Re: [Qemu-devel] qemu-ga : Guest Agent : Windows 2008 : Unknown command guest-fsfreeze-freeze

[Luiz Capitulino <lcapitulino@redhat.com>]

On Mon, 20 Aug 2012 14:34:34 -0500
Michael Roth <mdroth@linux.vnet.ibm.com> wrote:

> On Mon, Aug 20, 2012 at 10:54:29AM -0300, Luiz Capitulino wrote:
> > On Fri, 17 Aug 2012 10:11:29 -0700 (PDT)
> > desi babu <vdesibabu@yahoo.com> wrote:
> > 
> > > Guest-Agent : Windows 2008 Error : Relase 1.1.90
> > > 
> > > error : internal error unable to execute QEMU command 'guest-fsfreeze-freeze': this feature or command is not currently supported.
> > 
> > That's correct, fsfreze is not supported on Windows.
> > 
> > > Guest-info shows the command is available.  Is there any information available on the list of commands supported inside Windows ? Appreciate if you have any pointers.
> > 
> > That's a qemu-ga bug. CC'ing Michael to check if he has a fix in mind for this.
> > 
> 
> I've been thinking about this one for a while. It's considered expected
> behavior, but I realize it sucks for discoverability. I doubt we want to
> do platform-specific QAPI schema definitions, so the only option I can
> think of is some kind of [de-]registration mechanism where we can mark
> commands as being not available for a particular build/platform in the
> cases where we stub out command implementations.

Yes, I guess the first idea I had is similar. I thought about adding
PlatformOps and let win32 and posix register the commands they
implement. Then, qmp_guest_info() could check if the in-use PlatformOps
supports the command before adding it to the supported list.

> I think we can expose this to existing clients by no longer listing commands
> marked as unsupported in the list provided by the guest-info command. It
> should "just work". Can probably do it for 1.3. For now, clients will
> have to catch it in the error-handling path.

Agreed it's 1.3 material.