xref: /openbmc/linux/arch/x86/xen/p2m.c (revision 6774def6)
1 /*
2  * Xen leaves the responsibility for maintaining p2m mappings to the
3  * guests themselves, but it must also access and update the p2m array
4  * during suspend/resume when all the pages are reallocated.
5  *
6  * The p2m table is logically a flat array, but we implement it as a
7  * three-level tree to allow the address space to be sparse.
8  *
9  *                               Xen
10  *                                |
11  *     p2m_top              p2m_top_mfn
12  *       /  \                   /   \
13  * p2m_mid p2m_mid	p2m_mid_mfn p2m_mid_mfn
14  *    / \      / \         /           /
15  *  p2m p2m p2m p2m p2m p2m p2m ...
16  *
17  * The p2m_mid_mfn pages are mapped by p2m_top_mfn_p.
18  *
19  * The p2m_top and p2m_top_mfn levels are limited to 1 page, so the
20  * maximum representable pseudo-physical address space is:
21  *  P2M_TOP_PER_PAGE * P2M_MID_PER_PAGE * P2M_PER_PAGE pages
22  *
23  * P2M_PER_PAGE depends on the architecture, as a mfn is always
24  * unsigned long (8 bytes on 64-bit, 4 bytes on 32), leading to
25  * 512 and 1024 entries respectively.
26  *
27  * In short, these structures contain the Machine Frame Number (MFN) of the PFN.
28  *
29  * However not all entries are filled with MFNs. Specifically for all other
30  * leaf entries, or for the top  root, or middle one, for which there is a void
31  * entry, we assume it is  "missing". So (for example)
32  *  pfn_to_mfn(0x90909090)=INVALID_P2M_ENTRY.
33  *
34  * We also have the possibility of setting 1-1 mappings on certain regions, so
35  * that:
36  *  pfn_to_mfn(0xc0000)=0xc0000
37  *
38  * The benefit of this is, that we can assume for non-RAM regions (think
39  * PCI BARs, or ACPI spaces), we can create mappings easily because we
40  * get the PFN value to match the MFN.
41  *
42  * For this to work efficiently we have one new page p2m_identity and
43  * allocate (via reserved_brk) any other pages we need to cover the sides
44  * (1GB or 4MB boundary violations). All entries in p2m_identity are set to
45  * INVALID_P2M_ENTRY type (Xen toolstack only recognizes that and MFNs,
46  * no other fancy value).
47  *
48  * On lookup we spot that the entry points to p2m_identity and return the
49  * identity value instead of dereferencing and returning INVALID_P2M_ENTRY.
50  * If the entry points to an allocated page, we just proceed as before and
51  * return the PFN.  If the PFN has IDENTITY_FRAME_BIT set we unmask that in
52  * appropriate functions (pfn_to_mfn).
53  *
54  * The reason for having the IDENTITY_FRAME_BIT instead of just returning the
55  * PFN is that we could find ourselves where pfn_to_mfn(pfn)==pfn for a
56  * non-identity pfn. To protect ourselves against we elect to set (and get) the
57  * IDENTITY_FRAME_BIT on all identity mapped PFNs.
58  *
59  * This simplistic diagram is used to explain the more subtle piece of code.
60  * There is also a digram of the P2M at the end that can help.
61  * Imagine your E820 looking as so:
62  *
63  *                    1GB                                           2GB    4GB
64  * /-------------------+---------\/----\         /----------\    /---+-----\
65  * | System RAM        | Sys RAM ||ACPI|         | reserved |    | Sys RAM |
66  * \-------------------+---------/\----/         \----------/    \---+-----/
67  *                               ^- 1029MB                       ^- 2001MB
68  *
69  * [1029MB = 263424 (0x40500), 2001MB = 512256 (0x7D100),
70  *  2048MB = 524288 (0x80000)]
71  *
72  * And dom0_mem=max:3GB,1GB is passed in to the guest, meaning memory past 1GB
73  * is actually not present (would have to kick the balloon driver to put it in).
74  *
75  * When we are told to set the PFNs for identity mapping (see patch: "xen/setup:
76  * Set identity mapping for non-RAM E820 and E820 gaps.") we pass in the start
77  * of the PFN and the end PFN (263424 and 512256 respectively). The first step
78  * is to reserve_brk a top leaf page if the p2m[1] is missing. The top leaf page
79  * covers 512^2 of page estate (1GB) and in case the start or end PFN is not
80  * aligned on 512^2*PAGE_SIZE (1GB) we reserve_brk new middle and leaf pages as
81  * required to split any existing p2m_mid_missing middle pages.
82  *
83  * With the E820 example above, 263424 is not 1GB aligned so we allocate a
84  * reserve_brk page which will cover the PFNs estate from 0x40000 to 0x80000.
85  * Each entry in the allocate page is "missing" (points to p2m_missing).
86  *
87  * Next stage is to determine if we need to do a more granular boundary check
88  * on the 4MB (or 2MB depending on architecture) off the start and end pfn's.
89  * We check if the start pfn and end pfn violate that boundary check, and if
90  * so reserve_brk a (p2m[x][y]) leaf page. This way we have a much finer
91  * granularity of setting which PFNs are missing and which ones are identity.
92  * In our example 263424 and 512256 both fail the check so we reserve_brk two
93  * pages. Populate them with INVALID_P2M_ENTRY (so they both have "missing"
94  * values) and assign them to p2m[1][2] and p2m[1][488] respectively.
95  *
96  * At this point we would at minimum reserve_brk one page, but could be up to
97  * three. Each call to set_phys_range_identity has at maximum a three page
98  * cost. If we were to query the P2M at this stage, all those entries from
99  * start PFN through end PFN (so 1029MB -> 2001MB) would return
100  * INVALID_P2M_ENTRY ("missing").
101  *
102  * The next step is to walk from the start pfn to the end pfn setting
103  * the IDENTITY_FRAME_BIT on each PFN. This is done in set_phys_range_identity.
104  * If we find that the middle entry is pointing to p2m_missing we can swap it
105  * over to p2m_identity - this way covering 4MB (or 2MB) PFN space (and
106  * similarly swapping p2m_mid_missing for p2m_mid_identity for larger regions).
107  * At this point we do not need to worry about boundary aligment (so no need to
108  * reserve_brk a middle page, figure out which PFNs are "missing" and which
109  * ones are identity), as that has been done earlier.  If we find that the
110  * middle leaf is not occupied by p2m_identity or p2m_missing, we dereference
111  * that page (which covers 512 PFNs) and set the appropriate PFN with
112  * IDENTITY_FRAME_BIT. In our example 263424 and 512256 end up there, and we
113  * set from p2m[1][2][256->511] and p2m[1][488][0->256] with
114  * IDENTITY_FRAME_BIT set.
115  *
116  * All other regions that are void (or not filled) either point to p2m_missing
117  * (considered missing) or have the default value of INVALID_P2M_ENTRY (also
118  * considered missing). In our case, p2m[1][2][0->255] and p2m[1][488][257->511]
119  * contain the INVALID_P2M_ENTRY value and are considered "missing."
