Re: [PATCH] fix i486 boot failure due to stale %ds

[H. Peter Anvin]

Mikael, can you try this patch (rev 3) on your 486?

	-hpa
diff --git a/arch/x86/boot/pmjump.S b/arch/x86/boot/pmjump.S
index 2e55923..d93a0c2 100644
--- a/arch/x86/boot/pmjump.S
+++ b/arch/x86/boot/pmjump.S
@@ -28,17 +28,21 @@
  * void protected_mode_jump(u32 entrypoint, u32 bootparams);
  */
 protected_mode_jump:
-	xorl	%ebx, %ebx		# Flag to indicate this is a boot
 	movl	%edx, %esi		# Pointer to boot_params table
-	movl	%eax, 2f		# Patch ljmpl instruction
+	movl	%eax, 3f		# Patch ljmpl instruction
 	jmp	1f			# Short jump to flush instruction q.
-
 1:
+
 	movw	$__BOOT_DS, %cx
+	xorl	%ebx, %ebx		# Per protocol
+	xorl	%ebp, %ebp		# Per protocol
+	xorl	%edi, %edi		# Per protocol
 
 	movl	%cr0, %edx
 	orb	$1, %dl			# Protected mode (PE) bit
 	movl	%edx, %cr0
+	jmp	2f			# Short jump to serialize
+2:
 
 	movw	%cx, %ds
 	movw	%cx, %es
@@ -48,7 +52,7 @@ protected_mode_jump:
 
 	# Jump to the 32-bit entrypoint
 	.byte	0x66, 0xea		# ljmpl opcode
-2:	.long	0			# offset
+3:	.long	0			# offset
 	.word	__BOOT_CS		# segment
 
 	.size	protected_mode_jump, .-protected_mode_jump