Index: xen-4.17.2-testing/tools/pygrub/src/pygrub
===================================================================
--- xen-4.17.2-testing.orig/tools/pygrub/src/pygrub
+++ xen-4.17.2-testing/tools/pygrub/src/pygrub
@@ -579,7 +579,7 @@ class Grub:
                 self.cf.filename = f
                 break
         if self.__dict__.get('cf', None) is None:
-            raise RuntimeError("couldn't find bootloader config file in the image provided.")
+            return
         f = fs.open_file(self.cf.filename)
         # limit read size to avoid pathological cases
         buf = f.read(FS_READ_MAX)
@@ -754,6 +754,20 @@ def run_grub(file, entry, fs, cfg_args):
 
     g = Grub(file, fs)
 
+    # If missing config or grub has no menu entries to select, look for
+    # vmlinuz-xen and initrd-xen in /boot
+    if g.__dict__.get('cf', None) is None or len(g.cf.images) == 0 or re.search(r"xen(-pae)?\.gz",g.cf.images[0].kernel[1]):
+        if not list_entries:
+            chosencfg = { "kernel": None, "ramdisk": None, "args": "" }
+            chosencfg = sniff_xen_kernel(fs, incfg)
+            if chosencfg["kernel"] and chosencfg["ramdisk"]:
+                chosencfg["args"] = cfg_args
+                return chosencfg
+        if g.__dict__.get('cf', None) is None:
+            raise RuntimeError("couldn't find bootloader config file in the image provided.")
+        else:
+            return
+
     if list_entries:
         for i in range(len(g.cf.images)):
             img = g.cf.images[i]
@@ -840,6 +854,19 @@ def sniff_netware(fs, cfg):
 
     return cfg
 
+def sniff_xen_kernel(fs, cfg):
+    if not cfg["kernel"]:
+        if fs.file_exists('/boot/vmlinuz-xen'):
+            cfg["kernel"] = '/boot/vmlinuz-xen'
+        elif fs.file_exists('/boot/vmlinuz-xenpae'):
+            cfg["kernel"] = '/boot/vmlinuz-xenpae'
+    if cfg["kernel"] and not cfg["ramdisk"]:
+        if fs.file_exists('/boot/initrd-xen'):
+            cfg["ramdisk"] = '/boot/initrd-xen'
+        elif fs.file_exists('/boot/initrd-xenpae'):
+            cfg["ramdisk"] = '/boot/initrd-xenpae'
+    return cfg
+
 def format_sxp(kernel, ramdisk, args):
     s = "linux (kernel %s)" % repr(kernel)
     if ramdisk:
@@ -918,7 +945,7 @@ if __name__ == "__main__":
     debug = False
     not_really = False
     output_format = "sxp"
-    output_directory = "/var/run/xen/pygrub/"
+    output_directory = "/var/run/xen"
     uid = None
 
     # what was passed in