[PATCH AUTOSEL 4.9 14/15] efi/arm: Revert deferred unmap of early memmap mapping

[Sasha Levin <sashal@kernel.org>]

From: Ard Biesheuvel <ard.biesheuvel@linaro.org>

[ Upstream commit 33412b8673135b18ea42beb7f5117ed0091798b6 ]

Commit:

  3ea86495aef2 ("efi/arm: preserve early mapping of UEFI memory map longer for BGRT")

deferred the unmap of the early mapping of the UEFI memory map to
accommodate the ACPI BGRT code, which looks up the memory type that
backs the BGRT table to validate it against the requirements of the UEFI spec.

Unfortunately, this causes problems on ARM, which does not permit
early mappings to persist after paging_init() is called, resulting
in a WARN() splat. Since we don't support the BGRT table on ARM anway,
let's revert ARM to the old behaviour, which is to take down the
early mapping at the end of efi_init().

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-efi@vger.kernel.org
Fixes: 3ea86495aef2 ("efi/arm: preserve early mapping of UEFI memory ...")
Link: http://lkml.kernel.org/r/20181114175544.12860-3-ard.biesheuvel@linaro.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/firmware/efi/arm-init.c    | 4 ++++
 drivers/firmware/efi/arm-runtime.c | 2 +-
 drivers/firmware/efi/memmap.c      | 3 +++
 3 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/firmware/efi/arm-init.c b/drivers/firmware/efi/arm-init.c
index 1d1c9693ebfb..8ee91777abce 100644
--- a/drivers/firmware/efi/arm-init.c
+++ b/drivers/firmware/efi/arm-init.c
@@ -256,6 +256,10 @@ void __init efi_init(void)
 				    (params.mmap & ~PAGE_MASK)));
 
 	init_screen_info();
+
+	/* ARM does not permit early mappings to persist across paging_init() */
+	if (IS_ENABLED(CONFIG_ARM))
+		efi_memmap_unmap();
 }
 
 static int __init register_gop_device(void)
diff --git a/drivers/firmware/efi/arm-runtime.c b/drivers/firmware/efi/arm-runtime.c
index 4d788e0debfe..069c5a4479e6 100644
--- a/drivers/firmware/efi/arm-runtime.c
+++ b/drivers/firmware/efi/arm-runtime.c
@@ -118,7 +118,7 @@ static int __init arm_enable_runtime_services(void)
 {
 	u64 mapsize;
 
-	if (!efi_enabled(EFI_BOOT) || !efi_enabled(EFI_MEMMAP)) {
+	if (!efi_enabled(EFI_BOOT)) {
 		pr_info("EFI services will not be available.\n");
 		return 0;
 	}
diff --git a/drivers/firmware/efi/memmap.c b/drivers/firmware/efi/memmap.c
index 78686443cb37..3fd2b450c649 100644
--- a/drivers/firmware/efi/memmap.c
+++ b/drivers/firmware/efi/memmap.c
@@ -117,6 +117,9 @@ int __init efi_memmap_init_early(struct efi_memory_map_data *data)
 
 void __init efi_memmap_unmap(void)
 {
+	if (!efi_enabled(EFI_MEMMAP))
+		return;
+
 	if (!efi.memmap.late) {
 		unsigned long size;
 
-- 
2.17.1