Re: [libvirt] [PATCH] conf: Fix ABI stability check for spicevmc channel
On Fri, Aug 17, 2012 at 06:51:22 -0600, Eric Blake wrote:
On 08/17/2012 06:20 AM, Jiri Denemark wrote:
> Change device type of a virtio channel from/to spicevmc is not a user
> visible change. However, spicevmc channels use different default target
> name than other virtio channels. To maintain ABI stability during this
> change target name must be explicitly specified (and equal) in both
> configurations.
Can we go from 'non-spice, no name' to 'spice, explicit name that
matches old non-spice default name'? Can we go from 'spice, no name' to
'non-spice, explicit name that matches old spice default name'? Your
patch prevents those, even if it is technically possible.
For that matter, can we even go from 'non-spice, no name' to
'non-spice,
explicit default name'? If we can, then the user can achieve the
earlier task through two steps.
In theory, both can be done but both cases are forbidden by ABI stability
checks. The main reason is that ABI stability check is a generic code which
has no idea what the default values are. Moving the defaults from qemu driver
to conf is certainly doable but I think we should avoid doing so unless we
absolutely have to.
Jirka