.
+	 */
+	this_cpu_write(cpu_tlbstate.invalidate_other, true);
+}
+
+/*
+ * Flush one page in the user mapping
+ */
+STATIC_NOPV void native_flush_tlb_one_user(unsigned long addr)
+{
+	u32 loaded_mm_asid;
+	bool cpu_pcide;
+
+	/* Flush 'addr' from the kernel PCID: */
+	invlpg(addr);
+
+	/* If PTI is off there is no user PCID and nothing to flush. */
+	if (!cpu_feature_enabled(X86_FEATURE_PTI))
+		return;
+
+	loaded_mm_asid = this_cpu_read(cpu_tlbstate.loaded_mm_asid);
+	cpu_pcide      = this_cpu_read(cpu_tlbstate.cr4) & X86_CR4_PCIDE;
+
+	/*
+	 * invpcid_flush_one(pcid>0) will #GP if CR4.PCIDE==0.  Check
+	 * 'cpu_pcide' to ensure that *this* CPU will not trigger those
+	 * #GP's even if called before CR4.PCIDE has been initialized.
+	 */
+	if (boot_cpu_has(X86_FEATURE_INVPCID) && cpu_pcide)
+		invpcid_flush_one(user_pcid(loaded_mm_asid), addr);
+	else
+		invalidate_user_asid(loaded_mm_asid);
+}
+
+void flush_tlb_one_user(unsigned long addr)
+{
+	__flush_tlb_one_user(addr);
+}
+
+/*
+ * Flush everything
+ */
+STATIC_NOPV void native_flush_tlb_global(void)
+{
+	unsigned long flags;
+
+	if (cpu_feature_enabled(X86_FEATURE_INVPCID)) {
+		/*
+		 * Using INVPCID is considerably faster than a pair of writes
+		 * to CR4 sandwiched inside an IRQ flag save/restore.
+		 *
+		 * Note, this works with CR4.PCIDE=0 or 1.
+		 */
+		invpcid_flush_all();
+		return;
+	}
+
+	/*
+	 * Read-modify-write to CR4 - protect it from preemption and
+	 * from interrupts. (Use the raw variant because this code can
+	 * be called from deep inside debugging code.)
+	 */
+	raw_local_irq_save(flags);
+
+	__native_tlb_flush_global(this_cpu_read(cpu_tlbstate.cr4));
+
+	raw_local_irq_restore(flags);
+}
+
+/*
+ * Flush the entire current user mapping
+ */
+STATIC_NOPV void native_flush_tlb_local(void)
+{
+	/*
+	 * Preemption or interrupts must be disabled to protect the access
+	 * to the per CPU variable and to prevent being preempted between
+	 * read_cr3() and write_cr3().
+	 */
+	WARN_ON_ONCE(preemptible());
+
+	invalidate_user_asid(this_cpu_read(cpu_tlbstate.loaded_mm_asid));
+
+	/* If current->mm == NULL then the read_cr3() "borrows" an mm */
+	native_write_cr3(__native_read_cr3());
+}
+
+void flush_tlb_local(void)
+{
+	__flush_tlb_local();
+}
+
+/*
+ * Flush everything
+ */
+void __flush_tlb_all(void)
+{
+	/*
+	 * This is to catch users with enabled preemption and the PGE feature
+	 * and don't trigger the warning in __native_flush_tlb().
+	 */
+	VM_WARN_ON_ONCE(preemptible());
+
+	if (cpu_feature_enabled(X86_FEATURE_PGE)) {
+		__flush_tlb_global();
+	} else {
+		/*
+		 * !PGE -> !PCID (setup_pcid()), thus every flush is total.
