Fix regression. Make hot unlplug of CPU0 work again.

[tony@bakeyournoodle.com (Tony Breeds)]

Early in the 2.6.23 cycle we broke the ability to offline cpu0
(7ccb4a662462616f6be5053e26b79580e02f1529).  This patch fixes that by
ensuring that the (xics)  default irq server, will not be 0 when taking
cpu0 offline.

Also catches a use of irq, when virq should be used (I think that the
last one).

Signed-off-by: Tony Breeds <tony@bakeyournoodle.com>

---

Unless there is a problem with this patch, it'd be nice to get it into
2.6.23 :)

 arch/powerpc/platforms/pseries/xics.c |   11 ++++++++++-
 1 files changed, 10 insertions(+), 1 deletions(-)

diff --git a/arch/powerpc/platforms/pseries/xics.c b/arch/powerpc/platforms/pseries/xics.c
index f0b5ff1..2fb8fd0 100644
--- a/arch/powerpc/platforms/pseries/xics.c
+++ b/arch/powerpc/platforms/pseries/xics.c
@@ -837,6 +837,15 @@ void xics_migrate_irqs_away(void)
 	/* Allow IPIs again... */
 	xics_set_cpu_priority(cpu, DEFAULT_PRIORITY);
 
+	/* It would be bad to migrate any IRQs to the CPU we're taking down */
+	if (default_server == cpu) {
+		unsigned int new_server = first_cpu(cpu_online_map);
+
+		default_server = get_hard_smp_processor_id(new_server);
+		printk(KERN_WARNING "%s: default server was %d, reset to %d\n",
+		       __func__, cpu, default_server);
+	}
+
 	for_each_irq(virq) {
 		struct irq_desc *desc;
 		int xics_status[2];
@@ -882,7 +891,7 @@ void xics_migrate_irqs_away(void)
 
 		/* Reset affinity to all cpus */
 		desc->chip->set_affinity(virq, CPU_MASK_ALL);
-		irq_desc[irq].affinity = CPU_MASK_ALL;
+		irq_desc[virq].affinity = CPU_MASK_ALL;
 unlock:
 		spin_unlock_irqrestore(&desc->lock, flags);
 	}

Yours Tony

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