[PATCH 2/6] x86/head_32.S/head_64.S: Kernel entry code after waking up offline CPU via mwait or nmi

From: Fenghua Yu
Date: Mon Jun 04 2012 - 14:31:45 EST


From: Fenghua Yu <fenghua.yu@xxxxxxxxx>

start_cpu() is CPU entry point after it's waken up via mwait or nmi. It's called
from play_dead(). Everything has been set up already except stack. We just set
up stack here. Then call start_secondary().

Signed-off-by: Fenghua Yu <fenghua.yu@xxxxxxxxx>
---
arch/x86/include/asm/cpu.h | 1 +
arch/x86/kernel/head_32.S | 12 ++++++++++++
arch/x86/kernel/head_64.S | 14 ++++++++++++++
3 files changed, 27 insertions(+), 0 deletions(-)

diff --git a/arch/x86/include/asm/cpu.h b/arch/x86/include/asm/cpu.h
index 4564c8e..c2ad71c 100644
--- a/arch/x86/include/asm/cpu.h
+++ b/arch/x86/include/asm/cpu.h
@@ -28,6 +28,7 @@ struct x86_cpu {
#ifdef CONFIG_HOTPLUG_CPU
extern int arch_register_cpu(int num);
extern void arch_unregister_cpu(int);
+extern void __cpuinit start_cpu(void);
#endif

DECLARE_PER_CPU(int, cpu_state);
diff --git a/arch/x86/kernel/head_32.S b/arch/x86/kernel/head_32.S
index d42ab17..55981a7 100644
--- a/arch/x86/kernel/head_32.S
+++ b/arch/x86/kernel/head_32.S
@@ -266,6 +266,18 @@ num_subarch_entries = (. - subarch_entries) / 4
jmp default_entry
#endif /* CONFIG_PARAVIRT */

+#ifdef CONFIG_HOTPLUG_CPU
+/*
+ * Boot CPU entry point. It's called from play_dead(). Everything has been set
+ * up already except stack. We just set up stack here. Then call
+ * start_secondary().
+ */
+ENTRY(start_cpu)
+ movl stack_start, %ecx
+ movl %ecx, %esp
+ jmp *(initial_code)
+#endif
+
/*
* Non-boot CPU entry point; entered from trampoline.S
* We can't lgdt here, because lgdt itself uses a data segment, but
diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S
index 94bf9cc..84a8e1d 100644
--- a/arch/x86/kernel/head_64.S
+++ b/arch/x86/kernel/head_64.S
@@ -251,6 +251,20 @@ ENTRY(secondary_startup_64)
pushq $__KERNEL_CS # set correct cs
pushq %rax # target address in negative space
lretq
+#ifdef CONFIG_HOTPLUG_CPU
+/*
+ * Boot CPU entry point. It's called from play_dead(). Everything has been set
+ * up already except stack. We just set up stack here. Then call
+ * start_secondary().
+ */
+ENTRY(start_cpu)
+ movq stack_start(%rip),%rsp
+ movq initial_code(%rip),%rax
+ pushq $0 # fake return address to stop unwinder
+ pushq $__KERNEL_CS # set correct cs
+ pushq %rax # target address in negative space
+ lretq
+#endif

/* SMP bootup changes these two */
__REFDATA
--
1.6.0.3

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