+		 */
+		flush_tlb_local();
+	}
+}
+EXPORT_SYMBOL_FOR_KVM(__flush_tlb_all);
+
+void arch_tlbbatch_flush(struct arch_tlbflush_unmap_batch *batch)
+{
+	struct flush_tlb_info info;
+	bool remote_flush = false;
+	int cpu = get_cpu();
+
+	init_flush_tlb_info(&info, NULL, 0, TLB_FLUSH_ALL, 0, false,
+			    TLB_GENERATION_INVALID);
+	/*
+	 * flush_tlb_multi() is not optimized for the common case in which only
+	 * a local TLB flush is needed. Optimize this use-case by calling
+	 * flush_tlb_func_local() directly in this case.
+	 */
+	if (cpu_feature_enabled(X86_FEATURE_INVLPGB) && batch->unmapped_pages) {
+		invlpgb_flush_all_nonglobals();
+		batch->unmapped_pages = false;
+	} else if (cpumask_any_but(&batch->cpumask, cpu) < nr_cpu_ids) {
+		remote_flush = true;
+	} else if (cpumask_test_cpu(cpu, &batch->cpumask)) {
+		lockdep_assert_irqs_enabled();
+		local_irq_disable();
+		flush_tlb_func(&info);
+		local_irq_enable();
+	}
+
+	put_cpu();
+
+	if (remote_flush)
+		flush_tlb_multi(&batch->cpumask, &info);
+
+	cpumask_clear(&batch->cpumask);
+}
+
+/*
+ * Blindly accessing user memory from NMI context can be dangerous
+ * if we're in the middle of switching the current user task or
+ * switching the loaded mm.  It can also be dangerous if we
+ * interrupted some kernel code that was temporarily using a
+ * different mm.
+ */
+bool nmi_uaccess_okay(void)
+{
+	struct mm_struct *loaded_mm = this_cpu_read(cpu_tlbstate.loaded_mm);
+	struct mm_struct *current_mm = current->mm;
+
+	VM_WARN_ON_ONCE(!loaded_mm);
+
+	/*
+	 * The condition we want to check is
+	 * current_mm->pgd == __va(read_cr3_pa()).  This may be slow, though,
+	 * if we're running in a VM with shadow paging, and nmi_uaccess_okay()
+	 * is supposed to be reasonably fast.
+	 *
+	 * Instead, we check the almost equivalent but somewhat conservative
+	 * condition below, and we rely on the fact that switch_mm_irqs_off()
+	 * sets loaded_mm to LOADED_MM_SWITCHING before writing to CR3.
+	 */
+	if (loaded_mm != current_mm)
+		return false;
+
+	VM_WARN_ON_ONCE(__pa(current_mm->pgd) != read_cr3_pa());
+
+	return true;
+}
+
+static ssize_t tlbflush_read_file(struct file *file, char __user *user_buf,
+				  size_t count, loff_t *ppos)
+{
+	char buf[32];
+	unsigned int len;
+
+	len = sprintf(buf, "%ld\n", tlb_single_page_flush_ceiling);
+	return simple_read_from_buffer(user_buf, count, ppos, buf, len);
+}
+
+static ssize_t tlbflush_write_file(struct file *file, const char __user *user_buf,
+				   size_t count, loff_t *ppos)
+{
+	int ceiling;
+	int err;
+
+	err = kstrtoint_from_user(user_buf, count, 0, &ceiling);
+	if (err)
+		return err;
+
+	if (ceiling < 0)
+		return -EINVAL;
+
+	tlb_single_page_flush_ceiling = ceiling;
+	return count;
+}
+
+static const struct file_operations fops_tlbflush = {
+	.read = tlbflush_read_file,
+	.write = tlbflush_write_file,
+	.llseek = default_llseek,
+};
+
+static int __init create_tlb_single_page_flush_ceiling(void)
+{
+	debugfs_create_file("tlb_single_page_flush_ceiling", S_IRUSR | S_IWUSR,
+			    arch_debugfs_dir, NULL, &fops_tlbflush);
+	return 0;
+}
+late_initcall(create_tlb_single_page_flush_ceiling);