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

From: Marc Zyngier <[email-masked]>
Date: Tue, 20 Oct 2020 13:32:03 +0100

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...

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