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: virt_efi_set_variable() efi_delete_dummy_variable() efi_enter_virtual_mode() start_kernel() x86_64_start_reservations() x86_64_start_kernel() start_cpu() [ 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 panic. 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)) { efi_memmap_unmap(); clear_bit(EFI_RUNTIME_SERVICES, &efi.flags); return;
