Re: [Qemu-devel] [PATCH v2] RFC: qxl: allow to specify head limit to qxl driver

[Frediano Ziglio <fziglio@redhat.com>]

> 
> On Do, 2015-06-11 at 10:38 +0100, Frediano Ziglio wrote:
> > libvirt has this as a video card parameter (actually set to 1 but not
> > used). This parameter will allow to limit setting a use can do (which
> > could be confusing).
> 
> Hmm.  So heads is '1' by default but ignored today.  When this starts to
> be actually applied that will break existing multihead setups I suspect.
> 

Yes, unfortunately libvirt always set the default to 1 even if not used by driver.
However the Qemu default (with no parameter) is still unlimited so it's a libvirt issue more then Qemu.

> > This patch rely on some change in spice-protocol which are not still
> > accepted. See
> > http://lists.freedesktop.org/archives/spice-devel/2015-June/020221.html.
> 
> Spice-server changes, right?
> Needs #ifdefs so qemu continues to build with old spice-server versions.
> The spice-server changes need to be upstream first.
> 

Yes, I'll do.

> Also: when we pass on the limit to spice-server anyway spice-server can
> take care to apply the limit both ways and not call the
> ->client_monitors_config() callback with more than $limit monitors.  Has
> the advantage to reduce the test matrix:  Limit either works or doesn't.
> There will be no spice-server/qemu version combination where the limit
> is applied one way only.
> 
>   Gerd
> 

Is always Qemu that decide to apply the limitation, default (even for spice-server) is still unlimited. As Qemu compiled with option on won't run with older version there will never this problem. However I would agree that the patch for Qemu keeping all limits on one place would be smaller.

Frediano