x86: EFI runtime service support: document for EFI runtime services

This patch adds document for EFI x86_64 runtime services support.
Signed-off-by: NChandramouli Narayanan <mouli@linux.intel.com>
Signed-off-by: NHuang Ying <ying.huang@intel.com>
Cc: Andi Kleen <ak@suse.de>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>

Documentation/x86_64/boot-options.txt

@@ -110,7 +110,7 @@ Idle loop
 
 Rebooting
 
-   reboot=b[ios] | t[riple] | k[bd] | a[cpi] [, [w]arm | [c]old]
+   reboot=b[ios] | t[riple] | k[bd] | a[cpi] | e[fi] [, [w]arm | [c]old]
    bios	  Use the CPU reboot vector for warm reset
    warm   Don't set the cold reboot flag
    cold   Set the cold reboot flag
@@ -119,6 +119,9 @@ Rebooting
    acpi   Use the ACPI RESET_REG in the FADT. If ACPI is not configured or the
           ACPI reset does not work, the reboot path attempts the reset using
           the keyboard controller.
+   efi    Use efi reset_system runtime service. If EFI is not configured or the
+          EFI reset does not work, the reboot path attempts the reset using
+          the keyboard controller.
 
    Using warm reset will be much faster especially on big memory
    systems because the BIOS will not go through the memory check.
@@ -303,4 +306,8 @@ Debugging
 		newfallback: use new unwinder but fall back to old if it gets
 			stuck (default)
 
+EFI
+
+  noefi		Disable EFI support
+
 Miscellaneous

Documentation/x86_64/uefi.txt

@@ -19,6 +19,10 @@ Mechanics:
 - Build the kernel with the following configuration.
 	CONFIG_FB_EFI=y
 	CONFIG_FRAMEBUFFER_CONSOLE=y
+  If EFI runtime services are expected, the following configuration should
+  be selected.
+	CONFIG_EFI=y
+	CONFIG_EFI_VARS=y or m		# optional
 - Create a VFAT partition on the disk
 - Copy the following to the VFAT partition:
 	elilo bootloader with x86_64 support, elilo configuration file,
@@ -27,3 +31,8 @@ Mechanics:
 	can be found in the elilo sourceforge project.
 - Boot to EFI shell and invoke elilo choosing the kernel image built
   in first step.
+- If some or all EFI runtime services don't work, you can try following
+  kernel command line parameters to turn off some or all EFI runtime
+  services.
+	noefi		turn off all EFI runtime services
+	reboot_type=k	turn off EFI reboot runtime service