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
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