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.
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.
13 * p2m_mid p2m_mid p2m_mid_mfn p2m_mid_mfn
15 * p2m p2m p2m p2m p2m p2m p2m ...
17 * The p2m_mid_mfn pages are mapped by p2m_top_mfn_p.
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
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.
27 * In short, these structures contain the Machine Frame Number (MFN) of the PFN.
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.
34 * We also have the possibility of setting 1-1 mappings on certain regions, so
36 * pfn_to_mfn(0xc0000)=0xc0000
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.
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).
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).
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.
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:
64 * /-------------------+---------\/----\ /----------\ /---+-----\
65 * | System RAM | Sys RAM ||ACPI| | reserved | | Sys RAM |
66 * \-------------------+---------/\----/ \----------/ \---+-----/
69 * [1029MB = 263424 (0x40500), 2001MB = 512256 (0x7D100),
70 * 2048MB = 524288 (0x80000)]
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).
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.
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).
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.
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").
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.
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."
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).
124 * This is what the p2m ends up looking (for the E820 above) with this
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 * | \-----------------/
151 * | /-----------------\
152 * \-->| [p2m_identity] +---->[1]
153 * | [p2m_identity] +---->[1]
155 * \-----------------/
157 * where ~0 is INVALID_P2M_ENTRY. IDENTITY is (PFN | IDENTITY_BIT)
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>
167 #include <asm/cache.h>
168 #include <asm/setup.h>
170 #include <asm/xen/page.h>
171 #include <asm/xen/hypercall.h>
172 #include <asm/xen/hypervisor.h>
173 #include <xen/balloon.h>
174 #include <xen/grant_table.h>
177 #include "multicalls.h"
180 static void __init m2p_override_init(void);
182 unsigned long xen_max_p2m_pfn __read_mostly;
184 /* Placeholders for holes in the address space */
185 static RESERVE_BRK_ARRAY(unsigned long, p2m_missing, P2M_PER_PAGE);
186 static RESERVE_BRK_ARRAY(unsigned long *, p2m_mid_missing, P2M_MID_PER_PAGE);
187 static RESERVE_BRK_ARRAY(unsigned long, p2m_mid_missing_mfn, P2M_MID_PER_PAGE);
189 static RESERVE_BRK_ARRAY(unsigned long **, p2m_top, P2M_TOP_PER_PAGE);
190 static RESERVE_BRK_ARRAY(unsigned long, p2m_top_mfn, P2M_TOP_PER_PAGE);
191 static RESERVE_BRK_ARRAY(unsigned long *, p2m_top_mfn_p, P2M_TOP_PER_PAGE);
193 static RESERVE_BRK_ARRAY(unsigned long, p2m_identity, P2M_PER_PAGE);
194 static RESERVE_BRK_ARRAY(unsigned long *, p2m_mid_identity, P2M_MID_PER_PAGE);
195 static RESERVE_BRK_ARRAY(unsigned long, p2m_mid_identity_mfn, P2M_MID_PER_PAGE);
197 RESERVE_BRK(p2m_mid, PAGE_SIZE * (MAX_DOMAIN_PAGES / (P2M_PER_PAGE * P2M_MID_PER_PAGE)));
198 RESERVE_BRK(p2m_mid_mfn, PAGE_SIZE * (MAX_DOMAIN_PAGES / (P2M_PER_PAGE * P2M_MID_PER_PAGE)));
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
205 RESERVE_BRK(p2m_identity_remap, PAGE_SIZE * 2 * 3 * MAX_REMAP_RANGES);
207 static inline unsigned p2m_top_index(unsigned long pfn)
209 BUG_ON(pfn >= MAX_P2M_PFN);
210 return pfn / (P2M_MID_PER_PAGE * P2M_PER_PAGE);
213 static inline unsigned p2m_mid_index(unsigned long pfn)
215 return (pfn / P2M_PER_PAGE) % P2M_MID_PER_PAGE;
218 static inline unsigned p2m_index(unsigned long pfn)
220 return pfn % P2M_PER_PAGE;
223 static void p2m_top_init(unsigned long ***top)
227 for (i = 0; i < P2M_TOP_PER_PAGE; i++)
228 top[i] = p2m_mid_missing;
231 static void p2m_top_mfn_init(unsigned long *top)
235 for (i = 0; i < P2M_TOP_PER_PAGE; i++)
236 top[i] = virt_to_mfn(p2m_mid_missing_mfn);
239 static void p2m_top_mfn_p_init(unsigned long **top)
243 for (i = 0; i < P2M_TOP_PER_PAGE; i++)
244 top[i] = p2m_mid_missing_mfn;
247 static void p2m_mid_init(unsigned long **mid, unsigned long *leaf)
251 for (i = 0; i < P2M_MID_PER_PAGE; i++)
255 static void p2m_mid_mfn_init(unsigned long *mid, unsigned long *leaf)
259 for (i = 0; i < P2M_MID_PER_PAGE; i++)
260 mid[i] = virt_to_mfn(leaf);
263 static void p2m_init(unsigned long *p2m)
267 for (i = 0; i < P2M_MID_PER_PAGE; i++)
268 p2m[i] = INVALID_P2M_ENTRY;
272 * Build the parallel p2m_top_mfn and p2m_mid_mfn structures
274 * This is called both at boot time, and after resuming from suspend:
275 * - At boot time we're called very early, and must use extend_brk()
276 * to allocate memory.
