Re: [PATCH RFCv2 2/4] i386/pc: relocate 4g start to 1T where applicable

[Gerd Hoffmann]

  Hi,

> > And the upstream code is now pretty much identical except for the
> > default;  note that for TCG you do need to keep to 40 I think.
> 
> will TCG work with 40bits on host that supports less than that?

When I understand things correctly the problem is that the phys-bits
limit applies to the npt/ept tables too, effectively restricting guest
physical address space to host physical address space.

TCG is not affected by that and should work just fine.

Not sure what happens if you turn off npt/ept and run on softmmu.
Possibly that works fine too.

> Also quick look at host-phys-bits shows that it affects only 'host'
> cpu model and is NOP for all other models.

I don't think so.  microvm forces host-phys-bits=on and that works with
all cpu models.

take care,
  Gerd