linux-kernel - RE: [PATCH v6 01/13] x86/xsaves: Define and use fpu_user_xstate

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Date:	Wed, 11 May 2016 17:25:17 +0000
From:	"Yu, Fenghua" <fenghua.yu@...el.com>
To:	Borislav Petkov <bp@...e.de>,
	"Yu, Yu-cheng" <yu-cheng.yu@...el.com>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"x86@...nel.org" <x86@...nel.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	"Thomas Gleixner" <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	Andy Lutomirski <luto@...nel.org>,
	"Prakhya, Sai Praneeth" <sai.praneeth.prakhya@...el.com>,
	"Shankar, Ravi V" <ravi.v.shankar@...el.com>
Subject: RE: [PATCH v6 01/13] x86/xsaves: Define and use fpu_user_xstate_size

> From: Borislav Petkov [mailto:bp@...e.de]
> Sent: Wednesday, May 11, 2016 10:21 AM
> To: Yu, Yu-cheng <yu-cheng.yu@...el.com>
> Cc: linux-kernel@...r.kernel.org; x86@...nel.org; H. Peter Anvin
> <hpa@...or.com>; Thomas Gleixner <tglx@...utronix.de>; Ingo Molnar
> <mingo@...hat.com>; Dave Hansen <dave.hansen@...ux.intel.com>; Andy
> Lutomirski <luto@...nel.org>; Prakhya, Sai Praneeth
> <sai.praneeth.prakhya@...el.com>; Shankar, Ravi V
> <ravi.v.shankar@...el.com>; Yu, Fenghua <fenghua.yu@...el.com>
> Subject: Re: [PATCH v6 01/13] x86/xsaves: Define and use
> fpu_user_xstate_size
> 
> On Tue, May 10, 2016 at 04:29:53PM -0700, Yu-cheng Yu wrote:
> > The XSAVE area of kernel can be in standard or compacted format;
> 
> "The kernel xstate area... "
> 
> and can we call it the xstate area as there are a bunch of XSAVE* insns
> touching it. The file which deals with it is even called that:
> arch/x86/kernel/fpu/xstate.c
> 
> > it is always in standard format for user mode. When XSAVES is enabled,
> > the kernel uses the compacted format and it is necessary to use a
> > separate fpu_user_xstate_size for signal/ptrace frames.
> >
> > Based on an earlier patch from Fenghua Yu <fenghua.yu@...el.com>
> >
> > Signed-off-by: Fenghua Yu <fenghua.yu@...el.com>
> > [yu-cheng.yu@...el.com: rebase to current, rename to
> > fpu_user_xstate_size]
> > Signed-off-by: Yu-cheng Yu <yu-cheng.yu@...el.com>
> > Reviewed-by: Dave Hansen <dave.hansen@...el.com>
> 
> Maybe I wasn't as clear as I hoped to be. Let me be more specific:
> 
> So you either need to do:
> 
> ---
> From: Fenghua
> 
> ...
> 
> Signed-off-by: Fenghua
> Signed-off-by: You
> ...
> ---
> 
> or
> 
> ---
> 
> Based on an earlier patch from Fenghua Yu <fenghua.yu@...el.com>.
> 
> Signed-off-by: You
> 
> ---
> 
> with the second variant making you the author implicitly because you're the
> sender.
> 
> Makes more sense this way?

Is this possible to have the third one?

From: Yu-cheng

Signed-off-by: Yu-cheng
Signed-off-by: Fenghua

Thanks.

-Fenghua