278 * - After resume we're called from within stop_machine, but the mfn
279 * tree should alreay be completely allocated.
281 void __ref xen_build_mfn_list_list(void)
285 if (xen_feature(XENFEAT_auto_translated_physmap))
288 /* Pre-initialize p2m_top_mfn to be completely missing */
289 if (p2m_top_mfn == NULL) {
290 p2m_mid_missing_mfn = extend_brk(PAGE_SIZE, PAGE_SIZE);
291 p2m_mid_mfn_init(p2m_mid_missing_mfn, p2m_missing);
292 p2m_mid_identity_mfn = extend_brk(PAGE_SIZE, PAGE_SIZE);
293 p2m_mid_mfn_init(p2m_mid_identity_mfn, p2m_identity);
295 p2m_top_mfn_p = extend_brk(PAGE_SIZE, PAGE_SIZE);
296 p2m_top_mfn_p_init(p2m_top_mfn_p);
298 p2m_top_mfn = extend_brk(PAGE_SIZE, PAGE_SIZE);
299 p2m_top_mfn_init(p2m_top_mfn);
301 /* Reinitialise, mfn's all change after migration */
302 p2m_mid_mfn_init(p2m_mid_missing_mfn, p2m_missing);
303 p2m_mid_mfn_init(p2m_mid_identity_mfn, p2m_identity);
306 for (pfn = 0; pfn < xen_max_p2m_pfn; pfn += P2M_PER_PAGE) {
307 unsigned topidx = p2m_top_index(pfn);
308 unsigned mididx = p2m_mid_index(pfn);
310 unsigned long *mid_mfn_p;
312 mid = p2m_top[topidx];
313 mid_mfn_p = p2m_top_mfn_p[topidx];
315 /* Don't bother allocating any mfn mid levels if
316 * they're just missing, just update the stored mfn,
317 * since all could have changed over a migrate.
319 if (mid == p2m_mid_missing) {
321 BUG_ON(mid_mfn_p != p2m_mid_missing_mfn);
322 p2m_top_mfn[topidx] = virt_to_mfn(p2m_mid_missing_mfn);
323 pfn += (P2M_MID_PER_PAGE - 1) * P2M_PER_PAGE;
327 if (mid_mfn_p == p2m_mid_missing_mfn) {
329 * XXX boot-time only! We should never find
330 * missing parts of the mfn tree after
331 * runtime. extend_brk() will BUG if we call
334 mid_mfn_p = extend_brk(PAGE_SIZE, PAGE_SIZE);
335 p2m_mid_mfn_init(mid_mfn_p, p2m_missing);
337 p2m_top_mfn_p[topidx] = mid_mfn_p;
340 p2m_top_mfn[topidx] = virt_to_mfn(mid_mfn_p);
341 mid_mfn_p[mididx] = virt_to_mfn(mid[mididx]);
345 void xen_setup_mfn_list_list(void)
347 if (xen_feature(XENFEAT_auto_translated_physmap))
350 BUG_ON(HYPERVISOR_shared_info == &xen_dummy_shared_info);
352 HYPERVISOR_shared_info->arch.pfn_to_mfn_frame_list_list =
353 virt_to_mfn(p2m_top_mfn);
354 HYPERVISOR_shared_info->arch.max_pfn = xen_max_p2m_pfn;
357 /* Set up p2m_top to point to the domain-builder provided p2m pages */
358 void __init xen_build_dynamic_phys_to_machine(void)
360 unsigned long *mfn_list;
361 unsigned long max_pfn;
364 if (xen_feature(XENFEAT_auto_translated_physmap))
367 mfn_list = (unsigned long *)xen_start_info->mfn_list;
368 max_pfn = min(MAX_DOMAIN_PAGES, xen_start_info->nr_pages);
369 xen_max_p2m_pfn = max_pfn;
371 p2m_missing = extend_brk(PAGE_SIZE, PAGE_SIZE);
372 p2m_init(p2m_missing);
373 p2m_identity = extend_brk(PAGE_SIZE, PAGE_SIZE);
374 p2m_init(p2m_identity);
376 p2m_mid_missing = extend_brk(PAGE_SIZE, PAGE_SIZE);
377 p2m_mid_init(p2m_mid_missing, p2m_missing);
378 p2m_mid_identity = extend_brk(PAGE_SIZE, PAGE_SIZE);
379 p2m_mid_init(p2m_mid_identity, p2m_identity);
381 p2m_top = extend_brk(PAGE_SIZE, PAGE_SIZE);
382 p2m_top_init(p2m_top);
385 * The domain builder gives us a pre-constructed p2m array in
386 * mfn_list for all the pages initially given to us, so we just
387 * need to graft that into our tree structure.
