Re: [Qemu-devel] [PATCH v3] vl.c: Output error on invalid machine type provided

[Michal Novotny <minovotn@redhat.com>]

On 07/30/2013 09:29 PM, Eric Blake wrote:
> On 07/30/2013 01:10 PM, Michal Novotny wrote:
>> Output error message when user provides the invalid machine type
>> on the command line. This also saves time to find what issue is
>> when you upgrade from one version of qemu to another version that
>> doesn't support required machine type any longer.
> I know that has historically happened downstream (for example, Fedora 13
> made the mistake of creating a downstream-only fedora-13 machine type
> that corresponded roughly to qemu 0.13, it took some further Fedora
> patches to libvirt to modernize that name back to an upstream machine
> type on an upgrade path before finally being able to drop the downstream
> nonsense in Fedora 18 or so).  But isn't upstream qemu supposed to be
> guaranteeing command-line stability, in that a newer qemu will never
> take away a machine type supported by an older qemu?
>
> But even if the upstream upgrade path never hits this code, your patch
> will make it nicer if you _downgrade_ to a version of qemu (still with
> this patch, of course) that lacks support for a newer machine.  And the
> fact that downstream will take advantage of this even if upstream never
> causes the problem on upgrades still justifies using it.

You are correct, Eric. I sent a patch v4 to output error message to
stderr instead so I fixed the commit message.

Thanks,
Michal

-- 
Michal Novotny <minovotn@redhat.com>, RHCE, Red Hat
Virtualization | libvirt-php bindings | php-virt-control.org