From 57f0f512b273f60d52568b8c6b77e17f5636edc0 Mon Sep 17 00:00:00 2001 From: André Fabian Silva Delgado Date: Wed, 5 Aug 2015 17:04:01 -0300 Subject: Initial import --- arch/arm/mm/context.c | 266 ++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 266 insertions(+) create mode 100644 arch/arm/mm/context.c (limited to 'arch/arm/mm/context.c') diff --git a/arch/arm/mm/context.c b/arch/arm/mm/context.c new file mode 100644 index 000000000..845769e41 --- /dev/null +++ b/arch/arm/mm/context.c @@ -0,0 +1,266 @@ +/* + * 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 + * + * 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 +#include +#include +#include +#include + +#include +#include +#include +#include +#include + +/* + * 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 int is_reserved_asid(u64 asid) +{ + int cpu; + for_each_possible_cpu(cpu) + if (per_cpu(reserved_asids, cpu) == asid) + return 1; + return 0; +} + +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) { + /* + * If our current ASID was active during a rollover, we + * can continue to use it and this was just a false alarm. + */ + if (is_reserved_asid(asid)) + return generation | (asid & ~ASID_MASK); + + /* + * 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)) + goto bump_gen; + } + + /* + * 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; + +bump_gen: + asid |= generation; + cpumask_clear(mm_cpumask(mm)); + return asid; +} + +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); +} -- cgit v1.2.3-54-g00ecf