Re: [PATCH] cpu hotplug ppc64 bug

[Paul Mackerras <paulus@samba.org>]

Joel Schopp writes:

> On Power4 and earlier hardware there is no need to clear the CPPR (see 
> RPAp 479 section 18.5.4.7.2 for what little info there is on the CPPR) 
> when stopping a cpu. On hardware that uses Power5 an undocumented change 
> has been made that requires the CPPR to be cleared if an isolate is to 
> be done on the stopped cpu. So the following patch lets cpu hotplug work 
> on the recent hardware.

>  void cpu_die(void)
>  {
>  	local_irq_disable();
> +	/* Some hardware requires clearing the CPPR, while other hardware does not
> +	 * it is safe either way
> +	 */
> +	pSeriesLP_cppr_info(0, 0);
>  	rtas_stop_self();

I wanted to do this a bit differently - I was going to make cpu_die be
a platform-specific function called via a ppc_md function pointer,
rather than putting very pseries-specific stuff in smp.c, which is
used on all platforms.  But having been on vacation and then
travelling, I haven't got to it yet.

Paul.