linux-kernel - Re: [PATCH v2 01/17] asm: simd context helper API

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Date:   Thu, 6 Sep 2018 09:52:13 -0600
From:   "Jason A. Donenfeld" <Jason@...c4.com>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     Andrew Lutomirski <luto@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Netdev <netdev@...r.kernel.org>,
        David Miller <davem@...emloft.net>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Samuel Neves <sneves@....uc.pt>, linux-arch@...r.kernel.org,
        Rik van Riel <riel@...riel.com>
Subject: Re: [PATCH v2 01/17] asm: simd context helper API

Hi Thomas,

On Thu, Sep 6, 2018 at 9:29 AM Thomas Gleixner <tglx@...utronix.de> wrote:
>
> On Sat, 1 Sep 2018, Jason A. Donenfeld wrote:
> > On Sat, Sep 1, 2018 at 2:32 PM Andy Lutomirski <luto@...nel.org> wrote:
> > > I tend to think the right approach is to merge Jason's code and then
> > > make it better later.  Even with a totally perfect lazy FPU restore
> > > implementation on x86, we'll probably still need some way of dealing
> > > with SIMD contexts.  I think we're highly unlikely to ever a allow
> > > SIMD usage in all NMI contexts, for example, and there will always be
> > > cases where we specifically don't want to use all available SIMD
> > > capabilities even if we can.  For example, generating random numbers
> > > does crypto, but we probably don't want to do *SIMD* crypto, since
> > > that will force a save and restore and will probably fire up the
> > > AVX512 unit, and that's not worth it unless we're already using it for
> > > some other reason.
> > >
> > > Also, as Rik has discovered, lazy FPU restore is conceptually
> > > straightforward but isn't entirely trivial :)
> >
> > Sounds good. I'll move ahead on this basis.
>
> Fine with me.

Do you want to pull this single patch [01/17] into your tree now, and
then when I submit v3 of WireGuard and such, I can just drop this
patch from it, and then the rest will enter like usual networking
stuff through Dave's tree?

Jason