1/*
  2 * Copyright IBM Corporation, 2013
  3 * Author Aneesh Kumar K.V <aneesh.kumar@linux.vnet.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
 21int __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	rflags = htab_convert_pte_flags(new_pmd);
 55
 56#if 0
 57	if (!cpu_has_feature(CPU_FTR_COHERENT_ICACHE)) {
 58
 59		/*
 60		 * No CPU has hugepages but lacks no execute, so we
 61		 * don't need to worry about that case
 62		 */
 63		rflags = hash_page_do_lazy_icache(rflags, __pte(old_pte), trap);
 64	}
 65#endif
 66	/*
 67	 * Find the slot index details for this ea, using base page size.
 68	 */
 69	shift = mmu_psize_defs[psize].shift;
 70	index = (ea & ~HPAGE_PMD_MASK) >> shift;
 71	BUG_ON(index >= PTE_FRAG_SIZE);
 72
 73	vpn = hpt_vpn(ea, vsid, ssize);
 74	hpte_slot_array = get_hpte_slot_array(pmdp);
 75	if (psize == MMU_PAGE_4K) {
 76		/*
 77		 * invalidate the old hpte entry if we have that mapped via 64K
 78		 * base page size. This is because demote_segment won't flush
 79		 * hash page table entries.
 80		 */
 81		if ((old_pmd & H_PAGE_HASHPTE) && !(old_pmd & H_PAGE_COMBO)) {
 82			flush_hash_hugepage(vsid, ea, pmdp, MMU_PAGE_64K,
 83					    ssize, flags);
 84			/*
 85			 * With THP, we also clear the slot information with
 86			 * respect to all the 64K hash pte mapping the 16MB
 87			 * page. They are all invalid now. This make sure we
 88			 * don't find the slot valid when we fault with 4k
 89			 * base page size.
 90			 *
 91			 */
 92			memset(hpte_slot_array, 0, PTE_FRAG_SIZE);
 93		}
 94	}
 95
 96	valid = hpte_valid(hpte_slot_array, index);
 97	if (valid) {
 98		/* update the hpte bits */
 99		hash = hpt_hash(vpn, shift, ssize);
100		hidx =  hpte_hash_index(hpte_slot_array, index);
101		if (hidx & _PTEIDX_SECONDARY)
102			hash = ~hash;
103		slot = (hash & htab_hash_mask) * HPTES_PER_GROUP;
104		slot += hidx & _PTEIDX_GROUP_IX;
105
106		ret = mmu_hash_ops.hpte_updatepp(slot, rflags, vpn,
107						 psize, lpsize, ssize, flags);
108		/*
109		 * We failed to update, try to insert a new entry.
110		 */
111		if (ret == -1) {
112			/*
113			 * large pte is marked busy, so we can be sure
114			 * nobody is looking at hpte_slot_array. hence we can
115			 * safely update this here.
116			 */
117			valid = 0;
118			hpte_slot_array[index] = 0;
119		}
120	}
121
122	if (!valid) {
123		unsigned long hpte_group;
124
125		hash = hpt_hash(vpn, shift, ssize);
126		/* insert new entry */
127		pa = pmd_pfn(__pmd(old_pmd)) << PAGE_SHIFT;
128		new_pmd |= H_PAGE_HASHPTE;
129
130repeat:
131		hpte_group = ((hash & htab_hash_mask) * HPTES_PER_GROUP) & ~0x7UL;
132
133		/* Insert into the hash table, primary slot */
134		slot = mmu_hash_ops.hpte_insert(hpte_group, vpn, pa, rflags, 0,
135						psize, lpsize, ssize);
136		/*
137		 * Primary is full, try the secondary
138		 */
139		if (unlikely(slot == -1)) {
140			hpte_group = ((~hash & htab_hash_mask) *
141				      HPTES_PER_GROUP) & ~0x7UL;
142			slot = mmu_hash_ops.hpte_insert(hpte_group, vpn, pa,
143							rflags,
144							HPTE_V_SECONDARY,
145							psize, lpsize, ssize);
146			if (slot == -1) {
147				if (mftb() & 0x1)
148					hpte_group = ((hash & htab_hash_mask) *
149						      HPTES_PER_GROUP) & ~0x7UL;
150
151				mmu_hash_ops.hpte_remove(hpte_group);
152				goto repeat;
153			}
154		}
155		/*
156		 * Hypervisor failure. Restore old pmd and return -1
157		 * similar to __hash_page_*
158		 */
159		if (unlikely(slot == -2)) {
160			*pmdp = __pmd(old_pmd);
161			hash_failure_debug(ea, access, vsid, trap, ssize,
162					   psize, lpsize, old_pmd);
163			return -1;
164		}
165		/*
166		 * large pte is marked busy, so we can be sure
167		 * nobody is looking at hpte_slot_array. hence we can
168		 * safely update this here.
169		 */
170		mark_hpte_slot_valid(hpte_slot_array, index, slot);
171	}
172	/*
173	 * Mark the pte with H_PAGE_COMBO, if we are trying to hash it with
174	 * base page size 4k.
175	 */
176	if (psize == MMU_PAGE_4K)
177		new_pmd |= H_PAGE_COMBO;
178	/*
179	 * The hpte valid is stored in the pgtable whose address is in the
180	 * second half of the PMD. Order this against clearing of the busy bit in
181	 * huge pmd.
182	 */
183	smp_wmb();
184	*pmdp = __pmd(new_pmd & ~H_PAGE_BUSY);
185	return 0;
186}