Messages in this thread Patch in this message | | | Date | Mon, 30 Jun 2008 15:42:47 -0700 | From | "H. Peter Anvin" <> | Subject | Re: Regression: boot failure on AMD Elan TS-5500 |
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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.
Sean: could you try the following patch?
-hpa diff --git a/arch/x86/boot/pmjump.S b/arch/x86/boot/pmjump.S index ab049d4..141b6e2 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 | |