| #include <linux/gfp.h> |
| #include <linux/highmem.h> |
| #include <linux/kernel.h> |
| #include <linux/mmdebug.h> |
| #include <linux/mm_types.h> |
| #include <linux/pagemap.h> |
| #include <linux/rcupdate.h> |
| #include <linux/smp.h> |
| #include <linux/swap.h> |
| |
| #include <asm/pgalloc.h> |
| #include <asm/tlb.h> |
| |
| #ifndef CONFIG_MMU_GATHER_NO_GATHER |
| |
| static bool tlb_next_batch(struct mmu_gather *tlb) |
| { |
| struct mmu_gather_batch *batch; |
| |
| batch = tlb->active; |
| if (batch->next) { |
| tlb->active = batch->next; |
| return true; |
| } |
| |
| if (tlb->batch_count == MAX_GATHER_BATCH_COUNT) |
| return false; |
| |
| batch = (void *)__get_free_pages(GFP_NOWAIT | __GFP_NOWARN, 0); |
| if (!batch) |
| return false; |
| |
| tlb->batch_count++; |
| batch->next = NULL; |
| batch->nr = 0; |
| batch->max = MAX_GATHER_BATCH; |
| |
| tlb->active->next = batch; |
| tlb->active = batch; |
| |
| return true; |
| } |
| |
| static void tlb_batch_pages_flush(struct mmu_gather *tlb) |
| { |
| struct mmu_gather_batch *batch; |
| |
| for (batch = &tlb->local; batch && batch->nr; batch = batch->next) { |
| free_pages_and_swap_cache(batch->pages, batch->nr); |
| batch->nr = 0; |
| } |
| tlb->active = &tlb->local; |
| } |
| |
| static void tlb_batch_list_free(struct mmu_gather *tlb) |
| { |
| struct mmu_gather_batch *batch, *next; |
| |
| for (batch = tlb->local.next; batch; batch = next) { |
| next = batch->next; |
| free_pages((unsigned long)batch, 0); |
| } |
| tlb->local.next = NULL; |
| } |
| |
| bool __tlb_remove_page_size(struct mmu_gather *tlb, struct page *page, int page_size) |
| { |
| struct mmu_gather_batch *batch; |
| |
| VM_BUG_ON(!tlb->end); |
| |
| #ifdef CONFIG_MMU_GATHER_PAGE_SIZE |
| VM_WARN_ON(tlb->page_size != page_size); |
| #endif |
| |
| batch = tlb->active; |
| /* |
| * Add the page and check if we are full. If so |
| * force a flush. |
| */ |
| batch->pages[batch->nr++] = page; |
| if (batch->nr == batch->max) { |
| if (!tlb_next_batch(tlb)) |
| return true; |
| batch = tlb->active; |
| } |
| VM_BUG_ON_PAGE(batch->nr > batch->max, page); |
| |
| return false; |
| } |
| |
| #endif /* MMU_GATHER_NO_GATHER */ |
| |
| #ifdef CONFIG_MMU_GATHER_TABLE_FREE |
| |
| static void __tlb_remove_table_free(struct mmu_table_batch *batch) |
| { |
| int i; |
| |
| for (i = 0; i < batch->nr; i++) |
| __tlb_remove_table(batch->tables[i]); |
| |
| free_page((unsigned long)batch); |
| } |
| |
| #ifdef CONFIG_MMU_GATHER_RCU_TABLE_FREE |
| |
| /* |
| * Semi RCU freeing of the page directories. |
| * |
| * This is needed by some architectures to implement software pagetable walkers. |
| * |
| * gup_fast() and other software pagetable walkers do a lockless page-table |
| * walk and therefore needs some synchronization with the freeing of the page |
| * directories. The chosen means to accomplish that is by disabling IRQs over |
| * the walk. |
| * |
| * Architectures that use IPIs to flush TLBs will then automagically DTRT, |
| * since we unlink the page, flush TLBs, free the page. Since the disabling of |
| * IRQs delays the completion of the TLB flush we can never observe an already |
| * freed page. |
| * |
