Re: [Qemu-devel] [RESEND PATCH] q35: Remove old machine versions

[Eduardo Habkost]

On Thu, Dec 17, 2015 at 12:36:11PM -0500, John Snow wrote:
> 
> 
> On 12/17/2015 12:27 PM, Eduardo Habkost wrote:
> > Migration with q35 was not possible before commit
> > 04329029a8c539eb5f75dcb6d8b016f0c53a031a, because q35 unconditionally
> > creates an ich9-ahci device, that was marked as unmigratable. So all q35
> > machine classes before pc-q35-2.4 were not migratable, so there's no
> > point in keeping compatibility code for them.
> > 
> > Remove all old pc-q35 machine classes and keep only pc-q35-2.4.
> > 
> > Signed-off-by: Eduardo Habkost <address@hidden>
> > ---
> > Resubmitting this series, as I didn't see any convincing argument
> > to keep the old code around.
> > ---
> >  hw/i386/pc_q35.c | 163 
> > -------------------------------------------------------
> >  1 file changed, 163 deletions(-)
> > 
[...]
> 
> To recap, the main objection last time was that it might upset existing
> libvirt configurations because libvirt saves the machine types in the
> XML, and this will cause existing configurations to be unable to boot.
> 
> There was some discussion over "fudging" it so that we silently forced
> users onto 2.4+, but this was rejected as a bad idea in favor of just
> simply breaking anybody relying on pre-2.4 machine types.
> 
> So the question becomes:
> 
> What do we gain by deleting this? Is cleaning up this code worth
> breaking some configurations?

Developer time. We don't waste time reviewing, refactoring, and
fixing compat code that nobody should ever run. See, for example,
the patch sent by Gerd today:
  [PATCH 6/6] q35: skip q35-acpi-dsdt.aml load if not needed

-- 
Eduardo