1 /* 2 * Copyright IBM Corporation, 2013 3 * Author Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com> 4 * 5 * This program is free software; you can redistribute it and/or modify it 6 * under the terms of version 2.1 of the GNU Lesser General Public License 7 * as published by the Free Software Foundation. 8 * 9 * This program is distributed in the hope that it would be useful, but 10 * WITHOUT ANY WARRANTY; without even the implied warranty of 11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. 12 * 13 */ 14 15 /* 16 * PPC64 THP Support for hash based MMUs 17 */ 18 #include <linux/mm.h> 19 #include <asm/machdep.h> 20 21 int __hash_page_thp(unsigned long ea, unsigned long access, unsigned long vsid, 22 pmd_t *pmdp, unsigned long trap, unsigned long flags, 23 int ssize, unsigned int psize) 24 { 25 unsigned int index, valid; 26 unsigned char *hpte_slot_array; 27 unsigned long rflags, pa, hidx; 28 unsigned long old_pmd, new_pmd; 29 int ret, lpsize = MMU_PAGE_16M; 30 unsigned long vpn, hash, shift, slot; 31 32 /* 33 * atomically mark the linux large page PMD busy and dirty 34 */ 35 do { 36 pmd_t pmd = READ_ONCE(*pmdp); 37 38 old_pmd = pmd_val(pmd); 39 /* If PMD busy, retry the access */ 40 if (unlikely(old_pmd & H_PAGE_BUSY)) 41 return 0; 42 /* If PMD permissions don't match, take page fault */ 43 if (unlikely(!check_pte_access(access, old_pmd))) 44 return 1; 45 /* 46 * Try to lock the PTE, add ACCESSED and DIRTY if it was 47 * a write access 48 */ 49 new_pmd = old_pmd | H_PAGE_BUSY | _PAGE_ACCESSED; 50 if (access & _PAGE_WRITE) 51 new_pmd |= _PAGE_DIRTY; 52 } while (!pmd_xchg(pmdp, __pmd(old_pmd), __pmd(new_pmd))); 53 54 /* 55 * Make sure this is thp or devmap entry 56 */ 57 if (!(old_pmd & (H_PAGE_THP_HUGE | _PAGE_DEVMAP))) 58 return 0; 59 60 rflags = htab_convert_pte_flags(new_pmd, flags); 61 62 /* 63 * THPs are only supported on platforms that can do mixed page size 64 * segments (MPSS) and all such platforms have coherent icache. Hence we 65 * don't need to do lazy icache flush (hash_page_do_lazy_icache()) on 66 * noexecute fault. 67 */ 68 69 /* 70 * Find the slot index details for this ea, using base page size. 71 */ 72 shift = mmu_psize_defs[psize].shift; 73 index = (ea & ~HPAGE_PMD_MASK) >> shift; 74 BUG_ON(index >= PTE_FRAG_SIZE); 75 76 vpn = hpt_vpn(ea, vsid, ssize); 77 hpte_slot_array = get_hpte_slot_array(pmdp); 78 if (psize == MMU_PAGE_4K) { 79 /* 80 * invalidate the old hpte entry if we have that mapped via 64K 81 * base page size. This is because demote_segment won't flush 82 * hash page table entries. 83 */ 84 if ((old_pmd & H_PAGE_HASHPTE) && !(old_pmd & H_PAGE_COMBO)) { 85 flush_hash_hugepage(vsid, ea, pmdp, MMU_PAGE_64K, 86 ssize, flags); 87 /* 88 * With THP, we also clear the slot information with 89 * respect to all the 64K hash pte mapping the 16MB 90 * page. They are all invalid now. This make sure we 91 * don't find the slot valid when we fault with 4k 92 * base page size. 93 * 94 */ 95 memset(hpte_slot_array, 0, PTE_FRAG_SIZE); 96 } 97 } 98 99 valid = hpte_valid(hpte_slot_array, index); 100 if (valid) { 101 /* update the hpte bits */ 102 hash = hpt_hash(vpn, shift, ssize); 103 hidx = hpte_hash_index(hpte_slot_array, index); 104 if (hidx & _PTEIDX_SECONDARY) 105 hash = ~hash; 106 slot = (hash & htab_hash_mask) * HPTES_PER_GROUP; 107 slot += hidx & _PTEIDX_GROUP_IX; 108 109 ret = mmu_hash_ops.hpte_updatepp(slot, rflags, vpn, 110 psize, lpsize, ssize, flags); 111 /* 112 * We failed to update, try to insert a new entry. 113 */ 114 if (ret == -1) { 115 /* 116 * large pte is marked busy, so we can be sure 117 * nobody is looking at hpte_slot_array. hence we can 118 * safely update this here. 119 */ 120 valid = 0; 121 hpte_slot_array[index] = 0; 122 } 123 } 124 125 if (!valid) { 126 unsigned long hpte_group; 127 128 hash = hpt_hash(vpn, shift, ssize); 129 /* insert new entry */ 130 pa = pmd_pfn(__pmd(old_pmd)) << PAGE_SHIFT; 131 new_pmd |= H_PAGE_HASHPTE; 132 133 repeat: 134 hpte_group = (hash & htab_hash_mask) * HPTES_PER_GROUP; 135 136 /* Insert into the hash table, primary slot */ 137 slot = mmu_hash_ops.hpte_insert(hpte_group, vpn, pa, rflags, 0, 138 psize, lpsize, ssize); 139 /* 140 * Primary is full, try the secondary 141 */ 142 if (unlikely(slot == -1)) { 143 hpte_group = (~hash & htab_hash_mask) * HPTES_PER_GROUP; 144 slot = mmu_hash_ops.hpte_insert(hpte_group, vpn, pa, 145 rflags, 146 HPTE_V_SECONDARY, 147 psize, lpsize, ssize); 148 if (slot == -1) { 149 if (mftb() & 0x1) 150 hpte_group = (hash & htab_hash_mask) * 151 HPTES_PER_GROUP; 152 153 mmu_hash_ops.hpte_remove(hpte_group); 154 goto repeat; 155 } 156 } 157 /* 158 * Hypervisor failure. Restore old pmd and return -1 159 * similar to __hash_page_* 160 */ 161 if (unlikely(slot == -2)) { 162 *pmdp = __pmd(old_pmd); 163 hash_failure_debug(ea, access, vsid, trap, ssize, 164 psize, lpsize, old_pmd); 165 return -1; 166 } 167 /* 168 * large pte is marked busy, so we can be sure 169 * nobody is looking at hpte_slot_array. hence we can 170 * safely update this here. 171 */ 172 mark_hpte_slot_valid(hpte_slot_array, index, slot); 173 } 174 /* 175 * Mark the pte with H_PAGE_COMBO, if we are trying to hash it with 176 * base page size 4k. 177 */ 178 if (psize == MMU_PAGE_4K) 179 new_pmd |= H_PAGE_COMBO; 180 /* 181 * The hpte valid is stored in the pgtable whose address is in the 182 * second half of the PMD. Order this against clearing of the busy bit in 183 * huge pmd. 184 */ 185 smp_wmb(); 186 *pmdp = __pmd(new_pmd & ~H_PAGE_BUSY); 187 return 0; 188 } 189