This is a note to let you know that I've just added the patch titled
arm64: Use the reserved TTBR0 if context switching to the init_mm
to the 3.19-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
arm64-use-the-reserved-ttbr0-if-context-switching-to-the-init_mm.patch
and it can be found in the queue-3.19 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From e53f21bce4d35a93b23d8fa1a840860f6c74f59e Mon Sep 17 00:00:00 2001
From: Catalin Marinas <catalin.marinas@xxxxxxx>
Date: Mon, 23 Mar 2015 15:06:50 +0000
Subject: arm64: Use the reserved TTBR0 if context switching to the init_mm
From: Catalin Marinas <catalin.marinas@xxxxxxx>
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@xxxxxxxxxx>
Tested-by: Jon Medhurst (Tixy) <tixy@xxxxxxxxxx>
Signed-off-by: Catalin Marinas <catalin.marinas@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/arm64/include/asm/mmu_context.h | 9 +++++++++
1 file changed, 9 insertions(+)
--- 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
{
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);
}
Patches currently in stable-queue which might be from catalin.marinas@xxxxxxx are
queue-3.19/arm64-percpu-make-this_cpu-accessors-pre-empt-safe.patch
queue-3.19/arm64-use-the-reserved-ttbr0-if-context-switching-to-the-init_mm.patch
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