Linux/arch/x86/xen/p2m.c

  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 b/c 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
 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 loop on aligned 1GB PFNs from start pfn
 81  * to end pfn.  We reserve_brk top leaf pages if they are missing (means they
 82  * point to p2m_mid_missing).
 83  *
 84  * With the E820 example above, 263424 is not 1GB aligned so we allocate a
 85  * reserve_brk page which will cover the PFNs estate from 0x40000 to 0x80000.
 86  * Each entry in the allocate page is "missing" (points to p2m_missing).
 87  *
 88  * Next stage is to determine if we need to do a more granular boundary check
 89  * on the 4MB (or 2MB depending on architecture) off the start and end pfn's.
 90  * We check if the start pfn and end pfn violate that boundary check, and if
 91  * so reserve_brk a middle (p2m[x][y]) leaf page. This way we have a much finer
 92  * granularity of setting which PFNs are missing and which ones are identity.
 93  * In our example 263424 and 512256 both fail the check so we reserve_brk two
 94  * pages. Populate them with INVALID_P2M_ENTRY (so they both have "missing"
 95  * values) and assign them to p2m[1][2] and p2m[1][488] respectively.
 96  *
 97  * At this point we would at minimum reserve_brk one page, but could be up to
 98  * three. Each call to set_phys_range_identity has at maximum a three page
 99  * cost. If we were to query the P2M at this stage, all those entries from
100  * start PFN through end PFN (so 1029MB -> 2001MB) would return
101  * INVALID_P2M_ENTRY ("missing").
102  *
103  * The next step is to walk from the start pfn to the end pfn setting
104  * the IDENTITY_FRAME_BIT on each PFN. This is done in set_phys_range_identity.
105  * If we find that the middle leaf is pointing to p2m_missing we can swap it
106  * over to p2m_identity - this way covering 4MB (or 2MB) PFN space.  At this
107  * 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  * This is what the p2m ends up looking (for the E820 above) with this
122  * fabulous drawing:
123  *
124  *    p2m         /--------------\
125  *  /-----\       | &mfn_list[0],|                           /-----------------\
126  *  |  0  |------>| &mfn_list[1],|    /---------------\      | ~0, ~0, ..      |
127  *  |-----|       |  ..., ~0, ~0 |    | ~0, ~0, [x]---+----->| IDENTITY [@256] |
128  *  |  1  |---\   \--------------/    | [p2m_identity]+\     | IDENTITY [@257] |
129  *  |-----|    \                      | [p2m_identity]+\\    | ....            |
130  *  |  2  |--\  \-------------------->|  ...          | \\   \----------------/
131  *  |-----|   \                       \---------------/  \\
132  *  |  3  |\   \                                          \\  p2m_identity
133  *  |-----| \   \-------------------->/---------------\   /-----------------\
134  *  | ..  +->+                        | [p2m_identity]+-->| ~0, ~0, ~0, ... |
135  *  \-----/ /                         | [p2m_identity]+-->| ..., ~0         |
136  *         / /---------------\        | ....          |   \-----------------/
137  *        /  | IDENTITY[@0]  |      /-+-[x], ~0, ~0.. |
138  *       /   | IDENTITY[@256]|<----/  \---------------/
139  *      /    | ~0, ~0, ....  |
140  *     |     \---------------/
141  *     |
142  *     p2m_missing             p2m_missing
143  * /------------------\     /------------\
144  * | [p2m_mid_missing]+---->| ~0, ~0, ~0 |
145  * | [p2m_mid_missing]+---->| ..., ~0    |
146  * \------------------/     \------------/
147  *
148  * where ~0 is INVALID_P2M_ENTRY. IDENTITY is (PFN | IDENTITY_BIT)
149  */
150 
151 #include <linux/init.h>
152 #include <linux/module.h>
153 #include <linux/list.h>
154 #include <linux/hash.h>
155 #include <linux/sched.h>
156 #include <linux/seq_file.h>
157 
158 #include <asm/cache.h>
159 #include <asm/setup.h>
160 
161 #include <asm/xen/page.h>
162 #include <asm/xen/hypercall.h>
163 #include <asm/xen/hypervisor.h>
164 #include <xen/grant_table.h>
165 
166 #include "multicalls.h"
167 #include "xen-ops.h"
168 
169 static void __init m2p_override_init(void);
170 
171 unsigned long xen_max_p2m_pfn __read_mostly;
172 
173 #define P2M_PER_PAGE            (PAGE_SIZE / sizeof(unsigned long))
174 #define P2M_MID_PER_PAGE        (PAGE_SIZE / sizeof(unsigned long *))
175 #define P2M_TOP_PER_PAGE        (PAGE_SIZE / sizeof(unsigned long **))
176 