389 for (pfn = 0; pfn < max_pfn; pfn += P2M_PER_PAGE) {
390 unsigned topidx = p2m_top_index(pfn);
391 unsigned mididx = p2m_mid_index(pfn);
393 if (p2m_top[topidx] == p2m_mid_missing) {
394 unsigned long **mid = extend_brk(PAGE_SIZE, PAGE_SIZE);
395 p2m_mid_init(mid, p2m_missing);
397 p2m_top[topidx] = mid;
401 * As long as the mfn_list has enough entries to completely
402 * fill a p2m page, pointing into the array is ok. But if
403 * not the entries beyond the last pfn will be undefined.
405 if (unlikely(pfn + P2M_PER_PAGE > max_pfn)) {
406 unsigned long p2midx;
408 p2midx = max_pfn % P2M_PER_PAGE;
409 for ( ; p2midx < P2M_PER_PAGE; p2midx++)
410 mfn_list[pfn + p2midx] = INVALID_P2M_ENTRY;
412 p2m_top[topidx][mididx] = &mfn_list[pfn];
418 #include <linux/bootmem.h>
419 unsigned long __init xen_revector_p2m_tree(void)
421 unsigned long va_start;
422 unsigned long va_end;
424 unsigned long pfn_free = 0;
425 unsigned long *mfn_list = NULL;
428 va_start = xen_start_info->mfn_list;
429 /*We copy in increments of P2M_PER_PAGE * sizeof(unsigned long),
430 * so make sure it is rounded up to that */
431 size = PAGE_ALIGN(xen_start_info->nr_pages * sizeof(unsigned long));
432 va_end = va_start + size;
434 /* If we were revectored already, don't do it again. */
435 if (va_start <= __START_KERNEL_map && va_start >= __PAGE_OFFSET)
438 mfn_list = alloc_bootmem_align(size, PAGE_SIZE);
440 pr_warn("Could not allocate space for a new P2M tree!\n");
441 return xen_start_info->mfn_list;
443 /* Fill it out with INVALID_P2M_ENTRY value */
444 memset(mfn_list, 0xFF, size);
446 for (pfn = 0; pfn < ALIGN(MAX_DOMAIN_PAGES, P2M_PER_PAGE); pfn += P2M_PER_PAGE) {
447 unsigned topidx = p2m_top_index(pfn);
449 unsigned long *mid_p;
451 if (!p2m_top[topidx])
454 if (p2m_top[topidx] == p2m_mid_missing)
457 mididx = p2m_mid_index(pfn);
458 mid_p = p2m_top[topidx][mididx];
461 if ((mid_p == p2m_missing) || (mid_p == p2m_identity))
464 if ((unsigned long)mid_p == INVALID_P2M_ENTRY)
467 /* The old va. Rebase it on mfn_list */
468 if (mid_p >= (unsigned long *)va_start && mid_p <= (unsigned long *)va_end) {
471 if (pfn_free > (size / sizeof(unsigned long))) {
472 WARN(1, "Only allocated for %ld pages, but we want %ld!\n",
473 size / sizeof(unsigned long), pfn_free);
476 new = &mfn_list[pfn_free];
478 copy_page(new, mid_p);
479 p2m_top[topidx][mididx] = &mfn_list[pfn_free];
480 p2m_top_mfn_p[topidx][mididx] = virt_to_mfn(&mfn_list[pfn_free]);
482 pfn_free += P2M_PER_PAGE;
485 /* This should be the leafs allocated for identity from _brk. */
487 return (unsigned long)mfn_list;
491 unsigned long __init xen_revector_p2m_tree(void)
496 unsigned long get_phys_to_machine(unsigned long pfn)
498 unsigned topidx, mididx, idx;
500 if (unlikely(pfn >= MAX_P2M_PFN))
501 return IDENTITY_FRAME(pfn);
503 topidx = p2m_top_index(pfn);
504 mididx = p2m_mid_index(pfn);
505 idx = p2m_index(pfn);
508 * The INVALID_P2M_ENTRY is filled in both p2m_*identity
509 * and in p2m_*missing, so returning the INVALID_P2M_ENTRY
512 if (p2m_top[topidx][mididx] == p2m_identity)
513 return IDENTITY_FRAME(pfn);
515 return p2m_top[topidx][mididx][idx];
517 EXPORT_SYMBOL_GPL(get_phys_to_machine);
519 static void *alloc_p2m_page(void)
521 return (void *)__get_free_page(GFP_KERNEL | __GFP_REPEAT);
524 static void free_p2m_page(void *p)
526 free_page((unsigned long)p);
530 * Fully allocate the p2m structure for a given pfn. We need to check
531 * that both the top and mid levels are allocated, and make sure the
532 * parallel mfn tree is kept in sync. We may race with other cpus, so
533 * the new pages are installed with cmpxchg; if we lose the race then
534 * simply free the page we allocated and use the one that's there.
