[RFC PATCH v4 4/5] arm64: neon: Remove support for nested or hardirq kernel-mode NEON

[Catalin Marinas]

On Fri, Jul 28, 2017 at 02:50:23PM +0100, Dave P Martin wrote:
> Support for kernel-mode NEON to be nested and/or used in hardirq
> context adds significant complexity, and the benefits may be
> marginal.  In practice, kernel-mode NEON is not used in hardirq
> context, and is rarely used in softirq context (by certain mac80211
> drivers).

Just for clarification, the issue we had with hardirq contexts was that
we could be interrupted while saving the current FPSIMD state as we
don't want to disable IRQs during this. If this was the only aspect,
your patch looks fine. Note that softirqs may be executed as result of
an IRQ (via the irq_exit() function) but local_bh_disable() should
protect against such race.

-- 
Catalin