Re: [Qemu-devel] [Qemu-ppc] [PATCHv3 for-2.9 0/6] HPT resizing for pseries guests (qemu part)

[Andrea Bolognani]

On Tue, 2016-12-20 at 10:47 +1100, David Gibson wrote:
> > Do we want to expose a knob for controlling this
> > to the user at the libvirt level, or should we just enable
> > resize-hpt unconditionally whenever we detect that the QEMU
> > binary supports it?
> 
> I'm not sure if we need a knob.  I think in general enabling for
> pseries-2.9 and later machine types is correct.  The difficulty is
> that for HV guests, we can only enable it if the host kernel also has
> support.  Explicitly setting "resize-hpt=enable" means qemu will not
> start if the kernel doesn't support it.

I thought that would be the case for resize-hpt=required,
not resized-hpt=enabled.

> My inclination would be to enable unconditionally for pseries-2.9 and
> later machine types.

So I guess the question is, will users want to enable this
manually for older machine types, or is it reasonable to
expect them to simply switch to pseries-2.9 if they want
the feature?

Moreover, do you foresee any situation in which users
might reasonably want to turn the feature off even though
the entire stack (host kernel, QEMU, guest kernel)
understands it?

-- 
Andrea Bolognani / Red Hat / Virtualization