From: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
Date: Fri, 18 Dec 2020 17:33:07 +0100
Subject: arm64: mm: Fix ARCH_LOW_ADDRESS_LIMIT when !CONFIG_ZONE_DMA
Git-commit: 095507dc1350b3a2b8b39fdc05edba0c10859eca
Patch-mainline: v5.11-rc3
References: git-fixes

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>
---
 arch/arm64/include/asm/processor.h |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/arch/arm64/include/asm/processor.h
+++ b/arch/arm64/include/asm/processor.h
@@ -92,7 +92,8 @@
 #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