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This reverts commit 5ac846e42e5b7e0475f6aa9cc1e0b0c8dac84d44. After further discussions with Alon Levy, I learned the following: The use of '-vga qxl' vs. '-device qxl-vga' is completely orthogonal to whether ram_size can be exposed. Downstream distros are interested in backporting support for multi-head qxl, but this can be done in one of two ways: 1. Support one head per PCI device. If you do this, then it makes sense to have full control over the PCI address of each device. For full control, you need '-device qxl-vga' instead of '-vga qxl'. 2. Support multiple heads through a single PCI device. If you do this, then you need to allocate more RAM to that PCI device (enough ram to cover the multiple screens). Here, the device is hard-coded to 0:0:2.0, both in qemu and libvirt code. Apparently, backporting ram_size changes to allow multiple heads in a single device is much easier than backporting multiple device support. Furthermore, the presence or absence of qxl-vga.surfaces is no different than the presence or absence of qxl-vga.ram_size; both properties can be applied regardless of whether you have one PCI device (-vga qxl) or multiple (-device qxl-vga), so this property is NOT a good witness of whether '-device qxl-vga' support has been backported. Downstream RHEL will NOT be using this patch; and worse, leaving this patch in risks doing the wrong thing if compiling upstream libvirt on RHEL, so the best course of action is to revert it. That means that libvirt will go back to only using '-device qxl-vga' for qemu >= 1.2, but this is just fine because we know of no distros that plan on backporting multiple PCI address support to any older version of qemu. Meanwhile, downstream can still use ram_size to pack multiple heads through a single PCI device.
LibVirt : simple API for virtualization
Libvirt is a C toolkit to interact with the virtualization capabilities
of recent versions of Linux (and other OSes). It is free software
available under the GNU Lesser General Public License. Virtualization of
the Linux Operating System means the ability to run multiple instances of
Operating Systems concurrently on a single hardware system where the basic
resources are driven by a Linux instance. The library aim at providing
long term stable C API initially for the Xen paravirtualization but
should be able to integrate other virtualization mechanisms if needed.
Daniel Veillard <veillard@redhat.com>