// SPDX-License-Identifier: GPL-2.0 /* * Virtual Memory Map support * * (C) 2007 sgi. Christoph Lameter. * * Virtual memory maps allow VM primitives pfn_to_page, page_to_pfn, * virt_to_page, page_address() to be implemented as a base offset * calculation without memory access. * * However, virtual mappings need a page table and TLBs. Many Linux * architectures already map their physical space using 1-1 mappings * via TLBs. For those arches the virtual memory map is essentially * for free if we use the same page size as the 1-1 mappings. In that * case the overhead consists of a few additional pages that are * allocated to create a view of memory for vmemmap. * * The architecture is expected to provide a vmemmap_populate() function * to instantiate the mapping. */ #include <linux/mm.h> #include <linux/mmzone.h> #include <linux/memblock.h> #include <linux/memremap.h> #include <linux/highmem.h> #include <linux/slab.h> #include <linux/spinlock.h> #include <linux/vmalloc.h> #include <linux/sched.h> #include <linux/pgtable.h> #include <linux/bootmem_info.h> #include <asm/dma.h> #include <asm/pgalloc.h> #include <asm/tlbflush.h> /** * struct vmemmap_remap_walk - walk vmemmap page table * * @remap_pte: called for each lowest-level entry (PTE). * @nr_walked: the number of walked pte. * @reuse_page: the page which is reused for the tail vmemmap pages. * @reuse_addr: the virtual address of the @reuse_page page. * @vmemmap_pages: the list head of the vmemmap pages that can be freed * or is mapped from. */ struct vmemmap_remap_walk { void (*remap_pte)(pte_t *pte, unsigned long addr, struct vmemmap_remap_walk *walk); unsigned long nr_walked; struct page *reuse_page; unsigned long reuse_addr; struct list_head *vmemmap_pages; }; static int split_vmemmap_huge_pmd(pmd_t *pmd, unsigned long start, struct vmemmap_remap_walk *walk) { pmd_t __pmd; int i; unsigned long addr = start; struct page *page = pmd_page(*pmd); pte_t *pgtable = pte_alloc_one_kernel(&init_mm); if (!pgtable) return -ENOMEM; pmd_populate_kernel(&init_mm, &__pmd, pgtable); for (i = 0; i < PMD_SIZE / PAGE_SIZE; i++, addr += PAGE_SIZE) { pte_t entry, *pte; pgprot_t pgprot = PAGE_KERNEL; entry = mk_pte(page + i, pgprot); pte = pte_offset_kernel(&__pmd, addr); set_pte_at(&init_mm, addr, pte, entry); } /* Make pte visible before pmd. See comment in pmd_install(). */ smp_wmb(); pmd_populate_kernel(&init_mm, pmd, pgtable); flush_tlb_kernel_range(start, start + PMD_SIZE); return 0; } static void vmemmap_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end, struct vmemmap_remap_walk *walk) { pte_t *pte = pte_offset_kernel(pmd, addr); /* * The reuse_page is found 'first' in table walk before we start * remapping (which is calling @walk->remap_pte). */ if (!walk->reuse_page) { walk->reuse_page = pte_page(*pte); /* * Because the reuse address is part of the range that we are * walking, skip the reuse address range. */ addr += PAGE_SIZE; pte++; walk->nr_walked++; } for (; addr != end; addr += PAGE_SIZE, pte++) { walk->remap_pte(pte, addr, walk); walk->nr_walked++; } } static int vmemmap_pmd_range(pud_t *pud, unsigned long addr, unsigned long end, struct vmemmap_remap_walk *walk) { pmd_t *pmd; unsigned long next; pmd = pmd_offset(pud, addr); do { if (pmd_leaf(*pmd)) { int ret; ret = split_vmemmap_huge_pmd(pmd, addr & PMD_MASK, walk); if (ret) return ret; } next = pmd_addr_end(addr, end); vmemmap_pte_range(pmd, addr, next, walk); } while (pmd++, addr = next, addr != end); return 0; } static int vmemmap_pud_range(p4d_t *p4d, unsigned long addr, unsigned long end, struct vmemmap_remap_walk *walk) { pud_t *pud; unsigned long next; pud = pud_offset(p4d, addr); do { int ret; next = pud_addr_end(addr, end); ret = vmemmap_pmd_range(pud, addr, next, walk); if (ret) return ret; } while (pud++, addr = next, addr != end); return 0; } static int vmemmap_p4d_range(pgd_t *pgd, unsigned long addr, unsigned long end, struct vmemmap_remap_walk *walk) { p4d_t *p4d; unsigned long next; p4d = p4d_offset(pgd, addr); do { int ret; next = p4d_addr_end(addr, end); ret = vmemmap_pud_range(p4d, addr, next, walk); if (ret) return ret; } while (p4d++, addr = next, addr != end); return 0; } static int vmemmap_remap_range(unsigned long start, unsigned long end, struct vmemmap_remap_walk *walk) { unsigned long addr = start; unsigned long next; pgd_t *pgd; VM_BUG_ON(!IS_ALIGNED(start, PAGE_SIZE)); VM_BUG_ON(!IS_ALIGNED(end, PAGE_SIZE)); pgd = pgd_offset_k(addr); do { int ret; next = pgd_addr_end(addr, end); ret = vmemmap_p4d_range(pgd, addr, next, walk); if (ret) return ret; } while (pgd++, addr = next, addr != end); /* * We only change the mapping of the vmemmap virtual address range * [@start + PAGE_SIZE, end), so we only need to flush the TLB which * belongs to the range. */ flush_tlb_kernel_range(start + PAGE_SIZE, end); return 0; } /* * Free a vmemmap page. A vmemmap page can be allocated from the memblock * allocator or buddy allocator. If the PG_reserved flag is set, it means * that it allocated from the memblock allocator, just free it via the * free_bootmem_page(). Otherwise, use __free_page(). */ static inline void free_vmemmap_page(struct page *page) { if (PageReserved(page)) free_bootmem_page(page); else __free_page(page); } /* Free a list of the vmemmap pages */ static void free_vmemmap_page_list(struct list_head *list) { struct page *page, *next; list_for_each_entry_safe(page, next, list, lru) { list_del(&page->lru); free_vmemmap_page(page); } } static void vmemmap_remap_pte(pte_t *pte, unsigned long addr, struct vmemmap_remap_walk *walk) { /* * Remap the tail pages as read-only to catch illegal write operation * to the tail pages. */ pgprot_t pgprot = PAGE_KERNEL_RO; pte_t entry = mk_pte(walk->reuse_page, pgprot); struct page *page = pte_page(*pte); list_add_tail(&page->lru, walk->vmemmap_pages); set_pte_at(&init_mm, addr, pte, entry); } static void vmemmap_restore_pte(pte_t *pte, unsigned long addr, struct vmemmap_remap_walk *walk) { pgprot_t pgprot = PAGE_KERNEL; struct page *page; void *to; BUG_ON(pte_page(*pte) != walk->reuse_page); page = list_first_entry(walk->vmemmap_pages, struct page, lru); list_del(&page->lru); to = page_to_virt(page); copy_page(to, (void *)walk->reuse_addr); set_pte_at(&init_mm, addr, pte, mk_pte(page, pgprot)); } /** * vmemmap_remap_free - remap the vmemmap virtual address range [@start, @end) * to the page which @reuse is mapped to, then free vmemmap * which the range are mapped to. * @start: start address of the vmemmap virtual address range that we want * to remap. * @end: end address of the vmemmap virtual address range that we want to * remap. * @reuse: reuse address. * * Return: %0 on success, negative error code otherwise. */ int vmemmap_remap_free(unsigned long start, unsigned long end, unsigned long reuse) { int ret; LIST_HEAD(vmemmap_pages); struct vmemmap_remap_walk walk = { .remap_pte = vmemmap_remap_pte, .reuse_addr = reuse, .vmemmap_pages = &vmemmap_pages, }; /* * In order to make remapping routine most efficient for the huge pages, * the routine of vmemmap page table walking has the following rules * (see more details from the vmemmap_pte_range()): * * - The range [@start, @end) and the range [@reuse, @reuse + PAGE_SIZE) * should be continuous. * - The @reuse address is part of the range [@reuse, @end) that we are * walking which is passed to vmemmap_remap_range(). * - The @reuse address is the first in the complete range. * * So we need to make sure that @start and @reuse meet the above rules. */ BUG_ON(start - reuse != PAGE_SIZE); mmap_write_lock(&init_mm); ret = vmemmap_remap_range(reuse, end, &walk); mmap_write_downgrade(&init_mm); if (ret && walk.nr_walked) { end = reuse + walk.nr_walked * PAGE_SIZE; /* * vmemmap_pages contains pages from the previous * vmemmap_remap_range call which failed. These * are pages which were removed from the vmemmap. * They will be restored in the following call. */ walk = (struct vmemmap_remap_walk) { .remap_pte = vmemmap_restore_pte, .reuse_addr = reuse, .vmemmap_pages = &vmemmap_pages, }; vmemmap_remap_range(reuse, end, &walk); } mmap_read_unlock(&init_mm); free_vmemmap_page_list(&vmemmap_pages); return ret; } static int alloc_vmemmap_page_list(unsigned long start, unsigned long end, gfp_t gfp_mask, struct list_head *list) { unsigned long nr_pages = (end - start) >> PAGE_SHIFT; int nid = page_to_nid((struct page *)start); struct page *page, *next; while (nr_pages--) { page = alloc_pages_node(nid, gfp_mask, 0); if (!page) goto out; list_add_tail(&page->lru, list); } return 0; out: list_for_each_entry_safe(page, next, list, lru) __free_pages(page, 0); return -ENOMEM; } /** * vmemmap_remap_alloc - remap the vmemmap virtual address range [@start, end) * to the page which is from the @vmemmap_pages * respectively. * @start: start address of the vmemmap virtual address range that we want * to remap. * @end: end address of the vmemmap virtual address range that we want to * remap. * @reuse: reuse address. * @gfp_mask: GFP flag for allocating vmemmap pages. * * Return: %0 on success, negative error code otherwise. */ int vmemmap_remap_alloc(unsigned long start, unsigned long end, unsigned long reuse, gfp_t gfp_mask) { LIST_HEAD(vmemmap_pages); struct vmemmap_remap_walk walk = { .remap_pte = vmemmap_restore_pte, .reuse_addr = reuse, .vmemmap_pages = &vmemmap_pages, }; /* See the comment in the vmemmap_remap_free(). */ BUG_ON(start - reuse != PAGE_SIZE); if (alloc_vmemmap_page_list(start, end, gfp_mask, &vmemmap_pages)) return -ENOMEM; mmap_read_lock(&init_mm); vmemmap_remap_range(reuse, end, &walk); mmap_read_unlock(&init_mm); return 0; } /* * Allocate a block of memory to be used to back the virtual memory map * or to back the page tables that are used to create the mapping. * Uses the main allocators if they are available, else bootmem. */ static void * __ref __earlyonly_bootmem_alloc(int node, unsigned long size, unsigned long align, unsigned long goal) { return memblock_alloc_try_nid_raw(size, align, goal, MEMBLOCK_ALLOC_ACCESSIBLE, node); } void * __meminit vmemmap_alloc_block(unsigned long size, int node) { /* If the main allocator is up use that, fallback to bootmem. */ if (slab_is_available()) { gfp_t gfp_mask = GFP_KERNEL|__GFP_RETRY_MAYFAIL|__GFP_NOWARN; int order = get_order(size); static bool warned; struct page *page; page = alloc_pages_node(node, gfp_mask, order); if (page) return page_address(page); if (!warned) { warn_alloc(gfp_mask & ~__GFP_NOWARN, NULL, "vmemmap alloc failure: order:%u", order); warned = true; } return NULL; } else return __earlyonly_bootmem_alloc(node, size, size, __pa(MAX_DMA_ADDRESS)); } static void * __meminit altmap_alloc_block_buf(unsigned long size, struct vmem_altmap *altmap); /* need to make sure size is all the same during early stage */ void * __meminit vmemmap_alloc_block_buf(unsigned long size, int node, struct vmem_altmap *altmap) { void *ptr; if (altmap) return altmap_alloc_block_buf(size, altmap); ptr = sparse_buffer_alloc(size); if (!ptr) ptr = vmemmap_alloc_block(size, node); return ptr; } static unsigned long __meminit vmem_altmap_next_pfn(struct vmem_altmap *altmap) { return altmap->base_pfn + altmap->reserve + altmap->alloc + altmap->align; } static unsigned long __meminit vmem_altmap_nr_free(struct vmem_altmap *altmap) { unsigned long allocated = altmap->alloc + altmap->align; if (altmap->free > allocated) return altmap->free - allocated; return 0; } static void * __meminit altmap_alloc_block_buf(unsigned long size, struct vmem_altmap *altmap) { unsigned long pfn, nr_pfns, nr_align; if (size & ~PAGE_MASK) { pr_warn_once("%s: allocations must be multiple of PAGE_SIZE (%ld)\n", __func__, size); return NULL; } pfn = vmem_altmap_next_pfn(altmap); nr_pfns = size >> PAGE_SHIFT; nr_align = 1UL << find_first_bit(&nr_pfns, BITS_PER_LONG); nr_align = ALIGN(pfn, nr_align) - pfn; if (nr_pfns + nr_align > vmem_altmap_nr_free(altmap)) return NULL; altmap->alloc += nr_pfns; altmap->align += nr_align; pfn += nr_align; pr_debug("%s: pfn: %#lx alloc: %ld align: %ld nr: %#lx\n", __func__, pfn, altmap->alloc, altmap->align, nr_pfns); return __va(__pfn_to_phys(pfn)); } void __meminit vmemmap_verify(pte_t *pte, int node, unsigned long start, unsigned long end) { unsigned long pfn = pte_pfn(*pte); int actual_node = early_pfn_to_nid(pfn); if (node_distance(actual_node, node) > LOCAL_DISTANCE) pr_warn("[%lx-%lx] potential offnode page_structs\n", start, end - 1); } pte_t * __meminit vmemmap_pte_populate(pmd_t *pmd, unsigned long addr, int node, struct vmem_altmap *altmap) { pte_t *pte = pte_offset_kernel(pmd, addr); if (pte_none(*pte)) { pte_t entry; void *p; p = vmemmap_alloc_block_buf(PAGE_SIZE, node, altmap); if (!p) return NULL; entry = pfn_pte(__pa(p) >> PAGE_SHIFT, PAGE_KERNEL); set_pte_at(&init_mm, addr, pte, entry); } return pte; } static void * __meminit vmemmap_alloc_block_zero(unsigned long size, int node) { void *p = vmemmap_alloc_block(size, node); if (!p) return NULL; memset(p, 0, size); return p; } pmd_t * __meminit vmemmap_pmd_populate(pud_t *pud, unsigned long addr, int node) { pmd_t *pmd = pmd_offset(pud, addr); if (pmd_none(*pmd)) { void *p = vmemmap_alloc_block_zero(PAGE_SIZE, node); if (!p) return NULL; pmd_populate_kernel(&init_mm, pmd, p); } return pmd; } pud_t * __meminit vmemmap_pud_populate(p4d_t *p4d, unsigned long addr, int node) { pud_t *pud = pud_offset(p4d, addr); if (pud_none(*pud)) { void *p = vmemmap_alloc_block_zero(PAGE_SIZE, node); if (!p) return NULL; pud_populate(&init_mm, pud, p); } return pud; } p4d_t * __meminit vmemmap_p4d_populate(pgd_t *pgd, unsigned long addr, int node) { p4d_t *p4d = p4d_offset(pgd, addr); if (p4d_none(*p4d)) { void *p = vmemmap_alloc_block_zero(PAGE_SIZE, node); if (!p) return NULL; p4d_populate(&init_mm, p4d, p); } return p4d; } pgd_t * __meminit vmemmap_pgd_populate(unsigned long addr, int node) { pgd_t *pgd = pgd_offset_k(addr); if (pgd_none(*pgd)) { void *p = vmemmap_alloc_block_zero(PAGE_SIZE, node); if (!p) return NULL; pgd_populate(&init_mm, pgd, p); } return pgd; } int __meminit vmemmap_populate_basepages(unsigned long start, unsigned long end, int node, struct vmem_altmap *altmap) { unsigned long addr = start; pgd_t *pgd; p4d_t *p4d; pud_t *pud; pmd_t *pmd; pte_t *pte; for (; addr < end; addr += PAGE_SIZE) { pgd = vmemmap_pgd_populate(addr, node); if (!pgd) return -ENOMEM; p4d = vmemmap_p4d_populate(pgd, addr, node); if (!p4d) return -ENOMEM; pud = vmemmap_pud_populate(p4d, addr, node); if (!pud) return -ENOMEM; pmd = vmemmap_pmd_populate(pud, addr, node); if (!pmd) return -ENOMEM; pte = vmemmap_pte_populate(pmd, addr, node, altmap); if (!pte) return -ENOMEM; vmemmap_verify(pte, node, addr, addr + PAGE_SIZE); } return 0; } struct page * __meminit __populate_section_memmap(unsigned long pfn, unsigned long nr_pages, int nid, struct vmem_altmap *altmap) { unsigned long start = (unsigned long) pfn_to_page(pfn); unsigned long end = start + nr_pages * sizeof(struct page); if (WARN_ON_ONCE(!IS_ALIGNED(pfn, PAGES_PER_SUBSECTION) || !IS_ALIGNED(nr_pages, PAGES_PER_SUBSECTION))) return NULL; if (vmemmap_populate(start, end, nid, altmap)) return NULL; return pfn_to_page(pfn); }