Commit 078194f8 authored Apr 26, 2016 by Andy Lutomirski Committed by Ingo Molnar Apr 28, 2016

x86/mm, sched/core: Turn off IRQs in switch_mm()



Potential races between switch_mm() and TLB-flush or LDT-flush IPIs
could be very messy.  AFAICT the code is currently okay, whether by
accident or by careful design, but enabling PCID will make it
considerably more complicated and will no longer be obviously safe.

Fix it with a big hammer: run switch_mm() with IRQs off.

To avoid a performance hit in the scheduler, we take advantage of
our knowledge that the scheduler already has IRQs disabled when it
calls switch_mm().

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Reviewed-by: Borislav Petkov <bp@suse.de>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/f19baf759693c9dcae64bbff76189db77cb13398.1461688545.git.luto@kernel.org


Signed-off-by: Ingo Molnar <mingo@kernel.org>

parent 69c0319a

arch/x86/include/asm/mmu_context.h

+3 −0

Original line number	Diff line number	Diff line
		@@ -118,6 +118,9 @@ static inline void destroy_context(struct mm_struct *mm)
		extern void switch_mm(struct mm_struct prev, struct mm_struct next,
		struct task_struct *tsk);

		extern void switch_mm_irqs_off(struct mm_struct prev, struct mm_struct next,
		struct task_struct *tsk);
		#define switch_mm_irqs_off switch_mm_irqs_off

		#define activate_mm(prev, next) \
		do { \

arch/x86/mm/tlb.c

+10 −0

Original line number	Diff line number	Diff line
		@@ -63,6 +63,16 @@ EXPORT_SYMBOL_GPL(leave_mm);

		void switch_mm(struct mm_struct prev, struct mm_struct next,
		struct task_struct *tsk)
		{
		unsigned long flags;

		local_irq_save(flags);
		switch_mm_irqs_off(prev, next, tsk);
		local_irq_restore(flags);
		}

		void switch_mm_irqs_off(struct mm_struct prev, struct mm_struct next,
		struct task_struct *tsk)
		{
		unsigned cpu = smp_processor_id();

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