diff -ru old/xen-tools-4.2.1-r2.ebuild new/xen-tools-4.2.1-r2.ebuild
--- old/xen-tools-4.2.1-r2.ebuild	2013-02-18 14:16:47.000000000 +0100
+++ new/xen-tools-4.2.1-r2.ebuild	2013-02-18 14:09:55.000000000 +0100
@@ -102,7 +102,7 @@
 		eerror "HVM (VT-x and AMD-v) cannot be built on this system. An x86 or"
 		eerror "an amd64 multilib profile is required. Remove the hvm use flag"
 		eerror "to build xen-tools on your current profile."
-		die "USE=hvm is unsupported on this system."
+		#die "USE=hvm is unsupported on this system."
 	fi
 
 	if [[ -z ${XEN_TARGET_ARCH} ]] ; then
@@ -196,7 +196,9 @@
 	epatch "${FILESDIR}"/xen-4-CVE-2012-6075-XSA-41.patch
 
 	if use hvm; then
-		cp -r "${FILESDIR}"/stubs-32.h xen/tools/include || die "copy of header file failed"
+		mkdir -p "${WORKDIR}"/extra-headers/gnu || die "mkdir failed"
+		cp "${FILESDIR}"/stubs-32.h "${WORKDIR}"/extra-headers/gnu || die "copy of header file failed"
+		export CPATH="${WORKDIR}"/extra-headers
 		einfo "stubs-32.h added"
 	fi
 }