Re: [PATCH 2/2] I386 convert pae wmb to non smp

[Nick Piggin]

Zachary Amsden wrote:

> Similar to the last bug, on set_pte, we don't want the compiler to re-order
> the write of the PTE, even in non-SMP configurations, since if the write of
> the low word occurs first, the TLB could prefetch a bad highmem mapping which
> has been aliased into low memory.

wmb() means that it also orders IO memory. It is no difference for
i386, but smp_wmb() actually has the right semantics of the abstract
Linux memory model.

> Signed-off-by: Zachary Amsden <zach@xxxxxxxxxx>
>
> Index: linux-2.6.17-rc/include/asm-i386/pgtable-3level.h
> ===================================================================
> --- linux-2.6.17-rc.orig/include/asm-i386/pgtable-3level.h	2006-04-26 08:38:57.000000000 -0700
> +++ linux-2.6.17-rc/include/asm-i386/pgtable-3level.h	2006-04-26 14:45:12.000000000 -0700
> @@ -53,7 +53,7 @@ static inline int pte_exec_kernel(pte_t 
> static inline void set_pte(pte_t *ptep, pte_t pte)
> {
> 	ptep->pte_high = pte.pte_high;
> -	smp_wmb();
> +	wmb();
> 	ptep->pte_low = pte.pte_low;
> }
> #define set_pte_at(mm,addr,ptep,pteval) set_pte(ptep,pteval)
>
>  

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