linux-kernel - Re: [RFC 0/3] Basic support for LWP

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Message-ID: <4CADDD9F.3030806@zytor.com>
Date:	Thu, 07 Oct 2010 07:47:59 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Stephane Eranian <eranian@...gle.com>
CC:	mingo@...e.hu, Hans.Rosenfeld@....com, robert.richter@....com,
	tglx@...utronix.de, linux-kernel@...r.kernel.org,
	Andreas.Herrmann3@....com, peterz@...radead.org,
	fweisbec@...il.com, rostedt@...dmis.org, acme@...hat.com,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>, eranian@...il.com
Subject: Re: [RFC 0/3] Basic support for LWP

On 10/07/2010 07:25 AM, Stephane Eranian wrote:
>>
>> No, but you wouldn't be able to use lazy FPU.
>>
> You mean lazy restore, I am guessing here.
> Is that to say, you cannot figure out whether the FPU state in
> the CPU on ctxsw in is yours anymore?
> 

Lazy save/restore, and more or less, yes.  Really, XSAVE was designed to
be saved/restored as a unit, with unused state skipped.

	-hpa

-- 
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.

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