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

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Message-Id: <1272996209.2833.1.camel@sbs-t61.sc.intel.com>
Date:	Tue, 04 May 2010 11:03:29 -0700
From:	Suresh Siddha <suresh.b.siddha@...el.com>
To:	Avi Kivity <avi@...hat.com>
Cc:	"Cui, Dexuan" <dexuan.cui@...el.com>,
	Sheng Yang <sheng@...ux.intel.com>,
	Ingo Molnar <mingo@...e.hu>, "H. Peter Anvin" <hpa@...or.com>,
	"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 Sun, 2010-05-02 at 07:53 -0700, Avi Kivity wrote:
> The fpu code currently uses current->thread_info->status & TS_XSAVE as
> a way to distinguish between XSAVE capable processors and older processors.
> The decision is not really task specific; instead we use the task status to
> avoid a global memory reference - the value should be the same across all
> threads.
> 
> Eliminate this tie-in into the task structure by using an alternative
> instruction keyed off the XSAVE cpu feature; this results in shorter and
> faster code, without introducing a global memory reference.
> 
> Signed-off-by: Avi Kivity <avi@...hat.com>

Acked-by: Suresh Siddha <suresh.b.siddha@...el.com>

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