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x86/mm: Remove preempt_disable/enable() from __native_flush_tlb()

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The preempt_disable/enable() pair in __native_flush_tlb() was added in
commit:

  5cf0791da5 ("x86/mm: Disable preemption during CR3 read+write")

... to protect the UP variant of flush_tlb_mm_range().

That preempt_disable/enable() pair should have been added to the UP variant
of flush_tlb_mm_range() instead.

The UP variant was removed with commit:

  ce4a4e565f ("x86/mm: Remove the UP asm/tlbflush.h code, always use the (formerly) SMP code")

... but the preempt_disable/enable() pair stayed around.

The latest change to __native_flush_tlb() in commit:

  6fd166aae7 ("x86/mm: Use/Fix PCID to optimize user/kernel switches")

... added an access to a per CPU variable outside the preempt disabled
regions, which makes no sense at all. __native_flush_tlb() must always
be called with at least preemption disabled.

Remove the preempt_disable/enable() pair and add a WARN_ON_ONCE() to catch
bad callers independent of the smp_processor_id() debugging.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: <stable@vger.kernel.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Dominik Brodowski <linux@dominikbrodowski.net>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linuxfoundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20171230211829.679325424@linutronix.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Thomas Gleixner 2017-12-30 22:13:54 +01:00 committed by Ingo Molnar
parent 322f8b8b34
commit decab0888e
1 changed files with 8 additions and 6 deletions
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14
arch/x86/include/asm/tlbflush.h
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@ -345,15 +345,17 @@ static inline void invalidate_user_asid(u16 asid)
*/
static inline void __native_flush_tlb(void)
{
invalidate_user_asid(this_cpu_read(cpu_tlbstate.loaded_mm_asid));
/*
* If current->mm == NULL then we borrow a mm which may change
* during a task switch and therefore we must not be preempted
* while we write CR3 back:
* Preemption or interrupts must be disabled to protect the access
* to the per CPU variable and to prevent being preempted between
* read_cr3() and write_cr3().
*/
preempt_disable();
WARN_ON_ONCE(preemptible());
invalidate_user_asid(this_cpu_read(cpu_tlbstate.loaded_mm_asid));
/* If current->mm == NULL then the read_cr3() "borrows" an mm */
native_write_cr3(__native_read_cr3());
preempt_enable();
}
/*