Re: [pm] Strange cleanups in -test8 kernel/acpi/wakeup.S

["Mika Penttilä" <mika.penttila@kolumbus.fi>]

Patrick Mochel wrote:

>>Some more changes landed in -test8. I have not seen them
>>before. Patrick, please, if you change something, can you post patch
>>somewhere for review before merging with Linus?
>>    
>>
>
>Pavel, I wrote the code in the first place, before you littered your
>'debug hacks' throughout it. I have merely been trying to simplify it for 
>debugging on other processors that are known not to work. While I 
>understand your generic plea for review, I fail to see how it would help 
>with this assembly.. 
>
>  
>
>>bkcvs info is:
>>BitKeeper to RCS/CVS export
>>----------------------------
>>revision 1.5
>>date: 2003/10/08 22:55:45;  author: mochel;  state: Exp;  lines: +37
>>-89
>>[power] Clean up ACPI STR assembly.
>>    
>>
>
>It might help if you read the full changeset comments. 
>
>  
>
>>diff -Nru a/arch/i386/kernel/acpi/wakeup.S
>>b/arch/i386/kernel/acpi/wakeup.S
>>--- a/arch/i386/kernel/acpi/wakeup.S    Fri Oct 17 14:43:50 2003
>>+++ b/arch/i386/kernel/acpi/wakeup.S    Fri Oct 17 14:43:50 2003
>>@@ -172,14 +172,13 @@
>> .org   0x1000
>>
>> wakeup_pmode_return:
>>-       movl    $__KERNEL_DS, %eax
>>-       movl    %eax, %ds
>>-       movw    $0x0e00 + 'u', %ds:(0xb8016)
>>-
>>-       # restore other segment registers
>>-       xorl    %eax, %eax
>>+       movw    $__KERNEL_DS, %ax
>>+       movw    %ax, %ss
>>+       movw    %ax, %ds
>>+       movw    %ax, %es
>>        movw    %ax, %fs
>>        movw    %ax, %gs
>>+       movw    $0x0e00 + 'u', 0xb8016
>>
>>        # reload the gdt, as we need the full 32 bit address
>>        lgdt    saved_gdt
>>	~~~~~~~~~~~~~~~~~
>>
>>Notice lgdt here. You have moved setup of segment registers before
>>loading gdt. This is actually okay, if you can be sure that all such
>>registers are in gdt (and not in ldt, for example).
>>    
>>
>
>All segments are in the GDT, as we use the same GDT in real mode as we do 
>in protected mode. However, you must reload the GDT in protected mode 
>because the GDTR is only 24 bits in real mode, but 32 in protected mode. 
>
>  
>
To be exact, GDTR is always 48 bits in x86. Reloading it twice seems 
pretty pointless.

--Mika