x86: efi: Turn off efi_enabled after setup on mixed fw/kernel

When 32-bit EFI is used with 64-bit kernel (or vice versa), turn off
efi_enabled once setup is done. Beyond setup, it is normally used to
determine if runtime services are available and we will have none.

This will resolve issues stemming from efivars modprobe panicking on a
32/64-bit setup, as well as some reboot issues on similar setups.

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=45991

Reported-by: Marko Kohtala <marko.kohtala@gmail.com>
Reported-by: Maxim Kammerer <mk@dee.su>
Signed-off-by: Olof Johansson <olof@lixom.net>
Acked-by: Maarten Lankhorst <maarten.lankhorst@canonical.com>
Cc: stable@kernel.org # 3.4 - 3.6
Cc: Matthew Garrett <mjg@redhat.com>
Signed-off-by: Matt Fleming <matt.fleming@intel.com>

1 files changed, 12 insertions, 0 deletions

diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index a2bb18e02839..6fd7752cee96 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -1035,6 +1035,18 @@ void __init setup_arch(char **cmdline_p)
         arch_init_ideal_nops();
 
         register_refined_jiffies(CLOCK_TICK_RATE);
+
+#ifdef CONFIG_EFI
+        /* Once setup is done above, disable efi_enabled on mismatched
+         * firmware/kernel archtectures since there is no support for
+         * runtime services.
+         */
+        if (efi_enabled && IS_ENABLED(CONFIG_X86_64) != efi_64bit) {
+                pr_info("efi: Setup done, disabling due to 32/64-bit mismatch\n");
+                efi_unmap_memmap();
+                efi_enabled = 0;
+        }
+#endif
 }
 
 #ifdef CONFIG_X86_32