177 #define MAX_P2M_PFN             (P2M_TOP_PER_PAGE * P2M_MID_PER_PAGE * P2M_PER_PAGE)
178 
179 /* Placeholders for holes in the address space */
180 static RESERVE_BRK_ARRAY(unsigned long, p2m_missing, P2M_PER_PAGE);
181 static RESERVE_BRK_ARRAY(unsigned long *, p2m_mid_missing, P2M_MID_PER_PAGE);
182 static RESERVE_BRK_ARRAY(unsigned long, p2m_mid_missing_mfn, P2M_MID_PER_PAGE);
183 
184 static RESERVE_BRK_ARRAY(unsigned long **, p2m_top, P2M_TOP_PER_PAGE);
185 static RESERVE_BRK_ARRAY(unsigned long, p2m_top_mfn, P2M_TOP_PER_PAGE);
186 static RESERVE_BRK_ARRAY(unsigned long *, p2m_top_mfn_p, P2M_TOP_PER_PAGE);
187 
188 static RESERVE_BRK_ARRAY(unsigned long, p2m_identity, P2M_PER_PAGE);
189 
190 RESERVE_BRK(p2m_mid, PAGE_SIZE * (MAX_DOMAIN_PAGES / (P2M_PER_PAGE * P2M_MID_PER_PAGE)));
191 RESERVE_BRK(p2m_mid_mfn, PAGE_SIZE * (MAX_DOMAIN_PAGES / (P2M_PER_PAGE * P2M_MID_PER_PAGE)));
192 
193 /* We might hit two boundary violations at the start and end, at max each
194  * boundary violation will require three middle nodes. */
195 RESERVE_BRK(p2m_mid_identity, PAGE_SIZE * 2 * 3);
196 
197 static inline unsigned p2m_top_index(unsigned long pfn)
198 {
199         BUG_ON(pfn >= MAX_P2M_PFN);
200         return pfn / (P2M_MID_PER_PAGE * P2M_PER_PAGE);
201 }
202 
203 static inline unsigned p2m_mid_index(unsigned long pfn)
204 {
205         return (pfn / P2M_PER_PAGE) % P2M_MID_PER_PAGE;
206 }
207 
208 static inline unsigned p2m_index(unsigned long pfn)
209 {
210         return pfn % P2M_PER_PAGE;
211 }
212 
213 static void p2m_top_init(unsigned long ***top)
214 {
215         unsigned i;
216 
217         for (i = 0; i < P2M_TOP_PER_PAGE; i++)
218                 top[i] = p2m_mid_missing;
219 }
220 
221 static void p2m_top_mfn_init(unsigned long *top)
222 {
223         unsigned i;
224 
225         for (i = 0; i < P2M_TOP_PER_PAGE; i++)
226                 top[i] = virt_to_mfn(p2m_mid_missing_mfn);
227 }
228 
229 static void p2m_top_mfn_p_init(unsigned long **top)
230 {
231         unsigned i;
232 
233         for (i = 0; i < P2M_TOP_PER_PAGE; i++)
234                 top[i] = p2m_mid_missing_mfn;
235 }
236 
237 static void p2m_mid_init(unsigned long **mid)
238 {
239         unsigned i;
240 
241         for (i = 0; i < P2M_MID_PER_PAGE; i++)
242                 mid[i] = p2m_missing;
243 }
244 
245 static void p2m_mid_mfn_init(unsigned long *mid)
246 {
247         unsigned i;
248 
249         for (i = 0; i < P2M_MID_PER_PAGE; i++)
250                 mid[i] = virt_to_mfn(p2m_missing);
251 }
252 
253 static void p2m_init(unsigned long *p2m)
254 {
255         unsigned i;
256 
257         for (i = 0; i < P2M_MID_PER_PAGE; i++)
258                 p2m[i] = INVALID_P2M_ENTRY;
259 }
260 
261 /*
262  * Build the parallel p2m_top_mfn and p2m_mid_mfn structures
263  *
264  * This is called both at boot time, and after resuming from suspend:
265  * - At boot time we're called very early, and must use extend_brk()
266  *   to allocate memory.
267  *
268  * - After resume we're called from within stop_machine, but the mfn
269  *   tree should alreay be completely allocated.
270  */
271 void __ref xen_build_mfn_list_list(void)
272 {
273         unsigned long pfn;
274 
275         /* Pre-initialize p2m_top_mfn to be completely missing */
276         if (p2m_top_mfn == NULL) {
277                 p2m_mid_missing_mfn = extend_brk(PAGE_SIZE, PAGE_SIZE);
278                 p2m_mid_mfn_init(p2m_mid_missing_mfn);
279 
280                 p2m_top_mfn_p = extend_brk(PAGE_SIZE, PAGE_SIZE);
281                 p2m_top_mfn_p_init(p2m_top_mfn_p);
282 
283                 p2m_top_mfn = extend_brk(PAGE_SIZE, PAGE_SIZE);
284                 p2m_top_mfn_init(p2m_top_mfn);
285         } else {
286                 /* Reinitialise, mfn's all change after migration */
287                 p2m_mid_mfn_init(p2m_mid_missing_mfn);
288         }
289 
290         for (pfn = 0; pfn < xen_max_p2m_pfn; pfn += P2M_PER_PAGE) {
291                 unsigned topidx = p2m_top_index(pfn);
292                 unsigned mididx = p2m_mid_index(pfn);
293                 unsigned long **mid;
294                 unsigned long *mid_mfn_p;
295 
296                 mid = p2m_top[topidx];
297                 mid_mfn_p = p2m_top_mfn_p[topidx];
298 
299                 /* Don't bother allocating any mfn mid levels if
300                  * they're just missing, just update the stored mfn,
301                  * since all could have changed over a migrate.
