References: bsc#1180047
Xen PV doesn't support uefi or BIOS booting

Index: virt-manager-3.2.0/virtManager/details/details.py
===================================================================
--- virt-manager-3.2.0.orig/virtManager/details/details.py
+++ virt-manager-3.2.0/virtManager/details/details.py
@@ -696,7 +696,7 @@ class vmmDetails(vmmGObjectUI):
             not self.is_customize_dialog)
         show_firmware = ((self.conn.is_qemu() or
                           self.conn.is_test() or
-                          self.conn.is_xen()) and
+                          (self.conn.is_xen() and not self.vm.is_xenpv())) and
                          domcaps.arch_can_uefi())
         uiutil.set_grid_row_visible(
             self.widget("overview-firmware-title"), show_firmware)