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SubjectRe: [patch] genapic: default to physical mode on hotplug CPU kernels

* Siddha, Suresh B <suresh.b.siddha@intel.com> wrote:

> On Tue, Nov 28, 2006 at 09:23:22PM +0100, Ingo Molnar wrote:
> >
> > * Siddha, Suresh B <suresh.b.siddha@intel.com> wrote:
> >
> > > On Tue, Nov 28, 2006 at 07:33:46AM +0100, Ingo Molnar wrote:
> > > > - if (clusters <= 1 && max_cluster <= 8 && cluster_cnt[0] == max_cluster)
> > > > + if (max_apic < 8)
> > >
> > > Patch mostly looks good. Instead of checking for max_apic, can we use
> > > cpus_weight(cpu_possible_map) <= 8
> >
> > ok - but i think it's still possible the BIOS tells us APIC IDs that are
> > larger than 7, even if there are fewer CPUs. So i think the patch below
> > should cover it. Agreed?
> >
>
> I think it is ok to use flat mode even when APIC IDs are larger than
> 7, as we rely on LDR's which are programmed using smp_processor_id().
>
> IMO, cpus_weight check should be fine.

hm - indeed. Then we can indeed do the patch below. Nice simplification!

Ingo

-------------------->
From: Ingo Molnar <mingo@elte.hu>
Subject: [patch] genapic: default to physical mode on hotplug CPU kernels
default to physical mode on hotplug CPU kernels. Furher simplify and
clean up the APIC initialization code.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
---
arch/x86_64/kernel/genapic.c | 20 +++-----------------
arch/x86_64/kernel/mpparse.c | 2 +-
include/asm-x86_64/apic.h | 2 +-
3 files changed, 5 insertions(+), 19 deletions(-)
Index: linux/arch/x86_64/kernel/genapic.c
===================================================================
--- linux.orig/arch/x86_64/kernel/genapic.c
+++ linux/arch/x86_64/kernel/genapic.c
@@ -33,25 +33,11 @@ u8 x86_cpu_to_log_apicid[NR_CPUS] = { [0
struct genapic __read_mostly *genapic = &apic_flat;

/*
- * Check the APIC IDs in bios_cpu_apicid and choose the APIC mode.
+ * Choose the APIC routing mode:
*/
-void __init clustered_apic_check(void)
+void __init setup_apic_routing(void)
{
- unsigned int i, max_apic = 0;
- u8 id;
-
- /*
- * Determine the maximum APIC ID in use:
- */
- for (i = 0; i < NR_CPUS; i++) {
- id = bios_cpu_apicid[i];
- if (id == BAD_APICID)
- continue;
- if (id > max_apic)
- max_apic = id;
- }
-
- if (max_apic < 8)
+ if (cpus_weight(cpu_possible_map) <= 8)
genapic = &apic_flat;
else
genapic = &apic_physflat;
Index: linux/arch/x86_64/kernel/mpparse.c
===================================================================
--- linux.orig/arch/x86_64/kernel/mpparse.c
+++ linux/arch/x86_64/kernel/mpparse.c
@@ -302,7 +302,7 @@ static int __init smp_read_mpc(struct mp
}
}
}
- clustered_apic_check();
+ setup_apic_routing();
if (!num_processors)
printk(KERN_ERR "MPTABLE: no processors registered!\n");
return num_processors;
Index: linux/include/asm-x86_64/apic.h
===================================================================
--- linux.orig/include/asm-x86_64/apic.h
+++ linux/include/asm-x86_64/apic.h
@@ -82,7 +82,7 @@ extern void setup_secondary_APIC_clock (
extern int APIC_init_uniprocessor (void);
extern void disable_APIC_timer(void);
extern void enable_APIC_timer(void);
-extern void clustered_apic_check(void);
+extern void setup_apic_routing(void);
static inline void lapic_timer_idle_broadcast(int broadcast) { }

extern void setup_APIC_extened_lvt(unsigned char lvt_off, unsigned char vector,
-
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