302                  */
303                 if (mid == p2m_mid_missing) {
304                         BUG_ON(mididx);
305                         BUG_ON(mid_mfn_p != p2m_mid_missing_mfn);
306                         p2m_top_mfn[topidx] = virt_to_mfn(p2m_mid_missing_mfn);
307                         pfn += (P2M_MID_PER_PAGE - 1) * P2M_PER_PAGE;
308                         continue;
309                 }
310 
311                 if (mid_mfn_p == p2m_mid_missing_mfn) {
312                         /*
313                          * XXX boot-time only!  We should never find
314                          * missing parts of the mfn tree after
315                          * runtime.  extend_brk() will BUG if we call
316                          * it too late.
317                          */
318                         mid_mfn_p = extend_brk(PAGE_SIZE, PAGE_SIZE);
319                         p2m_mid_mfn_init(mid_mfn_p);
320 
321                         p2m_top_mfn_p[topidx] = mid_mfn_p;
322                 }
323 
324                 p2m_top_mfn[topidx] = virt_to_mfn(mid_mfn_p);
325                 mid_mfn_p[mididx] = virt_to_mfn(mid[mididx]);
326         }
327 }
328 
329 void xen_setup_mfn_list_list(void)
330 {
331         BUG_ON(HYPERVISOR_shared_info == &xen_dummy_shared_info);
332 
333         HYPERVISOR_shared_info->arch.pfn_to_mfn_frame_list_list =
334                 virt_to_mfn(p2m_top_mfn);
335         HYPERVISOR_shared_info->arch.max_pfn = xen_max_p2m_pfn;
336 }
337 
338 /* Set up p2m_top to point to the domain-builder provided p2m pages */
339 void __init xen_build_dynamic_phys_to_machine(void)
340 {
341         unsigned long *mfn_list = (unsigned long *)xen_start_info->mfn_list;
342         unsigned long max_pfn = min(MAX_DOMAIN_PAGES, xen_start_info->nr_pages);
343         unsigned long pfn;
344 
345         xen_max_p2m_pfn = max_pfn;
346 
347         p2m_missing = extend_brk(PAGE_SIZE, PAGE_SIZE);
348         p2m_init(p2m_missing);
349 
350         p2m_mid_missing = extend_brk(PAGE_SIZE, PAGE_SIZE);
351         p2m_mid_init(p2m_mid_missing);
352 
353         p2m_top = extend_brk(PAGE_SIZE, PAGE_SIZE);
354         p2m_top_init(p2m_top);
355 
356         p2m_identity = extend_brk(PAGE_SIZE, PAGE_SIZE);
357         p2m_init(p2m_identity);
358 
359         /*
360          * The domain builder gives us a pre-constructed p2m array in
361          * mfn_list for all the pages initially given to us, so we just
362          * need to graft that into our tree structure.
363          */
364         for (pfn = 0; pfn < max_pfn; pfn += P2M_PER_PAGE) {
365                 unsigned topidx = p2m_top_index(pfn);
366                 unsigned mididx = p2m_mid_index(pfn);
367 
368                 if (p2m_top[topidx] == p2m_mid_missing) {
369                         unsigned long **mid = extend_brk(PAGE_SIZE, PAGE_SIZE);
370                         p2m_mid_init(mid);
371 
372                         p2m_top[topidx] = mid;
373                 }
374 
375                 /*
376                  * As long as the mfn_list has enough entries to completely
377                  * fill a p2m page, pointing into the array is ok. But if
378                  * not the entries beyond the last pfn will be undefined.
379                  */
380                 if (unlikely(pfn + P2M_PER_PAGE > max_pfn)) {
381                         unsigned long p2midx;
382 
383                         p2midx = max_pfn % P2M_PER_PAGE;
384                         for ( ; p2midx < P2M_PER_PAGE; p2midx++)
385                                 mfn_list[pfn + p2midx] = INVALID_P2M_ENTRY;
386                 }
387                 p2m_top[topidx][mididx] = &mfn_list[pfn];
388         }
389 
390         m2p_override_init();
391 }
392 
393 unsigned long get_phys_to_machine(unsigned long pfn)
394 {
395         unsigned topidx, mididx, idx;
396 
397         if (unlikely(pfn >= MAX_P2M_PFN))
398                 return INVALID_P2M_ENTRY;
399 
400         topidx = p2m_top_index(pfn);
401         mididx = p2m_mid_index(pfn);
402         idx = p2m_index(pfn);
403 
404         /*
405          * The INVALID_P2M_ENTRY is filled in both p2m_*identity
406          * and in p2m_*missing, so returning the INVALID_P2M_ENTRY
407          * would be wrong.