120  *
121  * Finally, the region beyond the end of of the E820 (4 GB in this example)
122  * is set to be identity (in case there are MMIO regions placed here).
123  *
124  * This is what the p2m ends up looking (for the E820 above) with this
125  * fabulous drawing:
126  *
127  *    p2m         /--------------\
128  *  /-----\       | &mfn_list[0],|                           /-----------------\
129  *  |  0  |------>| &mfn_list[1],|    /---------------\      | ~0, ~0, ..      |
130  *  |-----|       |  ..., ~0, ~0 |    | ~0, ~0, [x]---+----->| IDENTITY [@256] |
131  *  |  1  |---\   \--------------/    | [p2m_identity]+\     | IDENTITY [@257] |
132  *  |-----|    \                      | [p2m_identity]+\\    | ....            |
133  *  |  2  |--\  \-------------------->|  ...          | \\   \----------------/
134  *  |-----|   \                       \---------------/  \\
135  *  |  3  |-\  \                                          \\  p2m_identity [1]
136  *  |-----|  \  \-------------------->/---------------\   /-----------------\
137  *  | ..  |\  |                       | [p2m_identity]+-->| ~0, ~0, ~0, ... |
138  *  \-----/ | |                       | [p2m_identity]+-->| ..., ~0         |
139  *          | |                       | ....          |   \-----------------/
140  *          | |                       +-[x], ~0, ~0.. +\
141  *          | |                       \---------------/ \
142  *          | |                                          \-> /---------------\
143  *          | V  p2m_mid_missing       p2m_missing           | IDENTITY[@0]  |
144  *          | /-----------------\     /------------\         | IDENTITY[@256]|
145  *          | | [p2m_missing]   +---->| ~0, ~0, ...|         | ~0, ~0, ....  |
146  *          | | [p2m_missing]   +---->| ..., ~0    |         \---------------/
147  *          | | ...             |     \------------/
148  *          | \-----------------/
149  *          |
150  *          |     p2m_mid_identity
151  *          |   /-----------------\
152  *          \-->| [p2m_identity]  +---->[1]
153  *              | [p2m_identity]  +---->[1]
154  *              | ...             |
155  *              \-----------------/
156  *
157  * where ~0 is INVALID_P2M_ENTRY. IDENTITY is (PFN | IDENTITY_BIT)
158  */
159 
160 #include <linux/init.h>
161 #include <linux/module.h>
162 #include <linux/list.h>
163 #include <linux/hash.h>
164 #include <linux/sched.h>
165 #include <linux/seq_file.h>
166 #include <linux/bootmem.h>
167 
168 #include <asm/cache.h>
169 #include <asm/setup.h>
170 
171 #include <asm/xen/page.h>
172 #include <asm/xen/hypercall.h>
173 #include <asm/xen/hypervisor.h>
174 #include <xen/balloon.h>
175 #include <xen/grant_table.h>
176 
177 #include "p2m.h"
178 #include "multicalls.h"
179 #include "xen-ops.h"
180 
181 static void __init m2p_override_init(void);
182 
183 unsigned long xen_max_p2m_pfn __read_mostly;
184 
185 static unsigned long *p2m_mid_missing_mfn;
186 static unsigned long *p2m_top_mfn;
187 static unsigned long **p2m_top_mfn_p;
188 
189 /* Placeholders for holes in the address space */
190 static RESERVE_BRK_ARRAY(unsigned long, p2m_missing, P2M_PER_PAGE);
191 static RESERVE_BRK_ARRAY(unsigned long *, p2m_mid_missing, P2M_MID_PER_PAGE);
192 
193 static RESERVE_BRK_ARRAY(unsigned long **, p2m_top, P2M_TOP_PER_PAGE);
194 
195 static RESERVE_BRK_ARRAY(unsigned long, p2m_identity, P2M_PER_PAGE);
196 static RESERVE_BRK_ARRAY(unsigned long *, p2m_mid_identity, P2M_MID_PER_PAGE);
197 
198 RESERVE_BRK(p2m_mid, PAGE_SIZE * (MAX_DOMAIN_PAGES / (P2M_PER_PAGE * P2M_MID_PER_PAGE)));
199 
200 /* For each I/O range remapped we may lose up to two leaf pages for the boundary
201  * violations and three mid pages to cover up to 3GB. With
202  * early_can_reuse_p2m_middle() most of the leaf pages will be reused by the
203  * remapped region.
204  */
205 RESERVE_BRK(p2m_identity_remap, PAGE_SIZE * 2 * 3 * MAX_REMAP_RANGES);
206 
207 static inline unsigned p2m_top_index(unsigned long pfn)
208 {
209 	BUG_ON(pfn >= MAX_P2M_PFN);
210 	return pfn / (P2M_MID_PER_PAGE * P2M_PER_PAGE);
211 }
212 
213 static inline unsigned p2m_mid_index(unsigned long pfn)
214 {
215 	return (pfn / P2M_PER_PAGE) % P2M_MID_PER_PAGE;
216 }
217 
218 static inline unsigned p2m_index(unsigned long pfn)
219 {
220 	return pfn % P2M_PER_PAGE;
221 }
222 
223 static void p2m_top_init(unsigned long ***top)
224 {
225 	unsigned i;
226 
227 	for (i = 0; i < P2M_TOP_PER_PAGE; i++)
228 		top[i] = p2m_mid_missing;
229 }
230 
231 static void p2m_top_mfn_init(unsigned long *top)
232 {
233 	unsigned i;
234 
235 	for (i = 0; i < P2M_TOP_PER_PAGE; i++)
236 		top[i] = virt_to_mfn(p2m_mid_missing_mfn);
237 }
238 
239 static void p2m_top_mfn_p_init(unsigned long **top)
240 {
241 	unsigned i;
242 
243 	for (i = 0; i < P2M_TOP_PER_PAGE; i++)
244 		top[i] = p2m_mid_missing_mfn;
245 }
246 
247 static void p2m_mid_init(unsigned long **mid, unsigned long *leaf)
248 {
249 	unsigned i;
250 
251 	for (i = 0; i < P2M_MID_PER_PAGE; i++)
252 		mid[i] = leaf;
253 }
254 
255 static void p2m_mid_mfn_init(unsigned long *mid, unsigned long *leaf)
256 {
257 	unsigned i;
258 
259 	for (i = 0; i < P2M_MID_PER_PAGE; i++)
260 		mid[i] = virt_to_mfn(leaf);
261 }
262 
263 static void p2m_init(unsigned long *p2m)
264 {
265 	unsigned i;
266 
267 	for (i = 0; i < P2M_MID_PER_PAGE; i++)
268 		p2m[i] = INVALID_P2M_ENTRY;
269 }
270 
271 /*
272  * Build the parallel p2m_top_mfn and p2m_mid_mfn structures
273  *
274  * This is called both at boot time, and after resuming from suspend:
275  * - At boot time we're called rather early, and must use alloc_bootmem*()
276  *   to allocate memory.
277  *
278  * - After resume we're called from within stop_machine, but the mfn
279  *   tree should already be completely allocated.
