Subject: Re: [patch 1/1] Hot plug CPU to support physical add of new
	processors (i386)
From: Shaohua Li <shaohua.li@intel.com>
To: Natalie.Protasevich@unisys.com
Cc: zwane@arm.linux.org.uk, "Raj, Ashok" <ashok.raj@intel.com>, akpm@osdl.org,
       ak@suse.de, lhcs-devel@lists.sourceforge.net,
       linux-kernel@vger.kernel.org, hotplug_sig@lists.osdl.org
In-Reply-To: <20050831121311.5FC7C57D99@linux.site>
References: <20050831121311.5FC7C57D99@linux.site>
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Date: Thu, 01 Sep 2005 16:00:58 +0800
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Hi,
On Wed, 2005-08-31 at 20:13 +0800, Natalie.Protasevich@unisys.com wrote:
> Current IA32 CPU hotplug code doesn't allow bringing up processors
> that were not present in the boot configuration.  
> To make existing hot plug facility more practical for physical hot
> plug, possible processors should be encountered  
> during boot for potentual hot add/replace/remove. On ES7000, ACPI
> marks all the sockets that are empty or not assigned 
> to the partitionas as "disabled". The patch allows arrays/masks with
> APIC info for disabled processors to be  
> initialized. Then the OS can bring up a processor that was inserted in
> the socked and brought into configuration  
> during runtime.  
> To test the code, one can boot the system with maxcpu=1 and then bring
> the rest of the processors up, which was not  
> possible so far (only maxcpus number of nodes were created). 
> The patch also makes proc entry for interrupts dynamically change to
> only show current onlined processors.
Could we clean up the cpu_present_map a bit, like IA64 does? Eg, if a
new CPU is inserted, we allocated cpu id for it and set cpu_present_map.
Current alloc_cpu_id is just a workaround for suspend/resume use, but
isn't ok for physical cpu hotplug to me.

Thanks,
Shaohua

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