408          */
409         if (p2m_top[topidx][mididx] == p2m_identity)
410                 return IDENTITY_FRAME(pfn);
411 
412         return p2m_top[topidx][mididx][idx];
413 }
414 EXPORT_SYMBOL_GPL(get_phys_to_machine);
415 
416 static void *alloc_p2m_page(void)
417 {
418         return (void *)__get_free_page(GFP_KERNEL | __GFP_REPEAT);
419 }
420 
421 static void free_p2m_page(void *p)
422 {
423         free_page((unsigned long)p);
424 }
425 
426 /* 
427  * Fully allocate the p2m structure for a given pfn.  We need to check
428  * that both the top and mid levels are allocated, and make sure the
429  * parallel mfn tree is kept in sync.  We may race with other cpus, so
430  * the new pages are installed with cmpxchg; if we lose the race then
431  * simply free the page we allocated and use the one that's there.
432  */
433 static bool alloc_p2m(unsigned long pfn)
434 {
435         unsigned topidx, mididx;
436         unsigned long ***top_p, **mid;
437         unsigned long *top_mfn_p, *mid_mfn;
438 
439         topidx = p2m_top_index(pfn);
440         mididx = p2m_mid_index(pfn);
441 
442         top_p = &p2m_top[topidx];
443         mid = *top_p;
444 
445         if (mid == p2m_mid_missing) {
446                 /* Mid level is missing, allocate a new one */
447                 mid = alloc_p2m_page();
448                 if (!mid)
449                         return false;
450 
451                 p2m_mid_init(mid);
452 
453                 if (cmpxchg(top_p, p2m_mid_missing, mid) != p2m_mid_missing)
454                         free_p2m_page(mid);
455         }
456 
457         top_mfn_p = &p2m_top_mfn[topidx];
458         mid_mfn = p2m_top_mfn_p[topidx];
459 
460         BUG_ON(virt_to_mfn(mid_mfn) != *top_mfn_p);
461 
462         if (mid_mfn == p2m_mid_missing_mfn) {
463                 /* Separately check the mid mfn level */
464                 unsigned long missing_mfn;
465                 unsigned long mid_mfn_mfn;
466 
467                 mid_mfn = alloc_p2m_page();
468                 if (!mid_mfn)
469                         return false;
470 
471                 p2m_mid_mfn_init(mid_mfn);
472 
473                 missing_mfn = virt_to_mfn(p2m_mid_missing_mfn);
474                 mid_mfn_mfn = virt_to_mfn(mid_mfn);
475                 if (cmpxchg(top_mfn_p, missing_mfn, mid_mfn_mfn) != missing_mfn)
476                         free_p2m_page(mid_mfn);
477                 else
478                         p2m_top_mfn_p[topidx] = mid_mfn;
479         }
480 
481         if (p2m_top[topidx][mididx] == p2m_identity ||
482             p2m_top[topidx][mididx] == p2m_missing) {
483                 /* p2m leaf page is missing */
484                 unsigned long *p2m;
485                 unsigned long *p2m_orig = p2m_top[topidx][mididx];
486 
487                 p2m = alloc_p2m_page();
488                 if (!p2m)
489                         return false;
490 
491                 p2m_init(p2m);
492 
493                 if (cmpxchg(&mid[mididx], p2m_orig, p2m) != p2m_orig)
494                         free_p2m_page(p2m);
495                 else
496                         mid_mfn[mididx] = virt_to_mfn(p2m);
497         }
498 
499         return true;
500 }
501 
502 static bool __init early_alloc_p2m_middle(unsigned long pfn, bool check_boundary)
503 {
504         unsigned topidx, mididx, idx;
505         unsigned long *p2m;
506         unsigned long *mid_mfn_p;
507 
508         topidx = p2m_top_index(pfn);
509         mididx = p2m_mid_index(pfn);
510         idx = p2m_index(pfn);
511 
512         /* Pfff.. No boundary cross-over, lets get out. */
513         if (!idx && check_boundary)
514                 return false;
515 
516         WARN(p2m_top[topidx][mididx] == p2m_identity,
517                 "P2M[%d][%d] == IDENTITY, should be MISSING (or alloced)!\n",
518                 topidx, mididx);
519 
520         /*
521          * Could be done by xen_build_dynamic_phys_to_machine..
