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 
21 /*
22  * Return true, if the entry has a slot value which
23  * the software considers as invalid.
24  */
25 static inline bool hpte_soft_invalid(unsigned long hidx)
26 {
27 	return ((hidx & 0xfUL) == 0xfUL);
28 }
29 
30 /*
31  * index from 0 - 15
32  */
33 bool __rpte_sub_valid(real_pte_t rpte, unsigned long index)
34 {
35 	return !(hpte_soft_invalid(__rpte_to_hidx(rpte, index)));
36 }
37 
38 int __hash_page_4K(unsigned long ea, unsigned long access, unsigned long vsid,
39 		   pte_t *ptep, unsigned long trap, unsigned long flags,
40 		   int ssize, int subpg_prot)
41 {
42 	real_pte_t rpte;
43 	unsigned long hpte_group;
44 	unsigned int subpg_index;
45 	unsigned long rflags, pa;
46 	unsigned long old_pte, new_pte, subpg_pte;
47 	unsigned long vpn, hash, slot, gslot;
48 	unsigned long shift = mmu_psize_defs[MMU_PAGE_4K].shift;
49 
50 	/*
51 	 * atomically mark the linux large page PTE busy and dirty
52 	 */
53 	do {
54 		pte_t pte = READ_ONCE(*ptep);
55 
56 		old_pte = pte_val(pte);
57 		/* If PTE busy, retry the access */
58 		if (unlikely(old_pte & H_PAGE_BUSY))
59 			return 0;
60 		/* If PTE permissions don't match, take page fault */
61 		if (unlikely(!check_pte_access(access, old_pte)))
62 			return 1;
63 		/*
64 		 * Try to lock the PTE, add ACCESSED and DIRTY if it was
65 		 * a write access. Since this is 4K insert of 64K page size
66 		 * also add H_PAGE_COMBO
67 		 */
68 		new_pte = old_pte | H_PAGE_BUSY | _PAGE_ACCESSED | H_PAGE_COMBO;
69 		if (access & _PAGE_WRITE)
70 			new_pte |= _PAGE_DIRTY;
71 	} while (!pte_xchg(ptep, __pte(old_pte), __pte(new_pte)));
72 
73 	/*
74 	 * Handle the subpage protection bits
75 	 */
76 	subpg_pte = new_pte & ~subpg_prot;
77 	rflags = htab_convert_pte_flags(subpg_pte, flags);
78 
79 	if (cpu_has_feature(CPU_FTR_NOEXECUTE) &&
80 	    !cpu_has_feature(CPU_FTR_COHERENT_ICACHE)) {
81 
82 		/*
83 		 * No CPU has hugepages but lacks no execute, so we
84 		 * don't need to worry about that case
85 		 */
86 		rflags = hash_page_do_lazy_icache(rflags, __pte(old_pte), trap);
87 	}
88 
89 	subpg_index = (ea & (PAGE_SIZE - 1)) >> shift;
90 	vpn  = hpt_vpn(ea, vsid, ssize);
91 	rpte = __real_pte(__pte(old_pte), ptep, PTRS_PER_PTE);
92 	/*
93 	 *None of the sub 4k page is hashed
94 	 */
95 	if (!(old_pte & H_PAGE_HASHPTE))
96 		goto htab_insert_hpte;
97 	/*
98 	 * Check if the pte was already inserted into the hash table
99 	 * as a 64k HW page, and invalidate the 64k HPTE if so.
100 	 */
101 	if (!(old_pte & H_PAGE_COMBO)) {
102 		flush_hash_page(vpn, rpte, MMU_PAGE_64K, ssize, flags);
103 		/*
104 		 * clear the old slot details from the old and new pte.
105 		 * On hash insert failure we use old pte value and we don't
106 		 * want slot information there if we have a insert failure.
107 		 */
108 		old_pte &= ~H_PAGE_HASHPTE;
109 		new_pte &= ~H_PAGE_HASHPTE;
110 		goto htab_insert_hpte;
111 	}
112 	/*
113 	 * Check for sub page valid and update
114 	 */
115 	if (__rpte_sub_valid(rpte, subpg_index)) {
116 		int ret;
117 
118 		gslot = pte_get_hash_gslot(vpn, shift, ssize, rpte,
119 					   subpg_index);
120 		ret = mmu_hash_ops.hpte_updatepp(gslot, rflags, vpn,
121 						 MMU_PAGE_4K, MMU_PAGE_4K,
122 						 ssize, flags);
123 
124 		/*
125 		 * If we failed because typically the HPTE wasn't really here
126 		 * we try an insertion.
