Re: [PATCH] x86/mm: disable preemption during CR3 read+write

[Rik van Riel]

On Fri, 2016-08-05 at 15:37 +0200, Sebastian Andrzej Siewior wrote:
>Â
> +++ b/arch/x86/include/asm/tlbflush.h
> @@ -135,7 +135,14 @@ static inline void
> cr4_set_bits_and_update_boot(unsigned long mask)
> Â
> Âstatic inline void __native_flush_tlb(void)
> Â{
> +	/*
> +	Â* if current->mm == NULL then we borrow a mm which may
> change during a
> +	Â* task switch and therefore we must not be preempted while
> we write CR3
> +	Â* back.
> +	Â*/
> +	preempt_disable();
> Â	native_write_cr3(native_read_cr3());
> +	preempt_enable();
> Â}

That is one subtle race!

Acked-by: Rik van Riel <riel@xxxxxxxxxx>

-- 

All Rights Reversed.

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