linux-kernel - Re: [PATCH 1/5] resources: add arch hook for preventing allocation in reserved areas

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Message-Id: <201012141709.46610.bjorn.helgaas@hp.com>
Date:	Tue, 14 Dec 2010 17:09:45 -0700
From:	Bjorn Helgaas <bjorn.helgaas@...com>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	"Rafael J. Wysocki" <rjw@...k.pl>,
	Jesse Barnes <jbarnes@...tuousgeek.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Len Brown <lenb@...nel.org>, linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-acpi@...r.kernel.org,
	"H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Adam Belay <abelay@....edu>, Matthew Garrett <mjg@...hat.com>,
	Dan Williams <dcbw@...hat.com>
Subject: Re: [PATCH 1/5] resources: add arch hook for preventing allocation in reserved areas

On Monday, December 13, 2010 06:47:39 am Ingo Molnar wrote:
> 
> * Bjorn Helgaas <bjorn.helgaas@...com> wrote:
> 
> > > OK, so I guess the best thing we can do for 2.6.37 is to revert 1af3c2e (x86: 
> > > allocate space within a region top-down), right?
> > 
> > That's a possibility, but I'm not sure it's the best.  It would avoid the nx6325 
> > landmine, but we could easily step on a different one on other machines.
> > 
> > If Windows uses the end of available space first, that's the best-tested 
> > territory, and I think it's better to try to stay in it rather revert 1af3c2e and 
> > start mapping different territory that really isn't tested by Windows at all.
> > 
> > On the nx6325, we stray out of that tested territory because Linux opens windows 
> > on subtractive-decode bridges and allocates more space to CardBus bridges.
> > 
> > I think it'd be fairly simple to leave subtractive-decode bridges alone, and that 
> > might make the nx6325 work well enough for .37, even without the quirk.  This 
> > feels like a change that might be the right thing to do in general.  Using 
> > subtractive rather than positive decode would give up a little performance, but I 
> > doubt it's important
> 
> Is there a patch for that that people could try?

Yes.  https://bugzilla.kernel.org/show_bug.cgi?id=23332#c22

It works for me, but it's such a new idea to me that I'm not quite
used to it and don't know how confident to be yet.

Bjorn
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