[RFC PATCH 4/4] x86: according to nr_cpu_ids to decide if need toleave logical flat

From: Yinghai Lu
Date: Mon Jan 11 2010 - 21:49:48 EST


should use nr_cpu_ids instead of num_processor, in case we have hotplug cpus.

if current only have 8 cpus is up, but if we will have more cpus that
will be hot added later, we should use physical flat at first.

nr_cpu_ids is the total cpus that could be supported.

Signed-off-by: Yinghai Lu <yinghai@xxxxxxxxxx>

---
arch/x86/kernel/apic/probe_32.c | 20 ++++++++++++++++++--
arch/x86/kernel/apic/probe_64.c | 3 ++-
arch/x86/kernel/smpboot.c | 2 --
3 files changed, 20 insertions(+), 5 deletions(-)

Index: linux-2.6/arch/x86/kernel/apic/probe_32.c
===================================================================
--- linux-2.6.orig/arch/x86/kernel/apic/probe_32.c
+++ linux-2.6/arch/x86/kernel/apic/probe_32.c
@@ -52,7 +52,7 @@ static int __init print_ipi_mode(void)
}
late_initcall(print_ipi_mode);

-void default_setup_apic_routing(void)
+static void local_default_setup_apic_routing(void)
{
#ifdef CONFIG_X86_IO_APIC
printk(KERN_INFO
@@ -103,7 +103,7 @@ struct apic apic_default = {
.init_apic_ldr = default_init_apic_ldr,

.ioapic_phys_id_map = default_ioapic_phys_id_map,
- .setup_apic_routing = default_setup_apic_routing,
+ .setup_apic_routing = local_default_setup_apic_routing,
.multi_timer_check = NULL,
.apicid_to_node = default_apicid_to_node,
.cpu_to_logical_apicid = default_cpu_to_logical_apicid,
@@ -207,6 +207,22 @@ void __init generic_bigsmp_probe(void)
apic = &apic_bigsmp;
printk(KERN_INFO "Overriding APIC driver with %s\n",
apic->name);
+ }
+ }
+#endif
+}
+
+void default_setup_apic_routing(void)
+{
+#ifdef CONFIG_X86_BIGSMP
+ /*
+ * make sure we go to bigsmp according to real nr_cpu_ids
+ */
+ if (!cmdline_apic && apic == &apic_default) {
+ if (nr_cpu_ids > 8) {
+ apic = &apic_bigsmp;
+ printk(KERN_INFO "Overriding APIC driver with %s\n",
+ apic->name);
}
}
#endif
Index: linux-2.6/arch/x86/kernel/smpboot.c
===================================================================
--- linux-2.6.orig/arch/x86/kernel/smpboot.c
+++ linux-2.6/arch/x86/kernel/smpboot.c
@@ -1084,9 +1084,7 @@ void __init native_smp_prepare_cpus(unsi
set_cpu_sibling_map(0);

enable_IR_x2apic();
-#ifdef CONFIG_X86_64
default_setup_apic_routing();
-#endif

if (smp_sanity_check(max_cpus) < 0) {
printk(KERN_INFO "SMP disabled\n");
Index: linux-2.6/arch/x86/kernel/apic/probe_64.c
===================================================================
--- linux-2.6.orig/arch/x86/kernel/apic/probe_64.c
+++ linux-2.6/arch/x86/kernel/apic/probe_64.c
@@ -67,7 +67,8 @@ void __init default_setup_apic_routing(v
}
#endif

- if (apic == &apic_flat && num_processors > 8)
+ /* not just num_processors, we could have hotplug cpus */
+ if (apic == &apic_flat && nr_cpu_ids > 8)
apic = &apic_physflat;

printk(KERN_INFO "Setting APIC routing to %s\n", apic->name);
--
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