linux-kernel - [tip:x86/asm] x86/boot/64: Use a common function for starting CPUs

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Date:   Thu, 20 Oct 2016 04:11:12 -0700
From:   tip-bot for Josh Poimboeuf <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     brgerst@...il.com, nilayvaish@...il.com, bp@...en8.de,
        linux-kernel@...r.kernel.org, mingo@...nel.org,
        torvalds@...ux-foundation.org, dvlasenk@...hat.com,
        jpoimboe@...hat.com, luto@...nel.org, hpa@...or.com,
        tglx@...utronix.de, peterz@...radead.org
Subject: [tip:x86/asm] x86/boot/64: Use a common function for starting CPUs

Commit-ID:  a9468df5ad48d06e5237fc2b56fb04c52f79c8c4
Gitweb:     http://git.kernel.org/tip/a9468df5ad48d06e5237fc2b56fb04c52f79c8c4
Author:     Josh Poimboeuf <jpoimboe@...hat.com>
AuthorDate: Wed, 21 Sep 2016 16:04:04 -0500
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Thu, 20 Oct 2016 09:15:23 +0200

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@...hat.com>
Cc: Andy Lutomirski <luto@...nel.org>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Brian Gerst <brgerst@...il.com>
Cc: Denys Vlasenko <dvlasenk@...hat.com>
Cc: H. Peter Anvin <hpa@...or.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Nilay Vaish <nilayvaish@...il.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Link: http://lkml.kernel.org/r/1d692ffa62fcb3cc835a5b254e953f2d9bab3549.1474480779.git.jpoimboe@redhat.com
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 arch/x86/kernel/head_64.S | 22 +++++++++++-----------
 1 file changed, 11 insertions(+), 11 deletions(-)

diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S
index b4421cc..3631777 100644
--- 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