linux-kernel - Re: [patch 7/7] x86, cpa: global flush tlb after splitting large page and before doing cpa

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Date:	Sat, 13 Sep 2008 10:10:53 -0700
From:	Jeremy Fitzhardinge <jeremy@...p.org>
To:	Suresh Siddha <suresh.b.siddha@...el.com>
CC:	mingo@...e.hu, hpa@...or.com, tglx@...utronix.de,
	arjan@...ux.intel.com, linux-kernel@...r.kernel.org
Subject: Re: [patch 7/7] x86, cpa: global flush tlb after splitting large
 page and before doing cpa

Suresh Siddha wrote:
> Do a global flush tlb after splitting the large page and before we do the
> actual change page attribute in the PTE.
>
> With out this, we violate the TLB application note, which says
>     "The TLBs may contain both ordinary and large-page translations for
>      a 4-KByte range of linear addresses. This may occur if software
>      modifies the paging structures so that the page size used for the
>      address range changes. If the two translations differ with respect
>      to page frame or attributes (e.g., permissions), processor behavior
>      is undefined and may be implementation-specific."
>
> Signed-off-by: Suresh Siddha <suresh.b.siddha@...el.com>
> ---
>
> Index: tip/arch/x86/mm/pageattr.c
> ===================================================================
> --- tip.orig/arch/x86/mm/pageattr.c	2008-09-11 13:25:55.000000000 -0700
> +++ tip/arch/x86/mm/pageattr.c	2008-09-11 13:25:57.000000000 -0700
> @@ -131,6 +131,18 @@
>  	mb();
>  }
>  
> +static void __global_flush_tlb(void *arg)
> +{
> +	__flush_tlb_all();
> +}
> +
> +static void global_flush_tlb(void)
> +{
> +	BUG_ON(irqs_disabled());
> +
> +	on_each_cpu(__global_flush_tlb, NULL, 1);
> +}
>   

Use flush_tlb_others(), which will get paravirtualized properly.

    J
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