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

[Hao, Xudong]

> -----Original Message-----
> From: Avi Kivity [mailto:avi@xxxxxxxxxx]
> Sent: Monday, May 21, 2012 6:48 PM
> To: Hao, Xudong
> Cc: Marcelo Tosatti; Xudong Hao; kvm@xxxxxxxxxxxxxxx;
> linux-kernel@xxxxxxxxxxxxxxx; 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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