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

[Jason A. Donenfeld]

On Sat, Sep 1, 2018 at 2:32 PM Andy Lutomirski <luto@xxxxxxxxxx> 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.