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

Bjorn Helgaas
2010-12-15T00:12:40Z

On Monday, December 13, 2010 06:47:39 am Ingo Molnar wrote:
>
> * Bjorn Helgaas <bjorn.helgaas@hp.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