Hi Thomas,

On Thu, Sep 6, 2018 at 9:29 AM Thomas Gleixner [off-list ref] wrote:

On Sat, 1 Sep 2018, Jason A. Donenfeld wrote:

quoted

On Sat, Sep 1, 2018 at 2:32 PM Andy Lutomirski [off-list ref] wrote:

quoted

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