If I don't have app-emulation/xen emerging libvirt with USE="xen", I get the following. checking for xen/xen.h... no configure: error: Cannot find standard Xen headers. Is xen-devel installed? Installing app-emulation/xen first fixes this problem, since it provides xen/xen.h. Reproducible: Always
emerge -pv libvirt output, please.
Calculating dependencies... done! [ebuild R ] app-emulation/libvirt-0.3.3 USE="xen -qemu" 0 kB
Created attachment 145089 [details, diff] libvirt-0.3.3-xen.patch This should patch the ebuild just fine.
This will be fixed in 0.4.2, which I'm about to add.