1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3  * Copyright 2005, Paul Mackerras, IBM Corporation.
4  * Copyright 2009, Benjamin Herrenschmidt, IBM Corporation.
5  * Copyright 2015-2016, Aneesh Kumar K.V, IBM Corporation.
6  */
7 
8 #include <linux/sched.h>
9 #include <linux/mm_types.h>
10 #include <linux/mm.h>
11 
12 #include <asm/sections.h>
13 #include <asm/mmu.h>
14 #include <asm/tlb.h>
15 
16 #include <mm/mmu_decl.h>
17 
18 #define CREATE_TRACE_POINTS
19 #include <trace/events/thp.h>
20 
21 #if H_PGTABLE_RANGE > (USER_VSID_RANGE * (TASK_SIZE_USER64 / TASK_CONTEXT_SIZE))
22 #warning Limited user VSID range means pagetable space is wasted
23 #endif
24 
25 #ifdef CONFIG_SPARSEMEM_VMEMMAP
26 /*
27  * vmemmap is the starting address of the virtual address space where
28  * struct pages are allocated for all possible PFNs present on the system
29  * including holes and bad memory (hence sparse). These virtual struct
30  * pages are stored in sequence in this virtual address space irrespective
31  * of the fact whether the corresponding PFN is valid or not. This achieves
32  * constant relationship between address of struct page and its PFN.
33  *
34  * During boot or memory hotplug operation when a new memory section is
35  * added, physical memory allocation (including hash table bolting) will
36  * be performed for the set of struct pages which are part of the memory
37  * section. This saves memory by not allocating struct pages for PFNs
38  * which are not valid.
39  *
40  *		----------------------------------------------
41  *		| PHYSICAL ALLOCATION OF VIRTUAL STRUCT PAGES|
42  *		----------------------------------------------
43  *
44  *	   f000000000000000                  c000000000000000
45  * vmemmap +--------------+                  +--------------+
46  *  +      |  page struct | +--------------> |  page struct |
47  *  |      +--------------+                  +--------------+
48  *  |      |  page struct | +--------------> |  page struct |
49  *  |      +--------------+ |                +--------------+
50  *  |      |  page struct | +       +------> |  page struct |
51  *  |      +--------------+         |        +--------------+
52  *  |      |  page struct |         |   +--> |  page struct |
53  *  |      +--------------+         |   |    +--------------+
54  *  |      |  page struct |         |   |
55  *  |      +--------------+         |   |
56  *  |      |  page struct |         |   |
57  *  |      +--------------+         |   |
58  *  |      |  page struct |         |   |
59  *  |      +--------------+         |   |
60  *  |      |  page struct |         |   |
61  *  |      +--------------+         |   |
62  *  |      |  page struct | +-------+   |
63  *  |      +--------------+             |
64  *  |      |  page struct | +-----------+
65  *  |      +--------------+
66  *  |      |  page struct | No mapping
67  *  |      +--------------+
68  *  |      |  page struct | No mapping
69  *  v      +--------------+
70  *
71  *		-----------------------------------------
72  *		| RELATION BETWEEN STRUCT PAGES AND PFNS|
73  *		-----------------------------------------
74  *
75  * vmemmap +--------------+                 +---------------+
76  *  +      |  page struct | +-------------> |      PFN      |
77  *  |      +--------------+                 +---------------+
78  *  |      |  page struct | +-------------> |      PFN      |
79  *  |      +--------------+                 +---------------+
80  *  |      |  page struct | +-------------> |      PFN      |
81  *  |      +--------------+                 +---------------+
82  *  |      |  page struct | +-------------> |      PFN      |
83  *  |      +--------------+                 +---------------+
84  *  |      |              |
85  *  |      +--------------+
86  *  |      |              |
87  *  |      +--------------+
88  *  |      |              |
89  *  |      +--------------+                 +---------------+
90  *  |      |  page struct | +-------------> |      PFN      |
91  *  |      +--------------+                 +---------------+
92  *  |      |              |
93  *  |      +--------------+
94  *  |      |              |
95  *  |      +--------------+                 +---------------+
96  *  |      |  page struct | +-------------> |      PFN      |
97  *  |      +--------------+                 +---------------+
98  *  |      |  page struct | +-------------> |      PFN      |
99  *  v      +--------------+                 +---------------+
100  */
101 /*
102  * On hash-based CPUs, the vmemmap is bolted in the hash table.
