linux-kernel - Re: [PATCH], issue EOI to APIC prior to calling crash_kexec in die

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Message-ID: <47AA16CA.6000003@zytor.com>
Date:	Wed, 06 Feb 2008 12:21:30 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Neil Horman <nhorman@...hat.com>
CC:	Vivek Goyal <vgoyal@...hat.com>,
	Neil Horman <nhorman@...driver.com>, tglx@...utronix.de,
	mingo@...hat.com, kexec@...ts.infradead.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH], issue EOI to APIC prior to calling crash_kexec in die_nmi
 path

Neil Horman wrote:
> Can an APIC accept an NMI while already handling an NMI?  I didn't think they
> would interrupt one another, but rather, pend until such time as the previous
> NMI was cleared

The CPU certainly won't (there is a hidden flag that's cleared on IRET 
which disables NMI; it's possible to re-enable NMI by executing a dummy 
IRET inside the NMI handler.)

	-hpa
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