522          */
523         if (p2m_top[topidx][mididx] != p2m_missing)
524                 return false;
525 
526         /* Boundary cross-over for the edges: */
527         p2m = extend_brk(PAGE_SIZE, PAGE_SIZE);
528 
529         p2m_init(p2m);
530 
531         p2m_top[topidx][mididx] = p2m;
532 
533         /* For save/restore we need to MFN of the P2M saved */
534 
535         mid_mfn_p = p2m_top_mfn_p[topidx];
536         WARN(mid_mfn_p[mididx] != virt_to_mfn(p2m_missing),
537                 "P2M_TOP_P[%d][%d] != MFN of p2m_missing!\n",
538                 topidx, mididx);
539         mid_mfn_p[mididx] = virt_to_mfn(p2m);
540 
541         return true;
542 }
543 
544 static bool __init early_alloc_p2m(unsigned long pfn)
545 {
546         unsigned topidx = p2m_top_index(pfn);
547         unsigned long *mid_mfn_p;
548         unsigned long **mid;
549 
550         mid = p2m_top[topidx];
551         mid_mfn_p = p2m_top_mfn_p[topidx];
552         if (mid == p2m_mid_missing) {
553                 mid = extend_brk(PAGE_SIZE, PAGE_SIZE);
554 
555                 p2m_mid_init(mid);
556 
557                 p2m_top[topidx] = mid;
558 
559                 BUG_ON(mid_mfn_p != p2m_mid_missing_mfn);
560         }
561         /* And the save/restore P2M tables.. */
562         if (mid_mfn_p == p2m_mid_missing_mfn) {
563                 mid_mfn_p = extend_brk(PAGE_SIZE, PAGE_SIZE);
564                 p2m_mid_mfn_init(mid_mfn_p);
565 
566                 p2m_top_mfn_p[topidx] = mid_mfn_p;
567                 p2m_top_mfn[topidx] = virt_to_mfn(mid_mfn_p);
568                 /* Note: we don't set mid_mfn_p[midix] here,
569                  * look in early_alloc_p2m_middle */
570         }
571         return true;
572 }
573 bool __init early_set_phys_to_machine(unsigned long pfn, unsigned long mfn)
574 {
575         if (unlikely(!__set_phys_to_machine(pfn, mfn)))  {
576                 if (!early_alloc_p2m(pfn))
577                         return false;
578 
579                 if (!early_alloc_p2m_middle(pfn, false /* boundary crossover OK!*/))
580                         return false;
581 
582                 if (!__set_phys_to_machine(pfn, mfn))
583                         return false;
584         }
585 
586         return true;
587 }
588 unsigned long __init set_phys_range_identity(unsigned long pfn_s,
589                                       unsigned long pfn_e)
590 {
591         unsigned long pfn;
592 
593         if (unlikely(pfn_s >= MAX_P2M_PFN || pfn_e >= MAX_P2M_PFN))
594                 return 0;
595 
596         if (unlikely(xen_feature(XENFEAT_auto_translated_physmap)))
597                 return pfn_e - pfn_s;
598 
599         if (pfn_s > pfn_e)
600                 return 0;
601 
602         for (pfn = (pfn_s & ~(P2M_MID_PER_PAGE * P2M_PER_PAGE - 1));
603                 pfn < ALIGN(pfn_e, (P2M_MID_PER_PAGE * P2M_PER_PAGE));
604                 pfn += P2M_MID_PER_PAGE * P2M_PER_PAGE)
605         {
606                 WARN_ON(!early_alloc_p2m(pfn));
607         }
608 
609         early_alloc_p2m_middle(pfn_s, true);
610         early_alloc_p2m_middle(pfn_e, true);
611 
612         for (pfn = pfn_s; pfn < pfn_e; pfn++)
613                 if (!__set_phys_to_machine(pfn, IDENTITY_FRAME(pfn)))
614                         break;
615 
616         if (!WARN((pfn - pfn_s) != (pfn_e - pfn_s),
617                 "Identity mapping failed. We are %ld short of 1-1 mappings!\n",
618                 (pfn_e - pfn_s) - (pfn - pfn_s)))
619                 printk(KERN_DEBUG "1-1 mapping on %lx->%lx\n", pfn_s, pfn);
620 
621         return pfn - pfn_s;
622 }
623 
624 /* Try to install p2m mapping; fail if intermediate bits missing */
625 bool __set_phys_to_machine(unsigned long pfn, unsigned long mfn)
626 {
627         unsigned topidx, mididx, idx;
628 
629         if (unlikely(xen_feature(XENFEAT_auto_translated_physmap))) {
630                 BUG_ON(pfn != mfn && mfn != INVALID_P2M_ENTRY);
631                 return true;
632         }
633         if (unlikely(pfn >= MAX_P2M_PFN)) {
634                 BUG_ON(mfn != INVALID_P2M_ENTRY);
635                 return true;
636         }
637 
638         topidx = p2m_top_index(pfn);
639         mididx = p2m_mid_index(pfn);
640         idx = p2m_index(pfn);
641 
642         /* For sparse holes were the p2m leaf has real PFN along with
643          * PCI holes, stick in the PFN as the MFN value.