103  *
104  */
105 int __meminit hash__vmemmap_create_mapping(unsigned long start,
106 				       unsigned long page_size,
107 				       unsigned long phys)
108 {
109 	int rc;
110 
111 	if ((start + page_size) >= H_VMEMMAP_END) {
112 		pr_warn("Outside the supported range\n");
113 		return -1;
114 	}
115 
116 	rc = htab_bolt_mapping(start, start + page_size, phys,
117 			       pgprot_val(PAGE_KERNEL),
118 			       mmu_vmemmap_psize, mmu_kernel_ssize);
119 	if (rc < 0) {
120 		int rc2 = htab_remove_mapping(start, start + page_size,
121 					      mmu_vmemmap_psize,
122 					      mmu_kernel_ssize);
123 		BUG_ON(rc2 && (rc2 != -ENOENT));
124 	}
125 	return rc;
126 }
127 
128 #ifdef CONFIG_MEMORY_HOTPLUG
129 void hash__vmemmap_remove_mapping(unsigned long start,
130 			      unsigned long page_size)
131 {
132 	int rc = htab_remove_mapping(start, start + page_size,
133 				     mmu_vmemmap_psize,
134 				     mmu_kernel_ssize);
135 	BUG_ON((rc < 0) && (rc != -ENOENT));
136 	WARN_ON(rc == -ENOENT);
137 }
138 #endif
139 #endif /* CONFIG_SPARSEMEM_VMEMMAP */
140 
141 /*
142  * map_kernel_page currently only called by __ioremap
143  * map_kernel_page adds an entry to the ioremap page table
144  * and adds an entry to the HPT, possibly bolting it
145  */
146 int hash__map_kernel_page(unsigned long ea, unsigned long pa, pgprot_t prot)
147 {
148 	pgd_t *pgdp;
149 	p4d_t *p4dp;
150 	pud_t *pudp;
151 	pmd_t *pmdp;
152 	pte_t *ptep;
153 
154 	BUILD_BUG_ON(TASK_SIZE_USER64 > H_PGTABLE_RANGE);
155 	if (slab_is_available()) {
156 		pgdp = pgd_offset_k(ea);
157 		p4dp = p4d_offset(pgdp, ea);
158 		pudp = pud_alloc(&init_mm, p4dp, ea);
159 		if (!pudp)
160 			return -ENOMEM;
161 		pmdp = pmd_alloc(&init_mm, pudp, ea);
162 		if (!pmdp)
163 			return -ENOMEM;
164 		ptep = pte_alloc_kernel(pmdp, ea);
165 		if (!ptep)
166 			return -ENOMEM;
167 		set_pte_at(&init_mm, ea, ptep, pfn_pte(pa >> PAGE_SHIFT, prot));
168 	} else {
169 		/*
170 		 * If the mm subsystem is not fully up, we cannot create a
171 		 * linux page table entry for this mapping.  Simply bolt an
172 		 * entry in the hardware page table.
173 		 *
174 		 */
175 		if (htab_bolt_mapping(ea, ea + PAGE_SIZE, pa, pgprot_val(prot),
176 				      mmu_io_psize, mmu_kernel_ssize)) {
177 			printk(KERN_ERR "Failed to do bolted mapping IO "
178 			       "memory at %016lx !\n", pa);
179 			return -ENOMEM;
180 		}
181 	}
182 
183 	smp_wmb();
184 	return 0;
185 }
186 
187 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
188 
189 unsigned long hash__pmd_hugepage_update(struct mm_struct *mm, unsigned long addr,
190 				    pmd_t *pmdp, unsigned long clr,
191 				    unsigned long set)
192 {
193 	__be64 old_be, tmp;
194 	unsigned long old;
195 
196 #ifdef CONFIG_DEBUG_VM
197 	WARN_ON(!hash__pmd_trans_huge(*pmdp) && !pmd_devmap(*pmdp));
198 	assert_spin_locked(pmd_lockptr(mm, pmdp));
199 #endif
200 
201 	__asm__ __volatile__(
202 	"1:	ldarx	%0,0,%3\n\
203 		and.	%1,%0,%6\n\
204 		bne-	1b \n\
205 		andc	%1,%0,%4 \n\
206 		or	%1,%1,%7\n\
207 		stdcx.	%1,0,%3 \n\
208 		bne-	1b"
209 	: "=&r" (old_be), "=&r" (tmp), "=m" (*pmdp)
210 	: "r" (pmdp), "r" (cpu_to_be64(clr)), "m" (*pmdp),
211 	  "r" (cpu_to_be64(H_PAGE_BUSY)), "r" (cpu_to_be64(set))
212 	: "cc" );
213 
214 	old = be64_to_cpu(old_be);
215 
216 	trace_hugepage_update(addr, old, clr, set);
217 	if (old & H_PAGE_HASHPTE)
218 		hpte_do_hugepage_flush(mm, addr, pmdp, old);
219 	return old;
220 }
221 
222 pmd_t hash__pmdp_collapse_flush(struct vm_area_struct *vma, unsigned long address,
223 			    pmd_t *pmdp)
224 {
225 	pmd_t pmd;
226 
227 	VM_BUG_ON(address & ~HPAGE_PMD_MASK);
228 	VM_BUG_ON(pmd_trans_huge(*pmdp));
229 	VM_BUG_ON(pmd_devmap(*pmdp));
230 
231 	pmd = *pmdp;
232 	pmd_clear(pmdp);
233 	/*
234 	 * Wait for all pending hash_page to finish. This is needed
235 	 * in case of subpage collapse. When we collapse normal pages
236 	 * to hugepage, we first clear the pmd, then invalidate all
237 	 * the PTE entries. The assumption here is that any low level
238 	 * page fault will see a none pmd and take the slow path that
239 	 * will wait on mmap_lock. But we could very well be in a
240 	 * hash_page with local ptep pointer value. Such a hash page
241 	 * can result in adding new HPTE entries for normal subpages.
