linux-kernel - Re: [PATCH RFC 1/3] fpu/x86: add make_fpregs_active(

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Message-ID: <CALCETrU5R46RzT010tkDk+pSnGHZ7Rc0cgk+BD1RVtu_kcbudA@mail.gmail.com>
Date:   Mon, 17 Oct 2016 18:23:03 -0700
From:   Andy Lutomirski <luto@...capital.net>
To:     Yu-cheng Yu <yu-cheng.yu@...el.com>
Cc:     Rik van Riel <riel@...hat.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>, Borislav Petkov <bp@...en8.de>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Andrew Lutomirski <luto@...nel.org>,
        dave.hansen@...el.linux.com, Thomas Gleixner <tglx@...utronix.de>,
        "H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH RFC 1/3] fpu/x86: add make_fpregs_active(_newstate) helper functions

On Mon, Oct 17, 2016 at 4:45 PM, Yu-cheng Yu <yu-cheng.yu@...el.com> wrote:
> On Mon, Oct 17, 2016 at 04:30:47PM -0700, Andy Lutomirski wrote:
>> Rik wants to add a different form of FPU laziness, and it would be
>> simpler if we could just always copy from a kernel buffer.  Does code
>> to do that exist in the tree?
>
> If we know fpregs are not active at the time of the copy and compacted format
> is the concern, can we use copyout_from_xsaves() in xstate.c?
>

Right, that.  Rik, that could be an alternative solution.

--Andy