[PATCH v2 2/2] ARM: permit non-nested kernel mode NEON in softirq context

[Linus Walleij]

On Wed, Dec 7, 2022 at 11:39 AM Ard Biesheuvel <ardb at kernel.org> wrote:

> We currently only permit kernel mode NEON in process context, to avoid
> the need to preserve/restore the NEON register file when taking an
> exception while running in the kernel.
>
> Like we did on arm64, we can relax this restriction substantially, by
> permitting kernel mode NEON from softirq context, while ensuring that
> softirq processing is disabled when the NEON is being used in task
> context. This guarantees that only NEON context belonging to user space
> needs to be preserved and restored, which is already taken care of.
>
> This is especially relevant for network encryption, where incoming
> frames are typically handled in softirq context, and deferring software
> decryption to a kernel thread or falling back to C code are both
> undesirable from a performance PoV.
>
> Signed-off-by: Ard Biesheuvel <ardb at kernel.org>

So boosting WireGuard as primary SW network encryption user?
This is really neat, BTW:
Reviewed-by: Linus Walleij <linus.walleij at linaro.org>

Yours,
Linus Walleij