On Wed, Jun 09, 2021 at 01:49:21PM +0200, Gerd Hoffmann wrote: > On Wed, Jun 09, 2021 at 12:29:58PM +0100, Daniel P. Berrangé wrote: > > On Wed, Jun 09, 2021 at 01:24:05PM +0200, Gerd Hoffmann wrote: > > > On Wed, Jun 09, 2021 at 12:02:40PM +0200, Thomas Huth wrote: > > > > Libvirt's "domcapabilities" command has a way to state whether > > > > certain graphic frontends are available in QEMU or not. Originally, > > > > libvirt looked at the "--help" output of the QEMU binary to determine > > > > whether SDL was available or not (by looking for the "-sdl" parameter > > > > in the help text), but since libvirt stopped doing this analysis of > > > > the help text, the detection of SDL is currently broken, see: > > > > > > > > https://bugzilla.redhat.com/show_bug.cgi?id=1790902 > > > > > > > > QEMU should provide a way via the QMP interface instead. The simplest > > > > way, without introducing additional commands, is to make the DisplayType > > > > enum entries conditional, so that the enum only contains the entries if > > > > the corresponding CONFIG_xxx switches have been set. > > > > > > Hmm, that'll break for the "dnf remove qemu-ui-sdl" case ... > > > > Note tht libvirt invalidates its cache of QEMU capabilities when it > > sees the /usr/lib64/qemu directory timestamp change. So it ought to > > pick up changes caused by installing/removing QEMU modules, and apply > > this to future queries for domcapabilities, or when starting future > > QEMU guests. > > That'll work fine for modules implementing qom objects / devices, > because the list of available objects changes accordingly and libvirt > can see that. > > The #if CONFIG_SDL approach will not work because qemu will continue to > report sdl as supported even when the sdl module is not installed any > more. Ah see what you mean now. So libvirt can't merely query members of the DisplayType enum. We need an actual 'query-display-types' command that returns an array of DisplayType values corresponding to what is actually built-in or available as a module at that instant. Regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|
