linux-kernel - Re: [PATCH 02/19] x86, fpu: Wrap get_xsave

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Message-ID: <556729FE.1020007@sr71.net>
Date:	Thu, 28 May 2015 07:45:18 -0700
From:	Dave Hansen <dave@...1.net>
To:	Ingo Molnar <mingo@...nel.org>
CC:	linux-kernel@...r.kernel.org, x86@...nel.org, tglx@...utronix.de,
	dave.hansen@...ux.intel.com, oleg@...hat.com, bp@...en8.de,
	riel@...hat.com, sbsiddha@...il.com, luto@...capital.net,
	mingo@...hat.com, hpa@...or.com, fenghua.yu@...el.com
Subject: Re: [PATCH 02/19] x86, fpu: Wrap get_xsave_addr() to make it safer

On 05/28/2015 01:41 AM, Ingo Molnar wrote:
> What you want here is to make the (in-memory) FPU state valid and current, before 
> reading it, and the function to use for that is fpu__activate_fpstate_read() 
> (available in the latest tip:x86/fpu tree).

Do we really want to unconditionally activate the FPU?

Let's say supporting MPX didn't require eager mode and someone called
get_xsave_addr().  We would ideally want to keep the FPU inactive and
just return NULL.  Right?
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