Commit 2ee2394b authored Jun 30, 2008 by H. Peter Anvin Committed by Ingo Molnar Jul 01, 2008

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>

parent 908ec7af

arch/x86/boot/pmjump.S

+2 −2

Original line number	Diff line number	Diff line
		@@ -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

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