Subject: Re: MP interrupt problems with PRIMERGY RX300 --- Success
To: Frank van der Linden <>
From: Peter O'Kane <>
List: tech-smp
Date: 12/20/2004 18:30:45
This was a deduction from the observed behavior, i.e. everything worked in 
the single physical processor case (with/without HTT enabled) and was 
independent of which single physical processor was enabled. therefore it 
must be something to do with the not fully fired up second physical 
processor. Abstract question: Does it make sense to specify "processor 
executing at lowest priority" along with a physical address specifying only 
one processor? Answer: Probably not. Experiment: Change the definitions to 
make certain fixed rather than low priority is used.
Result: It boots on the RX300. I have done a kernel build with all 4 
processors running with no problems.

Tucked away on page 8-27 Vol 3 of the IA-32 Intel(R) Architecture Software 
Developer's Manual is the following little gem:
"A broadcast IPI (bits 28-31 of the MDA are 1's) or I/O subsystem initiated 
interrupt with lowest
priority delivery mode is not supported in physical destination mode and 
must not be configured
by software. Also, for any non-broadcast IPI or I/O subsystem initiated 
interrupt with lowest
priority delivery mode, software must ensure that APICs defined in the 
interrupt address are
present and enabled to receive interrupts."

--On 20 December 2004 10:29 +0100 Frank van der Linden <> 

> On Fri, Dec 17, 2004 at 05:01:30PM +0000, Peter O'Kane wrote:
>> O.K. I have got my RX300 running with all four logical processors.
>> Problem appears to be that, at the point where the ioapics are enabled,
>> the  local apic on the second physical processor is not properly
>> initialized to  take part in the negotiations needed for lowest priority
>> delivery mode and  that, even though only the BSP is specified as the
>> interrupt target the  LOPRI delivery mode is being specified.
> That's an interesting observation.. I wasn't actually aware that this
> could happen. Where in the Intel documentation is this described? It
> may explain some other problems, and I'd like to fix it.
> - Frank

Peter O'Kane                  
Information Technology Department,      Voice: +353 91 492527
National University of Ireland, Galway. Fax: +353 91 494501