644          */
645         if (mfn != INVALID_P2M_ENTRY && (mfn & IDENTITY_FRAME_BIT)) {
646                 if (p2m_top[topidx][mididx] == p2m_identity)
647                         return true;
648 
649                 /* Swap over from MISSING to IDENTITY if needed. */
650                 if (p2m_top[topidx][mididx] == p2m_missing) {
651                         WARN_ON(cmpxchg(&p2m_top[topidx][mididx], p2m_missing,
652                                 p2m_identity) != p2m_missing);
653                         return true;
654                 }
655         }
656 
657         if (p2m_top[topidx][mididx] == p2m_missing)
658                 return mfn == INVALID_P2M_ENTRY;
659 
660         p2m_top[topidx][mididx][idx] = mfn;
661 
662         return true;
663 }
664 
665 bool set_phys_to_machine(unsigned long pfn, unsigned long mfn)
666 {
667         if (unlikely(!__set_phys_to_machine(pfn, mfn)))  {
668                 if (!alloc_p2m(pfn))
669                         return false;
670 
671                 if (!__set_phys_to_machine(pfn, mfn))
672                         return false;
673         }
674 
675         return true;
676 }
677 
678 #define M2P_OVERRIDE_HASH_SHIFT 10
679 #define M2P_OVERRIDE_HASH       (1 << M2P_OVERRIDE_HASH_SHIFT)
680 
681 static RESERVE_BRK_ARRAY(struct list_head, m2p_overrides, M2P_OVERRIDE_HASH);
682 static DEFINE_SPINLOCK(m2p_override_lock);
683 
684 static void __init m2p_override_init(void)
685 {
686         unsigned i;
687 
688         m2p_overrides = extend_brk(sizeof(*m2p_overrides) * M2P_OVERRIDE_HASH,
689                                    sizeof(unsigned long));
690 
691         for (i = 0; i < M2P_OVERRIDE_HASH; i++)
692                 INIT_LIST_HEAD(&m2p_overrides[i]);
693 }
694 
695 static unsigned long mfn_hash(unsigned long mfn)
696 {
697         return hash_long(mfn, M2P_OVERRIDE_HASH_SHIFT);
698 }
699 
700 /* Add an MFN override for a particular page */
701 int m2p_add_override(unsigned long mfn, struct page *page,
702                 struct gnttab_map_grant_ref *kmap_op)
703 {
704         unsigned long flags;
705         unsigned long pfn;
706         unsigned long uninitialized_var(address);
707         unsigned level;
708         pte_t *ptep = NULL;
709         int ret = 0;
710 
711         pfn = page_to_pfn(page);
712         if (!PageHighMem(page)) {
713                 address = (unsigned long)__va(pfn << PAGE_SHIFT);
714                 ptep = lookup_address(address, &level);
715                 if (WARN(ptep == NULL || level != PG_LEVEL_4K,
716                                         "m2p_add_override: pfn %lx not mapped", pfn))
717                         return -EINVAL;
718         }
719         WARN_ON(PagePrivate(page));
720         SetPagePrivate(page);
721         set_page_private(page, mfn);
722         page->index = pfn_to_mfn(pfn);
723 
724         if (unlikely(!set_phys_to_machine(pfn, FOREIGN_FRAME(mfn))))
725                 return -ENOMEM;
726 
727         if (kmap_op != NULL) {
728                 if (!PageHighMem(page)) {
729                         struct multicall_space mcs =
730                                 xen_mc_entry(sizeof(*kmap_op));
731 
732                         MULTI_grant_table_op(mcs.mc,
733                                         GNTTABOP_map_grant_ref, kmap_op, 1);
734 
735                         xen_mc_issue(PARAVIRT_LAZY_MMU);
736                 }
737                 /* let's use dev_bus_addr to record the old mfn instead */
738                 kmap_op->dev_bus_addr = page->index;
739                 page->index = (unsigned long) kmap_op;
740         }
741         spin_lock_irqsave(&m2p_override_lock, flags);
742         list_add(&page->lru,  &m2p_overrides[mfn_hash(mfn)]);
743         spin_unlock_irqrestore(&m2p_override_lock, flags);
744 
745         /* p2m(m2p(mfn)) == mfn: the mfn is already present somewhere in
746          * this domain. Set the FOREIGN_FRAME_BIT in the p2m for the other
747          * pfn so that the following mfn_to_pfn(mfn) calls will return the
748          * pfn from the m2p_override (the backend pfn) instead.
749          * We need to do this because the pages shared by the frontend
750          * (xen-blkfront) can be already locked (lock_page, called by
751          * do_read_cache_page); when the userspace backend tries to use them
752          * with direct_IO, mfn_to_pfn returns the pfn of the frontend, so
753          * do_blockdev_direct_IO is going to try to lock the same pages
754          * again resulting in a deadlock.
