Re: [PATCH 3/7] multiboot2: Add support for the load type header tag

["Vladimir 'phcoder' Serbinenko" <phcoder@xxxxxxxxx>]

Not a full review. Just one blocking problem

     }
+  case MULTIBOOT_LOAD_TYPE_PE:
+      grub_fatal ("Unsupported load type: %u\n", mld.load_type);
+  default:
+    /* should be impossible */
+    grub_fatal ("Unknown load type: %u\n", mld.load_type);

Don't use grub_fatal for this. grub_fatal is only when continue to execute grub is unwise. Here you just have an unsupported file. This is definitely a GRUB_ERR_BAD_OS