diff -r 7c5c3aa858cc xen/arch/x86/acpi/boot.c
--- a/xen/arch/x86/acpi/boot.c	Tue Jul 31 15:09:45 2007 +0100
+++ b/xen/arch/x86/acpi/boot.c	Thu Aug 09 09:08:52 2007 -0400
@@ -473,6 +476,12 @@ static int __init acpi_parse_fadt(unsign
 		return 0;
 	}
 
+	if (strncmp(fadt->signature, "FADT", 4)) {
+		printk(KERN_ERR PREFIX "Invalid FADT signature %.4s\n",
+			fadt->signature);
+		return 0;
+	}
+
 #ifdef	CONFIG_ACPI_INTERPRETER
 	/* initialize sci_int early for INT_SRC_OVR MADT parsing */
 	acpi_fadt.sci_int = fadt->sci_int;