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

From: Jason A. Donenfeld
Date: Sun Aug 26 2018 - 09:45:32 EST


Hey Thomas,

On Sun, Aug 26, 2018 at 6:10 AM Thomas Gleixner <tglx@xxxxxxxxxxxxx> wrote:
> I'm not too fond of this simply because it requires that relax() step in
> all code pathes. I'd rather make that completely transparent by just
> marking the task as FPU using and let the context switch code deal with it
> in case that it gets preempted. I'll let one of my engineers look into
> that next week.

Do you mean to say you intend to make kernel_fpu_end() and
kernel_neon_end() only actually do something upon context switch, but
not when it's actually called? So that multiple calls to
kernel_fpu_begin() and kernel_neon_begin() can be made without
penalty? If so, that'd be great, and I'd certainly prefer this to the
simd_context_t passing. I consider the simd_get/put/relax API a
stopgap measure until something like that is implemented.

Jason