From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:55388) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Z2GBN-0002Rd-PH for qemu-devel@nongnu.org; Tue, 09 Jun 2015 05:50:59 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Z2GBJ-00058X-Ex for qemu-devel@nongnu.org; Tue, 09 Jun 2015 05:50:57 -0400 Received: from mx1.redhat.com ([209.132.183.28]:40972) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Z2GBI-00057R-KO for qemu-devel@nongnu.org; Tue, 09 Jun 2015 05:50:52 -0400 Date: Tue, 9 Jun 2015 10:50:48 +0100 From: "Daniel P. Berrange" Message-ID: <20150609095047.GE2089@redhat.com> References: <1433839784-5634-1-git-send-email-fziglio@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <1433839784-5634-1-git-send-email-fziglio@redhat.com> Subject: Re: [Qemu-devel] [Spice-devel] [PATCH] RFC: qxl: allow to specify head limit to qxl driver Reply-To: "Daniel P. Berrange" List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Frediano Ziglio Cc: spice-devel@lists.freedesktop.org, Gerd Hoffmann , qemu-devel@nongnu.org On Tue, Jun 09, 2015 at 09:49:44AM +0100, Frediano Ziglio wrote: > This patch allow to limit number of heads using qxl driver. By default > qxl driver is not limited on any kind on head use so can decide to use > as much heads. > > 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). > > This patch rely on some change in spice-protocol which are not still > accepted. See > http://lists.freedesktop.org/archives/spice-devel/2015-June/020160.html. > > Main question and stop over are parameter name. Consider that this > parameter is actually more a hint to drivers. I'm looking anyway to > a way to enforce this in spice-server. What is the actual benefit of being able to limit the number of heads in QXL / SPICE ? I know libvirt has the 'heads' attribute for specifying the number of video outputs. This is used in hypervisors which only support a fixed number of outputs and need up-front configuration. Since QXL/SPICE can dynamically enable/disable heads, there is no need to support this libvirt configuration attribute - it is better from a usability POV to have the head count totally dynamic, than to add a fixed limit. IOW, unless there's some need to use this limit in order to go above the 16 head maximum the code currently has, I think adding this manual limit to QXL/SPICE is a step backwards really. It feels like a feature in search of a purpose IMHO. Regards, Daniel -- |: http://berrange.com -o- http://www.flickr.com/photos/dberrange/ :| |: http://libvirt.org -o- http://virt-manager.org :| |: http://autobuild.org -o- http://search.cpan.org/~danberr/ :| |: http://entangle-photo.org -o- http://live.gnome.org/gtk-vnc :|