lkml.org 
[lkml]   [2012]   [May]   [21]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH 4/4] Enabling Access bit when doing memory swapping
On 05/21/2012 02:17 PM, Hao, Xudong wrote:
> > -----Original Message-----
> > From: Avi Kivity [mailto:avi@redhat.com]
> > Sent: Monday, May 21, 2012 6:48 PM
> > To: Hao, Xudong
> > Cc: Marcelo Tosatti; Xudong Hao; kvm@vger.kernel.org;
> > linux-kernel@vger.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?

I think it's fine.

> > IIRC
> > bsfl is slow, but this shouldn't be a problem here.
> >
>
> I do not know the story...
>

No story, bsf is a relatively slow instruction, but it shouldn't affect
us here; this isn't a fast path and in any case it's only a few cycles.

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



\
 
 \ /
  Last update: 2012-05-21 14:01    [W:0.066 / U:1.200 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site