Re: swsusp: which page should be saved?

[Pavel Machek <pavel@suse.cz>]

On Pá 17-03-06 09:12:15, Shaohua Li wrote:
> On Thu, 2006-03-16 at 07:08 +0800, Pavel Machek wrote:
> > On Thu 16-03-06 11:53:27, Shaohua Li wrote: 
> > > I thought there was a discussion before, but I still saw many pages
> > like 
> > > BIOS reserved are saved/restored in swsusp. Pages reserved by BIOS,
> > not 
> > > used by OS and kernel text should be skipped in swsusp to me. Below 
> > > patch works in my test. Any thought?
> > 
> > This will need quite a lot of testing.
> > 
> > Does it actually fix anything?
> No, it doesn't. Just want to speed up swsusp.
> 
> > I'm afraid that some of the BIOSs state is actually shared knowledge 
> > with kernel, and that we should better save it, so that kernel's and 
> > BIOS's view are consistent after resume.
> Fair enough. ACPI BIOS does communicate with OS by reserved memory. But
> in the mean time, blindly save/restore such mem might be dangerous. If
> all ACPI devices have their suspend/resume method, reserved memory
> should not be saved.

Ok, I guess it is okay to go in if it stays in -mm for long enough to
get a lot of testing.

> Anyway, skipping kernel text should be safe, isn't it?

It probably is. But you need to save modules. And we do use some
self-modifying code these days, no? (Called runtime patching or
something like that.) Ouch and IIRC top-level pagedir or something
like that lives in kernel "text" -- it is in assembly and wrongly
placed.

So yes, it would be nice, but yes, it might be tricky.

								Pavel
-- 
82:        return SampleTable;