linux/drivers/firmware/efi
Ard Biesheuvel 7cc8cbcf82 efi/arm64: Don't apply MEMBLOCK_NOMAP to UEFI memory map mapping
Commit 4dffbfc48d ("arm64/efi: mark UEFI reserved regions as
MEMBLOCK_NOMAP") updated the mapping logic of both the RuntimeServices
regions as well as the kernel's copy of the UEFI memory map to set the
MEMBLOCK_NOMAP flag, which causes these regions to be omitted from the
kernel direct mapping, and from being covered by a struct page.
For the RuntimeServices regions, this is an obvious win, since the contents
of these regions have significance to the firmware executable code itself,
and are mapped in the EFI page tables using attributes that are described in
the UEFI memory map, and which may differ from the attributes we use for
mapping system RAM. It also prevents the contents from being modified
inadvertently, since the EFI page tables are only live during runtime
service invocations.

None of these concerns apply to the allocation that covers the UEFI memory
map, since it is entirely owned by the kernel. Setting the MEMBLOCK_NOMAP on
the region did allow us to use ioremap_cache() to map it both on arm64 and
on ARM, since the latter does not allow ioremap_cache() to be used on
regions that are covered by a struct page.

The ioremap_cache() on ARM restriction will be lifted in the v4.7 timeframe,
but in the mean time, it has been reported that commit 4dffbfc48d causes
a regression on 64k granule kernels. This is due to the fact that, given
the 64 KB page size, the region that we end up removing from the kernel
direct mapping is rounded up to 64 KB, and this 64 KB page frame may be
shared with the initrd when booting via GRUB (which does not align its
EFI_LOADER_DATA allocations to 64 KB like the stub does). This will crash
the kernel as soon as it tries to access the initrd.

Since the issue is specific to arm64, revert back to memblock_reserve()'ing
the UEFI memory map when running on arm64. This is a temporary fix for v4.5
and v4.6, and will be superseded in the v4.7 timeframe when we will be able
to move back to memblock_reserve() unconditionally.

Fixes: 4dffbfc48d ("arm64/efi: mark UEFI reserved regions as MEMBLOCK_NOMAP")
Reported-by: Mark Salter <msalter@redhat.com>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Acked-by: Will Deacon <will.deacon@arm.com>
Cc: Leif Lindholm <leif.lindholm@linaro.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Jeremy Linton <jeremy.linton@arm.com>
Cc: Mark Langsdorf <mlangsdo@redhat.com>
Cc: <stable@vger.kernel.org> # v4.5
Signed-off-by: Matt Fleming <matt@codeblueprint.co.uk>
2016-03-31 21:33:50 +01:00
..
libstub kernel: add kcov code coverage 2016-03-22 15:36:02 -07:00
arm-init.c efi/arm64: Don't apply MEMBLOCK_NOMAP to UEFI memory map mapping 2016-03-31 21:33:50 +01:00
arm-runtime.c arm64/efi: refactor EFI init and runtime code for reuse by 32-bit ARM 2015-12-09 16:57:23 +00:00
cper.c efi: Handle memory error structures produced based on old versions of standard 2015-07-15 13:30:38 +01:00
efi-pstore.c Half dozen small cleanups plus change to allow pstore 2015-11-05 11:51:18 -08:00
efi.c efi: Add Persistent Memory type name 2016-02-03 11:41:20 +01:00
efivars.c drivers/firmware/efi/efivars.c: use in_compat_syscall() to check for compat callers 2016-03-22 15:36:02 -07:00
esrt.c efi/esrt: Don't preformat name 2015-12-14 15:24:03 +00:00
fake_mem.c efi: Fix warning of int-to-pointer-cast on x86 32-bit builds 2015-10-28 12:28:06 +01:00
Kconfig * Make the EFI System Resource Table (ESRT) driver explicitly 2015-10-14 16:51:34 +02:00
Makefile ARM: wire up UEFI init and runtime support 2015-12-13 19:18:30 +01:00
reboot.c x86/reboot: Add EFI reboot quirk for ACPI Hardware Reduced flag 2014-07-18 21:23:52 +01:00
runtime-map.c efi: Fix error handling in add_sysfs_runtime_map_entry() 2015-05-05 16:20:13 +01:00
runtime-wrappers.c efi/runtime-wrappers: Run UEFI Runtime Services with interrupts enabled 2016-02-22 08:26:25 +01:00
vars.c Linux 4.5-rc5 2016-02-22 08:26:05 +01:00