[RFC PATCH v2 02/18] x86/asm/head: use a common function for starting CPUs

Josh Poimboeuf
2016-04-28T20:45:15Z

There are two different pieces of code for starting a CPU: start_cpu0()
and the end of secondary_startup_64(). They're identical except for the
stack setup. Combine the common parts into a shared start_cpu()
function.

Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
---
arch/x86/kernel/head_64.S | 19 +++++++++----------
1 file changed, 9 insertions(+), 10 deletions(-)

diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S
index 792c3bb..6dbd2c0 100644
--- a/arch/x86/kernel/head_64.S
+++ b/arch/x86/kernel/head_64.S
@@ -264,13 +264,15 @@ ENTRY(secondary_startup_64)
movl $MSR_GS_BASE,%ecx
movl initial_gs(%rip),%eax
movl initial_gs+4(%rip),%edx
- wrmsr
+ wrmsr

/* rsi is pointer to real mode structure with interesting info.
pass it to C */
movq %rsi, %rdi
-
- /* Finally jump to run C code and to be on real kernel address
+
+ENTRY(start_cpu)
+ /*
+ * Jump to run C code and to be on a real kernel address.
* Since we are running on identity-mapped space we have to jump
* to the full 64bit address, this is only possible as indirect
* jump. In addition we need to ensure %cs is set so we make this
@@ -299,6 +301,7 @@ ENTRY(secondary_startup_64)
pushq $__KERNEL_CS # set correct cs
pushq %rax # target address in negative space
lretq
+ENDPROC(start_cpu)

#include "verify_cpu.S"

@@ -306,15 +309,11 @@ ENTRY(secondary_startup_64)
/*
* Boot CPU0 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().
+ * start_secondary() via start_cpu().
*/
ENTRY(start_cpu0)
- movq initial_stack(%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
+ movq initial_stack(%rip), %rsp
+ jmp start_cpu
ENDPROC(start_cpu0)
#endif

--
2.4.11