[PATCH v2 1/2] x86, apic: Add boot_cpu_is_bsp() to check if boot cpu is BSP

HATAYAMA Daisuke
2013-10-15T05:43:49Z

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>
---
arch/x86/include/asm/mpspec.h | 7 +++++++
arch/x86/kernel/apic/apic.c | 16 ++++++++++++++++
arch/x86/kernel/setup.c | 2 ++
3 files changed, 25 insertions(+)

diff --git a/arch/x86/include/asm/mpspec.h b/arch/x86/include/asm/mpspec.h
index 626cf70..54d5f98 100644
--- a/arch/x86/include/asm/mpspec.h
+++ b/arch/x86/include/asm/mpspec.h
@@ -47,11 +47,18 @@ 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;

#ifdef CONFIG_X86_LOCAL_APIC
+extern void boot_cpu_is_bsp_init(void);
+#else
+static inline void boot_cpu_is_bsp_init(void) { };
+#endif
+
+#ifdef CONFIG_X86_LOCAL_APIC
extern int smp_found_config;
#else
# define smp_found_config 0
diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c
index a7eb82d..62ee365 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 +2595,13 @@ static int __init lapic_insert_resource(void)
* that is using request_resource
*/
late_initcall(lapic_insert_resource);
+
+void __init boot_cpu_is_bsp_init(void)
+{
+ if (cpu_has_apic) {
+ u32 l, h;
+
+ rdmsr_safe(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.
*/