powerpc/mpic: don't reset affinity for secondary MPIC on boot

Submitted by Arnd Bergmann on Nov. 19, 2008, 1:50 p.m.

Details

Message ID 200811191450.59361.arnd@arndb.de
State New
Headers show

Commit Message

Arnd Bergmann Nov. 19, 2008, 1:50 p.m.
Kexec/kdump currently fails on the IBM QS2x blades when the kexec happens
on a CPU other than the initial boot CPU.  It turns out that this is the
result of mpic_init trying to set affinity of each interrupt vector to the
current boot CPU.

As far as I can tell,  the same problem is likely to exist on any
secondary MPIC, because they have to deliver interrupts to the first
output all the time. There are two potential solutions for this: either
not set up affinity at all for secondary MPICs, or assume that CPU
output 0 is connected to the upstream interrupt controller and hardcode
affinity to that.

This patch implements the first approach, because it can work on
machines that have a secondary controller that needs to deliver
interrupts to a destination other than CPU 0. The disadvantage
is that it requires the system to set up the affinity register
correctly on bootup.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>

---

Comments

Benjamin Herrenschmidt Nov. 20, 2008, 7:30 a.m.
On Wed, 2008-11-19 at 14:50 +0100, Arnd Bergmann wrote:
> This patch implements the first approach, because it can work on
> machines that have a secondary controller that needs to deliver
> interrupts to a destination other than CPU 0. The disadvantage
> is that it requires the system to set up the affinity register
> correctly on bootup.
> 
That won't fly with MPICs that get reset.

I would rather, for non primary, set it to a cpu provided as
either a new argument or an mpic struct member initially set to 1 with
an accessor to change it if necessary. Or should we define a flag to
have it read it at init time from the chip ?

Ben.

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Index: linux-2.6/arch/powerpc/sysdev/mpic.c
===================================================================
--- linux-2.6.orig/arch/powerpc/sysdev/mpic.c
+++ linux-2.6/arch/powerpc/sysdev/mpic.c
@@ -1323,8 +1323,9 @@  void __init mpic_init(struct mpic *mpic)
 			continue;
 		/* init hw */
 		mpic_irq_write(i, MPIC_INFO(IRQ_VECTOR_PRI), vecpri);
-		mpic_irq_write(i, MPIC_INFO(IRQ_DESTINATION),
-			       1 << hard_smp_processor_id());
+		if (mpic->flags & MPIC_PRIMARY)
+			mpic_irq_write(i, MPIC_INFO(IRQ_DESTINATION),
+				       1 << hard_smp_processor_id());
 	}
 	
 	/* Init spurious vector */