[coreboot] Discussion about dynamic PCI MMIO size on x86

ron minnich rminnich at gmail.com
Mon Jun 6 21:36:47 CEST 2016


I'm getting the sense here that reasonably modern CPUs can easily handle
the 2G hole. From what I've seen, it would not cause trouble for older CPUs
because they're most likely to be in small systems that are not likely to
have more than 2G memory anyway (I'm thinking of the vortex).

The 2G hole seems like a reasonable way go to.

ron

On Mon, Jun 6, 2016 at 1:01 AM Gerd Hoffmann <kraxel at redhat.com> wrote:

>   Hi,
>
> > I think one can go with 2GB MMIO hole.
>
> Agreeing here.  We have PAE.  Non-ancient 32bit kernels should support
> and use it, for both security reasons (nox support requires PAE page
> table format) and accessing physical address space above 4G.
>
> > The PCIe > 4GB is a question, I don't
> > think Windows have good support for this.
>
> Depends on the version.  Recent windows versions have no problems
> handling it.  WinXP throws a BSOD though in case it finds a 64bit mmio
> window described in \_SB.PCI0._CRS ...
>
> cheers,
>   Gerd
>
>
> --
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>
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