On Wed, 17 Feb 2021 11:49:23 +0000,
Mark Rutland [off-list ref] wrote:

Hi Hector,

On Mon, Feb 15, 2021 at 09:16:57PM +0900, Hector Martin wrote:

quoted

From: Marc Zyngier <maz@kernel.org>

By default, FIQ exceptions trigger a panic. On platforms that need to
deliver interrupts via FIQ, this gets redirected via an alternative to
instead handle FIQ the same way as IRQ. It is up to the irqchip handler
to discriminate between the two.

Signed-off-by: Marc Zyngier <maz@kernel.org>
Signed-off-by: Hector Martin <redacted>

Since the use of FIQ is a platform integration detail rather than a CPU
implementation detail (and e.g. can differ across bare-metal and VM),
I'd prefer to always have separate registered handlers for IRQ/FIQ (also
avoiding the need for patching). That way we can explicitly opt-in to
FIQ when required, and avoid edge-cases where an unexpected FIQ could
livelock an unaware IRQ handler.

Marc and I had a quick play with that, and I have a series of patches
I've pushed to:

https://git.kernel.org/pub/scm/linux/kernel/git/mark/linux.git/log/?h=arm64/fiq
git://git.kernel.org/pub/scm/linux/kernel/git/mark/linux.git arm64/fiq

... which I'll post out shortly.

FWIW, I've just posted a more complete version of the first patch in
this series[1], which you may want to use directly (though I plan to
take it as a fix for 5.12).

Thanks,

	M.

[1] https://lore.kernel.org/r/20210217142800.2547737-1-maz@kernel.org (local)

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

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel