linux-kernel - RE: [PATCH 4/4] Enabling Access bit when doing memory swapping

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Message-ID: <403610A45A2B5242BD291EDAE8B37D300FDC6F2E@SHSMSX102.ccr.corp.intel.com>
Date:	Mon, 21 May 2012 11:17:32 +0000
From:	"Hao, Xudong" <xudong.hao@...el.com>
To:	Avi Kivity <avi@...hat.com>
CC:	Marcelo Tosatti <mtosatti@...hat.com>,
	Xudong Hao <xudong.hao@...ux.intel.com>,
	"kvm@...r.kernel.org" <kvm@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"Shan, Haitao" <haitao.shan@...el.com>,
	"Zhang, Xiantao" <xiantao.zhang@...el.com>
Subject: RE: [PATCH 4/4] Enabling Access bit when doing memory swapping

> -----Original Message-----
> From: Avi Kivity [mailto:avi@...hat.com]
> Sent: Monday, May 21, 2012 6:48 PM
> To: Hao, Xudong
> Cc: Marcelo Tosatti; Xudong Hao; kvm@...r.kernel.org;
> linux-kernel@...r.kernel.org; Shan, Haitao; Zhang, Xiantao
> Subject: Re: [PATCH 4/4] Enabling Access bit when doing memory swapping
> 
> On 05/21/2012 01:35 PM, Hao, Xudong wrote:
> > >
> > > That doesn't answer the question.  An atomic operation is now
> non-atomic.
> > >
> > > You can calculate shadow_accessed_bit and keep on using clear_bit(), or
> > > switch to cmpxchg64(), but don't just drop the dirty bit here.
> > >
> >
> > I know your meaning. How about this changes:
> >
> > ...
> >             young = 1;
> > +            if (enable_ept_ad_bits)
> > +                clear_bit(ffs(shadow_accessed_mask), (unsigned long
> *)spte);
> 
> ffs() returns an off-by-one result, so this needs to be adjusted. 

Yes, it need to decrease 1, I'll send v3 version for patch4, any other comments?

> IIRC
> bsfl is slow, but this shouldn't be a problem here.
> 

I do not know the story...

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

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