linux-kernel - Re: [PATCH 08/10] x86/xsaves: Fix PTRACE frames for XSAVES

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Date:	Mon, 22 Feb 2016 14:19:05 -0800
From:	Dave Hansen <dave.hansen@...ux.intel.com>
To:	Yu-cheng Yu <yu-cheng.yu@...el.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 08/10] x86/xsaves: Fix PTRACE frames for XSAVES

On 02/22/2016 12:48 PM, Yu-cheng Yu wrote:
> It should have been:
> 
> 	xsave->header.xfeatures = xfeatures |
> 		(xsave->header.xfeatures & XFEATURE_MASK_SUPERVISOR);
> 
> I'll fix it.

Can we break it out to make it more clear?

/*
 * The state that came in from userspace was user-state only.
 * Mask all the user states out of 'xfeatures'.
 */
xsave->header.xfeatures &= XFEATURE_MASK_SUPERVISOR;
/*
 * add back in the features that came in from userspace
 */
xsave->header.xfeatures |= xfeatures