1/*
2 * Copyright IBM Corporation, 2015
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 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#include <linux/mm.h>
16#include <asm/machdep.h>
17#include <asm/mmu.h>
18
19int __hash_page_4K(unsigned long ea, unsigned long access, unsigned long vsid,
20		   pte_t *ptep, unsigned long trap, unsigned long flags,
21		   int ssize, int subpg_prot)
22{
23	real_pte_t rpte;
24	unsigned long hpte_group;
25	unsigned long rflags, pa;
26	unsigned long old_pte, new_pte;
27	unsigned long vpn, hash, slot;
28	unsigned long shift = mmu_psize_defs[MMU_PAGE_4K].shift;
29
30	/*
31	 * atomically mark the linux large page PTE busy and dirty
32	 */
33	do {
34		pte_t pte = READ_ONCE(*ptep);
35
36		old_pte = pte_val(pte);
37		/* If PTE busy, retry the access */
38		if (unlikely(old_pte & H_PAGE_BUSY))
39			return 0;
40		/* If PTE permissions don't match, take page fault */
41		if (unlikely(!check_pte_access(access, old_pte)))
42			return 1;
43		/*
44		 * Try to lock the PTE, add ACCESSED and DIRTY if it was
45		 * a write access. Since this is 4K insert of 64K page size
46		 * also add H_PAGE_COMBO
47		 */
48		new_pte = old_pte | H_PAGE_BUSY | _PAGE_ACCESSED;
49		if (access & _PAGE_WRITE)
50			new_pte |= _PAGE_DIRTY;
51	} while (!pte_xchg(ptep, __pte(old_pte), __pte(new_pte)));
52
53	/*
54	 * PP bits. _PAGE_USER is already PP bit 0x2, so we only
55	 * need to add in 0x1 if it's a read-only user page
56	 */
57	rflags = htab_convert_pte_flags(new_pte);
58	rpte = __real_pte(__pte(old_pte), ptep, PTRS_PER_PTE);
59
60	if (cpu_has_feature(CPU_FTR_NOEXECUTE) &&
61	    !cpu_has_feature(CPU_FTR_COHERENT_ICACHE))
62		rflags = hash_page_do_lazy_icache(rflags, __pte(old_pte), trap);
63
64	vpn  = hpt_vpn(ea, vsid, ssize);
65	if (unlikely(old_pte & H_PAGE_HASHPTE)) {
66		/*
67		 * There MIGHT be an HPTE for this pte
68		 */
69		unsigned long gslot = pte_get_hash_gslot(vpn, shift, ssize,
70							 rpte, 0);
71
72		if (mmu_hash_ops.hpte_updatepp(gslot, rflags, vpn, MMU_PAGE_4K,
73					       MMU_PAGE_4K, ssize, flags) == -1)
74			old_pte &= ~_PAGE_HPTEFLAGS;
75	}
76
77	if (likely(!(old_pte & H_PAGE_HASHPTE))) {
78
79		pa = pte_pfn(__pte(old_pte)) << PAGE_SHIFT;
80		hash = hpt_hash(vpn, shift, ssize);
81
82repeat:
83		hpte_group = (hash & htab_hash_mask) * HPTES_PER_GROUP;
84
85		/* Insert into the hash table, primary slot */
86		slot = mmu_hash_ops.hpte_insert(hpte_group, vpn, pa, rflags, 0,
87						MMU_PAGE_4K, MMU_PAGE_4K, ssize);
88		/*
89		 * Primary is full, try the secondary
90		 */
91		if (unlikely(slot == -1)) {
92			hpte_group = (~hash & htab_hash_mask) * HPTES_PER_GROUP;
93			slot = mmu_hash_ops.hpte_insert(hpte_group, vpn, pa,
94							rflags,
95							HPTE_V_SECONDARY,
96							MMU_PAGE_4K,
97							MMU_PAGE_4K, ssize);
98			if (slot == -1) {
99				if (mftb() & 0x1)
100					hpte_group = (hash & htab_hash_mask) *
101							HPTES_PER_GROUP;
102				mmu_hash_ops.hpte_remove(hpte_group);
103				/*
104				 * FIXME!! Should be try the group from which we removed ?
105				 */
106				goto repeat;
107			}
108		}
109		/*
110		 * Hypervisor failure. Restore old pte and return -1
111		 * similar to __hash_page_*
112		 */
113		if (unlikely(slot == -2)) {
114			*ptep = __pte(old_pte);
115			hash_failure_debug(ea, access, vsid, trap, ssize,
116					   MMU_PAGE_4K, MMU_PAGE_4K, old_pte);
117			return -1;
118		}
119		new_pte = (new_pte & ~_PAGE_HPTEFLAGS) | H_PAGE_HASHPTE;
120		new_pte |= pte_set_hidx(ptep, rpte, 0, slot, PTRS_PER_PTE);
121	}
122	*ptep = __pte(new_pte & ~H_PAGE_BUSY);
123	return 0;
124}
125