| * Architectures that do not have this (PPC) need to delay the freeing by some |
| * other means, this is that means. |
| * |
| * What we do is batch the freed directory pages (tables) and RCU free them. |
| * We use the sched RCU variant, as that guarantees that IRQ/preempt disabling |
| * holds off grace periods. |
| * |
| * However, in order to batch these pages we need to allocate storage, this |
| * allocation is deep inside the MM code and can thus easily fail on memory |
| * pressure. To guarantee progress we fall back to single table freeing, see |
| * the implementation of tlb_remove_table_one(). |
| * |
| */ |
| |
| static void tlb_remove_table_smp_sync(void *arg) |
| { |
| /* Simply deliver the interrupt */ |
| } |
| |
| void tlb_remove_table_sync_one(void) |
| { |
| /* |
| * This isn't an RCU grace period and hence the page-tables cannot be |
| * assumed to be actually RCU-freed. |
| * |
| * It is however sufficient for software page-table walkers that rely on |
| * IRQ disabling. |
| */ |
| smp_call_function(tlb_remove_table_smp_sync, NULL, 1); |
| } |
| |
| static void tlb_remove_table_rcu(struct rcu_head *head) |
| { |
| __tlb_remove_table_free(container_of(head, struct mmu_table_batch, rcu)); |
| } |
| |
| static void tlb_remove_table_free(struct mmu_table_batch *batch) |
| { |
| call_rcu(&batch->rcu, tlb_remove_table_rcu); |
| } |
| |
| #else /* !CONFIG_MMU_GATHER_RCU_TABLE_FREE */ |
| |
| static void tlb_remove_table_free(struct mmu_table_batch *batch) |
| { |
| __tlb_remove_table_free(batch); |
| } |
| |
| #endif /* CONFIG_MMU_GATHER_RCU_TABLE_FREE */ |
| |
| /* |
| * If we want tlb_remove_table() to imply TLB invalidates. |
| */ |
| static inline void tlb_table_invalidate(struct mmu_gather *tlb) |
| { |
| if (tlb_needs_table_invalidate()) { |
| /* |
| * Invalidate page-table caches used by hardware walkers. Then |
| * we still need to RCU-sched wait while freeing the pages |
| * because software walkers can still be in-flight. |
| */ |
| tlb_flush_mmu_tlbonly(tlb); |
| } |
| } |
| |
| static void tlb_remove_table_one(void *table) |
| { |
| tlb_remove_table_sync_one(); |
| __tlb_remove_table(table); |
| } |
| |
| static void tlb_table_flush(struct mmu_gather *tlb) |
| { |
| struct mmu_table_batch **batch = &tlb->batch; |
| |
| if (*batch) { |
| tlb_table_invalidate(tlb); |
| tlb_remove_table_free(*batch); |
| *batch = NULL; |
| } |
| } |
| |
| void tlb_remove_table(struct mmu_gather *tlb, void *table) |
| { |
| struct mmu_table_batch **batch = &tlb->batch; |
| |
| if (*batch == NULL) { |
| *batch = (struct mmu_table_batch *)__get_free_page(GFP_NOWAIT | __GFP_NOWARN); |
| if (*batch == NULL) { |
| tlb_table_invalidate(tlb); |
| tlb_remove_table_one(table); |
| return; |
| } |
| (*batch)->nr = 0; |
| } |
| |
| (*batch)->tables[(*batch)->nr++] = table; |
| if ((*batch)->nr == MAX_TABLE_BATCH) |
| tlb_table_flush(tlb); |
| } |
| |
| static inline void tlb_table_init(struct mmu_gather *tlb) |
| { |
| tlb->batch = NULL; |
| } |
| |
| #else /* !CONFIG_MMU_GATHER_TABLE_FREE */ |
| |
| static inline void tlb_table_flush(struct mmu_gather *tlb) { } |
| static inline void tlb_table_init(struct mmu_gather *tlb) { } |
| |
