v4.19.13 snapshot.
diff --git a/arch/arm/mm/context.c b/arch/arm/mm/context.c
new file mode 100644
index 0000000..c8c8b9e
--- /dev/null
+++ b/arch/arm/mm/context.c
@@ -0,0 +1,280 @@
+/*
+ * linux/arch/arm/mm/context.c
+ *
+ * Copyright (C) 2002-2003 Deep Blue Solutions Ltd, all rights reserved.
+ * Copyright (C) 2012 ARM Limited
+ *
+ * Author: Will Deacon <will.deacon@arm.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+#include <linux/init.h>
+#include <linux/sched.h>
+#include <linux/mm.h>
+#include <linux/smp.h>
+#include <linux/percpu.h>
+
+#include <asm/mmu_context.h>
+#include <asm/smp_plat.h>
+#include <asm/thread_notify.h>
+#include <asm/tlbflush.h>
+#include <asm/proc-fns.h>
+
+/*
+ * On ARMv6, we have the following structure in the Context ID:
+ *
+ * 31 7 0
+ * +-------------------------+-----------+
+ * | process ID | ASID |
+ * +-------------------------+-----------+
+ * | context ID |
+ * +-------------------------------------+
+ *
+ * The ASID is used to tag entries in the CPU caches and TLBs.
+ * The context ID is used by debuggers and trace logic, and
+ * should be unique within all running processes.
+ *
+ * In big endian operation, the two 32 bit words are swapped if accessed
+ * by non-64-bit operations.
+ */
+#define ASID_FIRST_VERSION (1ULL << ASID_BITS)
+#define NUM_USER_ASIDS ASID_FIRST_VERSION
+
+static DEFINE_RAW_SPINLOCK(cpu_asid_lock);
+static atomic64_t asid_generation = ATOMIC64_INIT(ASID_FIRST_VERSION);
+static DECLARE_BITMAP(asid_map, NUM_USER_ASIDS);
+
+static DEFINE_PER_CPU(atomic64_t, active_asids);
+static DEFINE_PER_CPU(u64, reserved_asids);
+static cpumask_t tlb_flush_pending;
+
+#ifdef CONFIG_ARM_ERRATA_798181
+void a15_erratum_get_cpumask(int this_cpu, struct mm_struct *mm,
+ cpumask_t *mask)
+{
+ int cpu;
+ unsigned long flags;
+ u64 context_id, asid;
+
+ raw_spin_lock_irqsave(&cpu_asid_lock, flags);
+ context_id = mm->context.id.counter;
+ for_each_online_cpu(cpu) {
+ if (cpu == this_cpu)
+ continue;
+ /*
+ * We only need to send an IPI if the other CPUs are
+ * running the same ASID as the one being invalidated.
+ */
+ asid = per_cpu(active_asids, cpu).counter;
+ if (asid == 0)
+ asid = per_cpu(reserved_asids, cpu);
+ if (context_id == asid)
+ cpumask_set_cpu(cpu, mask);
+ }
+ raw_spin_unlock_irqrestore(&cpu_asid_lock, flags);
+}
+#endif
+
+#ifdef CONFIG_ARM_LPAE
+/*
+ * With LPAE, the ASID and page tables are updated atomicly, so there is
+ * no need for a reserved set of tables (the active ASID tracking prevents
+ * any issues across a rollover).
+ */
+#define cpu_set_reserved_ttbr0()
+#else
+static void cpu_set_reserved_ttbr0(void)
+{
+ u32 ttb;
+ /*
+ * Copy TTBR1 into TTBR0.
+ * This points at swapper_pg_dir, which contains only global
+ * entries so any speculative walks are perfectly safe.
+ */
+ asm volatile(
+ " mrc p15, 0, %0, c2, c0, 1 @ read TTBR1\n"
+ " mcr p15, 0, %0, c2, c0, 0 @ set TTBR0\n"
+ : "=r" (ttb));
+ isb();
+}
+#endif
+
+#ifdef CONFIG_PID_IN_CONTEXTIDR
+static int contextidr_notifier(struct notifier_block *unused, unsigned long cmd,
+ void *t)
+{
+ u32 contextidr;
+ pid_t pid;
+ struct thread_info *thread = t;
+
+ if (cmd != THREAD_NOTIFY_SWITCH)
+ return NOTIFY_DONE;
+
+ pid = task_pid_nr(thread->task) << ASID_BITS;
+ asm volatile(
+ " mrc p15, 0, %0, c13, c0, 1\n"
+ " and %0, %0, %2\n"
+ " orr %0, %0, %1\n"
+ " mcr p15, 0, %0, c13, c0, 1\n"
+ : "=r" (contextidr), "+r" (pid)
+ : "I" (~ASID_MASK));
+ isb();
+
+ return NOTIFY_OK;
+}
+
+static struct notifier_block contextidr_notifier_block = {
+ .notifier_call = contextidr_notifier,
+};
+
+static int __init contextidr_notifier_init(void)
+{
+ return thread_register_notifier(&contextidr_notifier_block);
+}
+arch_initcall(contextidr_notifier_init);
+#endif
+
+static void flush_context(unsigned int cpu)
+{
+ int i;
+ u64 asid;
+
+ /* Update the list of reserved ASIDs and the ASID bitmap. */
+ bitmap_clear(asid_map, 0, NUM_USER_ASIDS);
+ for_each_possible_cpu(i) {
+ asid = atomic64_xchg(&per_cpu(active_asids, i), 0);
+ /*
+ * If this CPU has already been through a
+ * rollover, but hasn't run another task in
+ * the meantime, we must preserve its reserved
+ * ASID, as this is the only trace we have of
+ * the process it is still running.