536 static bool alloc_p2m(unsigned long pfn)
538 unsigned topidx, mididx;
539 unsigned long ***top_p, **mid;
540 unsigned long *top_mfn_p, *mid_mfn;
542 topidx = p2m_top_index(pfn);
543 mididx = p2m_mid_index(pfn);
545 top_p = &p2m_top[topidx];
548 if (mid == p2m_mid_missing) {
549 /* Mid level is missing, allocate a new one */
550 mid = alloc_p2m_page();
554 p2m_mid_init(mid, p2m_missing);
556 if (cmpxchg(top_p, p2m_mid_missing, mid) != p2m_mid_missing)
560 top_mfn_p = &p2m_top_mfn[topidx];
561 mid_mfn = p2m_top_mfn_p[topidx];
563 BUG_ON(virt_to_mfn(mid_mfn) != *top_mfn_p);
565 if (mid_mfn == p2m_mid_missing_mfn) {
566 /* Separately check the mid mfn level */
567 unsigned long missing_mfn;
568 unsigned long mid_mfn_mfn;
570 mid_mfn = alloc_p2m_page();
574 p2m_mid_mfn_init(mid_mfn, p2m_missing);
576 missing_mfn = virt_to_mfn(p2m_mid_missing_mfn);
577 mid_mfn_mfn = virt_to_mfn(mid_mfn);
578 if (cmpxchg(top_mfn_p, missing_mfn, mid_mfn_mfn) != missing_mfn)
579 free_p2m_page(mid_mfn);
581 p2m_top_mfn_p[topidx] = mid_mfn;
584 if (p2m_top[topidx][mididx] == p2m_identity ||
585 p2m_top[topidx][mididx] == p2m_missing) {
586 /* p2m leaf page is missing */
588 unsigned long *p2m_orig = p2m_top[topidx][mididx];
590 p2m = alloc_p2m_page();
596 if (cmpxchg(&mid[mididx], p2m_orig, p2m) != p2m_orig)
599 mid_mfn[mididx] = virt_to_mfn(p2m);
605 static bool __init early_alloc_p2m(unsigned long pfn, bool check_boundary)
607 unsigned topidx, mididx, idx;
609 unsigned long *mid_mfn_p;
611 topidx = p2m_top_index(pfn);
612 mididx = p2m_mid_index(pfn);
613 idx = p2m_index(pfn);
615 /* Pfff.. No boundary cross-over, lets get out. */
616 if (!idx && check_boundary)
619 WARN(p2m_top[topidx][mididx] == p2m_identity,
620 "P2M[%d][%d] == IDENTITY, should be MISSING (or alloced)!\n",
624 * Could be done by xen_build_dynamic_phys_to_machine..
626 if (p2m_top[topidx][mididx] != p2m_missing)
629 /* Boundary cross-over for the edges: */
630 p2m = extend_brk(PAGE_SIZE, PAGE_SIZE);
634 p2m_top[topidx][mididx] = p2m;
636 /* For save/restore we need to MFN of the P2M saved */
638 mid_mfn_p = p2m_top_mfn_p[topidx];
639 WARN(mid_mfn_p[mididx] != virt_to_mfn(p2m_missing),
640 "P2M_TOP_P[%d][%d] != MFN of p2m_missing!\n",
642 mid_mfn_p[mididx] = virt_to_mfn(p2m);
647 static bool __init early_alloc_p2m_middle(unsigned long pfn)
649 unsigned topidx = p2m_top_index(pfn);
650 unsigned long *mid_mfn_p;
653 mid = p2m_top[topidx];
654 mid_mfn_p = p2m_top_mfn_p[topidx];
655 if (mid == p2m_mid_missing) {
656 mid = extend_brk(PAGE_SIZE, PAGE_SIZE);
658 p2m_mid_init(mid, p2m_missing);
660 p2m_top[topidx] = mid;
662 BUG_ON(mid_mfn_p != p2m_mid_missing_mfn);
664 /* And the save/restore P2M tables.. */
665 if (mid_mfn_p == p2m_mid_missing_mfn) {
666 mid_mfn_p = extend_brk(PAGE_SIZE, PAGE_SIZE);
667 p2m_mid_mfn_init(mid_mfn_p, p2m_missing);
669 p2m_top_mfn_p[topidx] = mid_mfn_p;
670 p2m_top_mfn[topidx] = virt_to_mfn(mid_mfn_p);
671 /* Note: we don't set mid_mfn_p[midix] here,
672 * look in early_alloc_p2m() */
678 * Skim over the P2M tree looking at pages that are either filled with
679 * INVALID_P2M_ENTRY or with 1:1 PFNs. If found, re-use that page and
680 * replace the P2M leaf with a p2m_missing or p2m_identity.
681 * Stick the old page in the new P2M tree location.
