Hi, these two patches extend the features libvirt reports in the capabilities XML; in particular, features are now reported for the QEMU driver, and features for both Xen and QEMU include information on ACPI/APIC support. Tools that rely on feature reporting, in general, need to know whether a certain feature is on or off by default, and whether that can be toggled, because users will be asking for one of three things for their VM: * Feature X (e.g., ACPI) must be on/present in the VM * Feature X must not be on/present in the VM * It doesn't matter whether feature X is there or not For example, in QEMU, ACPI is on by default, but can be turned off. The APIC on the other hand, is always there and can't be turned off. That is now reported as <features> <acpi default="on" toggle="yes"/> <apic default="on" toggle="no"/> </features> It's unfortunate that the format for PAE (<pae/> vs. <nonpae/>) reporting doesn't fit into this scheme. I didn't want to start with having tags <X/> and <nonX/> for each feature; that means that parsers need to special case PAE. It's probably too late, but it would be nice if PAE was reported in a similar format, with <pae> correponding to <pae default="on" toggle="no"/>, <nonpae/> corresponding to <pae default="yes" toggle="no"/>, and having both together corresponding to <pae default="yes" toggle="yes"/>, but that's a separate discussion from these patches. David