linux-kernel - Re: [PATCH 04/14] x86/fpu: Remove 'kbuf' parameter from the copy_xstate_to

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Date:   Mon, 30 Jan 2017 09:23:04 -0800
From:   Yu-cheng Yu <yu-cheng.yu@...el.com>
To:     Borislav Petkov <bp@...en8.de>
Cc:     Ingo Molnar <mingo@...nel.org>, linux-kernel@...r.kernel.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        Andy Lutomirski <luto@...capital.net>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Fenghua Yu <fenghua.yu@...el.com>,
        "H . Peter Anvin" <hpa@...or.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Oleg Nesterov <oleg@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Rik van Riel <riel@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH 04/14] x86/fpu: Remove 'kbuf' parameter from the
 copy_xstate_to_user() APIs

On Mon, Jan 30, 2017 at 04:45:21PM +0100, Borislav Petkov wrote:
> On Mon, Jan 30, 2017 at 10:57:28AM +0100, Ingo Molnar wrote:
> > Would anyone object to using u32 in these prototypes?
> 
> Well, would there be any disadvantage to forcing them to u32?
> Potentially by something else wanting to use those interfaces besides
> the regset thing and that something else doesn't like u32s?
> 
> Otherwise, I don't see a problem.
> 
> I mean, if 4G are not enough for xstate dimensions then we have a whole
> different problem.

This function pair was intended to be similar to user_regset_copyout(), 
user_regset_copyin() used for the standard-format XSAVE area copying.
I totally agree it is complex and should be simplified.  Why don't we
do both places? 

Yu-cheng