683 bool __init early_can_reuse_p2m_middle(unsigned long set_pfn, unsigned long set_mfn)
690 unsigned long *mid_mfn_p;
694 /* We only look when this entails a P2M middle layer */
695 if (p2m_index(set_pfn))
698 for (pfn = 0; pfn < MAX_DOMAIN_PAGES; pfn += P2M_PER_PAGE) {
699 topidx = p2m_top_index(pfn);
701 if (!p2m_top[topidx])
704 if (p2m_top[topidx] == p2m_mid_missing)
707 mididx = p2m_mid_index(pfn);
708 p2m = p2m_top[topidx][mididx];
712 if ((p2m == p2m_missing) || (p2m == p2m_identity))
715 if ((unsigned long)p2m == INVALID_P2M_ENTRY)
720 for (idx = 0; idx < P2M_PER_PAGE; idx++) {
721 /* IDENTITY_PFNs are 1:1 */
722 if (p2m[idx] == IDENTITY_FRAME(pfn + idx))
724 else if (p2m[idx] == INVALID_P2M_ENTRY)
729 if ((ident_pfns == P2M_PER_PAGE) || (inv_pfns == P2M_PER_PAGE))
734 /* Found one, replace old with p2m_identity or p2m_missing */
735 p2m_top[topidx][mididx] = (ident_pfns ? p2m_identity : p2m_missing);
736 /* And the other for save/restore.. */
737 mid_mfn_p = p2m_top_mfn_p[topidx];
738 /* NOTE: Even if it is a p2m_identity it should still be point to
739 * a page filled with INVALID_P2M_ENTRY entries. */
740 mid_mfn_p[mididx] = virt_to_mfn(p2m_missing);
742 /* Reset where we want to stick the old page in. */
743 topidx = p2m_top_index(set_pfn);
744 mididx = p2m_mid_index(set_pfn);
746 /* This shouldn't happen */
747 if (WARN_ON(p2m_top[topidx] == p2m_mid_missing))
748 early_alloc_p2m_middle(set_pfn);
750 if (WARN_ON(p2m_top[topidx][mididx] != p2m_missing))
754 p2m_top[topidx][mididx] = p2m;
755 mid_mfn_p = p2m_top_mfn_p[topidx];
756 mid_mfn_p[mididx] = virt_to_mfn(p2m);
760 bool __init early_set_phys_to_machine(unsigned long pfn, unsigned long mfn)
762 if (unlikely(!__set_phys_to_machine(pfn, mfn))) {
763 if (!early_alloc_p2m_middle(pfn))
766 if (early_can_reuse_p2m_middle(pfn, mfn))
767 return __set_phys_to_machine(pfn, mfn);
769 if (!early_alloc_p2m(pfn, false /* boundary crossover OK!*/))
772 if (!__set_phys_to_machine(pfn, mfn))
779 static void __init early_split_p2m(unsigned long pfn)
781 unsigned long mididx, idx;
783 mididx = p2m_mid_index(pfn);
784 idx = p2m_index(pfn);
787 * Allocate new middle and leaf pages if this pfn lies in the
791 early_alloc_p2m_middle(pfn);
793 early_alloc_p2m(pfn, false);
796 unsigned long __init set_phys_range_identity(unsigned long pfn_s,
801 if (unlikely(pfn_s >= MAX_P2M_PFN))
804 if (unlikely(xen_feature(XENFEAT_auto_translated_physmap)))
805 return pfn_e - pfn_s;
810 if (pfn_e > MAX_P2M_PFN)
813 early_split_p2m(pfn_s);
814 early_split_p2m(pfn_e);
816 for (pfn = pfn_s; pfn < pfn_e;) {
817 unsigned topidx = p2m_top_index(pfn);
818 unsigned mididx = p2m_mid_index(pfn);
820 if (!__set_phys_to_machine(pfn, IDENTITY_FRAME(pfn)))
825 * If the PFN was set to a middle or leaf identity
826 * page the remainder must also be identity, so skip
827 * ahead to the next middle or leaf entry.
829 if (p2m_top[topidx] == p2m_mid_identity)
830 pfn = ALIGN(pfn, P2M_MID_PER_PAGE * P2M_PER_PAGE);
831 else if (p2m_top[topidx][mididx] == p2m_identity)
832 pfn = ALIGN(pfn, P2M_PER_PAGE);
835 WARN((pfn - pfn_s) != (pfn_e - pfn_s),
836 "Identity mapping failed. We are %ld short of 1-1 mappings!\n",
837 (pfn_e - pfn_s) - (pfn - pfn_s));
842 /* Try to install p2m mapping; fail if intermediate bits missing */
843 bool __set_phys_to_machine(unsigned long pfn, unsigned long mfn)
845 unsigned topidx, mididx, idx;
847 /* don't track P2M changes in autotranslate guests */
848 if (unlikely(xen_feature(XENFEAT_auto_translated_physmap)))
851 if (unlikely(pfn >= MAX_P2M_PFN)) {
852 BUG_ON(mfn != INVALID_P2M_ENTRY);
856 topidx = p2m_top_index(pfn);
857 mididx = p2m_mid_index(pfn);
858 idx = p2m_index(pfn);
860 /* For sparse holes were the p2m leaf has real PFN along with
861 * PCI holes, stick in the PFN as the MFN value.
863 * set_phys_range_identity() will have allocated new middle
864 * and leaf pages as required so an existing p2m_mid_missing
865 * or p2m_missing mean that whole range will be identity so
866 * these can be switched to p2m_mid_identity or p2m_identity.