280  */
281 void __ref xen_build_mfn_list_list(void)
282 {
283 	unsigned long pfn;
284 
285 	if (xen_feature(XENFEAT_auto_translated_physmap))
286 		return;
287 
288 	/* Pre-initialize p2m_top_mfn to be completely missing */
289 	if (p2m_top_mfn == NULL) {
290 		p2m_mid_missing_mfn = alloc_bootmem_align(PAGE_SIZE, PAGE_SIZE);
291 		p2m_mid_mfn_init(p2m_mid_missing_mfn, p2m_missing);
292 
293 		p2m_top_mfn_p = alloc_bootmem_align(PAGE_SIZE, PAGE_SIZE);
294 		p2m_top_mfn_p_init(p2m_top_mfn_p);
295 
296 		p2m_top_mfn = alloc_bootmem_align(PAGE_SIZE, PAGE_SIZE);
297 		p2m_top_mfn_init(p2m_top_mfn);
298 	} else {
299 		/* Reinitialise, mfn's all change after migration */
300 		p2m_mid_mfn_init(p2m_mid_missing_mfn, p2m_missing);
301 	}
302 
303 	for (pfn = 0; pfn < xen_max_p2m_pfn; pfn += P2M_PER_PAGE) {
304 		unsigned topidx = p2m_top_index(pfn);
305 		unsigned mididx = p2m_mid_index(pfn);
306 		unsigned long **mid;
307 		unsigned long *mid_mfn_p;
308 
309 		mid = p2m_top[topidx];
310 		mid_mfn_p = p2m_top_mfn_p[topidx];
311 
312 		/* Don't bother allocating any mfn mid levels if
313 		 * they're just missing, just update the stored mfn,
314 		 * since all could have changed over a migrate.
315 		 */
316 		if (mid == p2m_mid_missing) {
317 			BUG_ON(mididx);
318 			BUG_ON(mid_mfn_p != p2m_mid_missing_mfn);
319 			p2m_top_mfn[topidx] = virt_to_mfn(p2m_mid_missing_mfn);
320 			pfn += (P2M_MID_PER_PAGE - 1) * P2M_PER_PAGE;
321 			continue;
322 		}
323 
324 		if (mid_mfn_p == p2m_mid_missing_mfn) {
325 			/*
326 			 * XXX boot-time only!  We should never find
327 			 * missing parts of the mfn tree after
328 			 * runtime.
329 			 */
330 			mid_mfn_p = alloc_bootmem_align(PAGE_SIZE, PAGE_SIZE);
331 			p2m_mid_mfn_init(mid_mfn_p, p2m_missing);
332 
333 			p2m_top_mfn_p[topidx] = mid_mfn_p;
334 		}
335 
336 		p2m_top_mfn[topidx] = virt_to_mfn(mid_mfn_p);
337 		mid_mfn_p[mididx] = virt_to_mfn(mid[mididx]);
338 	}
339 }
340 
341 void xen_setup_mfn_list_list(void)
342 {
343 	if (xen_feature(XENFEAT_auto_translated_physmap))
344 		return;
345 
346 	BUG_ON(HYPERVISOR_shared_info == &xen_dummy_shared_info);
347 
348 	HYPERVISOR_shared_info->arch.pfn_to_mfn_frame_list_list =
349 		virt_to_mfn(p2m_top_mfn);
350 	HYPERVISOR_shared_info->arch.max_pfn = xen_max_p2m_pfn;
351 }
352 
353 /* Set up p2m_top to point to the domain-builder provided p2m pages */
354 void __init xen_build_dynamic_phys_to_machine(void)
355 {
356 	unsigned long *mfn_list;
357 	unsigned long max_pfn;
358 	unsigned long pfn;
359 
360 	 if (xen_feature(XENFEAT_auto_translated_physmap))
361 		return;
362 
363 	mfn_list = (unsigned long *)xen_start_info->mfn_list;
364 	max_pfn = min(MAX_DOMAIN_PAGES, xen_start_info->nr_pages);
365 	xen_max_p2m_pfn = max_pfn;
366 
367 	p2m_missing = extend_brk(PAGE_SIZE, PAGE_SIZE);
368 	p2m_init(p2m_missing);
369 	p2m_identity = extend_brk(PAGE_SIZE, PAGE_SIZE);
370 	p2m_init(p2m_identity);
371 
372 	p2m_mid_missing = extend_brk(PAGE_SIZE, PAGE_SIZE);
373 	p2m_mid_init(p2m_mid_missing, p2m_missing);
374 	p2m_mid_identity = extend_brk(PAGE_SIZE, PAGE_SIZE);
375 	p2m_mid_init(p2m_mid_identity, p2m_identity);
376 
377 	p2m_top = extend_brk(PAGE_SIZE, PAGE_SIZE);
378 	p2m_top_init(p2m_top);
379 
380 	/*
381 	 * The domain builder gives us a pre-constructed p2m array in
382 	 * mfn_list for all the pages initially given to us, so we just
383 	 * need to graft that into our tree structure.
384 	 */
385 	for (pfn = 0; pfn < max_pfn; pfn += P2M_PER_PAGE) {
386 		unsigned topidx = p2m_top_index(pfn);
387 		unsigned mididx = p2m_mid_index(pfn);
388 
389 		if (p2m_top[topidx] == p2m_mid_missing) {
390 			unsigned long **mid = extend_brk(PAGE_SIZE, PAGE_SIZE);
391 			p2m_mid_init(mid, p2m_missing);
392 
393 			p2m_top[topidx] = mid;
394 		}
395 
396 		/*
397 		 * As long as the mfn_list has enough entries to completely
398 		 * fill a p2m page, pointing into the array is ok. But if
399 		 * not the entries beyond the last pfn will be undefined.