755          * As a side effect get_user_pages_fast might not be safe on the
756          * frontend pages while they are being shared with the backend,
757          * because mfn_to_pfn (that ends up being called by GUPF) will
758          * return the backend pfn rather than the frontend pfn. */
759         ret = __get_user(pfn, &machine_to_phys_mapping[mfn]);
760         if (ret == 0 && get_phys_to_machine(pfn) == mfn)
761                 set_phys_to_machine(pfn, FOREIGN_FRAME(mfn));
762 
763         return 0;
764 }
765 EXPORT_SYMBOL_GPL(m2p_add_override);
766 int m2p_remove_override(struct page *page, bool clear_pte)
767 {
768         unsigned long flags;
769         unsigned long mfn;
770         unsigned long pfn;
771         unsigned long uninitialized_var(address);
772         unsigned level;
773         pte_t *ptep = NULL;
774         int ret = 0;
775 
776         pfn = page_to_pfn(page);
777         mfn = get_phys_to_machine(pfn);
778         if (mfn == INVALID_P2M_ENTRY || !(mfn & FOREIGN_FRAME_BIT))
779                 return -EINVAL;
780 
781         if (!PageHighMem(page)) {
782                 address = (unsigned long)__va(pfn << PAGE_SHIFT);
783                 ptep = lookup_address(address, &level);
784 
785                 if (WARN(ptep == NULL || level != PG_LEVEL_4K,
786                                         "m2p_remove_override: pfn %lx not mapped", pfn))
787                         return -EINVAL;
788         }
789 
790         spin_lock_irqsave(&m2p_override_lock, flags);
791         list_del(&page->lru);
792         spin_unlock_irqrestore(&m2p_override_lock, flags);
793         WARN_ON(!PagePrivate(page));
794         ClearPagePrivate(page);
795 
796         if (clear_pte) {
797                 struct gnttab_map_grant_ref *map_op =
798                         (struct gnttab_map_grant_ref *) page->index;
799                 set_phys_to_machine(pfn, map_op->dev_bus_addr);
800                 if (!PageHighMem(page)) {
801                         struct multicall_space mcs;
802                         struct gnttab_unmap_grant_ref *unmap_op;
803 
804                         /*
805                          * It might be that we queued all the m2p grant table
806                          * hypercalls in a multicall, then m2p_remove_override
807                          * get called before the multicall has actually been
808                          * issued. In this case handle is going to -1 because
809                          * it hasn't been modified yet.
810                          */
811                         if (map_op->handle == -1)
812                                 xen_mc_flush();
813                         /*
814                          * Now if map_op->handle is negative it means that the
815                          * hypercall actually returned an error.
816                          */
817                         if (map_op->handle == GNTST_general_error) {
818                                 printk(KERN_WARNING "m2p_remove_override: "
819                                                 "pfn %lx mfn %lx, failed to modify kernel mappings",
820                                                 pfn, mfn);
821                                 return -1;
822                         }
823 
824                         mcs = xen_mc_entry(
825                                         sizeof(struct gnttab_unmap_grant_ref));
826                         unmap_op = mcs.args;
827                         unmap_op->host_addr = map_op->host_addr;
828                         unmap_op->handle = map_op->handle;
829                         unmap_op->dev_bus_addr = 0;
830 
831                         MULTI_grant_table_op(mcs.mc,
832                                         GNTTABOP_unmap_grant_ref, unmap_op, 1);
833 
834                         xen_mc_issue(PARAVIRT_LAZY_MMU);
835 
836                         set_pte_at(&init_mm, address, ptep,
837                                         pfn_pte(pfn, PAGE_KERNEL));
838                         __flush_tlb_single(address);
839                         map_op->host_addr = 0;
840                 }
841         } else
842                 set_phys_to_machine(pfn, page->index);
843 
844         /* p2m(m2p(mfn)) == FOREIGN_FRAME(mfn): the mfn is already present
845          * somewhere in this domain, even before being added to the
846          * m2p_override (see comment above in m2p_add_override).
847          * If there are no other entries in the m2p_override corresponding
848          * to this mfn, then remove the FOREIGN_FRAME_BIT from the p2m for
849          * the original pfn (the one shared by the frontend): the backend
850          * cannot do any IO on this page anymore because it has been
851          * unshared. Removing the FOREIGN_FRAME_BIT from the p2m entry of
852          * the original pfn causes mfn_to_pfn(mfn) to return the frontend
853          * pfn again. */
854         mfn &= ~FOREIGN_FRAME_BIT;
855         ret = __get_user(pfn, &machine_to_phys_mapping[mfn]);
856         if (ret == 0 && get_phys_to_machine(pfn) == FOREIGN_FRAME(mfn) &&
857                         m2p_find_override(mfn) == NULL)
858                 set_phys_to_machine(pfn, mfn);
859 
860         return 0;
861 }
862 EXPORT_SYMBOL_GPL(m2p_remove_override);
863 
864 struct page *m2p_find_override(unsigned long mfn)
865 {
866         unsigned long flags;
