linux-kernel - Re: [PATCH 08/13] xen/pvticketlock: disable interrupts while blocking

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Date:	Tue, 13 Sep 2011 15:27:06 -0400
From:	Don Zickus <dzickus@...hat.com>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	Avi Kivity <avi@...hat.com>, Jeremy Fitzhardinge <jeremy@...p.org>,
	Peter Zijlstra <peterz@...radead.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Ingo Molnar <mingo@...e.hu>,
	the arch/x86 maintainers <x86@...nel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Nick Piggin <npiggin@...nel.dk>,
	Marcelo Tosatti <mtosatti@...hat.com>,
	KVM <kvm@...r.kernel.org>,
	Xen Devel <xen-devel@...ts.xensource.com>,
	Jeremy Fitzhardinge <jeremy.fitzhardinge@...rix.com>,
	Stefano Stabellini <stefano.stabellini@...citrix.com>
Subject: Re: [PATCH 08/13] xen/pvticketlock: disable interrupts while blocking

On Tue, Sep 13, 2011 at 09:03:20PM +0200, Andi Kleen wrote:
> > So I got around to implementing this and it seems to work great.  The back
> > to back NMIs are detected properly using the %rip and that info is passed to
> > the NMI notifier.  That info is used to determine if only the first
> > handler to report 'handled' is executed or _all_ the handlers are
> > executed.
> > 
> > I think all the 'unknown' NMIs I generated with various perf runs have
> > disappeared.  I'll post a new version of my nmi notifier rewrite soon.
> 
> This will fail when the system is idle.

Oh one other thing I forgot to mention is that an NMI handler has to
return a value greater than 1, meaning that it handle multiple NMI events
during this NMI to even enable the 'NMI swallowing' algorithm.

Cheers,
Don
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