Re: [RFC PATCH] x86 NMI-safe INT3 and Page Fault (v5)

From: H. Peter Anvin
Date: Mon Apr 21 2008 - 11:15:40 EST


Mathieu Desnoyers wrote:

Just to be clear : the added cost on normal interrupt return is to add a
supplementary test of the thread flags already loaded in registers and
a conditional branch. This is used to detect if we are nested over an
NMI handler. I doubt anyone ever notice an impact caused by this added
test/branch.


Why the **** would you do this except in the handful of places where you actually *could* be nested over an NMI handler (basically #MC, #DB and INT3)?

-hpa

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