Please add the patches: commit 038bac2b02989acf1fc938cedcb7944c02672b9f upstream commit dfc9327ab7c99bc13e12106448615efba833886b upstream commit b17d9d1df3c33a4f1d2bf397e2257aecf9dc56d4 upstream to the 4.15 and 4.16 stable kernels. Those patches are needed to boot Linux as PVH guest on recent Xen. In PVH mode there is no guarantee the kernel can find the RSDP table at the legacy location in low memory, which is a requirement for the kernel to boot successful without those patches. For kernel 4.14 I'll send a slightly modified version of the patches soon. Juergen