Re: [PATCH v3 14/22] microvm: use 2G split unconditionally

[Gerd Hoffmann]

  Hi,

> >   (1) we loose a bit of memory.
>           it's probably not a big enough to care about, we do similar ovarlay 
> mapping on pc/q35
>           at the beginning of RAM

Yes, shouldn't be too much.

> >   (2) we loose a gigabyte page.
>           I'm not sure waht exactly we loose in this case.

The 1G page for 0xc0000000 -> 0xffffffff (as explained by paolo).

> >   (3) we wouldn't have guard pages (unused address space) between
> >       between ram and mmio space.
>            if it's holes' mmio,then do we really need them (access is going 
> to be terminated
>            either in always valid RAM or in valid mmio hole)?

Not required, but more robust.  Less likely that the guest touches mmio
by accident.

I'd expect it also requires some e820 hacks.

cheers,
  Gerd