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authorRussell King <rmk+kernel@arm.linux.org.uk>2012-11-19 11:30:49 +0000
committerRussell King <rmk+kernel@arm.linux.org.uk>2012-11-19 11:30:49 +0000
commit2079f30e9e83887ca95fa129d0bc734b2c4b406d (patch)
tree91dbfd05c27d757e4e05a265308542bf54d8d3b7 /arch/arm/mm
parentf27d9b7198a0a0ffbd872a4b795c7613cd759ea3 (diff)
parentbf51bb82ccd9a74e9702d06107b23e54b27a5707 (diff)
Merge branch 'asid-allocation' of git://git.kernel.org/pub/scm/linux/kernel/git/will/linux into devel-stable
Diffstat (limited to 'arch/arm/mm')
-rw-r--r--arch/arm/mm/context.c207
1 files changed, 108 insertions, 99 deletions
diff --git a/arch/arm/mm/context.c b/arch/arm/mm/context.c
index 4e07eec1270..7a27d7363be 100644
--- a/arch/arm/mm/context.c
+++ b/arch/arm/mm/context.c
@@ -2,6 +2,9 @@
* 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
@@ -14,14 +17,40 @@
#include <linux/percpu.h>
#include <asm/mmu_context.h>
+#include <asm/smp_plat.h>
#include <asm/thread_notify.h>
#include <asm/tlbflush.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.
+ */
+#define ASID_FIRST_VERSION (1ULL << ASID_BITS)
+#define NUM_USER_ASIDS (ASID_FIRST_VERSION - 1)
+
+#define ASID_TO_IDX(asid) ((asid & ~ASID_MASK) - 1)
+#define IDX_TO_ASID(idx) ((idx + 1) & ~ASID_MASK)
+
static DEFINE_RAW_SPINLOCK(cpu_asid_lock);
-unsigned int cpu_last_asid = ASID_FIRST_VERSION;
+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_LPAE
-void cpu_set_reserved_ttbr0(void)
+static void cpu_set_reserved_ttbr0(void)
{
unsigned long ttbl = __pa(swapper_pg_dir);
unsigned long ttbh = 0;
@@ -37,7 +66,7 @@ void cpu_set_reserved_ttbr0(void)
isb();
}
#else
-void cpu_set_reserved_ttbr0(void)
+static void cpu_set_reserved_ttbr0(void)
{
u32 ttb;
/* Copy TTBR1 into TTBR0 */
@@ -84,124 +113,104 @@ static int __init contextidr_notifier_init(void)
arch_initcall(contextidr_notifier_init);
#endif
-/*
- * We fork()ed a process, and we need a new context for the child
- * to run in.
- */
-void __init_new_context(struct task_struct *tsk, struct mm_struct *mm)
+static void flush_context(unsigned int cpu)
{
- mm->context.id = 0;
- raw_spin_lock_init(&mm->context.id_lock);
-}
+ 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) {
+ if (i == cpu) {
+ asid = 0;
+ } else {
+ asid = atomic64_xchg(&per_cpu(active_asids, i), 0);
+ __set_bit(ASID_TO_IDX(asid), asid_map);
+ }
+ per_cpu(reserved_asids, i) = asid;
+ }
-static void flush_context(void)
-{
- cpu_set_reserved_ttbr0();
- local_flush_tlb_all();
- if (icache_is_vivt_asid_tagged()) {
+ /* Queue a TLB invalidate and flush the I-cache if necessary. */
+ if (!tlb_ops_need_broadcast())
+ cpumask_set_cpu(cpu, &tlb_flush_pending);
+ else
+ cpumask_setall(&tlb_flush_pending);
+
+ if (icache_is_vivt_asid_tagged())
__flush_icache_all();
- dsb();
- }
}
-#ifdef CONFIG_SMP
+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 void set_mm_context(struct mm_struct *mm, unsigned int asid)
+static void new_context(struct mm_struct *mm, unsigned int cpu)
{
- unsigned long flags;
+ u64 asid = mm->context.id;
+ u64 generation = atomic64_read(&asid_generation);
- /*
- * Locking needed for multi-threaded applications where the
- * same mm->context.id could be set from different CPUs during
- * the broadcast. This function is also called via IPI so the
- * mm->context.id_lock has to be IRQ-safe.
- */
- raw_spin_lock_irqsave(&mm->context.id_lock, flags);
- if (likely((mm->context.id ^ cpu_last_asid) >> ASID_BITS)) {
+ if (asid != 0 && is_reserved_asid(asid)) {
/*
- * Old version of ASID found. Set the new one and
- * reset mm_cpumask(mm).
