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SubjectRE: [patch]pageattr: cache flush before tlb flush

>-----Original Message-----
>From: H. Peter Anvin []
>Sent: Tuesday, August 19, 2008 1:10 PM
>To: Li, Shaohua
>Cc: lkml; Andrew Morton; Ingo Molnar; Pallipadi, Venkatesh
>Subject: Re: [patch]pageattr: cache flush before tlb flush
>Shaohua Li wrote:
>> clflush uses a virtual address but cache line is physical indexed in
>> x86. In my understanding, clflush will do some pagetable walk, so doing
>> cache flush first should reduce some pagetable walk.
>> Signed-off-by: Shaohua Li <>
>I would say NAK on this.
>Doing the CLFLUSH first does cut down on page table walking, but opens a
>hole in the sequencing: first set PAT to an uncachable mode, then flush.
>If an unlucky prefetch comes in during this window, then you will have a
>dirty cache again.
>So no, this is not a good idea.
Ok, looks possible in theory.


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