| From | Luis Henriques <> | Subject | [PATCH 3.16.y-ckt 098/144] arm64: Use the reserved TTBR0 if context switching to the init_mm | Date | Tue, 21 Apr 2015 16:31:23 +0100 |
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3.16.7-ckt10 -stable review patch. If anyone has any objections, please let me know.
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From: Catalin Marinas <catalin.marinas@arm.com>
commit e53f21bce4d35a93b23d8fa1a840860f6c74f59e upstream.
The idle_task_exit() function may call switch_mm() with next == &init_mm. On arm64, init_mm.pgd cannot be used for user mappings, so this patch simply sets the reserved TTBR0.
Reported-by: Jon Medhurst (Tixy) <tixy@linaro.org> Tested-by: Jon Medhurst (Tixy) <tixy@linaro.org> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com> Signed-off-by: Luis Henriques <luis.henriques@canonical.com> --- arch/arm64/include/asm/mmu_context.h | 9 +++++++++ 1 file changed, 9 insertions(+)
diff --git a/arch/arm64/include/asm/mmu_context.h b/arch/arm64/include/asm/mmu_context.h index a9eee33dfa62..101a42bde728 100644 --- a/arch/arm64/include/asm/mmu_context.h +++ b/arch/arm64/include/asm/mmu_context.h @@ -151,6 +151,15 @@ switch_mm(struct mm_struct *prev, struct mm_struct *next, { unsigned int cpu = smp_processor_id(); + /* + * init_mm.pgd does not contain any user mappings and it is always + * active for kernel addresses in TTBR1. Just set the reserved TTBR0. + */ + if (next == &init_mm) { + cpu_set_reserved_ttbr0(); + return; + } + if (!cpumask_test_and_set_cpu(cpu, mm_cpumask(next)) || prev != next) check_and_switch_context(next, tsk); }
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