From e53f21bce4d35a93b23d8fa1a840860f6c74f59e Mon Sep 17 00:00:00 2001 From: Catalin Marinas Date: Mon, 23 Mar 2015 15:06:50 +0000 Subject: [PATCH] arm64: Use the reserved TTBR0 if context switching to the init_mm 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. Cc: Reported-by: Jon Medhurst (Tixy) Tested-by: Jon Medhurst (Tixy) Signed-off-by: Catalin Marinas --- 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); } -- 2.34.1