+ */
+ if (asid == 0)
+ asid = per_cpu(reserved_asids, i);
+ __set_bit(asid & ~ASID_MASK, asid_map);
+ per_cpu(reserved_asids, i) = asid;
+ }
+
+ /* Queue a TLB invalidate and flush the I-cache if necessary. */
+ cpumask_setall(&tlb_flush_pending);
+
+ if (icache_is_vivt_asid_tagged())
+ __flush_icache_all();
+}
+
+static bool check_update_reserved_asid(u64 asid, u64 newasid)
+{
+ int cpu;
+ bool hit = false;
+
+ /*
+ * Iterate over the set of reserved ASIDs looking for a match.
+ * If we find one, then we can update our mm to use newasid
+ * (i.e. the same ASID in the current generation) but we can't
+ * exit the loop early, since we need to ensure that all copies
+ * of the old ASID are updated to reflect the mm. Failure to do
+ * so could result in us missing the reserved ASID in a future
+ * generation.
+ */
+ for_each_possible_cpu(cpu) {
+ if (per_cpu(reserved_asids, cpu) == asid) {
+ hit = true;
+ per_cpu(reserved_asids, cpu) = newasid;
+ }
+ }
+
+ return hit;
+}
+
+static u64 new_context(struct mm_struct *mm, unsigned int cpu)
+{
+ static u32 cur_idx = 1;
+ u64 asid = atomic64_read(&mm->context.id);
+ u64 generation = atomic64_read(&asid_generation);
+
+ if (asid != 0) {
+ u64 newasid = generation | (asid & ~ASID_MASK);
+
+ /*
+ * If our current ASID was active during a rollover, we
+ * can continue to use it and this was just a false alarm.
+ */
+ if (check_update_reserved_asid(asid, newasid))
+ return newasid;
+
+ /*
+ * We had a valid ASID in a previous life, so try to re-use
+ * it if possible.,
+ */
+ asid &= ~ASID_MASK;
+ if (!__test_and_set_bit(asid, asid_map))
+ return newasid;
+ }
+
+ /*
+ * Allocate a free ASID. If we can't find one, take a note of the
+ * currently active ASIDs and mark the TLBs as requiring flushes.
+ * We always count from ASID #1, as we reserve ASID #0 to switch
+ * via TTBR0 and to avoid speculative page table walks from hitting
+ * in any partial walk caches, which could be populated from
+ * overlapping level-1 descriptors used to map both the module
+ * area and the userspace stack.
+ */
+ asid = find_next_zero_bit(asid_map, NUM_USER_ASIDS, cur_idx);
+ if (asid == NUM_USER_ASIDS) {
+ generation = atomic64_add_return(ASID_FIRST_VERSION,
+ &asid_generation);
+ flush_context(cpu);
+ asid = find_next_zero_bit(asid_map, NUM_USER_ASIDS, 1);
+ }
+
+ __set_bit(asid, asid_map);
+ cur_idx = asid;
+ cpumask_clear(mm_cpumask(mm));
+ return asid | generation;
+}
+
+void check_and_switch_context(struct mm_struct *mm, struct task_struct *tsk)
+{
+ unsigned long flags;
+ unsigned int cpu = smp_processor_id();
+ u64 asid;
+
+ if (unlikely(mm->context.vmalloc_seq != init_mm.context.vmalloc_seq))
+ __check_vmalloc_seq(mm);
+
+ /*
+ * We cannot update the pgd and the ASID atomicly with classic
+ * MMU, so switch exclusively to global mappings to avoid
+ * speculative page table walking with the wrong TTBR.
+ */
+ cpu_set_reserved_ttbr0();
+
+ asid = atomic64_read(&mm->context.id);
+ if (!((asid ^ atomic64_read(&asid_generation)) >> ASID_BITS)
+ && atomic64_xchg(&per_cpu(active_asids, cpu), asid))
+ goto switch_mm_fastpath;
+
+ raw_spin_lock_irqsave(&cpu_asid_lock, flags);
+ /* Check that our ASID belongs to the current generation. */
+ asid = atomic64_read(&mm->context.id);
+ if ((asid ^ atomic64_read(&asid_generation)) >> ASID_BITS) {
+ asid = new_context(mm, cpu);
+ atomic64_set(&mm->context.id, asid);
+ }
+
+ if (cpumask_test_and_clear_cpu(cpu, &tlb_flush_pending)) {
+ local_flush_bp_all();
+ local_flush_tlb_all();
+ }
+
+ atomic64_set(&per_cpu(active_asids, cpu), asid);
+ cpumask_set_cpu(cpu, mm_cpumask(mm));
+ raw_spin_unlock_irqrestore(&cpu_asid_lock, flags);
+
+switch_mm_fastpath:
+ cpu_switch_mm(mm->pgd, mm);
+}