355 lines
8.5 KiB
C
355 lines
8.5 KiB
C
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/*
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* Page table allocation functions
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*
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* Copyright IBM Corp. 2016
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* Author(s): Martin Schwidefsky <schwidefsky@de.ibm.com>
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*/
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#include <linux/mm.h>
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#include <linux/sysctl.h>
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#include <asm/mmu_context.h>
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#include <asm/pgalloc.h>
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#include <asm/gmap.h>
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#include <asm/tlb.h>
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#include <asm/tlbflush.h>
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#ifdef CONFIG_PGSTE
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static int page_table_allocate_pgste_min = 0;
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static int page_table_allocate_pgste_max = 1;
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int page_table_allocate_pgste = 0;
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EXPORT_SYMBOL(page_table_allocate_pgste);
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static struct ctl_table page_table_sysctl[] = {
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{
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.procname = "allocate_pgste",
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.data = &page_table_allocate_pgste,
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.maxlen = sizeof(int),
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.mode = S_IRUGO | S_IWUSR,
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.proc_handler = proc_dointvec,
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.extra1 = &page_table_allocate_pgste_min,
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.extra2 = &page_table_allocate_pgste_max,
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},
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{ }
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};
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static struct ctl_table page_table_sysctl_dir[] = {
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{
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.procname = "vm",
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.maxlen = 0,
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.mode = 0555,
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.child = page_table_sysctl,
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},
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{ }
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};
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static int __init page_table_register_sysctl(void)
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{
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return register_sysctl_table(page_table_sysctl_dir) ? 0 : -ENOMEM;
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}
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__initcall(page_table_register_sysctl);
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#endif /* CONFIG_PGSTE */
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unsigned long *crst_table_alloc(struct mm_struct *mm)
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{
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struct page *page = alloc_pages(GFP_KERNEL, 2);
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if (!page)
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return NULL;
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return (unsigned long *) page_to_phys(page);
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}
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void crst_table_free(struct mm_struct *mm, unsigned long *table)
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{
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free_pages((unsigned long) table, 2);
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}
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static void __crst_table_upgrade(void *arg)
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{
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struct mm_struct *mm = arg;
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if (current->active_mm == mm) {
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clear_user_asce();
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set_user_asce(mm);
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}
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__tlb_flush_local();
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}
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int crst_table_upgrade(struct mm_struct *mm)
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{
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unsigned long *table, *pgd;
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/* upgrade should only happen from 3 to 4 levels */
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BUG_ON(mm->context.asce_limit != (1UL << 42));
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table = crst_table_alloc(mm);
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if (!table)
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return -ENOMEM;
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spin_lock_bh(&mm->page_table_lock);
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pgd = (unsigned long *) mm->pgd;
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crst_table_init(table, _REGION2_ENTRY_EMPTY);
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pgd_populate(mm, (pgd_t *) table, (pud_t *) pgd);
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mm->pgd = (pgd_t *) table;
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mm->context.asce_limit = 1UL << 53;
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mm->context.asce = __pa(mm->pgd) | _ASCE_TABLE_LENGTH |
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_ASCE_USER_BITS | _ASCE_TYPE_REGION2;
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mm->task_size = mm->context.asce_limit;
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spin_unlock_bh(&mm->page_table_lock);
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on_each_cpu(__crst_table_upgrade, mm, 0);
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return 0;
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}
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void crst_table_downgrade(struct mm_struct *mm)
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{
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pgd_t *pgd;
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/* downgrade should only happen from 3 to 2 levels (compat only) */
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BUG_ON(mm->context.asce_limit != (1UL << 42));
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if (current->active_mm == mm) {
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clear_user_asce();
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__tlb_flush_mm(mm);
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}
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pgd = mm->pgd;
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mm->pgd = (pgd_t *) (pgd_val(*pgd) & _REGION_ENTRY_ORIGIN);
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mm->context.asce_limit = 1UL << 31;
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mm->context.asce = __pa(mm->pgd) | _ASCE_TABLE_LENGTH |
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_ASCE_USER_BITS | _ASCE_TYPE_SEGMENT;
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mm->task_size = mm->context.asce_limit;
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crst_table_free(mm, (unsigned long *) pgd);
