[RFC PATCH v4 5/5] arm64: neon: Allow EFI runtime services to use FPSIMD in irq context

[Catalin Marinas]

On Fri, Jul 28, 2017 at 02:50:24PM +0100, Dave P Martin wrote:
> Now that kernel-mode NEON use is non-nestable and not allowed in
> hardirq/nmi context, we have a problem if the kernel decides to
> call into EFI during an interrupt that interrupted a
> kernel_neon_begin()..._end() block.  This will occur if the kernel
> tries to write diagnostic data to EFI persistent storage during
> a panic triggered by an NMI for example.
> 
> EFI runtime services specify an ABI that clobbers the FPSIMD state,
> rather than being able to use it optionally as an accelerator.
> This means that EFI is really a special case and can be handled
> separately.
> 
> To enable EFI calls from interrupts, this patch creates dedicated
> __efi_fpsimd_{begin,end}() helpers solely for this purpose, which
> save/restore to a separate percpu buffer if called in a context
> where kernel_neon_begin() is not usable.
> 
> Signed-off-by: Dave Martin <Dave.Martin at arm.com>

Should this patch be reordered with patch 4? It looks like patch 4 no
longer allows EFI runtime services in IRQ context.

-- 
Catalin