Re: [kvmtool test PATCH 24/24] kvmtool: arm: Add support for creating VM with PA size

[Peter Maydell]

On 4 July 2018 at 16:51, Will Deacon <will.deacon@xxxxxxx> wrote:
> On Wed, Jul 04, 2018 at 03:41:18PM +0100, Marc Zyngier wrote:
>> Not really. Let's say I want my IPA space split in two: memory covers
>> the low 47 bit, and I want MMIO spanning the top 47 bit. With your
>> scheme, you'd end-up with a 47bit IPA space, while you really want 48
>> bits (MMIO space implemented by userspace isn't registered to the
>> kernel).
>
> That still sounds quite niche for a VM. Does QEMU do that?

Not at 47 bits, but we have RAM up to the 256GB mark, and
MMIO above that (including a large PCI window), so the general
arrangement of having the top end of the IPA space not
necessarily be things we've told the kernel about definitely
exists.

thanks
-- PMM