| #endif /* CONFIG_MMU_GATHER_TABLE_FREE */ |
| |
| static void tlb_flush_mmu_free(struct mmu_gather *tlb) |
| { |
| tlb_table_flush(tlb); |
| #ifndef CONFIG_MMU_GATHER_NO_GATHER |
| tlb_batch_pages_flush(tlb); |
| #endif |
| } |
| |
| void tlb_flush_mmu(struct mmu_gather *tlb) |
| { |
| tlb_flush_mmu_tlbonly(tlb); |
| tlb_flush_mmu_free(tlb); |
| } |
| |
| /** |
| * tlb_gather_mmu - initialize an mmu_gather structure for page-table tear-down |
| * @tlb: the mmu_gather structure to initialize |
| * @mm: the mm_struct of the target address space |
| * @start: start of the region that will be removed from the page-table |
| * @end: end of the region that will be removed from the page-table |
| * |
| * Called to initialize an (on-stack) mmu_gather structure for page-table |
| * tear-down from @mm. The @start and @end are set to 0 and -1 |
| * respectively when @mm is without users and we're going to destroy |
| * the full address space (exit/execve). |
| */ |
| void tlb_gather_mmu(struct mmu_gather *tlb, struct mm_struct *mm, |
| unsigned long start, unsigned long end) |
| { |
| tlb->mm = mm; |
| |
| /* Is it from 0 to ~0? */ |
| tlb->fullmm = !(start | (end+1)); |
| |
| #ifndef CONFIG_MMU_GATHER_NO_GATHER |
| tlb->need_flush_all = 0; |
| tlb->local.next = NULL; |
| tlb->local.nr = 0; |
| tlb->local.max = ARRAY_SIZE(tlb->__pages); |
| tlb->active = &tlb->local; |
| tlb->batch_count = 0; |
| #endif |
| |
| tlb_table_init(tlb); |
| #ifdef CONFIG_MMU_GATHER_PAGE_SIZE |
| tlb->page_size = 0; |
| #endif |
| |
| __tlb_reset_range(tlb); |
| inc_tlb_flush_pending(tlb->mm); |
| } |
| |
| /** |
| * tlb_finish_mmu - finish an mmu_gather structure |
| * @tlb: the mmu_gather structure to finish |
| * @start: start of the region that will be removed from the page-table |
| * @end: end of the region that will be removed from the page-table |
| * |
| * Called at the end of the shootdown operation to free up any resources that |
| * were required. |
| */ |
| void tlb_finish_mmu(struct mmu_gather *tlb, |
| unsigned long start, unsigned long end) |
| { |
| /* |
| * If there are parallel threads are doing PTE changes on same range |
| * under non-exclusive lock (e.g., mmap_lock read-side) but defer TLB |
| * flush by batching, one thread may end up seeing inconsistent PTEs |
| * and result in having stale TLB entries. So flush TLB forcefully |
| * if we detect parallel PTE batching threads. |
| * |
| * However, some syscalls, e.g. munmap(), may free page tables, this |
| * needs force flush everything in the given range. Otherwise this |
| * may result in having stale TLB entries for some architectures, |
| * e.g. aarch64, that could specify flush what level TLB. |
| */ |
| if (mm_tlb_flush_nested(tlb->mm)) { |
| /* |
| * The aarch64 yields better performance with fullmm by |
| * avoiding multiple CPUs spamming TLBI messages at the |
| * same time. |
| * |
| * On x86 non-fullmm doesn't yield significant difference |
| * against fullmm. |
| */ |
| tlb->fullmm = 1; |
| __tlb_reset_range(tlb); |
| tlb->freed_tables = 1; |
| } |
| |
| tlb_flush_mmu(tlb); |
| |
| #ifndef CONFIG_MMU_GATHER_NO_GATHER |
| tlb_batch_list_free(tlb); |
| #endif |
| dec_tlb_flush_pending(tlb->mm); |
| } |