arm64/mm: Drop ARM64_KERNEL_USES_PMD_MAPS

Currently ARM64_KERNEL_USES_PMD_MAPS is an unnecessary abstraction. Kernel
mapping at PMD (aka huge page aka block) level, is only applicable with 4K
base page, which makes it 2MB aligned, a necessary requirement for linear
mapping and physical memory start address. This can be easily achieved by
directly checking against base page size itself. This drops off the macro
ARM64_KERNE_USES_PMD_MAPS which is redundant.

Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: linux-arm-kernel@lists.infradead.org
Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
Link: https://lore.kernel.org/r/20221108034406.2950071-1-anshuman.khandual@arm.comSigned-off-by: Will Deacon <will@kernel.org>

arch/arm64/include/asm/kernel-pgtable.h

@@ -18,11 +18,6 @@
  * with 4K (section size = 2M) but not with 16K (section size = 32M) or
  * 64K (section size = 512M).
  */
-#ifdef CONFIG_ARM64_4K_PAGES
-#define ARM64_KERNEL_USES_PMD_MAPS 1
-#else
-#define ARM64_KERNEL_USES_PMD_MAPS 0
-#endif
 
 /*
  * The idmap and swapper page tables need some space reserved in the kernel
@@ -34,7 +29,7 @@
  * VA range, so pages required to map highest possible PA are reserved in all
  * cases.
  */
-#if ARM64_KERNEL_USES_PMD_MAPS
+#ifdef CONFIG_ARM64_4K_PAGES
 #define SWAPPER_PGTABLE_LEVELS	(CONFIG_PGTABLE_LEVELS - 1)
 #else
 #define SWAPPER_PGTABLE_LEVELS	(CONFIG_PGTABLE_LEVELS)
@@ -96,7 +91,7 @@
 #define INIT_IDMAP_DIR_PAGES	EARLY_PAGES(KIMAGE_VADDR, _end + MAX_FDT_SIZE + SWAPPER_BLOCK_SIZE, 1)
 
 /* Initial memory map size */
-#if ARM64_KERNEL_USES_PMD_MAPS
+#ifdef CONFIG_ARM64_4K_PAGES
 #define SWAPPER_BLOCK_SHIFT	PMD_SHIFT
 #define SWAPPER_BLOCK_SIZE	PMD_SIZE
 #define SWAPPER_TABLE_SHIFT	PUD_SHIFT
@@ -112,7 +107,7 @@
 #define SWAPPER_PTE_FLAGS	(PTE_TYPE_PAGE | PTE_AF | PTE_SHARED)
 #define SWAPPER_PMD_FLAGS	(PMD_TYPE_SECT | PMD_SECT_AF | PMD_SECT_S)
 
-#if ARM64_KERNEL_USES_PMD_MAPS
+#ifdef CONFIG_ARM64_4K_PAGES
 #define SWAPPER_RW_MMUFLAGS	(PMD_ATTRINDX(MT_NORMAL) | SWAPPER_PMD_FLAGS)
 #define SWAPPER_RX_MMUFLAGS	(SWAPPER_RW_MMUFLAGS | PMD_SECT_RDONLY)
 #else

arch/arm64/mm/mmu.c

@@ -1196,7 +1196,7 @@ int __meminit vmemmap_populate(unsigned long start, unsigned long end, int node,
 
 	WARN_ON((start < VMEMMAP_START) || (end > VMEMMAP_END));
 
-	if (!ARM64_KERNEL_USES_PMD_MAPS)
+	if (!IS_ENABLED(CONFIG_ARM64_4K_PAGES))
 		return vmemmap_populate_basepages(start, end, node, altmap);
 
 	do {