868 if (mfn != INVALID_P2M_ENTRY && (mfn & IDENTITY_FRAME_BIT)) {
869 if (p2m_top[topidx] == p2m_mid_identity)
872 if (p2m_top[topidx] == p2m_mid_missing) {
873 WARN_ON(cmpxchg(&p2m_top[topidx], p2m_mid_missing,
874 p2m_mid_identity) != p2m_mid_missing);
878 if (p2m_top[topidx][mididx] == p2m_identity)
881 /* Swap over from MISSING to IDENTITY if needed. */
882 if (p2m_top[topidx][mididx] == p2m_missing) {
883 WARN_ON(cmpxchg(&p2m_top[topidx][mididx], p2m_missing,
884 p2m_identity) != p2m_missing);
889 if (p2m_top[topidx][mididx] == p2m_missing)
890 return mfn == INVALID_P2M_ENTRY;
892 p2m_top[topidx][mididx][idx] = mfn;
897 bool set_phys_to_machine(unsigned long pfn, unsigned long mfn)
899 if (unlikely(!__set_phys_to_machine(pfn, mfn))) {
903 if (!__set_phys_to_machine(pfn, mfn))
910 #define M2P_OVERRIDE_HASH_SHIFT 10
911 #define M2P_OVERRIDE_HASH (1 << M2P_OVERRIDE_HASH_SHIFT)
913 static RESERVE_BRK_ARRAY(struct list_head, m2p_overrides, M2P_OVERRIDE_HASH);
914 static DEFINE_SPINLOCK(m2p_override_lock);
916 static void __init m2p_override_init(void)
920 m2p_overrides = extend_brk(sizeof(*m2p_overrides) * M2P_OVERRIDE_HASH,
921 sizeof(unsigned long));
923 for (i = 0; i < M2P_OVERRIDE_HASH; i++)
924 INIT_LIST_HEAD(&m2p_overrides[i]);
927 static unsigned long mfn_hash(unsigned long mfn)
929 return hash_long(mfn, M2P_OVERRIDE_HASH_SHIFT);
932 int set_foreign_p2m_mapping(struct gnttab_map_grant_ref *map_ops,
933 struct gnttab_map_grant_ref *kmap_ops,
934 struct page **pages, unsigned int count)
940 if (xen_feature(XENFEAT_auto_translated_physmap))
945 paravirt_get_lazy_mode() == PARAVIRT_LAZY_NONE) {
946 arch_enter_lazy_mmu_mode();
950 for (i = 0; i < count; i++) {
951 unsigned long mfn, pfn;
953 /* Do not add to override if the map failed. */
954 if (map_ops[i].status)
957 if (map_ops[i].flags & GNTMAP_contains_pte) {
958 pte = (pte_t *) (mfn_to_virt(PFN_DOWN(map_ops[i].host_addr)) +
959 (map_ops[i].host_addr & ~PAGE_MASK));
962 mfn = PFN_DOWN(map_ops[i].dev_bus_addr);
964 pfn = page_to_pfn(pages[i]);
966 WARN_ON(PagePrivate(pages[i]));
967 SetPagePrivate(pages[i]);
968 set_page_private(pages[i], mfn);
969 pages[i]->index = pfn_to_mfn(pfn);
971 if (unlikely(!set_phys_to_machine(pfn, FOREIGN_FRAME(mfn)))) {
977 ret = m2p_add_override(mfn, pages[i], &kmap_ops[i]);
985 arch_leave_lazy_mmu_mode();
989 EXPORT_SYMBOL_GPL(set_foreign_p2m_mapping);
991 /* Add an MFN override for a particular page */
992 int m2p_add_override(unsigned long mfn, struct page *page,
993 struct gnttab_map_grant_ref *kmap_op)
997 unsigned long uninitialized_var(address);
1001 pfn = page_to_pfn(page);
1002 if (!PageHighMem(page)) {
1003 address = (unsigned long)__va(pfn << PAGE_SHIFT);
1004 ptep = lookup_address(address, &level);
1005 if (WARN(ptep == NULL || level != PG_LEVEL_4K,
1006 "m2p_add_override: pfn %lx not mapped", pfn))
1010 if (kmap_op != NULL) {
1011 if (!PageHighMem(page)) {
1012 struct multicall_space mcs =
1013 xen_mc_entry(sizeof(*kmap_op));
1015 MULTI_grant_table_op(mcs.mc,
1016 GNTTABOP_map_grant_ref, kmap_op, 1);
1018 xen_mc_issue(PARAVIRT_LAZY_MMU);
1021 spin_lock_irqsave(&m2p_override_lock, flags);
1022 list_add(&page->lru, &m2p_overrides[mfn_hash(mfn)]);
1023 spin_unlock_irqrestore(&m2p_override_lock, flags);
1025 /* p2m(m2p(mfn)) == mfn: the mfn is already present somewhere in
1026 * this domain. Set the FOREIGN_FRAME_BIT in the p2m for the other
1027 * pfn so that the following mfn_to_pfn(mfn) calls will return the
1028 * pfn from the m2p_override (the backend pfn) instead.
1029 * We need to do this because the pages shared by the frontend
1030 * (xen-blkfront) can be already locked (lock_page, called by
1031 * do_read_cache_page); when the userspace backend tries to use them
1032 * with direct_IO, mfn_to_pfn returns the pfn of the frontend, so
1033 * do_blockdev_direct_IO is going to try to lock the same pages
1034 * again resulting in a deadlock.
