RE: [patch] Fix GDT re-load on ACPI resume

[Li, Shaohua]

>The ACPI resume code currently uses a real-mode 16-bit lgdt instruction
to
>reload the GDT.  This only restores the lower 24 bits of the GDT base
>address.  In recent kernels, the GDT seems to have moved out of the
lower
>16 megs, thereby causing the ACPI resume to fail -- an invalid GDT was
>being loaded.
>
>This simple patch adds the 0x66 prefix to lgdt, which forces it to load
>all 32 bits of the GDT base address, thereby removing any restrictions
on
>where the GDT can be placed in memory.  This makes ACPI resume work for
me
>on a Thinkpad T40 laptop.
>
>-- kolya
>
>--- linux-2.6.9/arch/i386/kernel/acpi/wakeup.S	2004/11/15 09:00:34
1.1
>+++ linux-2.6.9/arch/i386/kernel/acpi/wakeup.S	2004/11/15 20:33:27
>@@ -67,6 +67,8 @@
> 	movw	$0x0e00 + 'i', %fs:(0x12)
>
> 	# need a gdt
>+	.byte	0x66			# force 32-bit operands in case
>+					# the GDT is past 16 megabytes
> 	lgdt	real_save_gdt - wakeup_code
>
> 	movl	real_save_cr0 - wakeup_code, %eax
There is a patch from hiroit@xxxxxxxxx to fix the GDT issue. You can try
it.
Please cc 'acpi-devel@xxxxxxxxxxxxxxxxxxxxx' for suspend/resume issue.

Thanks,
Shaohua

Attachment: wakeup_gdt2.patch
Description: wakeup_gdt2.patch