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
19#include "internal.h"
20
21int __hash_page_4K(unsigned long ea, unsigned long access, unsigned long vsid,
22		   pte_t *ptep, unsigned long trap, unsigned long flags,
23		   int ssize, int subpg_prot)
24{
25	real_pte_t rpte;
26	unsigned long hpte_group;
27	unsigned long rflags, pa;
28	unsigned long old_pte, new_pte;
29	unsigned long vpn, hash, slot;
30	unsigned long shift = mmu_psize_defs[MMU_PAGE_4K].shift;
31
32	/*
33	 * atomically mark the linux large page PTE busy and dirty
34	 */
35	do {
36		pte_t pte = READ_ONCE(*ptep);
37
38		old_pte = pte_val(pte);
39		/* If PTE busy, retry the access */
40		if (unlikely(old_pte & H_PAGE_BUSY))
41			return 0;
42		/* If PTE permissions don't match, take page fault */
43		if (unlikely(!check_pte_access(access, old_pte)))
44			return 1;
45		/*
46		 * Try to lock the PTE, add ACCESSED and DIRTY if it was
47		 * a write access. Since this is 4K insert of 64K page size
48		 * also add H_PAGE_COMBO
49		 */
50		new_pte = old_pte | H_PAGE_BUSY | _PAGE_ACCESSED;
51		if (access & _PAGE_WRITE)
52			new_pte |= _PAGE_DIRTY;
53	} while (!pte_xchg(ptep, __pte(old_pte), __pte(new_pte)));
54
55	/*
56	 * PP bits. _PAGE_USER is already PP bit 0x2, so we only
57	 * need to add in 0x1 if it's a read-only user page
58	 */
59	rflags = htab_convert_pte_flags(new_pte, flags);
60	rpte = __real_pte(__pte(old_pte), ptep, PTRS_PER_PTE);
61
62	if (cpu_has_feature(CPU_FTR_NOEXECUTE) &&
63	    !cpu_has_feature(CPU_FTR_COHERENT_ICACHE))
64		rflags = hash_page_do_lazy_icache(rflags, __pte(old_pte), trap);
65
66	vpn  = hpt_vpn(ea, vsid, ssize);
67	if (unlikely(old_pte & H_PAGE_HASHPTE)) {
68		/*
69		 * There MIGHT be an HPTE for this pte
70		 */
71		unsigned long gslot = pte_get_hash_gslot(vpn, shift, ssize,
72							 rpte, 0);
73
74		if (mmu_hash_ops.hpte_updatepp(gslot, rflags, vpn, MMU_PAGE_4K,
75					       MMU_PAGE_4K, ssize, flags) == -1)
76			old_pte &= ~_PAGE_HPTEFLAGS;
77	}
78
79	if (likely(!(old_pte & H_PAGE_HASHPTE))) {
80
81		pa = pte_pfn(__pte(old_pte)) << PAGE_SHIFT;
82		hash = hpt_hash(vpn, shift, ssize);
83
84repeat:
85		hpte_group = (hash & htab_hash_mask) * HPTES_PER_GROUP;
86
87		/* Insert into the hash table, primary slot */
88		slot = mmu_hash_ops.hpte_insert(hpte_group, vpn, pa, rflags, 0,
89						MMU_PAGE_4K, MMU_PAGE_4K, ssize);
90		/*
91		 * Primary is full, try the secondary
92		 */
93		if (unlikely(slot == -1)) {
94			hpte_group = (~hash & htab_hash_mask) * HPTES_PER_GROUP;
95			slot = mmu_hash_ops.hpte_insert(hpte_group, vpn, pa,
96							rflags,
97							HPTE_V_SECONDARY,
98							MMU_PAGE_4K,
99							MMU_PAGE_4K, ssize);
100			if (slot == -1) {
101				if (mftb() & 0x1)
102					hpte_group = (hash & htab_hash_mask) *
103							HPTES_PER_GROUP;
104				mmu_hash_ops.hpte_remove(hpte_group);
105				/*
106				 * FIXME!! Should be try the group from which we removed ?
107				 */
108				goto repeat;
109			}
110		}
111		/*
112		 * Hypervisor failure. Restore old pte and return -1
113		 * similar to __hash_page_*
114		 */
115		if (unlikely(slot == -2)) {
116			*ptep = __pte(old_pte);
117			hash_failure_debug(ea, access, vsid, trap, ssize,
118					   MMU_PAGE_4K, MMU_PAGE_4K, old_pte);
119			return -1;
120		}
121		new_pte = (new_pte & ~_PAGE_HPTEFLAGS) | H_PAGE_HASHPTE;
122		new_pte |= pte_set_hidx(ptep, rpte, 0, slot, PTRS_PER_PTE);
123
124		if (stress_hpt())
125			hpt_do_stress(ea, hpte_group);
126	}
127	*ptep = __pte(new_pte & ~H_PAGE_BUSY);
128	return 0;
129}
130