* Jesse Barnes <jbar...@virtuousgeek.org> wrote:
> On Thu, 25 Jul 2013 20:31:27 -0700
> "H. Peter Anvin" <h...@zytor.com> wrote:
>
> > On 07/25/2013 07:14 PM, Jesse Barnes wrote:
> > > To clarify: it'll either be marked reserved or not listed at all in e820,
> > > which is why I did this early, before any other e820 stuff like the "RAM
> > > buffer" are allocated, and before we could use the iomem resource (or
> > > maybe we could even early per Linus? I'll check).
> > >
> > > Jesse
> >
> > If it is marked reserved or not listed at all it is much less of an
> > issue. Reserved is in fact the correct thing; not listed at all really
> > isn't very problematic in most cases.
>
> Yeah the problems seem to fall into two categories:
> 1) mmio space is allocated in this range:
> https://bugs.freedesktop.org/show_bug.cgi?id=66726
> 2) range gets partially allocated to the "RAM buffer"
> https://bugs.freedesktop.org/show_bug.cgi?id=66844
>
> Case (1) is the one that worries me. I'm guessing it'll mainly be a
> problem on machines where MMIO space is limited or somehow structured
> such that PCI resources end up there when we allocate them. Depending
> on what gets put there and the decode priority, behavior may be poor.
>
> Case (2) isn't harmful, but ends up causing our driver to skip stolen
> memory initialization, because of the conflict.
>
> Anyway I'll look at Linus's suggestion of reserving in the iomem
> resource really early and roll in Chris's stuff if that doesn't work
> out.
Am I being too pedantic in expecting that we still mark it
e820-reserved?
This area really isnt an ordinary PCI resource such as a
BAR or an MMIO region. It's truly system RAM (which cannot
be moved/reallocated), used by graphics hardware, and the
firmware should have marked it reserved.
(The end result should be the same in any case, so this is
a detail.)
Thanks,
Ingo
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