linux-kernel - Re: [RFC][PATCH 1/2 -mm] kexec based hibernation: kexec jump

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Date:	Mon, 27 Aug 2007 18:48:29 +0000
From:	Pavel Machek <pavel@....cz>
To:	"Huang, Ying" <ying.huang@...el.com>
Cc:	"Eric W. Biederman" <ebiederm@...ssion.com>,
	nigel@...el.suspend2.net,
	Andrew Morton <akpm@...ux-foundation.org>,
	Jeremy Maitin-Shepard <jbms@....edu>,
	linux-kernel@...r.kernel.org, linux-pm@...ts.linux-foundation.org,
	Kexec Mailing List <kexec@...ts.infradead.org>
Subject: Re: [RFC][PATCH 1/2 -mm] kexec based hibernation: kexec jump

Hi!

> To support jumping back from kexeced kernel, before executing the new
> kernel, the devices are put into quiescent state (to be fully
> implemented), and the state of devices and CPU is saved. After jumping
> back from kexeced kernel, the state of devices and CPU are restored
> accordingly. The devices/CPU state save/restore code of software
> suspend is called to implement corresponding function.
> 
> Signed-off-by: Huang Ying <ying.huang@...el.com>

Looks quite ok to me...


> Index: linux-2.6.23-rc3/include/asm-i386/kexec.h
> ===================================================================
> --- linux-2.6.23-rc3.orig/include/asm-i386/kexec.h	2007-08-25 21:56:54.000000000 +0800
> +++ linux-2.6.23-rc3/include/asm-i386/kexec.h	2007-08-25 21:57:00.000000000 +0800
> @@ -94,6 +94,10 @@
>  		unsigned long start_address,
>  		unsigned int has_pae) ATTRIB_NORET;
>  
> +#ifdef CONFIG_KEXEC_JUMP
> +extern asmlinkage int machine_kexec_real_jump(void *buf);
> +#endif

Is it really neccessery to have ifdef here?

> +#ifdef CONFIG_KEXEC_JUMP
> +#define KEXEC_JUMP_FLAG_IS_KEXECED_KERNEL     0x1
> +#endif /* CONFIG_KEXEC_JUMP */

And here? ... It would be nice to use slightly shorter identifier.
'KJUMP_IS_KEXECED' should be enough.

> +/*
> + * Must be relocatable PIC code callable as a C function
> + */
> +#define HALF_PAGE_ALIGNED (1 << (PAGE_SHIFT-1))
> +
> +#define EBX	0x0
> +#define ESI	0x4
> +#define EDI	0x8
> +#define EBP	0xc
> +#define ESP	0x10
> +#define CR0	0x14
> +#define CR3	0x18
> +#define CR4	0x1c
> +#define FLAG	0x20
> +#define RET	0x24

Hmm, is this enough? Should it use struct ptregs for normal registers?
What about segment registers -- they could change between kernel
version. Should some kind of 'version of kjump protocol' be
introduced?

What about CX/DX/fpu state? GDT pointer?

Actually I think that you _do_ need to save FPU. You should probably
use relevant swsusp parts here.

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