+ * Our current ASID was active during a rollover, we can
+ * continue to use it and this was just a false alarm.
*/
- mm->context.id = asid;
+ asid = generation | (asid & ~ASID_MASK);
+ } else {
+ /*
+ * 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.
+ */
+ asid = find_first_zero_bit(asid_map, NUM_USER_ASIDS);
+ if (asid == NUM_USER_ASIDS) {
+ generation = atomic64_add_return(ASID_FIRST_VERSION,
+ &asid_generation);
+ flush_context(cpu);
+ asid = find_first_zero_bit(asid_map, NUM_USER_ASIDS);
+ }
+ __set_bit(asid, asid_map);
+ asid = generation | IDX_TO_ASID(asid);
cpumask_clear(mm_cpumask(mm));
}
- raw_spin_unlock_irqrestore(&mm->context.id_lock, flags);
- /*
- * Set the mm_cpumask(mm) bit for the current CPU.
- */
- cpumask_set_cpu(smp_processor_id(), mm_cpumask(mm));
+ mm->context.id = asid;
}
-/*
- * Reset the ASID on the current CPU. This function call is broadcast
- * from the CPU handling the ASID rollover and holding cpu_asid_lock.
- */
-static void reset_context(void *info)
+void check_and_switch_context(struct mm_struct *mm, struct task_struct *tsk)
{
- unsigned int asid;
+ unsigned long flags;
unsigned int cpu = smp_processor_id();
- struct mm_struct *mm = current->active_mm;
- smp_rmb();
- asid = cpu_last_asid + cpu + 1;
+ if (unlikely(mm->context.kvm_seq != init_mm.context.kvm_seq))
+ __check_kvm_seq(mm);
- flush_context();
- set_mm_context(mm, asid);
-
- /* set the new ASID */
- cpu_switch_mm(mm->pgd, mm);
-}
+ /*
+ * Required during context switch to avoid speculative page table
+ * walking with the wrong TTBR.
+ */
+ cpu_set_reserved_ttbr0();
-#else
+ if (!((mm->context.id ^ atomic64_read(&asid_generation)) >> ASID_BITS)
+ && atomic64_xchg(&per_cpu(active_asids, cpu), mm->context.id))
+ goto switch_mm_fastpath;
-static inline void set_mm_context(struct mm_struct *mm, unsigned int asid)
-{
- mm->context.id = asid;
- cpumask_copy(mm_cpumask(mm), cpumask_of(smp_processor_id()));
-}
+ raw_spin_lock_irqsave(&cpu_asid_lock, flags);
+ /* Check that our ASID belongs to the current generation. */
+ if ((mm->context.id ^ atomic64_read(&asid_generation)) >> ASID_BITS)
+ new_context(mm, cpu);
-#endif
+ atomic64_set(&per_cpu(active_asids, cpu), mm->context.id);
+ cpumask_set_cpu(cpu, mm_cpumask(mm));
-void __new_context(struct mm_struct *mm)
-{
- unsigned int asid;
+ if (cpumask_test_and_clear_cpu(cpu, &tlb_flush_pending))
+ local_flush_tlb_all();
+ raw_spin_unlock_irqrestore(&cpu_asid_lock, flags);
- raw_spin_lock(&cpu_asid_lock);
-#ifdef CONFIG_SMP
- /*
- * Check the ASID again, in case the change was broadcast from
- * another CPU before we acquired the lock.
- */
- if (unlikely(((mm->context.id ^ cpu_last_asid) >> ASID_BITS) == 0)) {
- cpumask_set_cpu(smp_processor_id(), mm_cpumask(mm));
- raw_spin_unlock(&cpu_asid_lock);
- return;
- }
-#endif
- /*
- * At this point, it is guaranteed that the current mm (with
- * an old ASID) isn't active on any other CPU since the ASIDs
- * are changed simultaneously via IPI.
- */
- asid = ++cpu_last_asid;
- if (asid == 0)
- asid = cpu_last_asid = ASID_FIRST_VERSION;
-
- /*
- * If we've used up all our ASIDs, we need
- * to start a new version and flush the TLB.
- */
- if (unlikely((asid & ~ASID_MASK) == 0)) {
- asid = cpu_last_asid + smp_processor_id() + 1;
- flush_context();
-#ifdef CONFIG_SMP
- smp_wmb();
- smp_call_function(reset_context, NULL, 1);
-#endif
- cpu_last_asid += NR_CPUS;
- }
-
- set_mm_context(mm, asid);
- raw_spin_unlock(&cpu_asid_lock);
+switch_mm_fastpath:
+ cpu_switch_mm(mm->pgd, mm);
}