linux-kernel - Re: [PATCH v2 9/9] x86/xsaves: Re-enable XSAVES

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Date:	Thu, 25 Feb 2016 13:03:03 -0800
From:	Yu-cheng Yu <yu-cheng.yu@...el.com>
To:	Dave Hansen <dave.hansen@...ux.intel.com>
Cc:	x86@...nel.org, "H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
	Andy Lutomirski <luto@...nel.org>,
	Borislav Petkov <bp@...e.de>,
	Sai Praneeth Prakhya <sai.praneeth.prakhya@...el.com>,
	"Ravi V. Shankar" <ravi.v.shankar@...el.com>,
	Fenghua Yu <fenghua.yu@...el.com>
Subject: Re: [PATCH v2 9/9] x86/xsaves: Re-enable XSAVES

On Thu, Feb 25, 2016 at 12:34:59PM -0800, Dave Hansen wrote:
> On 02/25/2016 12:26 PM, Yu-cheng Yu wrote:
> > -	 * ( This is easy to backport while we are fixing
> > -	 *   XSAVES* support. )
> > +	 * Most recent CPUs supporting XSAVES can run 64-bit mode.
> > +	 * Enable XSAVES for 64-bit.
> >  	 */
> > -	setup_clear_cpu_cap(X86_FEATURE_XSAVES);
> > +	if (!config_enabled(CONFIG_X86_64))
> > +		setup_clear_cpu_cap(X86_FEATURE_XSAVES);
> >  }
> 
> Is this intended to be permanent?  If so, we would not be able to
> support any future supervisor features on 32-bit.

I was thinking of the 64-bit-only change, but then decided to put it out
for discussion.   

Yu-cheng