Re: [PATCH 0/2] expose host-phys-bits to guest

[Gerd Hoffmann]

  Hi,

> > I don't see a need for that.  Live migration compatibility can be
> > handled just fine today using
> >     'host-phys-bits=on,host-phys-bits-limit=<xx>'
> > 
> > Which is simliar to 'phys-bits=<xx>'.
> 
> yes but what if user did not configure anything?

I expect that'll be less and less common.  The phys-bits=40 default used
by qemu becomes increasingly problematic for large guests which need
more than that, and we see activity implementing support for that in
libvirt.

> the point of the above is so we can eventually, in X years, change the guests
> to trust CPUID by default.

Well, we can flip host-phys-bits to default to 'on' in qemu for new
machine types (or new cpu versions).  That'll have the very same effect.

take care,
  Gerd