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@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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