1035 * As a side effect get_user_pages_fast might not be safe on the
1036 * frontend pages while they are being shared with the backend,
1037 * because mfn_to_pfn (that ends up being called by GUPF) will
1038 * return the backend pfn rather than the frontend pfn. */
1039 pfn = mfn_to_pfn_no_overrides(mfn);
1040 if (get_phys_to_machine(pfn) == mfn)
1041 set_phys_to_machine(pfn, FOREIGN_FRAME(mfn));
1045 EXPORT_SYMBOL_GPL(m2p_add_override);
1047 int clear_foreign_p2m_mapping(struct gnttab_unmap_grant_ref *unmap_ops,
1048 struct gnttab_map_grant_ref *kmap_ops,
1049 struct page **pages, unsigned int count)
1054 if (xen_feature(XENFEAT_auto_translated_physmap))
1059 paravirt_get_lazy_mode() == PARAVIRT_LAZY_NONE) {
1060 arch_enter_lazy_mmu_mode();
1064 for (i = 0; i < count; i++) {
1065 unsigned long mfn = get_phys_to_machine(page_to_pfn(pages[i]));
1066 unsigned long pfn = page_to_pfn(pages[i]);
1068 if (mfn == INVALID_P2M_ENTRY || !(mfn & FOREIGN_FRAME_BIT)) {
1073 set_page_private(pages[i], INVALID_P2M_ENTRY);
1074 WARN_ON(!PagePrivate(pages[i]));
1075 ClearPagePrivate(pages[i]);
1076 set_phys_to_machine(pfn, pages[i]->index);
1079 ret = m2p_remove_override(pages[i], &kmap_ops[i], mfn);
1086 arch_leave_lazy_mmu_mode();
1089 EXPORT_SYMBOL_GPL(clear_foreign_p2m_mapping);
1091 int m2p_remove_override(struct page *page,
1092 struct gnttab_map_grant_ref *kmap_op,
1095 unsigned long flags;
1097 unsigned long uninitialized_var(address);
1101 pfn = page_to_pfn(page);
1103 if (!PageHighMem(page)) {
1104 address = (unsigned long)__va(pfn << PAGE_SHIFT);
1105 ptep = lookup_address(address, &level);
1107 if (WARN(ptep == NULL || level != PG_LEVEL_4K,
1108 "m2p_remove_override: pfn %lx not mapped", pfn))
1112 spin_lock_irqsave(&m2p_override_lock, flags);
1113 list_del(&page->lru);
1114 spin_unlock_irqrestore(&m2p_override_lock, flags);
1116 if (kmap_op != NULL) {
1117 if (!PageHighMem(page)) {
1118 struct multicall_space mcs;
1119 struct gnttab_unmap_and_replace *unmap_op;
1120 struct page *scratch_page = get_balloon_scratch_page();
1121 unsigned long scratch_page_address = (unsigned long)
1122 __va(page_to_pfn(scratch_page) << PAGE_SHIFT);
1125 * It might be that we queued all the m2p grant table
1126 * hypercalls in a multicall, then m2p_remove_override
1127 * get called before the multicall has actually been
1128 * issued. In this case handle is going to -1 because
1129 * it hasn't been modified yet.
1131 if (kmap_op->handle == -1)
1134 * Now if kmap_op->handle is negative it means that the
1135 * hypercall actually returned an error.
1137 if (kmap_op->handle == GNTST_general_error) {
1138 printk(KERN_WARNING "m2p_remove_override: "
1139 "pfn %lx mfn %lx, failed to modify kernel mappings",
1141 put_balloon_scratch_page();
1147 mcs = __xen_mc_entry(
1148 sizeof(struct gnttab_unmap_and_replace));
1149 unmap_op = mcs.args;
1150 unmap_op->host_addr = kmap_op->host_addr;
1151 unmap_op->new_addr = scratch_page_address;
1152 unmap_op->handle = kmap_op->handle;
1154 MULTI_grant_table_op(mcs.mc,
1155 GNTTABOP_unmap_and_replace, unmap_op, 1);
1157 mcs = __xen_mc_entry(0);
1158 MULTI_update_va_mapping(mcs.mc, scratch_page_address,
1159 pfn_pte(page_to_pfn(scratch_page),
1160 PAGE_KERNEL_RO), 0);
1162 xen_mc_issue(PARAVIRT_LAZY_MMU);
1164 kmap_op->host_addr = 0;
1165 put_balloon_scratch_page();
1169 /* p2m(m2p(mfn)) == FOREIGN_FRAME(mfn): the mfn is already present
1170 * somewhere in this domain, even before being added to the
1171 * m2p_override (see comment above in m2p_add_override).
