1 From: Tony Ernst <tee@sgi.com>
2 Subject: sn2: preserve irq affinity set in PROM
3 Patch-mainline: No, this is a one-off from the mainline fix
6 The latest SLES11 has numerous changes in the
7 request_irq() path, the one of issue is irq_select_affinity(),
8 which reassigns an IRQ to a CPU. And, in the case of SN2 Altix,
9 it assigns every IRQ to the same CPU; CPU0 in most cases, except
10 on systems like rappel where it's CPU1, due to the Shub1.1 restrictions.
12 This is a problem. Unlike most platforms, on Altix, the assignment
13 of an IRQ to a CPU is determined and setup in the PROM, and the kernel
14 is not expected to change this, except in the case of a manual
17 Acked-by: Jeff Mahoney <jeffm@suse.com>
19 arch/ia64/sn/kernel/irq.c | 5 +++++
20 include/linux/irq.h | 1 +
21 kernel/irq/manage.c | 11 +++++++++++
22 3 files changed, 17 insertions(+)
24 --- a/arch/ia64/sn/kernel/irq.c 2008-10-09 17:13:53.000000000 -0500
25 +++ b/arch/ia64/sn/kernel/irq.c 2008-12-18 13:34:46.822283902 -0600
28 cpuphys = cpu_physical_id(cpu);
29 set_irq_affinity_info(sn_irq_info->irq_irq, cpuphys, 0);
31 + * Affinity was set by the PROM, prevent it from
32 + * being reset by the request_irq() path.
34 + irq_desc[sn_irq_info->irq_irq].status |= IRQ_AFFINITY_SET;
38 --- a/include/linux/irq.h 2008-12-16 11:27:10.000000000 -0600
39 +++ b/include/linux/irq.h 2008-12-18 13:49:23.519706754 -0600
41 #define IRQ_NO_BALANCING 0x00400000 /* IRQ is excluded from balancing */
42 #define IRQ_SPURIOUS_DISABLED 0x00800000 /* IRQ was disabled by the spurious trap */
43 #define IRQ_MOVE_PCNTXT 0x01000000 /* IRQ migration from process context */
44 +#define IRQ_AFFINITY_SET 0x02000000 /* IRQ affinity was previously set */
46 #ifdef CONFIG_IRQ_PER_CPU
47 # define CHECK_IRQ_PER_CPU(var) ((var) & IRQ_PER_CPU)
48 --- a/kernel/irq/manage.c 2008-12-16 11:27:10.000000000 -0600
49 +++ b/kernel/irq/manage.c 2008-12-18 13:36:15.693395542 -0600
52 cpus_and(mask, cpu_online_map, irq_default_affinity);
55 + * Preserve the affinity that was previously set, but make
56 + * sure one of the targets is online.
58 + if (irq_desc[irq].status & IRQ_AFFINITY_SET) {
59 + if (cpus_intersects(irq_desc[irq].affinity, cpu_online_map))
60 + mask = irq_desc[irq].affinity;
62 + irq_desc[irq].status &= ~IRQ_AFFINITY_SET;
65 irq_desc[irq].affinity = mask;
66 irq_desc[irq].chip->set_affinity(irq, mask);