arm64: Handle section maps for swapper/idmap

We use section maps with 4K page size to create the swapper/idmaps.
So far we have used !64K or 4K checks to handle the case where we
use the section maps.
This patch adds a new symbol, ARM64_SWAPPER_USES_SECTION_MAPS, to
handle cases where we use section maps, instead of using the page size
symbols.

Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Suzuki K. Poulose <suzuki.poulose@arm.com>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

2 files changed, 59 insertions, 52 deletions

diff --git a/arch/arm64/include/asm/kernel-pgtable.h b/arch/arm64/include/asm/kernel-pgtable.h
index 3c92fa7bad2b..4e08faabd9e4 100644
--- a/arch/arm64/include/asm/kernel-pgtable.h
+++ b/arch/arm64/include/asm/kernel-pgtable.h
@@ -19,6 +19,19 @@
 #ifndef __ASM_KERNEL_PGTABLE_H
 #define __ASM_KERNEL_PGTABLE_H
 
+
+/*
+ * The linear mapping and the start of memory are both 2M aligned (per
+ * the arm64 booting.txt requirements). Hence we can use section mapping
+ * with 4K (section size = 2M) but not with 16K (section size = 32M) or
+ * 64K (section size = 512M).
+ */
+#ifdef CONFIG_ARM64_4K_PAGES
+#define ARM64_SWAPPER_USES_SECTION_MAPS 1
+#else
+#define ARM64_SWAPPER_USES_SECTION_MAPS 0
+#endif
+
 /*
  * The idmap and swapper page tables need some space reserved in the kernel
  * image. Both require pgd, pud (4 levels only) and pmd tables to (section)
@@ -28,26 +41,28 @@
  * could be increased on the fly if system RAM is out of reach for the default
  * VA range, so 3 pages are reserved in all cases.
  */
-#ifdef CONFIG_ARM64_64K_PAGES
-#define SWAPPER_PGTABLE_LEVELS  (CONFIG_PGTABLE_LEVELS)
-#else
+#if ARM64_SWAPPER_USES_SECTION_MAPS
 #define SWAPPER_PGTABLE_LEVELS  (CONFIG_PGTABLE_LEVELS - 1)
+#else
+#define SWAPPER_PGTABLE_LEVELS  (CONFIG_PGTABLE_LEVELS)
 #endif
 
 #define SWAPPER_DIR_SIZE        (SWAPPER_PGTABLE_LEVELS * PAGE_SIZE)
 #define IDMAP_DIR_SIZE          (3 * PAGE_SIZE)
 
 /* Initial memory map size */
-#ifdef CONFIG_ARM64_64K_PAGES
-#define SWAPPER_BLOCK_SHIFT     PAGE_SHIFT
-#define SWAPPER_BLOCK_SIZE      PAGE_SIZE
-#define SWAPPER_TABLE_SHIFT     PMD_SHIFT
-#else
+#if ARM64_SWAPPER_USES_SECTION_MAPS
 #define SWAPPER_BLOCK_SHIFT     SECTION_SHIFT
 #define SWAPPER_BLOCK_SIZE      SECTION_SIZE
 #define SWAPPER_TABLE_SHIFT     PUD_SHIFT
+#else
+#define SWAPPER_BLOCK_SHIFT     PAGE_SHIFT
+#define SWAPPER_BLOCK_SIZE      PAGE_SIZE
+#define SWAPPER_TABLE_SHIFT     PMD_SHIFT
 #endif
 
+/* The size of the initial kernel direct mapping */
+#define SWAPPER_INIT_MAP_SIZE   (_AC(1, UL) << SWAPPER_TABLE_SHIFT)
 
 /*
  * Initial memory map attributes.
@@ -55,10 +70,10 @@
 #define SWAPPER_PTE_FLAGS       (PTE_TYPE_PAGE | PTE_AF | PTE_SHARED)
 #define SWAPPER_PMD_FLAGS       (PMD_TYPE_SECT | PMD_SECT_AF | PMD_SECT_S)
 
-#ifdef CONFIG_ARM64_64K_PAGES
-#define SWAPPER_MM_MMUFLAGS     (PTE_ATTRINDX(MT_NORMAL) | SWAPPER_PTE_FLAGS)
-#else
+#if ARM64_SWAPPER_USES_SECTION_MAPS
 #define SWAPPER_MM_MMUFLAGS     (PMD_ATTRINDX(MT_NORMAL) | SWAPPER_PMD_FLAGS)
+#else
+#define SWAPPER_MM_MMUFLAGS     (PTE_ATTRINDX(MT_NORMAL) | SWAPPER_PTE_FLAGS)
 #endif
 
 
diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index eed6d52f5e54..c2fa6b56613c 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -32,6 +32,7 @@
 
 #include <asm/cputype.h>
 #include <asm/fixmap.h>
+#include <asm/kernel-pgtable.h>
 #include <asm/sections.h>
 #include <asm/setup.h>
 #include <asm/sizes.h>
@@ -406,14 +407,11 @@ static void __init map_mem(void)
          * memory addressable from the initial direct kernel mapping.
          *
          * The initial direct kernel mapping, located at swapper_pg_dir, gives
-         * us PUD_SIZE (4K pages) or PMD_SIZE (64K pages) memory starting from
-         * PHYS_OFFSET (which must be aligned to 2MB as per
-         * Documentation/arm64/booting.txt).
+         * us PUD_SIZE (with SECTION maps) or PMD_SIZE (without SECTION maps,
+         * memory starting from PHYS_OFFSET (which must be aligned to 2MB as
+         * per Documentation/arm64/booting.txt).
          */
-        if (IS_ENABLED(CONFIG_ARM64_64K_PAGES))
-                limit = PHYS_OFFSET + PMD_SIZE;
-        else
-                limit = PHYS_OFFSET + PUD_SIZE;
+        limit = PHYS_OFFSET + SWAPPER_INIT_MAP_SIZE;
         memblock_set_current_limit(limit);
 