400 		 */
401 		if (unlikely(pfn + P2M_PER_PAGE > max_pfn)) {
402 			unsigned long p2midx;
403 
404 			p2midx = max_pfn % P2M_PER_PAGE;
405 			for ( ; p2midx < P2M_PER_PAGE; p2midx++)
406 				mfn_list[pfn + p2midx] = INVALID_P2M_ENTRY;
407 		}
408 		p2m_top[topidx][mididx] = &mfn_list[pfn];
409 	}
410 
411 	m2p_override_init();
412 }
413 #ifdef CONFIG_X86_64
414 unsigned long __init xen_revector_p2m_tree(void)
415 {
416 	unsigned long va_start;
417 	unsigned long va_end;
418 	unsigned long pfn;
419 	unsigned long pfn_free = 0;
420 	unsigned long *mfn_list = NULL;
421 	unsigned long size;
422 
423 	va_start = xen_start_info->mfn_list;
424 	/*We copy in increments of P2M_PER_PAGE * sizeof(unsigned long),
425 	 * so make sure it is rounded up to that */
426 	size = PAGE_ALIGN(xen_start_info->nr_pages * sizeof(unsigned long));
427 	va_end = va_start + size;
428 
429 	/* If we were revectored already, don't do it again. */
430 	if (va_start <= __START_KERNEL_map && va_start >= __PAGE_OFFSET)
431 		return 0;
432 
433 	mfn_list = alloc_bootmem_align(size, PAGE_SIZE);
434 	if (!mfn_list) {
435 		pr_warn("Could not allocate space for a new P2M tree!\n");
436 		return xen_start_info->mfn_list;
437 	}
438 	/* Fill it out with INVALID_P2M_ENTRY value */
439 	memset(mfn_list, 0xFF, size);
440 
441 	for (pfn = 0; pfn < ALIGN(MAX_DOMAIN_PAGES, P2M_PER_PAGE); pfn += P2M_PER_PAGE) {
442 		unsigned topidx = p2m_top_index(pfn);
443 		unsigned mididx;
444 		unsigned long *mid_p;
445 
446 		if (!p2m_top[topidx])
447 			continue;
448 
449 		if (p2m_top[topidx] == p2m_mid_missing)
450 			continue;
451 
452 		mididx = p2m_mid_index(pfn);
453 		mid_p = p2m_top[topidx][mididx];
454 		if (!mid_p)
455 			continue;
456 		if ((mid_p == p2m_missing) || (mid_p == p2m_identity))
457 			continue;
458 
459 		if ((unsigned long)mid_p == INVALID_P2M_ENTRY)
460 			continue;
461 
462 		/* The old va. Rebase it on mfn_list */
463 		if (mid_p >= (unsigned long *)va_start && mid_p <= (unsigned long *)va_end) {
464 			unsigned long *new;
465 
466 			if (pfn_free  > (size / sizeof(unsigned long))) {
467 				WARN(1, "Only allocated for %ld pages, but we want %ld!\n",
468 				     size / sizeof(unsigned long), pfn_free);
469 				return 0;
470 			}
471 			new = &mfn_list[pfn_free];
472 
473 			copy_page(new, mid_p);
474 			p2m_top[topidx][mididx] = &mfn_list[pfn_free];
475 
476 			pfn_free += P2M_PER_PAGE;
477 
478 		}
479 		/* This should be the leafs allocated for identity from _brk. */
480 	}
481 	return (unsigned long)mfn_list;
482 
483 }
484 #else
485 unsigned long __init xen_revector_p2m_tree(void)
486 {
487 	return 0;
488 }
489 #endif
490 unsigned long get_phys_to_machine(unsigned long pfn)
491 {
492 	unsigned topidx, mididx, idx;
493 
494 	if (unlikely(pfn >= MAX_P2M_PFN))
495 		return IDENTITY_FRAME(pfn);
496 
497 	topidx = p2m_top_index(pfn);
498 	mididx = p2m_mid_index(pfn);
499 	idx = p2m_index(pfn);
500 
501 	/*
502 	 * The INVALID_P2M_ENTRY is filled in both p2m_*identity
503 	 * and in p2m_*missing, so returning the INVALID_P2M_ENTRY
504 	 * would be wrong.
505 	 */
506 	if (p2m_top[topidx][mididx] == p2m_identity)
507 		return IDENTITY_FRAME(pfn);
508 
509 	return p2m_top[topidx][mididx][idx];
510 }
511 EXPORT_SYMBOL_GPL(get_phys_to_machine);
512 
513 static void *alloc_p2m_page(void)
514 {
515 	return (void *)__get_free_page(GFP_KERNEL | __GFP_REPEAT);
516 }
517 
518 static void free_p2m_page(void *p)
519 {
520 	free_page((unsigned long)p);
521 }
522 
523 /*
524  * Fully allocate the p2m structure for a given pfn.  We need to check
525  * that both the top and mid levels are allocated, and make sure the
526  * parallel mfn tree is kept in sync.  We may race with other cpus, so
527  * the new pages are installed with cmpxchg; if we lose the race then
528  * simply free the page we allocated and use the one that's there.
529  */
530 static bool alloc_p2m(unsigned long pfn)
531 {
532 	unsigned topidx, mididx;
533 	unsigned long ***top_p, **mid;
534 	unsigned long *top_mfn_p, *mid_mfn;
535 	unsigned long *p2m_orig;
536 
537 	topidx = p2m_top_index(pfn);
538 	mididx = p2m_mid_index(pfn);
539 
540 	top_p = &p2m_top[topidx];
541 	mid = ACCESS_ONCE(*top_p);
542 
543 	if (mid == p2m_mid_missing) {
544 		/* Mid level is missing, allocate a new one */
545 		mid = alloc_p2m_page();
546 		if (!mid)
547 			return false;
548 
549 		p2m_mid_init(mid, p2m_missing);
550 
551 		if (cmpxchg(top_p, p2m_mid_missing, mid) != p2m_mid_missing)
552 			free_p2m_page(mid);
553 	}
554 
555 	top_mfn_p = &p2m_top_mfn[topidx];
556 	mid_mfn = ACCESS_ONCE(p2m_top_mfn_p[topidx]);
557 
558 	BUG_ON(virt_to_mfn(mid_mfn) != *top_mfn_p);
559 
560 	if (mid_mfn == p2m_mid_missing_mfn) {
561 		/* Separately check the mid mfn level */
562 		unsigned long missing_mfn;
563 		unsigned long mid_mfn_mfn;
564 		unsigned long old_mfn;
565 
566 		mid_mfn = alloc_p2m_page();
567 		if (!mid_mfn)
568 			return false;
569 
570 		p2m_mid_mfn_init(mid_mfn, p2m_missing);
571 
572 		missing_mfn = virt_to_mfn(p2m_mid_missing_mfn);
573 		mid_mfn_mfn = virt_to_mfn(mid_mfn);
574 		old_mfn = cmpxchg(top_mfn_p, missing_mfn, mid_mfn_mfn);
575 		if (old_mfn != missing_mfn) {
576 			free_p2m_page(mid_mfn);
577 			mid_mfn = mfn_to_virt(old_mfn);
578 		} else {
579 			p2m_top_mfn_p[topidx] = mid_mfn;
580 		}
581 	}
582 
583 	p2m_orig = ACCESS_ONCE(p2m_top[topidx][mididx]);
584 	if (p2m_orig == p2m_identity || p2m_orig == p2m_missing) {
585 		/* p2m leaf page is missing */
586 		unsigned long *p2m;
587 
588 		p2m = alloc_p2m_page();
589 		if (!p2m)
590 			return false;
591 
592 		p2m_init(p2m);
593 
594 		if (cmpxchg(&mid[mididx], p2m_orig, p2m) != p2m_orig)
595 			free_p2m_page(p2m);
596 		else
597 			mid_mfn[mididx] = virt_to_mfn(p2m);
598 	}
599 
600 	return true;
601 }
602 
603 static bool __init early_alloc_p2m(unsigned long pfn, bool check_boundary)
604 {
605 	unsigned topidx, mididx, idx;
606 	unsigned long *p2m;
607 
608 	topidx = p2m_top_index(pfn);
609 	mididx = p2m_mid_index(pfn);
610 	idx = p2m_index(pfn);
611 
612 	/* Pfff.. No boundary cross-over, lets get out. */
613 	if (!idx && check_boundary)
614 		return false;
615 
616 	WARN(p2m_top[topidx][mididx] == p2m_identity,
617 		"P2M[%d][%d] == IDENTITY, should be MISSING (or alloced)!\n",
618 		topidx, mididx);
619 
620 	/*
621 	 * Could be done by xen_build_dynamic_phys_to_machine..
