[PATCH 5.10 073/103] arm64: mm: Fix ARCH_LOW_ADDRESS_LIMIT when !CONFIG_ZONE_DMA

Greg Kroah-Hartman
2021-01-15T12:38:45Z

From: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>

commit 095507dc1350b3a2b8b39fdc05edba0c10859eca upstream.

Systems configured with CONFIG_ZONE_DMA32, CONFIG_ZONE_NORMAL and
!CONFIG_ZONE_DMA will fail to properly setup ARCH_LOW_ADDRESS_LIMIT. The
limit will default to ~0ULL, effectively spanning the whole memory,
which is too high for a configuration that expects low memory to be
capped at 4GB.

Fix ARCH_LOW_ADDRESS_LIMIT by falling back to arm64_dma32_phys_limit
when arm64_dma_phys_limit isn't set. arm64_dma32_phys_limit will honour
CONFIG_ZONE_DMA32, or span the entire memory when not enabled.

Fixes: 1a8e1cef7603 ("arm64: use both ZONE_DMA and ZONE_DMA32")
Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
Link: https://lore.kernel.org/r/20201218163307.10150-1-nsaenzjulienne@suse.de
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
arch/arm64/include/asm/processor.h | 3 ++-
arch/arm64/mm/init.c | 2 +-
2 files changed, 3 insertions(+), 2 deletions(-)

--- a/arch/arm64/include/asm/processor.h
+++ b/arch/arm64/include/asm/processor.h
@@ -96,7 +96,8 @@
#endif /* CONFIG_ARM64_FORCE_52BIT */

extern phys_addr_t arm64_dma_phys_limit;
-#define ARCH_LOW_ADDRESS_LIMIT (arm64_dma_phys_limit - 1)
+extern phys_addr_t arm64_dma32_phys_limit;
+#define ARCH_LOW_ADDRESS_LIMIT ((arm64_dma_phys_limit ? : arm64_dma32_phys_limit) - 1)

struct debug_info {
#ifdef CONFIG_HAVE_HW_BREAKPOINT
--- a/arch/arm64/mm/init.c
+++ b/arch/arm64/mm/init.c
@@ -60,7 +60,7 @@ EXPORT_SYMBOL(memstart_addr);
* bit addressable memory area.
*/
phys_addr_t arm64_dma_phys_limit __ro_after_init;
-static phys_addr_t arm64_dma32_phys_limit __ro_after_init;
+phys_addr_t arm64_dma32_phys_limit __ro_after_init;

#ifdef CONFIG_KEXEC_CORE
/*