From 2ee2394b682c0ee99b0f083abe6c57727e6edb69 Mon Sep 17 00:00:00 2001 From: "H. Peter Anvin" Date: Mon, 30 Jun 2008 15:42:47 -0700 Subject: [PATCH] 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 --- arch/x86/boot/pmjump.S | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/arch/x86/boot/pmjump.S b/arch/x86/boot/pmjump.S index ab049d40a884..141b6e20ed31 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 -- 2.34.1