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Date:      Wed, 27 Aug 1997 23:37:34 -0600
From:      Steve Passe <smp@csn.net>
To:        Peter Wemm <peter@spinner.dialix.com.au>
Cc:        Simon Shapiro <Shimon@i-connect.net>, Christopher Petrilli <petrilli@amber.org>, smp@FreeBSD.ORG, Peter Stubbs <peters@gil.com.au>, Kyle Mestery <mestery@winternet.com>
Subject:   Re: A how does it work question. 
Message-ID:  <199708280537.XAA01750@Ilsa.StevesCafe.com>
In-Reply-To: Your message of "Thu, 28 Aug 1997 12:42:21 %2B0800." <199708280442.MAA19432@spinner.dialix.com.au> 

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Hi,

> It's fully symmetric (all cpu's are equal), just not reentrant enough in
> general (yet).
> 
> (However, I vaguely recall something about NMI only being handled on the 
> BSP though)

This is true, although I'm not sure if its the correct behaviour.  The
reasoning behind it is that the NMI INTerrupt is not distributed via the IO
APIC, but is strapped to each of the CPUs thru an LINT, typically LINT1.  The
info as to which is usually, BUT NOT ALWAYS, in the mptable.
So you could program all CPUs to respond to the NMI line, but they cant all
jump into the kernel at once, so why bother.

Right now I have the BSP catch it, the others ignore it.  The BSP could be
setup to send a stop CPU IPI to each of the other CPUs if necessary. Or all
the APs could be programmed to catch it and halt.  Its one of those things
thats not important enough to spend time on right now...

--
Steve Passe	| powered by 
smp@csn.net	|            Symmetric MultiProcessor FreeBSD





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