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Date: Wed, 7 Jun 2006 11:47:47 -0700
From: Rajesh Shah <rajesh.shah@intel.com>
To: Brendan Trotter <btrotter@gmail.com>
Cc: Keith Owens <kaos@sgi.com>, Andi Kleen <ak@suse.de>,
       Ashok Raj <ashok.raj@intel.com>, linux-kernel@vger.kernel.org
Subject: Re: NMI problems with Dell SMP Xeons
Message-ID: <20060607114747.A25548@unix-os.sc.intel.com>
Reply-To: Rajesh Shah <rajesh.shah@intel.com>
References: <200606070920.23436.ak@suse.de> <8446.1149666227@kao2.melbourne.sgi.com> <b1ebdcad0606070818l3024b264k89f6cd37ccb0b6f7@mail.gmail.com>
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In-Reply-To: <b1ebdcad0606070818l3024b264k89f6cd37ccb0b6f7@mail.gmail.com>; from btrotter@gmail.com on Wed, Jun 07, 2006 at 03:18:57PM +0000
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On Wed, Jun 07, 2006 at 03:18:57PM +0000, Brendan Trotter wrote:
> 
> > I will try forcing send_IPI_allbutself() to use the mask version rather
> > than the broadcast shortcut.  Later tonight ...
> 
> I've been looking into this a little - it appears that Linux tries to
> use one bit per CPU in the local APIC's "logical destination register"
> and that in all cases at least one bit is set for each valid CPU. As
> far as I can tell sending an NMI (or any other broadcast IPI) in
> logical mode with no shorthand and "destination = 0xFF" should work
> fine for both "cluster mode" and "flat mode". In this case I'd also
> suggest that "clear_local_APIC()" clear the destination format
> register (DFR) and the logical destination register (LDR) so that it
> doesn't receive broadcast NMIs if the CPU is taken offline.
> 
I will double-check with the CPU folks, but I don't think this
will do what you want it to do. If you send an NMI IPI with
destination set to 0xff, I think it will interrupt all CPUs,
including the non-started CPUs in the cli;hlt state. If I
remember right, the destination shorthand method simply
sends the interrupt on the bus with destination set to
0xff..

Rajesh