linux-kernel - Re: [PATCH 12/20] x86_64: wakeup.S Misc cleanup

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Date:	Sat, 18 Nov 2006 01:19:07 +0100
From:	Pavel Machek <pavel@....cz>
To:	Vivek Goyal <vgoyal@...ibm.com>
Cc:	linux kernel mailing list <linux-kernel@...r.kernel.org>,
	Reloc Kernel List <fastboot@...ts.osdl.org>,
	ebiederm@...ssion.com, akpm@...l.org, ak@...e.de, hpa@...or.com,
	magnus.damm@...il.com, lwang@...hat.com, dzickus@...hat.com,
	rjw@...k.pl
Subject: Re: [PATCH 12/20] x86_64: wakeup.S Misc cleanup

Hi!

> o Various cleanups. One of the main purpose of cleanups is that make
>   wakeup.S as close as possible to trampoline.S.
> 
> o Following are the changes
> 	- Indentations for comments.
> 	- Changed the gdt table to compact form and to resemble the
> 	  one in trampoline.S
> 	- Take the jump to 32bit from real mode using ljmpl. Makes code
> 	  more readable.
> 	- After enabling long mode, directly take a long jump for 64bit
> 	  mode. No need to take an extra jump to "reach_comaptibility_mode"
> 	- Stack is not used after real mode. So don't load stack in
>  	  32 bit mode.
> 	- No need to enable PGE here.
> 	- No need to do extra EFER read, anyway we trash the read contents.
> 	- No need to enable system call (EFER_SCE). Anyway it will be 
> 	  enabled when original EFER is restored.
> 	- No need to set MP, ET, NE, WP, AM bits in cr0. Very soon we will
>   	  reload the original cr0 while restroing the processor state.
> 
> Signed-off-by: Eric W. Biederman <ebiederm@...ssion.com>
> Signed-off-by: Vivek Goyal <vgoyal@...ibm.com>

ACK, minor nitpicks:

> +	/* ??? Why I need the accessed bit set in order for this to work? */

Yes, I'd like to know :-).

> +	.quad   0x00cf9b000000ffff              # __KERNEL32_CS
> +	.quad   0x00af9b000000ffff              # __KERNEL_CS
> +	.quad   0x00cf93000000ffff              # __KERNEL_DS

Can we get a comment telling us what to keep it in sync with?

									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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