[tip:x86/bsp-hotplug] x86, apic: Add boot_cpu_is_bsp() to check if boot cpu is BSP

[tip-bot for HATAYAMA Daisuke <tipbot@zytor.com>]

Commit-ID:  68c3467bb95a9e99f46d04cb96f60c04bb997ac8
Gitweb:     http://git.kernel.org/tip/68c3467bb95a9e99f46d04cb96f60c04bb997ac8
Author:     HATAYAMA Daisuke <d.hatayama@jp.fujitsu.com>
AuthorDate: Thu, 29 Aug 2013 18:27:58 +0900
Committer:  H. Peter Anvin <hpa@linux.intel.com>
CommitDate: Wed, 9 Oct 2013 15:41:10 -0700

x86, apic: Add boot_cpu_is_bsp() to check if boot cpu is BSP

Kexec can enter the kdump 2nd kernel on AP if crash happens on AP. To
check if boot cpu is BSP, introduce a helper function
boot_cpu_is_bsp().

Signed-off-by: HATAYAMA Daisuke <d.hatayama@jp.fujitsu.com>
Link: http://lkml.kernel.org/r/20130829092758.5476.90694.stgit@localhost6.localdomain6
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
---
 arch/x86/include/asm/mpspec.h |  3 +++
 arch/x86/kernel/apic/apic.c   | 14 ++++++++++++++
 arch/x86/kernel/setup.c       |  2 ++
 3 files changed, 19 insertions(+)

diff --git a/arch/x86/include/asm/mpspec.h b/arch/x86/include/asm/mpspec.h
index 626cf70..a8a4338 100644
--- a/arch/x86/include/asm/mpspec.h
+++ b/arch/x86/include/asm/mpspec.h
@@ -47,10 +47,13 @@ extern int mp_bus_id_to_type[MAX_MP_BUSSES];
 extern DECLARE_BITMAP(mp_bus_not_pci, MAX_MP_BUSSES);
 
 extern unsigned int boot_cpu_physical_apicid;
+extern bool boot_cpu_is_bsp;
 extern unsigned int max_physical_apicid;
 extern int mpc_default_type;
 extern unsigned long mp_lapic_addr;
 
+extern void boot_cpu_is_bsp_init(void);
+
 #ifdef CONFIG_X86_LOCAL_APIC
 extern int smp_found_config;
 #else
diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c
index a7eb82d..488709d 100644
--- a/arch/x86/kernel/apic/apic.c
+++ b/arch/x86/kernel/apic/apic.c
@@ -64,6 +64,12 @@ unsigned disabled_cpus;
 unsigned int boot_cpu_physical_apicid = -1U;
 
 /*
+ * Indicates whether the processor that is doing the boot up, is BSP
+ * processor or not.
+ */
+bool boot_cpu_is_bsp;
+
+/*
  * The highest APIC ID seen during enumeration.
  */
 unsigned int max_physical_apicid;
@@ -2589,3 +2595,11 @@ static int __init lapic_insert_resource(void)
  * that is using request_resource
  */
 late_initcall(lapic_insert_resource);
+
+void boot_cpu_is_bsp_init(void)
+{
+	u32 l, h;
+
+	rdmsr(MSR_IA32_APICBASE, l, h);
+	boot_cpu_is_bsp = (l & MSR_IA32_APICBASE_BSP) ? true : false;
+}
diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index f0de629..a30bc06 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -1166,6 +1166,8 @@ void __init setup_arch(char **cmdline_p)
 
 	early_quirks();
 
+	boot_cpu_is_bsp_init();
+
 	/*
 	 * Read APIC and some other early information from ACPI tables.
 	 */