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if (current->active_mm == mm)
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set_user_asce(mm);
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}
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static inline unsigned int atomic_xor_bits(atomic_t *v, unsigned int bits)
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{
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unsigned int old, new;
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do {
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old = atomic_read(v);
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new = old ^ bits;
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} while (atomic_cmpxchg(v, old, new) != old);
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return new;
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}
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#ifdef CONFIG_PGSTE
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struct page *page_table_alloc_pgste(struct mm_struct *mm)
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{
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struct page *page;
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unsigned long *table;
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page = alloc_page(GFP_KERNEL|__GFP_REPEAT);
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if (page) {
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table = (unsigned long *) page_to_phys(page);
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clear_table(table, _PAGE_INVALID, PAGE_SIZE/2);
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clear_table(table + PTRS_PER_PTE, 0, PAGE_SIZE/2);
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}
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return page;
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}
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void page_table_free_pgste(struct page *page)
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{
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__free_page(page);
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}
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#endif /* CONFIG_PGSTE */
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/*
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* page table entry allocation/free routines.
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*/
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unsigned long *page_table_alloc(struct mm_struct *mm)
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{
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unsigned long *table;
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struct page *page;
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unsigned int mask, bit;
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/* Try to get a fragment of a 4K page as a 2K page table */
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if (!mm_alloc_pgste(mm)) {
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table = NULL;
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spin_lock_bh(&mm->context.pgtable_lock);
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if (!list_empty(&mm->context.pgtable_list)) {
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page = list_first_entry(&mm->context.pgtable_list,
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struct page, lru);
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mask = atomic_read(&page->_mapcount);
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mask = (mask | (mask >> 4)) & 3;
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if (mask != 3) {
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table = (unsigned long *) page_to_phys(page);
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bit = mask & 1; /* =1 -> second 2K */
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if (bit)
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table += PTRS_PER_PTE;
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atomic_xor_bits(&page->_mapcount, 1U << bit);
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list_del(&page->lru);
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}
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}
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spin_unlock_bh(&mm->context.pgtable_lock);
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if (table)
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return table;
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}
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/* Allocate a fresh page */
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page = alloc_page(GFP_KERNEL);
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if (!page)
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return NULL;
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if (!pgtable_page_ctor(page)) {
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__free_page(page);
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return NULL;
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}
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/* Initialize page table */
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table = (unsigned long *) page_to_phys(page);
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if (mm_alloc_pgste(mm)) {
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/* Return 4K page table with PGSTEs */
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atomic_set(&page->_mapcount, 3);
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clear_table(table, _PAGE_INVALID, PAGE_SIZE/2);
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clear_table(table + PTRS_PER_PTE, 0, PAGE_SIZE/2);
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} else {
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/* Return the first 2K fragment of the page */
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atomic_set(&page->_mapcount, 1);
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clear_table(table, _PAGE_INVALID, PAGE_SIZE);
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spin_lock_bh(&mm->context.pgtable_lock);
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list_add(&page->lru, &mm->context.pgtable_list);
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spin_unlock_bh(&mm->context.pgtable_lock);
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}
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return table;
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}
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void page_table_free(struct mm_struct *mm, unsigned long *table)
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{
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struct page *page;
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unsigned int bit, mask;
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page = pfn_to_page(__pa(table) >> PAGE_SHIFT);
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if (!mm_alloc_pgste(mm)) {
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/* Free 2K page table fragment of a 4K page */
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bit = (__pa(table) & ~PAGE_MASK)/(PTRS_PER_PTE*sizeof(pte_t));
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spin_lock_bh(&mm->context.pgtable_lock);
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mask = atomic_xor_bits(&page->_mapcount, 1U << bit);
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if (mask & 3)
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list_add(&page->lru, &mm->context.pgtable_list);
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else
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list_del(&page->lru);
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spin_unlock_bh(&mm->context.pgtable_lock);
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if (mask != 0)
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return;
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}
