x86/boot/64: Use a common function for starting CPUs

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>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Nilay Vaish <nilayvaish@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1d692ffa62fcb3cc835a5b254e953f2d9bab3549.1474480779.git.jpoimboe@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S
index b4421cc..3631777 100644 (file)
--- a/arch/x86/kernel/head_64.S
+++ b/arch/x86/kernel/head_64.S
@@ -265,13 +265,17 @@ 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
+       jmp     start_cpu
+ENDPROC(secondary_startup_64)
+
+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
@@ -300,7 +304,7 @@ ENTRY(secondary_startup_64)
        pushq   $__KERNEL_CS    # set correct cs
        pushq   %rax            # target address in negative space
        lretq
-ENDPROC(secondary_startup_64)
+ENDPROC(start_cpu)
 
 #include "verify_cpu.S"
 
@@ -308,15 +312,11 @@ ENDPROC(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