diff options
| author | Will Deacon <will.deacon@arm.com> | 2015-10-06 18:46:27 +0100 |
|---|---|---|
| committer | Alex Shi <alex.shi@linaro.org> | 2016-05-23 21:09:03 +0800 |
| commit | f366d4a5cedd5c5b3d484f003c249ace1beaf1d3 (patch) | |
| tree | b620a8f1e3fe646356f434951a6d2ee42b31ad4a /arch | |
| parent | 8381eced73741750401bbc8fc5d76438b5f0eba2 (diff) | |
arm64: switch_mm: simplify mm and CPU checks
switch_mm performs some checks to try and avoid entering the ASID
allocator:
(1) If we're switching to the init_mm (no user mappings), then simply
set a reserved TTBR0 value with no page table (the zero page)
(2) If prev == next *and* the mm_cpumask indicates that we've run on
this CPU before, then we can skip the allocator.
However, there is plenty of redundancy here. With the new ASID allocator,
if prev == next, then we know that our ASID is valid and do not need to
worry about re-allocation. Consequently, we can drop the mm_cpumask check
in (2) and move the prev == next check before the init_mm check, since
if prev == next == init_mm then there's nothing to do.
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
(cherry picked from commit c2775b2ee5caca19f661ee2ab5af92462596db71)
Signed-off-by: Alex Shi <alex.shi@linaro.org>
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/arm64/include/asm/mmu_context.h | 6 | ||||
| -rw-r--r-- | arch/arm64/mm/context.c | 2 |
2 files changed, 5 insertions, 3 deletions
diff --git a/arch/arm64/include/asm/mmu_context.h b/arch/arm64/include/asm/mmu_context.h index f4c74a951b6c..c0e87898ba96 100644 --- a/arch/arm64/include/asm/mmu_context.h +++ b/arch/arm64/include/asm/mmu_context.h @@ -129,6 +129,9 @@ switch_mm(struct mm_struct *prev, struct mm_struct *next, { unsigned int cpu = smp_processor_id(); + if (prev == next) + return; + /* * init_mm.pgd does not contain any user mappings and it is always * active for kernel addresses in TTBR1. Just set the reserved TTBR0. @@ -138,8 +141,7 @@ switch_mm(struct mm_struct *prev, struct mm_struct *next, return; } - if (!cpumask_test_and_set_cpu(cpu, mm_cpumask(next)) || prev != next) - check_and_switch_context(next, tsk); + check_and_switch_context(next, cpu); } #define deactivate_mm(tsk,mm) do { } while (0) diff --git a/arch/arm64/mm/context.c b/arch/arm64/mm/context.c index e902229b1a3d..4b9ec4484e3f 100644 --- a/arch/arm64/mm/context.c +++ b/arch/arm64/mm/context.c @@ -166,10 +166,10 @@ void check_and_switch_context(struct mm_struct *mm, unsigned int cpu) 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: + cpumask_set_cpu(cpu, mm_cpumask(mm)); cpu_switch_mm(mm->pgd, mm); } |