linux-kernel - Re: swsusp status report

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Date:	26 Jul 2006 17:13:02 +0200
From:	Andi Kleen <ak@...e.de>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
Cc:	Linux PM <linux-pm@...l.org>, Pavel Machek <pavel@....cz>,
	linux-kernel@...r.kernel.org
Subject: Re: swsusp status report

"Rafael J. Wysocki" <rjw@...k.pl> writes:
> 
> The code that restores the memory state from the suspend image in step
> (11) also uses the kernel identity mapping to address memory, so it cannot
> access highmem pages on i386, but it practically has no other limitations as
> far as the image size is concerned.  In other words, it would be possible to
> restore suspend images as big as 80% or even 90% of RAM, or the normal zone
> on i386, if the 'snapshotting' code were able to create them.

Why can't you just kmap or ioremap them as needed and pass the pfns/struct
page * for IO?

> The code that performs steps (5) and (11) of the suspend-resume cycle is
> quite robust and there is only one known problem with it, which seems to
> be x86_64-specific.  Namely, on x86_64 machines with more than 2 GB of RAM
> there are memory gaps and/or reserved memory areas between the 2nd and 3rd
> Gbyte of physical memory and swsusp tries to save these areas as though
> they were RAM which leads to oopses.  This issue is now being worked on.

I guess we could just borrow a new struct page flags bit again and set it
during memory setup. That would fix your problem I guess. Should be fairly
easy to do. Let me know if you need it.

-Andi
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