Re: [PATCH 10/18] arm64: Introduce FIQ support

[Marc Zyngier <maz@kernel.org>]

On Sun, 07 Feb 2021 08:47:23 +0000,
Hector Martin 'marcan' <marcan@marcan.st> wrote:
> 
> On 07/02/2021 00.37, Marc Zyngier wrote:
> > See my digression in patch 8. I really wonder what the benefit is to
> > treat FIQ independently of IRQ, and we might as well generalise
> > this. We could always panic on getting a FIQ on platforms that don't
> > expect one.
> > 
> > It'd be good to rope in the other interested parties (Mark for the
> > early entry code, James for RAS and SError handling).
> 
> CCing Mark and James: TL;DR what do you think about unconditionally
> keeping DAIF.I == DAIF.F, would this break other platforms with
> spurious FIQs or conversely mask FIQs when we don't want to in some
> cases? The FIQ vector would remain a panic except on platforms that
> require using it, via an alternatives patch.
> 
> >>   	kernel_ventry	1, sync				// Synchronous EL1h
> >>   	kernel_ventry	1, irq				// IRQ EL1h
> >> -	kernel_ventry	1, fiq_invalid			// FIQ EL1h
> >> +							// FIQ EL1h
> >> +	kernel_ventry	1, fiq_invalid, 64, irq, ARM64_NEEDS_FIQ
> > 
> > It could be better to create a set of first class FIQ handlers rather
> > than this alternative target macro. I quickly hacked this instead,
> > which I find more readable.
> 
> I think I ended up with the macro change to keep it 1:1 with IRQ, vs a
> separate branch... but I didn't think of the fallthrough-with-nop
> trick, neat. It is definitely is more readable. Are you OK with me
> pulling this patch in for v2, with your name on it?

Up to you, I don't mind either way. This is just code! :D

> 
> > -	kernel_ventry	0, fiq_invalid_compat, 32	// FIQ 32-bit EL0
> > +	kernel_ventry	0, fiq, 32			// FIQ 32-bit EL0
> 
> fiq_compat here, right?

Of course.

Thanks,

	M.

-- 
Without deviation from the norm, progress is not possible.