linux-kernel - Re: [PATCH 3/4] KVM: MMU: track dirty page in speculative path properly

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Message-ID: <20100714110926.GA26033@amt.cnet>
Date:	Wed, 14 Jul 2010 08:09:27 -0300
From:	Marcelo Tosatti <mtosatti@...hat.com>
To:	Xiao Guangrong <xiaoguangrong@...fujitsu.com>
Cc:	Avi Kivity <avi@...hat.com>, LKML <linux-kernel@...r.kernel.org>,
	KVM list <kvm@...r.kernel.org>
Subject: Re: [PATCH 3/4] KVM: MMU: track dirty page in speculative path
 properly

On Wed, Jul 14, 2010 at 09:24:22AM +0800, Xiao Guangrong wrote:
> 
> 
> Marcelo Tosatti wrote:
> > On Tue, Jul 13, 2010 at 05:45:27PM +0800, Xiao Guangrong wrote:
> >> In speculative path, the page is not real write-access, no need mark it
> >> dirty, so clear dirty bit in this path and later examine this bit when
> >> we release the page
> >>
> >> Signed-off-by: Xiao Guangrong <xiaoguangrong@...fujitsu.com>
> >> ---
> >>  arch/x86/kvm/mmu.c |   24 +++++++++++-------------
> >>  1 files changed, 11 insertions(+), 13 deletions(-)
> > 
> > Unfortunately all pages that kvm creates translations for are marked
> > dirty due to get_user_pages(w=1), except KSM which makes them read-only
> > later.
> 
> Marcelo, i have looked into get_user_pages() function, but not catch where
> to make page dirty, could you point it out for me? :-)

See set_page_dirty call in mm/memory.c::follow_page.
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