[PATCH] Fix per-cpu allocation on oldworld SMP powermacs

[PATCH] Fix per-cpu allocation on oldworld SMP powermacs

[Paul Mackerras]

The per-cpu area(a) for the secondary CPU(s) isn't getting allocated
on old SMP powermacs that don't have the secondary CPU(s) listed in
the device tree, as per-cpu areas are now only allocated for CPUs in
the cpu_possible_map, and we aren't setting the bits for the secondary
CPU(s) until smp_prepare_cpus(), which is after per-cpu allocation.
Therefore this sets the bits for CPUs 1..3 in cpu_possible_map in
pmac_setup_arch, so they get per-cpu data allocated.

Signed-off-by: Paul Mackerras <paulus@samba.org>
---

diff --git a/arch/powerpc/platforms/powermac/setup.c b/arch/powerpc/platforms/powermac/setup.c
index 07b1c4e..c519b2a 100644
--- a/arch/powerpc/platforms/powermac/setup.c
+++ b/arch/powerpc/platforms/powermac/setup.c
@@ -363,8 +363,19 @@ static void __init pmac_setup_arch(void)
 		smp_ops = &core99_smp_ops;
 	}
 #ifdef CONFIG_PPC32
-	else
+	else {
+		/*
+		 * We have to set bits in cpu_possible_map here since the
+		 * secondary CPU(s) aren't in the device tree, and
+		 * setup_per_cpu_areas only allocates per-cpu data for
+		 * CPUs in the cpu_possible_map.
+		 */
+		int cpu;
+
+		for (cpu = 1; cpu < 4 && cpu < NR_CPUS; ++cpu)
+			cpu_set(cpu, cpu_possible_map);
 		smp_ops = &psurge_smp_ops;
+	}
 #endif
 #endif /* CONFIG_SMP */
 
diff --git a/arch/powerpc/platforms/powermac/smp.c b/arch/powerpc/platforms/powermac/smp.c
index 686ed82..cb2d894 100644
--- a/arch/powerpc/platforms/powermac/smp.c
+++ b/arch/powerpc/platforms/powermac/smp.c
@@ -317,7 +317,6 @@ static int __init smp_psurge_probe(void)
 		ncpus = NR_CPUS;
 	for (i = 1; i < ncpus ; ++i) {
 		cpu_set(i, cpu_present_map);
-		cpu_set(i, cpu_possible_map);
 		set_hard_smp_processor_id(i, i);
 	}
 

Re: [PATCH] Fix per-cpu allocation on oldworld SMP powermacs

[Benjamin Herrenschmidt]

On Thu, 2007-06-07 at 22:42 +1000, Paul Mackerras wrote:
> diff --git a/arch/powerpc/platforms/powermac/setup.c
> b/arch/powerpc/platforms/powermac/setup.c
> index 07b1c4e..c519b2a 100644
> --- a/arch/powerpc/platforms/powermac/setup.c
> +++ b/arch/powerpc/platforms/powermac/setup.c
> @@ -363,8 +363,19 @@ static void __init pmac_setup_arch(void)
>                 smp_ops = &core99_smp_ops;
>         }
>  #ifdef CONFIG_PPC32
> -       else
> +       else {
> +               /*
> +                * We have to set bits in cpu_possible_map here since
> the
> +                * secondary CPU(s) aren't in the device tree, and
> +                * setup_per_cpu_areas only allocates per-cpu data for
> +                * CPUs in the cpu_possible_map.
> +                */
> +               int cpu;
> +
> +               for (cpu = 1; cpu < 4 && cpu < NR_CPUS; ++cpu)
> +                       cpu_set(cpu, cpu_possible_map);
>                 smp_ops = &psurge_smp_ops;
> +       }
>  #endif
>  #endif /* CONFIG_SMP */ 

Why not use the result from probe() instead which returns the number of
possible CPUs ? That would catch more than just the powermac case ... we
might have similar issues when finally porting PReP over...

Ben.