On Fri, 2016-08-05 at 15:37 +0200, Sebastian Andrzej Siewior wrote:
>
> +++ b/arch/x86/include/asm/tlbflush.h
> @@ -135,7 +135,14 @@ static inline void
> cr4_set_bits_and_update_boot(unsigned long mask)
>
> static inline void __native_flush_tlb(void)
> {
> + /*
> + * 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.
> + */
> + preempt_disable();
> native_write_cr3(native_read_cr3());
> + preempt_enable();
> }
That is one subtle race!
Acked-by: Rik van Riel <riel@xxxxxxxxxx>
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