linux-kernel - Re: [PATCH 1/2] x86: eliminate TS

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Date:	Tue, 04 May 2010 11:15:27 -0700
From:	Suresh Siddha <suresh.b.siddha@...el.com>
To:	Avi Kivity <avi@...hat.com>
Cc:	"H. Peter Anvin" <hpa@...or.com>, Brian Gerst <brgerst@...il.com>,
	"Cui, Dexuan" <dexuan.cui@...el.com>,
	Sheng Yang <sheng@...ux.intel.com>,
	Ingo Molnar <mingo@...e.hu>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"kvm@...r.kernel.org" <kvm@...r.kernel.org>
Subject: Re: [PATCH 1/2] x86: eliminate TS_XSAVE

On Tue, 2010-05-04 at 00:41 -0700, Avi Kivity wrote:
> On 05/04/2010 12:45 AM, H. Peter Anvin wrote:
> >
> >> I was trying to avoid a performance regression relative to the current
> >> code, as it appears that some care was taken to avoid the memory reference.
> >>
> >> I agree that it's probably negligible compared to the save/restore
> >> code.  If the x86 maintainers agree as well, I'll replace it with
> >> cpu_has_xsave.
> >>
> >>      
> > I asked Suresh to comment on this, since he wrote the original code.  He
> > did confirm that the intent was to avoid a global memory reference.
> >
> >    
> 
> Ok, so you're happy with the patch as is?

As use_xsave() is in the hot context switch path, I would like to go
with Avi's proposal.

thanks,
suresh

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