622 	 */
623 	if (p2m_top[topidx][mididx] != p2m_missing)
624 		return false;
625 
626 	/* Boundary cross-over for the edges: */
627 	p2m = extend_brk(PAGE_SIZE, PAGE_SIZE);
628 
629 	p2m_init(p2m);
630 
631 	p2m_top[topidx][mididx] = p2m;
632 
633 	return true;
634 }
635 
636 static bool __init early_alloc_p2m_middle(unsigned long pfn)
637 {
638 	unsigned topidx = p2m_top_index(pfn);
639 	unsigned long **mid;
640 
641 	mid = p2m_top[topidx];
642 	if (mid == p2m_mid_missing) {
643 		mid = extend_brk(PAGE_SIZE, PAGE_SIZE);
644 
645 		p2m_mid_init(mid, p2m_missing);
646 
647 		p2m_top[topidx] = mid;
648 	}
649 	return true;
650 }
651 
652 /*
653  * Skim over the P2M tree looking at pages that are either filled with
654  * INVALID_P2M_ENTRY or with 1:1 PFNs. If found, re-use that page and
655  * replace the P2M leaf with a p2m_missing or p2m_identity.
656  * Stick the old page in the new P2M tree location.
657  */
658 static bool __init early_can_reuse_p2m_middle(unsigned long set_pfn)
659 {
660 	unsigned topidx;
661 	unsigned mididx;
662 	unsigned ident_pfns;
663 	unsigned inv_pfns;
664 	unsigned long *p2m;
665 	unsigned idx;
666 	unsigned long pfn;
667 
668 	/* We only look when this entails a P2M middle layer */
669 	if (p2m_index(set_pfn))
670 		return false;
671 
672 	for (pfn = 0; pfn < MAX_DOMAIN_PAGES; pfn += P2M_PER_PAGE) {
673 		topidx = p2m_top_index(pfn);
674 
675 		if (!p2m_top[topidx])
676 			continue;
677 
678 		if (p2m_top[topidx] == p2m_mid_missing)
679 			continue;
680 
681 		mididx = p2m_mid_index(pfn);
682 		p2m = p2m_top[topidx][mididx];
683 		if (!p2m)
684 			continue;
685 
686 		if ((p2m == p2m_missing) || (p2m == p2m_identity))
687 			continue;
688 
689 		if ((unsigned long)p2m == INVALID_P2M_ENTRY)
690 			continue;
691 
692 		ident_pfns = 0;
693 		inv_pfns = 0;
694 		for (idx = 0; idx < P2M_PER_PAGE; idx++) {
695 			/* IDENTITY_PFNs are 1:1 */
696 			if (p2m[idx] == IDENTITY_FRAME(pfn + idx))
697 				ident_pfns++;
698 			else if (p2m[idx] == INVALID_P2M_ENTRY)
699 				inv_pfns++;
700 			else
701 				break;
702 		}
703 		if ((ident_pfns == P2M_PER_PAGE) || (inv_pfns == P2M_PER_PAGE))
704 			goto found;
705 	}
706 	return false;
707 found:
708 	/* Found one, replace old with p2m_identity or p2m_missing */
709 	p2m_top[topidx][mididx] = (ident_pfns ? p2m_identity : p2m_missing);
710 
711 	/* Reset where we want to stick the old page in. */
712 	topidx = p2m_top_index(set_pfn);
713 	mididx = p2m_mid_index(set_pfn);
714 
715 	/* This shouldn't happen */
716 	if (WARN_ON(p2m_top[topidx] == p2m_mid_missing))
717 		early_alloc_p2m_middle(set_pfn);
718 
719 	if (WARN_ON(p2m_top[topidx][mididx] != p2m_missing))
720 		return false;
721 
722 	p2m_init(p2m);
723 	p2m_top[topidx][mididx] = p2m;
724 
725 	return true;
726 }
727 bool __init early_set_phys_to_machine(unsigned long pfn, unsigned long mfn)
728 {
729 	if (unlikely(!__set_phys_to_machine(pfn, mfn)))  {
730 		if (!early_alloc_p2m_middle(pfn))
731 			return false;
732 
733 		if (early_can_reuse_p2m_middle(pfn))
734 			return __set_phys_to_machine(pfn, mfn);
735 
736 		if (!early_alloc_p2m(pfn, false /* boundary crossover OK!*/))
737 			return false;
738 
739 		if (!__set_phys_to_machine(pfn, mfn))
740 			return false;
741 	}
742 
743 	return true;
744 }
745 
746 static void __init early_split_p2m(unsigned long pfn)
747 {
748 	unsigned long mididx, idx;
749 
750 	mididx = p2m_mid_index(pfn);
751 	idx = p2m_index(pfn);
752 
753 	/*
754 	 * Allocate new middle and leaf pages if this pfn lies in the
755 	 * middle of one.
756 	 */
757 	if (mididx || idx)
758 		early_alloc_p2m_middle(pfn);
759 	if (idx)
760 		early_alloc_p2m(pfn, false);
761 }
762 
763 unsigned long __init set_phys_range_identity(unsigned long pfn_s,
764 				      unsigned long pfn_e)
765 {
766 	unsigned long pfn;
767 
768 	if (unlikely(pfn_s >= MAX_P2M_PFN))
769 		return 0;
770 
771 	if (unlikely(xen_feature(XENFEAT_auto_translated_physmap)))
772 		return pfn_e - pfn_s;
773 
774 	if (pfn_s > pfn_e)
775 		return 0;
776 
777 	if (pfn_e > MAX_P2M_PFN)
778 		pfn_e = MAX_P2M_PFN;
779 
780 	early_split_p2m(pfn_s);
781 	early_split_p2m(pfn_e);
782 
783 	for (pfn = pfn_s; pfn < pfn_e;) {
784 		unsigned topidx = p2m_top_index(pfn);
785 		unsigned mididx = p2m_mid_index(pfn);
786 
787 		if (!__set_phys_to_machine(pfn, IDENTITY_FRAME(pfn)))
788 			break;
789 		pfn++;
790 
791 		/*
792 		 * If the PFN was set to a middle or leaf identity
793 		 * page the remainder must also be identity, so skip
794 		 * ahead to the next middle or leaf entry.