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pgtable_page_dtor(page);
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atomic_set(&page->_mapcount, -1);
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__free_page(page);
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}
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void page_table_free_rcu(struct mmu_gather *tlb, unsigned long *table,
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unsigned long vmaddr)
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{
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struct mm_struct *mm;
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struct page *page;
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unsigned int bit, mask;
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mm = tlb->mm;
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page = pfn_to_page(__pa(table) >> PAGE_SHIFT);
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if (mm_alloc_pgste(mm)) {
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gmap_unlink(mm, table, vmaddr);
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table = (unsigned long *) (__pa(table) | 3);
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tlb_remove_table(tlb, table);
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return;
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}
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bit = (__pa(table) & ~PAGE_MASK) / (PTRS_PER_PTE*sizeof(pte_t));
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spin_lock_bh(&mm->context.pgtable_lock);
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mask = atomic_xor_bits(&page->_mapcount, 0x11U << bit);
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if (mask & 3)
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list_add_tail(&page->lru, &mm->context.pgtable_list);
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else
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list_del(&page->lru);
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spin_unlock_bh(&mm->context.pgtable_lock);
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table = (unsigned long *) (__pa(table) | (1U << bit));
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tlb_remove_table(tlb, table);
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}
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static void __tlb_remove_table(void *_table)
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{
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unsigned int mask = (unsigned long) _table & 3;
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void *table = (void *)((unsigned long) _table ^ mask);
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struct page *page = pfn_to_page(__pa(table) >> PAGE_SHIFT);
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switch (mask) {
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case 0: /* pmd or pud */
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free_pages((unsigned long) table, 2);
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break;
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case 1: /* lower 2K of a 4K page table */
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case 2: /* higher 2K of a 4K page table */
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if (atomic_xor_bits(&page->_mapcount, mask << 4) != 0)
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break;
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/* fallthrough */
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case 3: /* 4K page table with pgstes */
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pgtable_page_dtor(page);
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atomic_set(&page->_mapcount, -1);
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__free_page(page);
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break;
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}
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}
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static void tlb_remove_table_smp_sync(void *arg)
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{
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/* Simply deliver the interrupt */
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}
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static void tlb_remove_table_one(void *table)
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{
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/*
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* This isn't an RCU grace period and hence the page-tables cannot be
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* assumed to be actually RCU-freed.
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*
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* It is however sufficient for software page-table walkers that rely
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* on IRQ disabling. See the comment near struct mmu_table_batch.
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*/
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smp_call_function(tlb_remove_table_smp_sync, NULL, 1);
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__tlb_remove_table(table);
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}
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static void tlb_remove_table_rcu(struct rcu_head *head)
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{
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struct mmu_table_batch *batch;
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int i;
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batch = container_of(head, struct mmu_table_batch, rcu);
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for (i = 0; i < batch->nr; i++)
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__tlb_remove_table(batch->tables[i]);
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free_page((unsigned long)batch);
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}
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void tlb_table_flush(struct mmu_gather *tlb)
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{
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struct mmu_table_batch **batch = &tlb->batch;
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if (*batch) {
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call_rcu_sched(&(*batch)->rcu, tlb_remove_table_rcu);
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*batch = NULL;
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}
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}
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void tlb_remove_table(struct mmu_gather *tlb, void *table)
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{
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struct mmu_table_batch **batch = &tlb->batch;
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tlb->mm->context.flush_mm = 1;
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if (*batch == NULL) {
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*batch = (struct mmu_table_batch *)
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__get_free_page(GFP_NOWAIT | __GFP_NOWARN);
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if (*batch == NULL) {
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__tlb_flush_mm_lazy(tlb->mm);
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tlb_remove_table_one(table);
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return;
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}
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(*batch)->nr = 0;
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}
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(*batch)->tables[(*batch)->nr++] = table;
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if ((*batch)->nr == MAX_TABLE_BATCH)
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tlb_flush_mmu(tlb);
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}
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