Re: [libvirt] [PATCH v4 3/3] hw/vfio/display: add ramfb support

> Well, it's simliar to qxl vs. qxl-vga. It's not qxl,vga={on,off} and > libvirt has no problems to deal with that ... > > Another more technical reason is (again) hotplug. ramfb needs an fw_cfg > entry for configuration, and fw_cfg entries can't be hotplugged. So > hotplugging vfio-pci with ramfb=on isn't going to fly. So we need a > separate device with hotplug turned off. Well if that's not supposed to work ever, libvirt's hotplug code could format the following FWIW: "-device vfio-pci [opts],ramfb=off" As such, new device wouldn't be that of an issue for libvirt if vfio-pci and vfio-pci-ramfb are back to back compatible with all the device options that are available for vfio-pci (I mean in terms of using an mdev). Because in that case, what libvirt could do is to look whether we're supposed to turn on the display, if so, then we need support for this in capabilities to query and then we could prefer this new device over the "legacy" vfio-pci one. However, if we expect a case where QEMU would succeed to start with an mdev mapped to this new ramfb device but not with vfio-pci, then that's an issue.

But I'm still curious about the ramfb=off possibility I asked above for hotplug nonetheless.