795 		 */
796 		if (p2m_top[topidx] == p2m_mid_identity)
797 			pfn = ALIGN(pfn, P2M_MID_PER_PAGE * P2M_PER_PAGE);
798 		else if (p2m_top[topidx][mididx] == p2m_identity)
799 			pfn = ALIGN(pfn, P2M_PER_PAGE);
800 	}
801 
802 	WARN((pfn - pfn_s) != (pfn_e - pfn_s),
803 		"Identity mapping failed. We are %ld short of 1-1 mappings!\n",
804 		(pfn_e - pfn_s) - (pfn - pfn_s));
805 
806 	return pfn - pfn_s;
807 }
808 
809 /* Try to install p2m mapping; fail if intermediate bits missing */
810 bool __set_phys_to_machine(unsigned long pfn, unsigned long mfn)
811 {
812 	unsigned topidx, mididx, idx;
813 
814 	/* don't track P2M changes in autotranslate guests */
815 	if (unlikely(xen_feature(XENFEAT_auto_translated_physmap)))
816 		return true;
817 
818 	if (unlikely(pfn >= MAX_P2M_PFN)) {
819 		BUG_ON(mfn != INVALID_P2M_ENTRY);
820 		return true;
821 	}
822 
823 	topidx = p2m_top_index(pfn);
824 	mididx = p2m_mid_index(pfn);
825 	idx = p2m_index(pfn);
826 
827 	/* For sparse holes were the p2m leaf has real PFN along with
828 	 * PCI holes, stick in the PFN as the MFN value.
829 	 *
830 	 * set_phys_range_identity() will have allocated new middle
831 	 * and leaf pages as required so an existing p2m_mid_missing
832 	 * or p2m_missing mean that whole range will be identity so
833 	 * these can be switched to p2m_mid_identity or p2m_identity.
834 	 */
835 	if (mfn != INVALID_P2M_ENTRY && (mfn & IDENTITY_FRAME_BIT)) {
836 		if (p2m_top[topidx] == p2m_mid_identity)
837 			return true;
838 
839 		if (p2m_top[topidx] == p2m_mid_missing) {
840 			WARN_ON(cmpxchg(&p2m_top[topidx], p2m_mid_missing,
841 					p2m_mid_identity) != p2m_mid_missing);
842 			return true;
843 		}
844 
845 		if (p2m_top[topidx][mididx] == p2m_identity)
846 			return true;
847 
848 		/* Swap over from MISSING to IDENTITY if needed. */
849 		if (p2m_top[topidx][mididx] == p2m_missing) {
850 			WARN_ON(cmpxchg(&p2m_top[topidx][mididx], p2m_missing,
851 				p2m_identity) != p2m_missing);
852 			return true;
853 		}
854 	}
855 
856 	if (p2m_top[topidx][mididx] == p2m_missing)
857 		return mfn == INVALID_P2M_ENTRY;
858 
859 	p2m_top[topidx][mididx][idx] = mfn;
860 
861 	return true;
862 }
863 
864 bool set_phys_to_machine(unsigned long pfn, unsigned long mfn)
865 {
866 	if (unlikely(!__set_phys_to_machine(pfn, mfn)))  {
867 		if (!alloc_p2m(pfn))
868 			return false;
869 
870 		if (!__set_phys_to_machine(pfn, mfn))
871 			return false;
872 	}
873 
874 	return true;
875 }
876 
877 #define M2P_OVERRIDE_HASH_SHIFT	10
878 #define M2P_OVERRIDE_HASH	(1 << M2P_OVERRIDE_HASH_SHIFT)
879 
880 static RESERVE_BRK_ARRAY(struct list_head, m2p_overrides, M2P_OVERRIDE_HASH);
881 static DEFINE_SPINLOCK(m2p_override_lock);
882 
883 static void __init m2p_override_init(void)
884 {
885 	unsigned i;
886 
887 	m2p_overrides = extend_brk(sizeof(*m2p_overrides) * M2P_OVERRIDE_HASH,
888 				   sizeof(unsigned long));
889 
890 	for (i = 0; i < M2P_OVERRIDE_HASH; i++)
891 		INIT_LIST_HEAD(&m2p_overrides[i]);
892 }
893 
894 static unsigned long mfn_hash(unsigned long mfn)
895 {
896 	return hash_long(mfn, M2P_OVERRIDE_HASH_SHIFT);
897 }
898 
899 int set_foreign_p2m_mapping(struct gnttab_map_grant_ref *map_ops,
900 			    struct gnttab_map_grant_ref *kmap_ops,
901 			    struct page **pages, unsigned int count)
902 {
903 	int i, ret = 0;
904 	bool lazy = false;
905 	pte_t *pte;
906 
907 	if (xen_feature(XENFEAT_auto_translated_physmap))
908 		return 0;
909 
910 	if (kmap_ops &&
911 	    !in_interrupt() &&
912 	    paravirt_get_lazy_mode() == PARAVIRT_LAZY_NONE) {
913 		arch_enter_lazy_mmu_mode();
914 		lazy = true;
915 	}
916 
917 	for (i = 0; i < count; i++) {
918 		unsigned long mfn, pfn;
919 
920 		/* Do not add to override if the map failed. */
921 		if (map_ops[i].status)
922 			continue;
923 
924 		if (map_ops[i].flags & GNTMAP_contains_pte) {
925 			pte = (pte_t *) (mfn_to_virt(PFN_DOWN(map_ops[i].host_addr)) +
926 				(map_ops[i].host_addr & ~PAGE_MASK));
927 			mfn = pte_mfn(*pte);
928 		} else {
929 			mfn = PFN_DOWN(map_ops[i].dev_bus_addr);
930 		}
931 		pfn = page_to_pfn(pages[i]);
932 
933 		WARN_ON(PagePrivate(pages[i]));
934 		SetPagePrivate(pages[i]);
935 		set_page_private(pages[i], mfn);
936 		pages[i]->index = pfn_to_mfn(pfn);
937 
938 		if (unlikely(!set_phys_to_machine(pfn, FOREIGN_FRAME(mfn)))) {
939 			ret = -ENOMEM;
940 			goto out;
941 		}
942 
943 		if (kmap_ops) {
944 			ret = m2p_add_override(mfn, pages[i], &kmap_ops[i]);
945 			if (ret)
946 				goto out;
947 		}
948 	}
949 
950 out:
951 	if (lazy)
952 		arch_leave_lazy_mmu_mode();
953 
954 	return ret;
955 }
956 EXPORT_SYMBOL_GPL(set_foreign_p2m_mapping);
957 
958 /* Add an MFN override for a particular page */
959 int m2p_add_override(unsigned long mfn, struct page *page,
960 		struct gnttab_map_grant_ref *kmap_op)
961 {
962 	unsigned long flags;
963 	unsigned long pfn;
964 	unsigned long uninitialized_var(address);
965 	unsigned level;
966 	pte_t *ptep = NULL;
967 
968 	pfn = page_to_pfn(page);
969 	if (!PageHighMem(page)) {
970 		address = (unsigned long)__va(pfn << PAGE_SHIFT);
971 		ptep = lookup_address(address, &level);
972 		if (WARN(ptep == NULL || level != PG_LEVEL_4K,
973 					"m2p_add_override: pfn %lx not mapped", pfn))
974 			return -EINVAL;
975 	}
976 
977 	if (kmap_op != NULL) {
978 		if (!PageHighMem(page)) {
979 			struct multicall_space mcs =
980 				xen_mc_entry(sizeof(*kmap_op));
981 
982 			MULTI_grant_table_op(mcs.mc,
983 					GNTTABOP_map_grant_ref, kmap_op, 1);
984 
985 			xen_mc_issue(PARAVIRT_LAZY_MMU);
986 		}
987 	}
988 	spin_lock_irqsave(&m2p_override_lock, flags);
989 	list_add(&page->lru,  &m2p_overrides[mfn_hash(mfn)]);
990 	spin_unlock_irqrestore(&m2p_override_lock, flags);
991 
992 	/* p2m(m2p(mfn)) == mfn: the mfn is already present somewhere in
993 	 * this domain. Set the FOREIGN_FRAME_BIT in the p2m for the other
994 	 * pfn so that the following mfn_to_pfn(mfn) calls will return the
995 	 * pfn from the m2p_override (the backend pfn) instead.