127 		 */
128 		if (ret == -1)
129 			goto htab_insert_hpte;
130 
131 		*ptep = __pte(new_pte & ~H_PAGE_BUSY);
132 		return 0;
133 	}
134 
135 htab_insert_hpte:
136 
137 	/*
138 	 * Initialize all hidx entries to invalid value, the first time
139 	 * the PTE is about to allocate a 4K HPTE.
140 	 */
141 	if (!(old_pte & H_PAGE_COMBO))
142 		rpte.hidx = INVALID_RPTE_HIDX;
143 
144 	/*
145 	 * handle H_PAGE_4K_PFN case
146 	 */
147 	if (old_pte & H_PAGE_4K_PFN) {
148 		/*
149 		 * All the sub 4k page have the same
150 		 * physical address.
151 		 */
152 		pa = pte_pfn(__pte(old_pte)) << HW_PAGE_SHIFT;
153 	} else {
154 		pa = pte_pfn(__pte(old_pte)) << PAGE_SHIFT;
155 		pa += (subpg_index << shift);
156 	}
157 	hash = hpt_hash(vpn, shift, ssize);
158 repeat:
159 	hpte_group = (hash & htab_hash_mask) * HPTES_PER_GROUP;
160 
161 	/* Insert into the hash table, primary slot */
162 	slot = mmu_hash_ops.hpte_insert(hpte_group, vpn, pa, rflags, 0,
163 					MMU_PAGE_4K, MMU_PAGE_4K, ssize);
164 	/*
165 	 * Primary is full, try the secondary
166 	 */
167 	if (unlikely(slot == -1)) {
168 		bool soft_invalid;
169 
170 		hpte_group = (~hash & htab_hash_mask) * HPTES_PER_GROUP;
171 		slot = mmu_hash_ops.hpte_insert(hpte_group, vpn, pa,
172 						rflags, HPTE_V_SECONDARY,
173 						MMU_PAGE_4K, MMU_PAGE_4K,
174 						ssize);
175 
176 		soft_invalid = hpte_soft_invalid(slot);
177 		if (unlikely(soft_invalid)) {
178 			/*
179 			 * We got a valid slot from a hardware point of view.
180 			 * but we cannot use it, because we use this special
181 			 * value; as defined by hpte_soft_invalid(), to track
182 			 * invalid slots. We cannot use it. So invalidate it.
183 			 */
184 			gslot = slot & _PTEIDX_GROUP_IX;
185 			mmu_hash_ops.hpte_invalidate(hpte_group + gslot, vpn,
186 						     MMU_PAGE_4K, MMU_PAGE_4K,
187 						     ssize, 0);
188 		}
189 
190 		if (unlikely(slot == -1 || soft_invalid)) {
191 			/*
192 			 * For soft invalid slot, let's ensure that we release a
193 			 * slot from the primary, with the hope that we will
194 			 * acquire that slot next time we try. This will ensure
195 			 * that we do not get the same soft-invalid slot.
196 			 */
197 			if (soft_invalid || (mftb() & 0x1))
198 				hpte_group = (hash & htab_hash_mask) * HPTES_PER_GROUP;
199 
200 			mmu_hash_ops.hpte_remove(hpte_group);
201 			/*
202 			 * FIXME!! Should be try the group from which we removed ?
203 			 */
204 			goto repeat;
205 		}
206 	}
207 	/*
208 	 * Hypervisor failure. Restore old pte and return -1
209 	 * similar to __hash_page_*
210 	 */
211 	if (unlikely(slot == -2)) {
212 		*ptep = __pte(old_pte);
213 		hash_failure_debug(ea, access, vsid, trap, ssize,
214 				   MMU_PAGE_4K, MMU_PAGE_4K, old_pte);
215 		return -1;
216 	}
217 
218 	new_pte |= pte_set_hidx(ptep, rpte, subpg_index, slot, PTRS_PER_PTE);
219 	new_pte |= H_PAGE_HASHPTE;
220 
221 	if (stress_hpt())
222 		hpt_do_stress(ea, hpte_group);
223 
224 	*ptep = __pte(new_pte & ~H_PAGE_BUSY);
225 	return 0;
226 }
227 
228 int __hash_page_64K(unsigned long ea, unsigned long access,
229 		    unsigned long vsid, pte_t *ptep, unsigned long trap,
230 		    unsigned long flags, int ssize)
231 {
232 	real_pte_t rpte;
233 	unsigned long hpte_group;
234 	unsigned long rflags, pa;
235 	unsigned long old_pte, new_pte;
236 	unsigned long vpn, hash, slot;
237 	unsigned long shift = mmu_psize_defs[MMU_PAGE_64K].shift;
238 
239 	/*
240 	 * atomically mark the linux large page PTE busy and dirty
241 	 */
242 	do {
243 		pte_t pte = READ_ONCE(*ptep);
244 
245 		old_pte = pte_val(pte);
246 		/* If PTE busy, retry the access */
247 		if (unlikely(old_pte & H_PAGE_BUSY))
248 			return 0;
249 		/* If PTE permissions don't match, take page fault */
250 		if (unlikely(!check_pte_access(access, old_pte)))
251 			return 1;
252 		/*
253 		 * Check if PTE has the cache-inhibit bit set
254 		 * If so, bail out and refault as a 4k page
255 		 */
256 		if (!mmu_has_feature(MMU_FTR_CI_LARGE_PAGE) &&
257 		    unlikely(pte_ci(pte)))
258 			return 0;
259 		/*
260 		 * Try to lock the PTE, add ACCESSED and DIRTY if it was
261 		 * a write access.
