From mboxrd@z Thu Jan  1 00:00:00 1970
From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Subject: Re: [RFC][KVM][PATCH 1/1] kvm:ppc:booke-64: soft-disable interrupts
Date: Fri, 10 May 2013 08:01:38 +1000
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Cc: "tiejun.chen" <tiejun.chen@windriver.com>,
	Caraman Mihai Claudiu-B02008 <B02008@freescale.com>,
	kvm@vger.kernel.org, Wood Scott-B07421 <B07421@freescale.com>,
	agraf@suse.de, kvm-ppc@vger.kernel.org,
	Bhushan Bharat-R65777 <R65777@freescale.com>,
	linuxppc-dev@lists.ozlabs.org
To: David Laight <David.Laight@ACULAB.COM>
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On Thu, 2013-05-09 at 14:28 +0100, David Laight wrote:
> That will happen if the IRQ goes away while the cpu is performing
> the IACK sequence.
> If the IRQ goes away while the cpu has interrupts masked then
> the cpu won't start the interrupt sequence and then try to
> read a vector when no interrupt is pending.

Right, and get a spurrious vector which shouldn't be a big deal.

We tend to call that a "short interrupt". There have been many other
cases of short interrupts in the past, for example on some MPICs, when
distribution is enabled, they occasionally shoot an interrupt to more
than one CPU at once :-)

Cheers,
Ben.