[PATCH] arm64/efi: add missing call to early_ioremap_reset()

[Ard Biesheuvel]

The early ioremap support introduced by patch bf4b558eba92
("arm64: add early_ioremap support") failed to add a call to
early_ioremap_reset() at an appropriate time. Without this call,
invocations of early_ioremap etc. that are done too late will go
unnoticed and may cause corruption.

This is exactly what happened when the first user of this feature
was added in patch f84d02755f5a ("arm64: add EFI runtime services").
The early mapping of the EFI memory map is unmapped during an early
initcall, at which time the early ioremap support is long gone.

Fix by adding the missing call to early_ioremap_reset() to
setup_arch(), and move the offending early_memunmap() to right after
the point where the early mapping of the EFI memory map is last used.

Fixes: f84d02755f5a ("arm64: add EFI runtime services")
Cc: <stable at vger.kernel.org>
Signed-off-by: Leif Lindholm <leif.lindholm at linaro.org>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel at linaro.org>
---

After discussing off-list between Mark Salter, Leif and myself, this is the
bare minimum to fix the early ioremap issue in kernels up to 3.19, combined
into a single patch. Considering that the early_ioremap support was added in
3.15 (eol), but not used until EFI runtime services support was added in 3.16,
there is no reason to split this up. Also, we have work underway to drastically
change the way runtime services etc are mapped during early boot [which we hope
will make it into 3.20] so it makes sense to do the bare minimum here and handle
any fallout in terms of style etc later.

 arch/arm64/kernel/efi.c   | 2 +-
 arch/arm64/kernel/setup.c | 1 +
 2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/kernel/efi.c b/arch/arm64/kernel/efi.c
index 6fac253bc783..2bb4347d0edf 100644
--- a/arch/arm64/kernel/efi.c
+++ b/arch/arm64/kernel/efi.c
@@ -326,6 +326,7 @@ void __init efi_idmap_init(void)
 
 	/* boot time idmap_pg_dir is incomplete, so fill in missing parts */
 	efi_setup_idmap();
+	early_memunmap(memmap.map, memmap.map_end - memmap.map);
 }
 
 static int __init remap_region(efi_memory_desc_t *md, void **new)
@@ -380,7 +381,6 @@ static int __init arm64_enter_virtual_mode(void)
 	}
 
 	mapsize = memmap.map_end - memmap.map;
-	early_memunmap(memmap.map, mapsize);
 
 	if (efi_runtime_disabled()) {
 		pr_info("EFI runtime services will be disabled.\n");
diff --git a/arch/arm64/kernel/setup.c b/arch/arm64/kernel/setup.c
index b80991166754..20fe2932ad0c 100644
--- a/arch/arm64/kernel/setup.c
+++ b/arch/arm64/kernel/setup.c
@@ -402,6 +402,7 @@ void __init setup_arch(char **cmdline_p)
 	request_standard_resources();
 
 	efi_idmap_init();
+	early_ioremap_reset();
 
 	unflatten_device_tree();
 
-- 
1.8.3.2