262 		 */
263 		new_pte = old_pte | H_PAGE_BUSY | _PAGE_ACCESSED;
264 		if (access & _PAGE_WRITE)
265 			new_pte |= _PAGE_DIRTY;
266 	} while (!pte_xchg(ptep, __pte(old_pte), __pte(new_pte)));
267 
268 	rflags = htab_convert_pte_flags(new_pte, flags);
269 	rpte = __real_pte(__pte(old_pte), ptep, PTRS_PER_PTE);
270 
271 	if (cpu_has_feature(CPU_FTR_NOEXECUTE) &&
272 	    !cpu_has_feature(CPU_FTR_COHERENT_ICACHE))
273 		rflags = hash_page_do_lazy_icache(rflags, __pte(old_pte), trap);
274 
275 	vpn  = hpt_vpn(ea, vsid, ssize);
276 	if (unlikely(old_pte & H_PAGE_HASHPTE)) {
277 		unsigned long gslot;
278 
279 		/*
280 		 * There MIGHT be an HPTE for this pte
281 		 */
282 		gslot = pte_get_hash_gslot(vpn, shift, ssize, rpte, 0);
283 		if (mmu_hash_ops.hpte_updatepp(gslot, rflags, vpn, MMU_PAGE_64K,
284 					       MMU_PAGE_64K, ssize,
285 					       flags) == -1)
286 			old_pte &= ~_PAGE_HPTEFLAGS;
287 	}
288 
289 	if (likely(!(old_pte & H_PAGE_HASHPTE))) {
290 
291 		pa = pte_pfn(__pte(old_pte)) << PAGE_SHIFT;
292 		hash = hpt_hash(vpn, shift, ssize);
293 
294 repeat:
295 		hpte_group = (hash & htab_hash_mask) * HPTES_PER_GROUP;
296 
297 		/* Insert into the hash table, primary slot */
298 		slot = mmu_hash_ops.hpte_insert(hpte_group, vpn, pa, rflags, 0,
299 						MMU_PAGE_64K, MMU_PAGE_64K,
300 						ssize);
301 		/*
302 		 * Primary is full, try the secondary
303 		 */
304 		if (unlikely(slot == -1)) {
305 			hpte_group = (~hash & htab_hash_mask) * HPTES_PER_GROUP;
306 			slot = mmu_hash_ops.hpte_insert(hpte_group, vpn, pa,
307 							rflags,
308 							HPTE_V_SECONDARY,
309 							MMU_PAGE_64K,
310 							MMU_PAGE_64K, ssize);
311 			if (slot == -1) {
312 				if (mftb() & 0x1)
313 					hpte_group = (hash & htab_hash_mask) *
314 							HPTES_PER_GROUP;
315 				mmu_hash_ops.hpte_remove(hpte_group);
316 				/*
317 				 * FIXME!! Should be try the group from which we removed ?
318 				 */
319 				goto repeat;
320 			}
321 		}
322 		/*
323 		 * Hypervisor failure. Restore old pte and return -1
324 		 * similar to __hash_page_*
325 		 */
326 		if (unlikely(slot == -2)) {
327 			*ptep = __pte(old_pte);
328 			hash_failure_debug(ea, access, vsid, trap, ssize,
329 					   MMU_PAGE_64K, MMU_PAGE_64K, old_pte);
330 			return -1;
331 		}
332 
333 		new_pte = (new_pte & ~_PAGE_HPTEFLAGS) | H_PAGE_HASHPTE;
334 		new_pte |= pte_set_hidx(ptep, rpte, 0, slot, PTRS_PER_PTE);
335 
336 		if (stress_hpt())
337 			hpt_do_stress(ea, hpte_group);
338 	}
339 
340 	*ptep = __pte(new_pte & ~H_PAGE_BUSY);
341 
342 	return 0;
343 }
344