         /* map all the memory banks */
@@ -424,21 +422,24 @@ static void __init map_mem(void)
                 if (start >= end)
                         break;
 
-#ifndef CONFIG_ARM64_64K_PAGES
-                /*
-                 * For the first memory bank align the start address and
-                 * current memblock limit to prevent create_mapping() from
-                 * allocating pte page tables from unmapped memory.
-                 * When 64K pages are enabled, the pte page table for the
-                 * first PGDIR_SIZE is already present in swapper_pg_dir.
-                 */
-                if (start < limit)
-                        start = ALIGN(start, PMD_SIZE);
-                if (end < limit) {
-                        limit = end & PMD_MASK;
-                        memblock_set_current_limit(limit);
+                if (ARM64_SWAPPER_USES_SECTION_MAPS) {
+                        /*
+                         * For the first memory bank align the start address and
+                         * current memblock limit to prevent create_mapping() from
+                         * allocating pte page tables from unmapped memory. With
+                         * the section maps, if the first block doesn't end on section
+                         * size boundary, create_mapping() will try to allocate a pte
+                         * page, which may be returned from an unmapped area.
+                         * When section maps are not used, the pte page table for the
+                         * current limit is already present in swapper_pg_dir.
+                         */
+                        if (start < limit)
+                                start = ALIGN(start, SECTION_SIZE);
+                        if (end < limit) {
+                                limit = end & SECTION_MASK;
+                                memblock_set_current_limit(limit);
+                        }
                 }
-#endif
                 __map_memblock(start, end);
         }
 
@@ -551,12 +552,12 @@ int kern_addr_valid(unsigned long addr)
         return pfn_valid(pte_pfn(*pte));
 }
 #ifdef CONFIG_SPARSEMEM_VMEMMAP
-#ifdef CONFIG_ARM64_64K_PAGES
+#if !ARM64_SWAPPER_USES_SECTION_MAPS
 int __meminit vmemmap_populate(unsigned long start, unsigned long end, int node)
 {
         return vmemmap_populate_basepages(start, end, node);
 }
-#else   /* !CONFIG_ARM64_64K_PAGES */
+#else   /* !ARM64_SWAPPER_USES_SECTION_MAPS */
 int __meminit vmemmap_populate(unsigned long start, unsigned long end, int node)
 {
         unsigned long addr = start;
@@ -691,7 +692,7 @@ void *__init fixmap_remap_fdt(phys_addr_t dt_phys)
 {
         const u64 dt_virt_base = __fix_to_virt(FIX_FDT);
         pgprot_t prot = PAGE_KERNEL | PTE_RDONLY;
-        int granularity, size, offset;
+        int size, offset;
         void *dt_virt;
 
         /*
@@ -717,24 +718,15 @@ void *__init fixmap_remap_fdt(phys_addr_t dt_phys)
          */
         BUILD_BUG_ON(dt_virt_base % SZ_2M);
 
-        if (IS_ENABLED(CONFIG_ARM64_64K_PAGES)) {
-                BUILD_BUG_ON(__fix_to_virt(FIX_FDT_END) >> PMD_SHIFT !=
-                             __fix_to_virt(FIX_BTMAP_BEGIN) >> PMD_SHIFT);
-
-                granularity = PAGE_SIZE;
-        } else {
-                BUILD_BUG_ON(__fix_to_virt(FIX_FDT_END) >> PUD_SHIFT !=
-                             __fix_to_virt(FIX_BTMAP_BEGIN) >> PUD_SHIFT);
-
-                granularity = PMD_SIZE;
-        }
+        BUILD_BUG_ON(__fix_to_virt(FIX_FDT_END) >> SWAPPER_TABLE_SHIFT !=
+                     __fix_to_virt(FIX_BTMAP_BEGIN) >> SWAPPER_TABLE_SHIFT);
 
-        offset = dt_phys % granularity;
+        offset = dt_phys % SWAPPER_BLOCK_SIZE;
         dt_virt = (void *)dt_virt_base + offset;
 
         /* map the first chunk so we can read the size from the header */
-        create_mapping(round_down(dt_phys, granularity), dt_virt_base,
-                       granularity, prot);
+        create_mapping(round_down(dt_phys, SWAPPER_BLOCK_SIZE), dt_virt_base,
+                       SWAPPER_BLOCK_SIZE, prot);
 
         if (fdt_check_header(dt_virt) != 0)
                 return NULL;
@@ -743,9 +735,9 @@ void *__init fixmap_remap_fdt(phys_addr_t dt_phys)
         if (size > MAX_FDT_SIZE)
                 return NULL;
 
-        if (offset + size > granularity)
-                create_mapping(round_down(dt_phys, granularity), dt_virt_base,
-                               round_up(offset + size, granularity), prot);
+        if (offset + size > SWAPPER_BLOCK_SIZE)
+                create_mapping(round_down(dt_phys, SWAPPER_BLOCK_SIZE), dt_virt_base,
+                               round_up(offset + size, SWAPPER_BLOCK_SIZE), prot);
 
         memblock_reserve(dt_phys, size);