996 	 * We need to do this because the pages shared by the frontend
997 	 * (xen-blkfront) can be already locked (lock_page, called by
998 	 * do_read_cache_page); when the userspace backend tries to use them
999 	 * with direct_IO, mfn_to_pfn returns the pfn of the frontend, so
1000 	 * do_blockdev_direct_IO is going to try to lock the same pages
1001 	 * again resulting in a deadlock.
1002 	 * As a side effect get_user_pages_fast might not be safe on the
1003 	 * frontend pages while they are being shared with the backend,
1004 	 * because mfn_to_pfn (that ends up being called by GUPF) will
1005 	 * return the backend pfn rather than the frontend pfn. */
1006 	pfn = mfn_to_pfn_no_overrides(mfn);
1007 	if (get_phys_to_machine(pfn) == mfn)
1008 		set_phys_to_machine(pfn, FOREIGN_FRAME(mfn));
1009 
1010 	return 0;
1011 }
1012 EXPORT_SYMBOL_GPL(m2p_add_override);
1013 
1014 int clear_foreign_p2m_mapping(struct gnttab_unmap_grant_ref *unmap_ops,
1015 			      struct gnttab_map_grant_ref *kmap_ops,
1016 			      struct page **pages, unsigned int count)
1017 {
1018 	int i, ret = 0;
1019 	bool lazy = false;
1020 
1021 	if (xen_feature(XENFEAT_auto_translated_physmap))
1022 		return 0;
1023 
1024 	if (kmap_ops &&
1025 	    !in_interrupt() &&
1026 	    paravirt_get_lazy_mode() == PARAVIRT_LAZY_NONE) {
1027 		arch_enter_lazy_mmu_mode();
1028 		lazy = true;
1029 	}
1030 
1031 	for (i = 0; i < count; i++) {
1032 		unsigned long mfn = get_phys_to_machine(page_to_pfn(pages[i]));
1033 		unsigned long pfn = page_to_pfn(pages[i]);
1034 
1035 		if (mfn == INVALID_P2M_ENTRY || !(mfn & FOREIGN_FRAME_BIT)) {
1036 			ret = -EINVAL;
1037 			goto out;
1038 		}
1039 
1040 		set_page_private(pages[i], INVALID_P2M_ENTRY);
1041 		WARN_ON(!PagePrivate(pages[i]));
1042 		ClearPagePrivate(pages[i]);
1043 		set_phys_to_machine(pfn, pages[i]->index);
1044 
1045 		if (kmap_ops)
1046 			ret = m2p_remove_override(pages[i], &kmap_ops[i], mfn);
1047 		if (ret)
1048 			goto out;
1049 	}
1050 
1051 out:
1052 	if (lazy)
1053 		arch_leave_lazy_mmu_mode();
1054 	return ret;
1055 }
1056 EXPORT_SYMBOL_GPL(clear_foreign_p2m_mapping);
1057 
1058 int m2p_remove_override(struct page *page,
1059 			struct gnttab_map_grant_ref *kmap_op,
1060 			unsigned long mfn)
1061 {
1062 	unsigned long flags;
1063 	unsigned long pfn;
1064 	unsigned long uninitialized_var(address);
1065 	unsigned level;
1066 	pte_t *ptep = NULL;
1067 
1068 	pfn = page_to_pfn(page);
1069 
1070 	if (!PageHighMem(page)) {
1071 		address = (unsigned long)__va(pfn << PAGE_SHIFT);
1072 		ptep = lookup_address(address, &level);
1073 
1074 		if (WARN(ptep == NULL || level != PG_LEVEL_4K,
1075 					"m2p_remove_override: pfn %lx not mapped", pfn))
1076 			return -EINVAL;
1077 	}
1078 
1079 	spin_lock_irqsave(&m2p_override_lock, flags);
1080 	list_del(&page->lru);
1081 	spin_unlock_irqrestore(&m2p_override_lock, flags);
1082 
1083 	if (kmap_op != NULL) {
1084 		if (!PageHighMem(page)) {
1085 			struct multicall_space mcs;
1086 			struct gnttab_unmap_and_replace *unmap_op;
1087 			struct page *scratch_page = get_balloon_scratch_page();
1088 			unsigned long scratch_page_address = (unsigned long)
1089 				__va(page_to_pfn(scratch_page) << PAGE_SHIFT);
1090 
1091 			/*
1092 			 * It might be that we queued all the m2p grant table
1093 			 * hypercalls in a multicall, then m2p_remove_override
1094 			 * get called before the multicall has actually been
1095 			 * issued. In this case handle is going to -1 because
1096 			 * it hasn't been modified yet.
1097 			 */
1098 			if (kmap_op->handle == -1)
1099 				xen_mc_flush();
1100 			/*
1101 			 * Now if kmap_op->handle is negative it means that the
1102 			 * hypercall actually returned an error.
1103 			 */
1104 			if (kmap_op->handle == GNTST_general_error) {
1105 				printk(KERN_WARNING "m2p_remove_override: "
1106 						"pfn %lx mfn %lx, failed to modify kernel mappings",
1107 						pfn, mfn);
1108 				put_balloon_scratch_page();
1109 				return -1;
1110 			}
1111 
1112 			xen_mc_batch();
1113 
1114 			mcs = __xen_mc_entry(
1115 					sizeof(struct gnttab_unmap_and_replace));
1116 			unmap_op = mcs.args;
1117 			unmap_op->host_addr = kmap_op->host_addr;
1118 			unmap_op->new_addr = scratch_page_address;
1119 			unmap_op->handle = kmap_op->handle;
1120 
1121 			MULTI_grant_table_op(mcs.mc,
1122 					GNTTABOP_unmap_and_replace, unmap_op, 1);
1123 
1124 			mcs = __xen_mc_entry(0);
1125 			MULTI_update_va_mapping(mcs.mc, scratch_page_address,
1126 					pfn_pte(page_to_pfn(scratch_page),
1127 					PAGE_KERNEL_RO), 0);
1128 
1129 			xen_mc_issue(PARAVIRT_LAZY_MMU);
1130 
1131 			kmap_op->host_addr = 0;
1132 			put_balloon_scratch_page();
1133 		}
1134 	}
1135 
1136 	/* p2m(m2p(mfn)) == FOREIGN_FRAME(mfn): the mfn is already present
1137 	 * somewhere in this domain, even before being added to the
1138 	 * m2p_override (see comment above in m2p_add_override).
