Re: [PATCH v5 1/5] arm64: Add framework to turn IPI as NMI

[Marc Zyngier]

On 2020-10-20 13:25, Daniel Thompson wrote:
> On Tue, Oct 20, 2020 at 04:52:43PM +0530, Sumit Garg wrote:

[...]

> > So in general, IPI as a normal IRQ is still useful for debugging but
> > it can't debug a core which is stuck in deadlock with interrupts
> > disabled.
> >
> > And since we choose override default implementations for pseudo NMI
> > support, we need to be backwards compatible for platforms which don't
> > possess pseudo NMI support.
>
> Do the fallback implementations require a new IPI? The fallbacks
> could rely on existing mechanisms such as the smp_call_function
> family.

Indeed. I'd be worried of using that mechanism for NMIs, but normal
IPIs should stick to the normal cross-call stuff.

The jury is still out on why this is a good idea, given that it
doesn't work in the only interesting case (deadlocked CPUs).

         M.
--
Jazz is not dead. It just smells funny...