linux-kernel - Re: [RFC][PATCH -mm 3/4] Hibernation: Pass CR3 in the image header on x86

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Message-ID: <20070822082825.GC2479@elf.ucw.cz>
Date:	Wed, 22 Aug 2007 10:28:25 +0200
From:	Pavel Machek <pavel@....cz>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
Cc:	Andi Kleen <ak@...e.de>, LKML <linux-kernel@...r.kernel.org>,
	pm list <linux-pm@...ts.linux-foundation.org>
Subject: Re: [RFC][PATCH -mm 3/4] Hibernation: Pass CR3 in the image header on x86_64

Hi!

> From: Rafael J. Wysocki <rjw@...k.pl>
> 
> Since we already pass the address of restore_registers() in the image header,
> we can also pass the value of the CR3 register from before the hibernation in
> the same way.  This will allow us to avoid using init_level4_pgt page tables
> during the restore.
> 
> Signed-off-by: Rafael J. Wysocki <rjw@...k.pl>

> @@ -253,10 +262,13 @@ int arch_hibernation_header_save(void *a
>  {
>  	struct restore_data_record *rdr = addr;
>  
> -	if (max_size < sizeof(struct restore_data_record))
> +	if (max_size < sizeof(*rdr))
>  		return -EOVERFLOW;
>  	rdr->jump_address = restore_jump_address;
> -	rdr->control = (restore_jump_address ^ RESTORE_MAGIC);
> +	rdr->cr3 = restore_cr3;
> +	rdr->magic = RESTORE_MAGIC;
> +	rdr->crc = 0;
> +	rdr->crc = crc32_le(0, addr, sizeof(*rdr));
>  	return 0;
>  }

No, I do not think I like that. I believe both -> control and -> crc
is just useless paranoia. Bitflip in this area is not going to be any
worse than bitflip anywhere else, we should not pretend this is
somehow "more important".

-> control should really be "protocol version"... probably should
contain some field that is easy to increment.
								Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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