linux-kernel - [RFC PATCH 4/4] x86: according to nr_cpu_ids to decide if need to leave logical flat

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Message-id: <1263264483-3959-3-git-send-email-yinghai@kernel.org>
Date:	Mon, 11 Jan 2010 18:48:02 -0800
From:	Yinghai Lu <yinghai@...nel.org>
To:	Suresh Siddha <suresh.b.siddha@...el.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	"ananth@...ibm.com" <ananth@...ibm.com>,
	Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	Andrew Morton <akpm@...ux-foundation.org>
Cc:	linux-kernel@...r.kernel.org, Yinghai Lu <yinghai@...nel.org>
Subject: [RFC PATCH 4/4] x86: according to nr_cpu_ids to decide if need to
 leave logical flat

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@...nel.org>

---
 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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