Re: [libvirt] [RFC] default video device type

On Mon, Oct 07, 2019 at 02:56:11PM +0200, Pavel Mores wrote: > > Hi, > > I'm looking into fixing > > https://bugzilla.redhat.com/show_bug.cgi?id=1668141 > > (as a short summary, if a graphics device is added to XML that has no > video > device, libvirt automatically adds a video device which is always of type > 'cirrus' - even if the underlying qemu doesn't support cirrus). > > I'm able to affect the behaviour in question by using qemu > capabilities in > qemuDomainDeviceVideoDefPostParse(), see proof-of-concept change in > [1].  I > have a couple of questions though: > > 1) is this a proper place and approach to fix the bug? I don't think so because the guest ABI could change.  Imagine there is an application that just starts a simple VM (with graphics with no model) and out of nowhere (after a long time) they upgrade libvirt and qemu and the VM will look differently. > 2) what would be the full specification of expected behaviour?  The > bug report >   only states that the video type shouldn't be cirrus but doesn't say > what it >   should be. [2] gives some information about the order of preference > of video >   device types but I was wondering if there are any opinions about > this on this >   list? > Reading the BZ it looks to me like virt-manager should allow choosing cirrus and the different default could be chosen in virt-manager.  The BZ is not well described, to be honest.