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

Ingo Molnar
2010-12-13T13:48:28Z

* 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?

The regression needs to be addressed one way or another: either by improving the
"compatible with Windows" approach to actually work (without quirks), or by
reverting to the tested-for-years Linux solution.

( What we always try to avoid is trading in a set of regressions for another set of
regressions. That way lies madness, it can not result in reliable, provable
progress. )

Thanks,

Ingo