1139 	 * If there are no other entries in the m2p_override corresponding
1140 	 * to this mfn, then remove the FOREIGN_FRAME_BIT from the p2m for
1141 	 * the original pfn (the one shared by the frontend): the backend
1142 	 * cannot do any IO on this page anymore because it has been
1143 	 * unshared. Removing the FOREIGN_FRAME_BIT from the p2m entry of
1144 	 * the original pfn causes mfn_to_pfn(mfn) to return the frontend
1145 	 * pfn again. */
1146 	mfn &= ~FOREIGN_FRAME_BIT;
1147 	pfn = mfn_to_pfn_no_overrides(mfn);
1148 	if (get_phys_to_machine(pfn) == FOREIGN_FRAME(mfn) &&
1149 			m2p_find_override(mfn) == NULL)
1150 		set_phys_to_machine(pfn, mfn);
1151 
1152 	return 0;
1153 }
1154 EXPORT_SYMBOL_GPL(m2p_remove_override);
1155 
1156 struct page *m2p_find_override(unsigned long mfn)
1157 {
1158 	unsigned long flags;
1159 	struct list_head *bucket = &m2p_overrides[mfn_hash(mfn)];
1160 	struct page *p, *ret;
1161 
1162 	ret = NULL;
1163 
1164 	spin_lock_irqsave(&m2p_override_lock, flags);
1165 
1166 	list_for_each_entry(p, bucket, lru) {
1167 		if (page_private(p) == mfn) {
1168 			ret = p;
1169 			break;
1170 		}
1171 	}
1172 
1173 	spin_unlock_irqrestore(&m2p_override_lock, flags);
1174 
1175 	return ret;
1176 }
1177 
1178 unsigned long m2p_find_override_pfn(unsigned long mfn, unsigned long pfn)
1179 {
1180 	struct page *p = m2p_find_override(mfn);
1181 	unsigned long ret = pfn;
1182 
1183 	if (p)
1184 		ret = page_to_pfn(p);
1185 
1186 	return ret;
1187 }
1188 EXPORT_SYMBOL_GPL(m2p_find_override_pfn);
1189 
1190 #ifdef CONFIG_XEN_DEBUG_FS
1191 #include <linux/debugfs.h>
1192 #include "debugfs.h"
1193 static int p2m_dump_show(struct seq_file *m, void *v)
1194 {
1195 	static const char * const level_name[] = { "top", "middle",
1196 						"entry", "abnormal", "error"};
1197 #define TYPE_IDENTITY 0
1198 #define TYPE_MISSING 1
1199 #define TYPE_PFN 2
1200 #define TYPE_UNKNOWN 3
1201 	static const char * const type_name[] = {
1202 				[TYPE_IDENTITY] = "identity",
1203 				[TYPE_MISSING] = "missing",
1204 				[TYPE_PFN] = "pfn",
1205 				[TYPE_UNKNOWN] = "abnormal"};
1206 	unsigned long pfn, prev_pfn_type = 0, prev_pfn_level = 0;
1207 	unsigned int uninitialized_var(prev_level);
1208 	unsigned int uninitialized_var(prev_type);
1209 
1210 	if (!p2m_top)
1211 		return 0;
1212 
1213 	for (pfn = 0; pfn < MAX_DOMAIN_PAGES; pfn++) {
1214 		unsigned topidx = p2m_top_index(pfn);
1215 		unsigned mididx = p2m_mid_index(pfn);
1216 		unsigned idx = p2m_index(pfn);
1217 		unsigned lvl, type;
1218 
1219 		lvl = 4;
1220 		type = TYPE_UNKNOWN;
1221 		if (p2m_top[topidx] == p2m_mid_missing) {
1222 			lvl = 0; type = TYPE_MISSING;
1223 		} else if (p2m_top[topidx] == NULL) {
1224 			lvl = 0; type = TYPE_UNKNOWN;
1225 		} else if (p2m_top[topidx][mididx] == NULL) {
1226 			lvl = 1; type = TYPE_UNKNOWN;
1227 		} else if (p2m_top[topidx][mididx] == p2m_identity) {
1228 			lvl = 1; type = TYPE_IDENTITY;
1229 		} else if (p2m_top[topidx][mididx] == p2m_missing) {
1230 			lvl = 1; type = TYPE_MISSING;
1231 		} else if (p2m_top[topidx][mididx][idx] == 0) {
1232 			lvl = 2; type = TYPE_UNKNOWN;
1233 		} else if (p2m_top[topidx][mididx][idx] == IDENTITY_FRAME(pfn)) {
1234 			lvl = 2; type = TYPE_IDENTITY;
1235 		} else if (p2m_top[topidx][mididx][idx] == INVALID_P2M_ENTRY) {
1236 			lvl = 2; type = TYPE_MISSING;
1237 		} else if (p2m_top[topidx][mididx][idx] == pfn) {
1238 			lvl = 2; type = TYPE_PFN;
1239 		} else if (p2m_top[topidx][mididx][idx] != pfn) {
1240 			lvl = 2; type = TYPE_PFN;
1241 		}
1242 		if (pfn == 0) {
1243 			prev_level = lvl;
1244 			prev_type = type;
1245 		}
1246 		if (pfn == MAX_DOMAIN_PAGES-1) {
1247 			lvl = 3;
1248 			type = TYPE_UNKNOWN;
1249 		}
1250 		if (prev_type != type) {
1251 			seq_printf(m, " [0x%lx->0x%lx] %s\n",
1252 				prev_pfn_type, pfn, type_name[prev_type]);
1253 			prev_pfn_type = pfn;
1254 			prev_type = type;
1255 		}
1256 		if (prev_level != lvl) {
1257 			seq_printf(m, " [0x%lx->0x%lx] level %s\n",
1258 				prev_pfn_level, pfn, level_name[prev_level]);
1259 			prev_pfn_level = pfn;
1260 			prev_level = lvl;
1261 		}
1262 	}
1263 	return 0;
1264 #undef TYPE_IDENTITY
1265 #undef TYPE_MISSING
1266 #undef TYPE_PFN
1267 #undef TYPE_UNKNOWN
1268 }
1269 
1270 static int p2m_dump_open(struct inode *inode, struct file *filp)
1271 {
1272 	return single_open(filp, p2m_dump_show, NULL);
1273 }
1274 
1275 static const struct file_operations p2m_dump_fops = {
1276 	.open		= p2m_dump_open,
1277 	.read		= seq_read,
1278 	.llseek		= seq_lseek,
1279 	.release	= single_release,
1280 };
1281 
1282 static struct dentry *d_mmu_debug;
1283 
1284 static int __init xen_p2m_debugfs(void)
1285 {
1286 	struct dentry *d_xen = xen_init_debugfs();
1287 
1288 	if (d_xen == NULL)
1289 		return -ENOMEM;
1290 
1291 	d_mmu_debug = debugfs_create_dir("mmu", d_xen);
1292 
1293 	debugfs_create_file("p2m", 0600, d_mmu_debug, NULL, &p2m_dump_fops);
1294 	return 0;
1295 }
1296 fs_initcall(xen_p2m_debugfs);
1297 #endif /* CONFIG_XEN_DEBUG_FS */
1298