Re: [PATCH] Fix interrupt distribution in ppc970

[Mohan Kumar M <mohan@in.ibm.com>]

On Tue, Apr 10, 2007 at 05:06:03PM +1000, Michael Ellerman wrote:
> So the core of the problem is that if we haven't onlined all cpus then
> we can't use the default_distrib_server value given to us by firmware,
> because some of the cpus in that queue won't be online.
> 
> We can detect this situation by comparing the number of cpus that are
> online vs the number that are present (not possible). This might even
> work if you boot with maxcpus=1 and then hotplug the rest in.
> 
> How about this:
> 

Right, This also solves the problem.

> Index: powerpc/arch/powerpc/platforms/pseries/xics.c
> ===================================================================
> --- powerpc.orig/arch/powerpc/platforms/pseries/xics.c
> +++ powerpc/arch/powerpc/platforms/pseries/xics.c
> @@ -167,7 +167,10 @@ static int get_irq_server(unsigned int v
>  		return default_server;
> 
>  	if (cpus_equal(cpumask, CPU_MASK_ALL)) {
> -		server = default_distrib_server;
> +		if (num_online_cpus() == num_present_cpus())
> +			server = default_distrib_server;
> +		else
> +			server = default_server;
>  	} else {
>  		cpus_and(tmp, cpu_online_map, cpumask);
> 
> @@ -415,7 +418,10 @@ static void xics_set_affinity(unsigned i
> 
>  	/* For the moment only implement delivery to all cpus or one cpu */
>  	if (cpus_equal(cpumask, CPU_MASK_ALL)) {
> -		newmask = default_distrib_server;
> +		if (num_online_cpus() == num_present_cpus())
> +			newmask = default_distrib_server;
> +		else
> +			newmask = default_server;
>  	} else {
>  		cpus_and(tmp, cpu_online_map, cpumask);
>  		if (cpus_empty(tmp))
>