arm64: mm: use fixmap when creating page tables

As a preparatory step to allow us to allocate early page tables from
unmapped memory using memblock_alloc, modify the __create_mapping
callees to map and unmap the tables they modify using fixmap entries.

All but the top-level pgd initialisation is performed via the fixmap.
Subsequent patches will inject the pgd physical address, and migrate to
using the FIX_PGD slot.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Tested-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Tested-by: Jeremy Linton <jeremy.linton@arm.com>
Cc: Laura Abbott <labbott@fedoraproject.org>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index 8879aed..5248b02 100644 (file)
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -63,19 +63,30 @@ pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn,
 }
 EXPORT_SYMBOL(phys_mem_access_prot);
 
-static void __init *early_pgtable_alloc(void)
+static phys_addr_t __init early_pgtable_alloc(void)
 {
        phys_addr_t phys;
        void *ptr;
 
        phys = memblock_alloc(PAGE_SIZE, PAGE_SIZE);
        BUG_ON(!phys);
-       ptr = __va(phys);
+
+       /*
+        * The FIX_{PGD,PUD,PMD} slots may be in active use, but the FIX_PTE
+        * slot will be free, so we can (ab)use the FIX_PTE slot to initialise
+        * any level of table.
+        */
+       ptr = pte_set_fixmap(phys);
+
        memset(ptr, 0, PAGE_SIZE);
 
-       /* Ensure the zeroed page is visible to the page table walker */
-       dsb(ishst);
-       return ptr;
+       /*
+        * Implicit barriers also ensure the zeroed page is visible to the page
+        * table walker
+        */
+       pte_clear_fixmap();
+
+       return phys;
 }
 
 /*
@@ -99,24 +110,28 @@ static void split_pmd(pmd_t *pmd, pte_t *pte)
 static void alloc_init_pte(pmd_t *pmd, unsigned long addr,
                                  unsigned long end, unsigned long pfn,
                                  pgprot_t prot,
-                                 void *(*pgtable_alloc)(void))
+                                 phys_addr_t (*pgtable_alloc)(void))
 {
        pte_t *pte;
 
        if (pmd_none(*pmd) || pmd_sect(*pmd)) {
-               pte = pgtable_alloc();
+               phys_addr_t pte_phys = pgtable_alloc();
+               pte = pte_set_fixmap(pte_phys);
                if (pmd_sect(*pmd))
                        split_pmd(pmd, pte);
-               __pmd_populate(pmd, __pa(pte), PMD_TYPE_TABLE);
+               __pmd_populate(pmd, pte_phys, PMD_TYPE_TABLE);
                flush_tlb_all();
+               pte_clear_fixmap();
        }
        BUG_ON(pmd_bad(*pmd));
 
-       pte = pte_offset_kernel(pmd, addr);
+       pte = pte_set_fixmap_offset(pmd, addr);
        do {
                set_pte(pte, pfn_pte(pfn, prot));
                pfn++;
        } while (pte++, addr += PAGE_SIZE, addr != end);
+
+       pte_clear_fixmap();
 }
 
 static void split_pud(pud_t *old_pud, pmd_t *pmd)
@@ -134,7 +149,7 @@ static void split_pud(pud_t *old_pud, pmd_t *pmd)
 static void alloc_init_pmd(struct mm_struct *mm, pud_t *pud,
                                  unsigned long addr, unsigned long end,
                                  phys_addr_t phys, pgprot_t prot,
-                                 void *(*pgtable_alloc)(void))
+                                 phys_addr_t (*pgtable_alloc)(void))
 {
        pmd_t *pmd;
        unsigned long next;
@@ -143,7 +158,8 @@ static void alloc_init_pmd(struct mm_struct *mm, pud_t *pud,
         * Check for initial section mappings in the pgd/pud and remove them.
         */
        if (pud_none(*pud) || pud_sect(*pud)) {
-               pmd = pgtable_alloc();
+               phys_addr_t pmd_phys = pgtable_alloc();
+               pmd = pmd_set_fixmap(pmd_phys);
                if (pud_sect(*pud)) {
                        /*
                         * need to have the 1G of mappings continue to be
@@ -151,12 +167,13 @@ static void alloc_init_pmd(struct mm_struct *mm, pud_t *pud,
                         */
                        split_pud(pud, pmd);
                }
-               pud_populate(mm, pud, pmd);
+               __pud_populate(pud, pmd_phys, PUD_TYPE_TABLE);
                flush_tlb_all();
+               pmd_clear_fixmap();
        }
        BUG_ON(pud_bad(*pud));
 
-       pmd = pmd_offset(pud, addr);
+       pmd = pmd_set_fixmap_offset(pud, addr);
        do {
                next = pmd_addr_end(addr, end);
                /* try section mapping first */
@@ -182,6 +199,8 @@ static void alloc_init_pmd(struct mm_struct *mm, pud_t *pud,
                }
                phys += next - addr;
        } while (pmd++, addr = next, addr != end);
+
+       pmd_clear_fixmap();
 }
 
 static inline bool use_1G_block(unsigned long addr, unsigned long next,
@@ -199,18 +218,18 @@ static inline bool use_1G_block(unsigned long addr, unsigned long next,
 static void alloc_init_pud(struct mm_struct *mm, pgd_t *pgd,
                                  unsigned long addr, unsigned long end,
                                  phys_addr_t phys, pgprot_t prot,
-                                 void *(*pgtable_alloc)(void))
+                                 phys_addr_t (*pgtable_alloc)(void))
 {
        pud_t *pud;
        unsigned long next;
 
        if (pgd_none(*pgd)) {
-               pud = pgtable_alloc();
-               pgd_populate(mm, pgd, pud);
+               phys_addr_t pud_phys = pgtable_alloc();
+               __pgd_populate(pgd, pud_phys, PUD_TYPE_TABLE);
        }
        BUG_ON(pgd_bad(*pgd));
 
-       pud = pud_offset(pgd, addr);
+       pud = pud_set_fixmap_offset(pgd, addr);
        do {
                next = pud_addr_end(addr, end);
 
@@ -243,6 +262,8 @@ static void alloc_init_pud(struct mm_struct *mm, pgd_t *pgd,
                }
                phys += next - addr;
        } while (pud++, addr = next, addr != end);
+
+       pud_clear_fixmap();
 }
 
 /*
@@ -252,7 +273,7 @@ static void alloc_init_pud(struct mm_struct *mm, pgd_t *pgd,
 static void  __create_mapping(struct mm_struct *mm, pgd_t *pgd,
                                    phys_addr_t phys, unsigned long virt,
                                    phys_addr_t size, pgprot_t prot,
-                                   void *(*pgtable_alloc)(void))
+                                   phys_addr_t (*pgtable_alloc)(void))
 {
        unsigned long addr, length, end, next;
 
@@ -275,14 +296,14 @@ static void  __create_mapping(struct mm_struct *mm, pgd_t *pgd,
        } while (pgd++, addr = next, addr != end);
 }
 
-static void *late_pgtable_alloc(void)
+static phys_addr_t late_pgtable_alloc(void)
 {
        void *ptr = (void *)__get_free_page(PGALLOC_GFP);
        BUG_ON(!ptr);
 
        /* Ensure the zeroed page is visible to the page table walker */
        dsb(ishst);
-       return ptr;
+       return __pa(ptr);
 }
 
 static void __init create_mapping(phys_addr_t phys, unsigned long virt,