4.9-stable review patch.  If anyone has any objections, please let me know.


From: Sai Praneeth <sai.praneeth.prak...@intel.com>

[ Upstream commit 4e52797d2efefac3271abdc54439a3435abd77b9 ]

Booting kexec kernel with "efi=old_map" in kernel command line hits
kernel panic as shown below.

 BUG: unable to handle kernel paging request at ffff88007fe78070
 IP: virt_efi_set_variable.part.7+0x63/0x1b0
 PGD 7ea28067
 PUD 7ea2b067
 PMD 7ea2d067
 PTE 0
 Call Trace:

[ efi=old_map was never intended to work with kexec. The problem with
  using efi=old_map is that the virtual addresses are assigned from the
  memory region used by other kernel mappings; vmalloc() space.
  Potentially there could be collisions when booting kexec if something
  else is mapped at the virtual address we allocated for runtime service
  regions in the initial boot - Matt Fleming ]

Since kexec was never intended to work with efi=old_map, disable
runtime services in kexec if booted with efi=old_map, so that we don't

Tested-by: Lee Chun-Yi <j...@suse.com>
Signed-off-by: Sai Praneeth Prakhya <sai.praneeth.prak...@intel.com>
Signed-off-by: Matt Fleming <m...@codeblueprint.co.uk>
Acked-by: Dave Young <dyo...@redhat.com>
Cc: Ard Biesheuvel <ard.biesheu...@linaro.org>
Cc: Borislav Petkov <b...@alien8.de>
Cc: Linus Torvalds <torva...@linux-foundation.org>
Cc: Peter Zijlstra <pet...@infradead.org>
Cc: Ravi Shankar <ravi.v.shan...@intel.com>
Cc: Ricardo Neri <ricardo.n...@intel.com>
Cc: Thomas Gleixner <t...@linutronix.de>
Cc: linux-...@vger.kernel.org
Link: http://lkml.kernel.org/r/20170526113652.21339-4-m...@codeblueprint.co.uk
Signed-off-by: Ingo Molnar <mi...@kernel.org>
Signed-off-by: Sasha Levin <alexander.le...@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
 arch/x86/platform/efi/efi.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

--- a/arch/x86/platform/efi/efi.c
+++ b/arch/x86/platform/efi/efi.c
@@ -832,9 +832,11 @@ static void __init kexec_enter_virtual_m
         * We don't do virtual mode, since we don't do runtime services, on
-        * non-native EFI
+        * non-native EFI. With efi=old_map, we don't do runtime services in
+        * kexec kernel because in the initial boot something else might
+        * have been mapped at these virtual addresses.
-       if (!efi_is_native()) {
+       if (!efi_is_native() || efi_enabled(EFI_OLD_MEMMAP)) {
                clear_bit(EFI_RUNTIME_SERVICES, &efi.flags);

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