Index: sys/amd64/amd64/machdep.c
===================================================================
--- sys/amd64/amd64/machdep.c
+++ sys/amd64/amd64/machdep.c
@@ -1169,10 +1169,6 @@
 	}
 }
 
-static char bootmethod[16] = "";
-SYSCTL_STRING(_machdep, OID_AUTO, bootmethod, CTLFLAG_RD, bootmethod, 0,
-    "System firmware boot method");
-
 static void
 native_parse_memmap(caddr_t kmdp, vm_paddr_t *physmap, int *physmap_idx)
 {
Index: sys/amd64/include/md_var.h
===================================================================
--- sys/amd64/include/md_var.h
+++ sys/amd64/include/md_var.h
@@ -55,6 +55,8 @@
  */
 extern char kernphys[];
 
+extern	char bootmethod[16];
+
 struct	savefpu;
 struct	sysentvec;
 
Index: sys/i386/i386/machdep.c
===================================================================
--- sys/i386/i386/machdep.c
+++ sys/i386/i386/machdep.c
@@ -1237,10 +1237,6 @@
 SYSCTL_ULONG(_machdep, OID_AUTO, guessed_bootdev,
 	CTLFLAG_RD, &bootdev, 0, "Maybe the Boot device (not in struct cdev *format)");
 
-static char bootmethod[16] = "BIOS";
-SYSCTL_STRING(_machdep, OID_AUTO, bootmethod, CTLFLAG_RD, bootmethod, 0,
-    "System firmware boot method");
-
 /*
  * Initialize 386 and configure to run kernel
  */
@@ -2348,6 +2344,9 @@
 	/* Init basic tunables, hz etc */
 	init_param1();
 
+	/* Set bootmethod to BIOS: it's the only supported on i386. */
+	strlcpy(bootmethod, "BIOS", sizeof(bootmethod));
+
 	/*
 	 * Make gdt memory segments.  All segments cover the full 4GB
 	 * of address space and permissions are enforced at page level.
Index: sys/i386/include/md_var.h
===================================================================
--- sys/i386/include/md_var.h
+++ sys/i386/include/md_var.h
@@ -49,6 +49,7 @@
 #endif
 extern  vm_offset_t proc0kstack;
 extern	uintptr_t setidt_disp;
+extern	char bootmethod[16];
 
 struct	segment_descriptor;
 union savefpu;
Index: sys/x86/x86/cpu_machdep.c
===================================================================
--- sys/x86/x86/cpu_machdep.c
+++ sys/x86/x86/cpu_machdep.c
@@ -111,6 +111,10 @@
 static volatile u_int	cpu_reset_proxy_active;
 #endif
 
+char bootmethod[16];
+SYSCTL_STRING(_machdep, OID_AUTO, bootmethod, CTLFLAG_RD, bootmethod, 0,
+    "System firmware boot method");
+
 struct msr_op_arg {
 	u_int msr;
 	int op;
Index: sys/x86/xen/pv.c
===================================================================
--- sys/x86/xen/pv.c
+++ sys/x86/xen/pv.c
@@ -48,6 +48,7 @@
 #include <sys/ctype.h>
 #include <sys/mutex.h>
 #include <sys/smp.h>
+#include <sys/efi.h>
 
 #include <vm/vm.h>
 #include <vm/vm_extern.h>
@@ -109,6 +110,8 @@
 extern char *dbg_stack;
 #endif
 
+extern char bootmethod[16];
+
 /*
  * Placed by the linker at the end of the bss section, which is the last
  * section loaded by Xen before loading the symtab and strtab.
@@ -630,6 +633,11 @@
 		if (envp != NULL)
 			envp += off;
 		xen_pvh_set_env(envp, reject_option);
+
+		if (MD_FETCH(kmdp, MODINFOMD_EFI_MAP, void *) != NULL)
+		    strlcpy(bootmethod, "UEFI", sizeof(bootmethod));
+		else
+		    strlcpy(bootmethod, "BIOS", sizeof(bootmethod));
 	} else {
 		/* Parse the extra boot information given by Xen */
 		if (start_info->cmdline_paddr != 0)
@@ -637,6 +645,7 @@
 			    (char *)(start_info->cmdline_paddr + KERNBASE),
 			    ",");
 		kmdp = NULL;
+		strlcpy(bootmethod, "XEN", sizeof(bootmethod));
 	}
 
 	boothowto |= boot_env_to_howto();