1172 * If there are no other entries in the m2p_override corresponding
1173 * to this mfn, then remove the FOREIGN_FRAME_BIT from the p2m for
1174 * the original pfn (the one shared by the frontend): the backend
1175 * cannot do any IO on this page anymore because it has been
1176 * unshared. Removing the FOREIGN_FRAME_BIT from the p2m entry of
1177 * the original pfn causes mfn_to_pfn(mfn) to return the frontend
1179 mfn &= ~FOREIGN_FRAME_BIT;
1180 pfn = mfn_to_pfn_no_overrides(mfn);
1181 if (get_phys_to_machine(pfn) == FOREIGN_FRAME(mfn) &&
1182 m2p_find_override(mfn) == NULL)
1183 set_phys_to_machine(pfn, mfn);
1187 EXPORT_SYMBOL_GPL(m2p_remove_override);
1189 struct page *m2p_find_override(unsigned long mfn)
1191 unsigned long flags;
1192 struct list_head *bucket = &m2p_overrides[mfn_hash(mfn)];
1193 struct page *p, *ret;
1197 spin_lock_irqsave(&m2p_override_lock, flags);
1199 list_for_each_entry(p, bucket, lru) {
1200 if (page_private(p) == mfn) {
1206 spin_unlock_irqrestore(&m2p_override_lock, flags);
1211 unsigned long m2p_find_override_pfn(unsigned long mfn, unsigned long pfn)
1213 struct page *p = m2p_find_override(mfn);
1214 unsigned long ret = pfn;
1217 ret = page_to_pfn(p);
1221 EXPORT_SYMBOL_GPL(m2p_find_override_pfn);
1223 #ifdef CONFIG_XEN_DEBUG_FS
1224 #include <linux/debugfs.h>
1225 #include "debugfs.h"
1226 static int p2m_dump_show(struct seq_file *m, void *v)
1228 static const char * const level_name[] = { "top", "middle",
1229 "entry", "abnormal", "error"};
1230 #define TYPE_IDENTITY 0
1231 #define TYPE_MISSING 1
1233 #define TYPE_UNKNOWN 3
1234 static const char * const type_name[] = {
1235 [TYPE_IDENTITY] = "identity",
1236 [TYPE_MISSING] = "missing",
1238 [TYPE_UNKNOWN] = "abnormal"};
1239 unsigned long pfn, prev_pfn_type = 0, prev_pfn_level = 0;
1240 unsigned int uninitialized_var(prev_level);
1241 unsigned int uninitialized_var(prev_type);
1246 for (pfn = 0; pfn < MAX_DOMAIN_PAGES; pfn++) {
1247 unsigned topidx = p2m_top_index(pfn);
1248 unsigned mididx = p2m_mid_index(pfn);
1249 unsigned idx = p2m_index(pfn);
1253 type = TYPE_UNKNOWN;
1254 if (p2m_top[topidx] == p2m_mid_missing) {
1255 lvl = 0; type = TYPE_MISSING;
1256 } else if (p2m_top[topidx] == NULL) {
1257 lvl = 0; type = TYPE_UNKNOWN;
1258 } else if (p2m_top[topidx][mididx] == NULL) {
1259 lvl = 1; type = TYPE_UNKNOWN;
1260 } else if (p2m_top[topidx][mididx] == p2m_identity) {
1261 lvl = 1; type = TYPE_IDENTITY;
1262 } else if (p2m_top[topidx][mididx] == p2m_missing) {
1263 lvl = 1; type = TYPE_MISSING;
1264 } else if (p2m_top[topidx][mididx][idx] == 0) {
1265 lvl = 2; type = TYPE_UNKNOWN;
1266 } else if (p2m_top[topidx][mididx][idx] == IDENTITY_FRAME(pfn)) {
1267 lvl = 2; type = TYPE_IDENTITY;
1268 } else if (p2m_top[topidx][mididx][idx] == INVALID_P2M_ENTRY) {
1269 lvl = 2; type = TYPE_MISSING;
1270 } else if (p2m_top[topidx][mididx][idx] == pfn) {
1271 lvl = 2; type = TYPE_PFN;
1272 } else if (p2m_top[topidx][mididx][idx] != pfn) {
1273 lvl = 2; type = TYPE_PFN;
1279 if (pfn == MAX_DOMAIN_PAGES-1) {
1281 type = TYPE_UNKNOWN;
1283 if (prev_type != type) {
1284 seq_printf(m, " [0x%lx->0x%lx] %s\n",
1285 prev_pfn_type, pfn, type_name[prev_type]);
1286 prev_pfn_type = pfn;
1289 if (prev_level != lvl) {
1290 seq_printf(m, " [0x%lx->0x%lx] level %s\n",
1291 prev_pfn_level, pfn, level_name[prev_level]);
1292 prev_pfn_level = pfn;
1297 #undef TYPE_IDENTITY
1303 static int p2m_dump_open(struct inode *inode, struct file *filp)
1305 return single_open(filp, p2m_dump_show, NULL);
1308 static const struct file_operations p2m_dump_fops = {
1309 .open = p2m_dump_open,
1311 .llseek = seq_lseek,
1312 .release = single_release,
1315 static struct dentry *d_mmu_debug;
1317 static int __init xen_p2m_debugfs(void)
1319 struct dentry *d_xen = xen_init_debugfs();
1324 d_mmu_debug = debugfs_create_dir("mmu", d_xen);
1326 debugfs_create_file("p2m", 0600, d_mmu_debug, NULL, &p2m_dump_fops);
1329 fs_initcall(xen_p2m_debugfs);
1330 #endif /* CONFIG_XEN_DEBUG_FS */