Subject: Re: Help port swsusp to ppc.
From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Pavel Machek <pavel@ucw.cz>
Cc: ncunningham@users.sourceforge.net, Hugang <hugang@soulinfo.com>,
       ncunningham@clear.net.nz,
       Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
       debian-powerpc@lists.debian.org
In-Reply-To: <20040120000435.GB837@elf.ucw.cz>
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> (1) There's routine during resume that copies pages to their old
> locations. If you (would want to) have different kernel during resume,
> how do you guarantee that that "kernel being resumed" does not use
> memory ocupied by copying routine?

By having the copy routine sit elsewhere. You can have the copy routine
be in a known location of the kernel beeing resumed (that is it uses
its own copy routine) that is aligned on a page boundary and knows how
to copy itself. Fairly trivial.

> (2) Plus number of problems with devices grows with number of versions
> squared. To guarantee it works properly you'd have to test all
> combinations of "suspend kernel" and "resume kernel".

Why ? You aren't passing any device/driver information from the boot
kernel and the resumed one... do you ?

> [(1) Could be solved by reserving 4KB somewhere for copy routine, and
> making sure copy routine is never bigger than 4KB etc. But I'd like to
> keep it simple and really don't want to deal with (2).]

Then you don't wnat to do things properly...

Ben.


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