Re: [Xen-devel] [PATCH v2 4/6] x86: track when in #NMI context

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 17/02/2020 18:43, Roger Pau Monne wrote:
> Add helpers to track when running in #MC context. This is modeled
> after the in_irq helpers, but does not support reentry.
>
> Note that there are no users of in_mc() introduced by the change,
> further users will be added by followup changes.
>
> Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>

You probably mean s/mc/nmi/ throughout the commit message, but I'm
afraid these are rather problematic.

NMIs can be recursively entered, especially on corner cases in the crash
path.  Asserting that the crash path is not recursive can lead to never
entering the crash kernel.

~Andrew

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