From: H. Peter Anvin <hpa@zytor.com>
Date: Mon, 30 Jun 2008 22:42:47 +0000 (-0700)
Subject: x86: fix regression: boot failure on AMD Elan TS-5500
X-Git-Tag: v2.6.27-rc1~1106^2~250^2~1
X-Git-Url: http://www.pilppa.org/gitweb/gitweb.cgi?a=commitdiff_plain;h=2ee2394b682c0ee99b0f083abe6c57727e6edb69;p=linux-2.6-omap-h63xx.git

x86: fix regression: boot failure on AMD Elan TS-5500

Jeremy Fitzhardinge wrote:
>
> Maybe it really does require the far jump immediately after setting PE
> in cr0...
>
> Hm, I don't remember this paragraph being in vol 3a, section 8.9.1
> before.  Is it a recent addition?
>
>    Random failures can occur if other instructions exist between steps
>    3 and 4 above.  Failures will be readily seen in some situations,
>    such as when instructions that reference memory are inserted between
>    steps 3 and 4 while in system management mode.
>

I don't remember that, either.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
---

diff --git a/arch/x86/boot/pmjump.S b/arch/x86/boot/pmjump.S
index ab049d40a88..141b6e20ed3 100644
--- a/arch/x86/boot/pmjump.S
+++ b/arch/x86/boot/pmjump.S
@@ -33,6 +33,8 @@ protected_mode_jump:
 	movw	%cs, %bx
 	shll	$4, %ebx
 	addl	%ebx, 2f
+	jmp	1f			# Short jump to serialize on 386/486
+1:
 
 	movw	$__BOOT_DS, %cx
 	movw	$__BOOT_TSS, %di
@@ -40,8 +42,6 @@ protected_mode_jump:
 	movl	%cr0, %edx
 	orb	$X86_CR0_PE, %dl	# Protected mode
 	movl	%edx, %cr0
-	jmp	1f			# Short jump to serialize on 386/486
-1:
 
 	# Transition to 32-bit mode
 	.byte	0x66, 0xea		# ljmpl opcode