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authorWill Deacon <will.deacon@arm.com>2015-10-06 18:46:27 +0100
committerCatalin Marinas <catalin.marinas@arm.com>2015-10-07 11:56:25 +0100
commitc2775b2ee5caca19f661ee2ab5af92462596db71 (patch)
treeebcc6eb88426e864d8f716543e69f398f1fc1c91 /arch/arm64/include/asm/mmu_context.h
parent5a7862e83000ccfd36db927c6f060458fe271157 (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>
Diffstat (limited to 'arch/arm64/include/asm/mmu_context.h')
-rw-r--r--arch/arm64/include/asm/mmu_context.h6
1 files changed, 4 insertions, 2 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)