From mboxrd@z Thu Jan 1 00:00:00 1970 From: Matt Fleming Subject: [PATCH 3/5] x86/efi: Disable runtime services on kexec kernel if booted with efi=old_map Date: Fri, 26 May 2017 12:36:49 +0100 Message-ID: <20170526113652.21339-4-matt@codeblueprint.co.uk> References: <20170526113652.21339-1-matt@codeblueprint.co.uk> Return-path: In-Reply-To: <20170526113652.21339-1-matt-mF/unelCI9GS6iBeEJttW/XRex20P6io@public.gmane.org> Sender: linux-efi-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Ingo Molnar , Thomas Gleixner , "H . Peter Anvin" Cc: Sai Praneeth , Ard Biesheuvel , linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-efi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Matt Fleming , Borislav Petkov , Dave Young , Lee Chun-Yi , Ravi Shankar , Ricardo Neri List-Id: linux-efi@vger.kernel.org From: Sai Praneeth 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+0x5d/0x70 efi_delete_dummy_variable+0x7a/0x80 efi_enter_virtual_mode+0x3f6/0x4a7 start_kernel+0x375/0x400 x86_64_start_reservations+0x2a/0x2c x86_64_start_kernel+0x168/0x176 start_cpu+0x14/0x14 [ 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. Signed-off-by: Sai Praneeth Prakhya Cc: Borislav Petkov Cc: Ricardo Neri Cc: Ard Biesheuvel Cc: Ravi Shankar Tested-by: Lee Chun-Yi Acked-by: Dave Young Signed-off-by: Matt Fleming --- arch/x86/platform/efi/efi.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/arch/x86/platform/efi/efi.c b/arch/x86/platform/efi/efi.c index 7e76a4d8304b..43b96f5f78ba 100644 --- a/arch/x86/platform/efi/efi.c +++ b/arch/x86/platform/efi/efi.c @@ -828,9 +828,11 @@ static void __init kexec_enter_virtual_mode(void) /* * 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; -- 2.12.2