867         struct list_head *bucket = &m2p_overrides[mfn_hash(mfn)];
868         struct page *p, *ret;
869 
870         ret = NULL;
871 
872         spin_lock_irqsave(&m2p_override_lock, flags);
873 
874         list_for_each_entry(p, bucket, lru) {
875                 if (page_private(p) == mfn) {
876                         ret = p;
877                         break;
878                 }
879         }
880 
881         spin_unlock_irqrestore(&m2p_override_lock, flags);
882 
883         return ret;
884 }
885 
886 unsigned long m2p_find_override_pfn(unsigned long mfn, unsigned long pfn)
887 {
888         struct page *p = m2p_find_override(mfn);
889         unsigned long ret = pfn;
890 
891         if (p)
892                 ret = page_to_pfn(p);
893 
894         return ret;
895 }
896 EXPORT_SYMBOL_GPL(m2p_find_override_pfn);
897 
898 #ifdef CONFIG_XEN_DEBUG_FS
899 #include <linux/debugfs.h>
900 #include "debugfs.h"
901 static int p2m_dump_show(struct seq_file *m, void *v)
902 {
903         static const char * const level_name[] = { "top", "middle",
904                                                 "entry", "abnormal", "error"};
905 #define TYPE_IDENTITY 0
906 #define TYPE_MISSING 1
907 #define TYPE_PFN 2
908 #define TYPE_UNKNOWN 3
909         static const char * const type_name[] = {
910                                 [TYPE_IDENTITY] = "identity",
911                                 [TYPE_MISSING] = "missing",
912                                 [TYPE_PFN] = "pfn",
913                                 [TYPE_UNKNOWN] = "abnormal"};
914         unsigned long pfn, prev_pfn_type = 0, prev_pfn_level = 0;
915         unsigned int uninitialized_var(prev_level);
916         unsigned int uninitialized_var(prev_type);
917 
918         if (!p2m_top)
919                 return 0;
920 
921         for (pfn = 0; pfn < MAX_DOMAIN_PAGES; pfn++) {
922                 unsigned topidx = p2m_top_index(pfn);
923                 unsigned mididx = p2m_mid_index(pfn);
924                 unsigned idx = p2m_index(pfn);
925                 unsigned lvl, type;
926 
927                 lvl = 4;
928                 type = TYPE_UNKNOWN;
929                 if (p2m_top[topidx] == p2m_mid_missing) {
930                         lvl = 0; type = TYPE_MISSING;
931                 } else if (p2m_top[topidx] == NULL) {
932                         lvl = 0; type = TYPE_UNKNOWN;
933                 } else if (p2m_top[topidx][mididx] == NULL) {
934                         lvl = 1; type = TYPE_UNKNOWN;
935                 } else if (p2m_top[topidx][mididx] == p2m_identity) {
936                         lvl = 1; type = TYPE_IDENTITY;
937                 } else if (p2m_top[topidx][mididx] == p2m_missing) {
938                         lvl = 1; type = TYPE_MISSING;
939                 } else if (p2m_top[topidx][mididx][idx] == 0) {
940                         lvl = 2; type = TYPE_UNKNOWN;
941                 } else if (p2m_top[topidx][mididx][idx] == IDENTITY_FRAME(pfn)) {
942                         lvl = 2; type = TYPE_IDENTITY;
943                 } else if (p2m_top[topidx][mididx][idx] == INVALID_P2M_ENTRY) {
944                         lvl = 2; type = TYPE_MISSING;
945                 } else if (p2m_top[topidx][mididx][idx] == pfn) {
946                         lvl = 2; type = TYPE_PFN;
947                 } else if (p2m_top[topidx][mididx][idx] != pfn) {
948                         lvl = 2; type = TYPE_PFN;
949                 }
950                 if (pfn == 0) {
951                         prev_level = lvl;
952                         prev_type = type;
953                 }
954                 if (pfn == MAX_DOMAIN_PAGES-1) {
955                         lvl = 3;
956                         type = TYPE_UNKNOWN;
957                 }
958                 if (prev_type != type) {
959                         seq_printf(m, " [0x%lx->0x%lx] %s\n",
960                                 prev_pfn_type, pfn, type_name[prev_type]);
961                         prev_pfn_type = pfn;
962                         prev_type = type;
963                 }
964                 if (prev_level != lvl) {
965                         seq_printf(m, " [0x%lx->0x%lx] level %s\n",
966                                 prev_pfn_level, pfn, level_name[prev_level]);
967                         prev_pfn_level = pfn;
968                         prev_level = lvl;
969                 }
970         }
971         return 0;
972 #undef TYPE_IDENTITY
973 #undef TYPE_MISSING
974 #undef TYPE_PFN
975 #undef TYPE_UNKNOWN
976 }
977 
978 static int p2m_dump_open(struct inode *inode, struct file *filp)
979 {
980         return single_open(filp, p2m_dump_show, NULL);
981 }
982 
983 static const struct file_operations p2m_dump_fops = {
984         .open           = p2m_dump_open,
985         .read           = seq_read,
986         .llseek         = seq_lseek,
987         .release        = single_release,
988 };
989 
990 static struct dentry *d_mmu_debug;
991 
992 static int __init xen_p2m_debugfs(void)
993 {
994         struct dentry *d_xen = xen_init_debugfs();
995 
996         if (d_xen == NULL)
997                 return -ENOMEM;
998 
999         d_mmu_debug = debugfs_create_dir("mmu", d_xen);
1000 
1001         debugfs_create_file("p2m", 0600, d_mmu_debug, NULL, &p2m_dump_fops);
1002         return 0;
1003 }
1004 fs_initcall(xen_p2m_debugfs);
1005 #endif /* CONFIG_XEN_DEBUG_FS */
1006 

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