linux-kernel - Re: [kvm-devel] [PATCH] mmu notifiers #v3

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Message-ID: <20080122144332.GE7331@v2.random>
Date:	Tue, 22 Jan 2008 15:43:32 +0100
From:	Andrea Arcangeli <andrea@...ranet.com>
To:	Avi Kivity <avi@...ranet.com>
Cc:	Izik Eidus <izike@...ranet.com>, Andrew Morton <akpm@...l.org>,
	Nick Piggin <npiggin@...e.de>, kvm-devel@...ts.sourceforge.net,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	steiner@....com, linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	daniel.blueman@...drics.com, holt@....com,
	Hugh Dickins <hugh@...itas.com>, clameter@....com
Subject: Re: [kvm-devel] [PATCH] mmu notifiers #v3

On Tue, Jan 22, 2008 at 04:12:34PM +0200, Avi Kivity wrote:
> Andrea Arcangeli wrote:
>> diff --git a/include/asm-generic/pgtable.h b/include/asm-generic/pgtable.h
>> --- a/include/asm-generic/pgtable.h
>> +++ b/include/asm-generic/pgtable.h
>> @@ -44,8 +44,10 @@
>>  ({									\
>>  	int __young;							\
>>  	__young = ptep_test_and_clear_young(__vma, __address, __ptep);	\
>> -	if (__young)							\
>> +	if (__young) {							\
>>  		flush_tlb_page(__vma, __address);			\
>> +		mmu_notifier(age_page, (__vma)->vm_mm, __address);	\
>> +	}								\
>>  	__young;							\
>>  })
>>   
>
> I think that unconditionally doing
>
>  __young |= mmu_notifier(test_and_clear_young, ...);
>
> allows hardware with accessed bits more control over what is going on.

Agreed, likely it'll have to be mmu_notifier_age_page().
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