242 	 * That means we could be modifying the page content as we
243 	 * copy them to a huge page. So wait for parallel hash_page
244 	 * to finish before invalidating HPTE entries. We can do this
245 	 * by sending an IPI to all the cpus and executing a dummy
246 	 * function there.
247 	 */
248 	serialize_against_pte_lookup(vma->vm_mm);
249 	/*
250 	 * Now invalidate the hpte entries in the range
251 	 * covered by pmd. This make sure we take a
252 	 * fault and will find the pmd as none, which will
253 	 * result in a major fault which takes mmap_lock and
254 	 * hence wait for collapse to complete. Without this
255 	 * the __collapse_huge_page_copy can result in copying
256 	 * the old content.
257 	 */
258 	flush_tlb_pmd_range(vma->vm_mm, &pmd, address);
259 	return pmd;
260 }
261 
262 /*
263  * We want to put the pgtable in pmd and use pgtable for tracking
264  * the base page size hptes
265  */
266 void hash__pgtable_trans_huge_deposit(struct mm_struct *mm, pmd_t *pmdp,
267 				  pgtable_t pgtable)
268 {
269 	pgtable_t *pgtable_slot;
270 
271 	assert_spin_locked(pmd_lockptr(mm, pmdp));
272 	/*
273 	 * we store the pgtable in the second half of PMD
274 	 */
275 	pgtable_slot = (pgtable_t *)pmdp + PTRS_PER_PMD;
276 	*pgtable_slot = pgtable;
277 	/*
278 	 * expose the deposited pgtable to other cpus.
279 	 * before we set the hugepage PTE at pmd level
280 	 * hash fault code looks at the deposted pgtable
281 	 * to store hash index values.
282 	 */
283 	smp_wmb();
284 }
285 
286 pgtable_t hash__pgtable_trans_huge_withdraw(struct mm_struct *mm, pmd_t *pmdp)
287 {
288 	pgtable_t pgtable;
289 	pgtable_t *pgtable_slot;
290 
291 	assert_spin_locked(pmd_lockptr(mm, pmdp));
292 
293 	pgtable_slot = (pgtable_t *)pmdp + PTRS_PER_PMD;
294 	pgtable = *pgtable_slot;
295 	/*
296 	 * Once we withdraw, mark the entry NULL.
297 	 */
298 	*pgtable_slot = NULL;
299 	/*
300 	 * We store HPTE information in the deposited PTE fragment.
301 	 * zero out the content on withdraw.
302 	 */
303 	memset(pgtable, 0, PTE_FRAG_SIZE);
304 	return pgtable;
305 }
306 
307 /*
308  * A linux hugepage PMD was changed and the corresponding hash table entries
309  * neesd to be flushed.
