linux-kernel - Re: [PATCH v3 11/11] KVM: MMU: improve write flooding detected

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Message-ID: <4E707AE5.2030704@redhat.com>
Date:	Wed, 14 Sep 2011 12:59:01 +0300
From:	Avi Kivity <avi@...hat.com>
To:	Xiao Guangrong <xiaoguangrong@...fujitsu.com>
CC:	Marcelo Tosatti <mtosatti@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>, KVM <kvm@...r.kernel.org>
Subject: Re: [PATCH v3 11/11] KVM: MMU: improve write flooding detected

On 09/13/2011 10:19 PM, Xiao Guangrong wrote:
> >
> >  The spte may not be accessed, but other sptes in the same page can be accessed.  An example is the fixmap area for kmap_atomic(), there will be a lot of pte writes but other sptes will be accessed without going through soft-mmu at all.
>
> I think this kind of shadow pae is mostly the last page table(level=1), maybe
> we can skip the write-flooding for the last shadow page, because the last shadow
> page can become unsync and it can not let page table write-protected.

Yes.

>
> >  I think you have to read the parent_ptes->spte.accessed bits to be sure.
> >
>
> I guess the overload of this way is little high:
> - it needs to walk parent ptes for every shadow pages
> - we need to clear the parent_ptes->spte.accessed bit when the page is written, and
>    the tlb flush is needed.
> no?
>

Right.

-- 
error compiling committee.c: too many arguments to function

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