310  */
311 void hpte_do_hugepage_flush(struct mm_struct *mm, unsigned long addr,
312 			    pmd_t *pmdp, unsigned long old_pmd)
313 {
314 	int ssize;
315 	unsigned int psize;
316 	unsigned long vsid;
317 	unsigned long flags = 0;
318 
319 	/* get the base page size,vsid and segment size */
320 #ifdef CONFIG_DEBUG_VM
321 	psize = get_slice_psize(mm, addr);
322 	BUG_ON(psize == MMU_PAGE_16M);
323 #endif
324 	if (old_pmd & H_PAGE_COMBO)
325 		psize = MMU_PAGE_4K;
326 	else
327 		psize = MMU_PAGE_64K;
328 
329 	if (!is_kernel_addr(addr)) {
330 		ssize = user_segment_size(addr);
331 		vsid = get_user_vsid(&mm->context, addr, ssize);
332 		WARN_ON(vsid == 0);
333 	} else {
334 		vsid = get_kernel_vsid(addr, mmu_kernel_ssize);
335 		ssize = mmu_kernel_ssize;
336 	}
337 
338 	if (mm_is_thread_local(mm))
339 		flags |= HPTE_LOCAL_UPDATE;
340 
341 	return flush_hash_hugepage(vsid, addr, pmdp, psize, ssize, flags);
342 }
343 
344 pmd_t hash__pmdp_huge_get_and_clear(struct mm_struct *mm,
345 				unsigned long addr, pmd_t *pmdp)
346 {
347 	pmd_t old_pmd;
348 	pgtable_t pgtable;
349 	unsigned long old;
350 	pgtable_t *pgtable_slot;
351 
352 	old = pmd_hugepage_update(mm, addr, pmdp, ~0UL, 0);
353 	old_pmd = __pmd(old);
354 	/*
355 	 * We have pmd == none and we are holding page_table_lock.
356 	 * So we can safely go and clear the pgtable hash
357 	 * index info.
358 	 */
359 	pgtable_slot = (pgtable_t *)pmdp + PTRS_PER_PMD;
360 	pgtable = *pgtable_slot;
361 	/*
362 	 * Let's zero out old valid and hash index details
363 	 * hash fault look at them.
364 	 */
365 	memset(pgtable, 0, PTE_FRAG_SIZE);
366 	return old_pmd;
367 }
368 
369 int hash__has_transparent_hugepage(void)
370 {
371 
372 	if (!mmu_has_feature(MMU_FTR_16M_PAGE))
373 		return 0;
374 	/*
375 	 * We support THP only if PMD_SIZE is 16MB.
376 	 */
377 	if (mmu_psize_defs[MMU_PAGE_16M].shift != PMD_SHIFT)
378 		return 0;
379 	/*
380 	 * We need to make sure that we support 16MB hugepage in a segement
381 	 * with base page size 64K or 4K. We only enable THP with a PAGE_SIZE
382 	 * of 64K.
383 	 */
384 	/*
385 	 * If we have 64K HPTE, we will be using that by default
386 	 */
387 	if (mmu_psize_defs[MMU_PAGE_64K].shift &&
388 	    (mmu_psize_defs[MMU_PAGE_64K].penc[MMU_PAGE_16M] == -1))
389 		return 0;
390 	/*
391 	 * Ok we only have 4K HPTE
392 	 */
393 	if (mmu_psize_defs[MMU_PAGE_4K].penc[MMU_PAGE_16M] == -1)
394 		return 0;
395 
396 	return 1;
397 }
398 EXPORT_SYMBOL_GPL(hash__has_transparent_hugepage);
399 
400 #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
401 
402 #ifdef CONFIG_STRICT_KERNEL_RWX
403 static bool hash__change_memory_range(unsigned long start, unsigned long end,
404 				      unsigned long newpp)
405 {
406 	unsigned long idx;
407 	unsigned int step, shift;
408 
409 	shift = mmu_psize_defs[mmu_linear_psize].shift;
410 	step = 1 << shift;
411 
412 	start = ALIGN_DOWN(start, step);
413 	end = ALIGN(end, step); // aligns up
414 
415 	if (start >= end)
416 		return false;
417 
418 	pr_debug("Changing page protection on range 0x%lx-0x%lx, to 0x%lx, step 0x%x\n",
419 		 start, end, newpp, step);
420 
421 	for (idx = start; idx < end; idx += step)
422 		/* Not sure if we can do much with the return value */
423 		mmu_hash_ops.hpte_updateboltedpp(newpp, idx, mmu_linear_psize,
424 							mmu_kernel_ssize);
425 
426 	return true;
427 }
428 
429 void hash__mark_rodata_ro(void)
430 {
431 	unsigned long start, end;
432 
433 	start = (unsigned long)_stext;
434 	end = (unsigned long)__init_begin;
435 
436 	WARN_ON(!hash__change_memory_range(start, end, PP_RXXX));
437 }
438 
439 void hash__mark_initmem_nx(void)
440 {
441 	unsigned long start, end, pp;
442 
443 	start = (unsigned long)__init_begin;
444 	end = (unsigned long)__init_end;
445 
446 	pp = htab_convert_pte_flags(pgprot_val(PAGE_KERNEL));
447 
448 	WARN_ON(!hash__change_memory_range(start, end, pp));
449 }
450 #endif
451