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TOMOYO Linux Cross Reference
Linux/arch/x86/xen/p2m.c

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  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 logical flat p2m table is mapped to a linear kernel memory area.
  7  * For accesses by Xen a three-level tree linked via mfns only is set up to
  8  * allow the address space to be sparse.
  9  *
 10  *               Xen
 11  *                |
 12  *          p2m_top_mfn
 13  *              /   \
 14  * p2m_mid_mfn p2m_mid_mfn
 15  *         /           /
 16  *  p2m p2m p2m ...
 17  *
 18  * The p2m_mid_mfn pages are mapped by p2m_top_mfn_p.
 19  *
 20  * The p2m_top_mfn level is limited to 1 page, so the maximum representable
 21  * pseudo-physical address space is:
 22  *  P2M_TOP_PER_PAGE * P2M_MID_PER_PAGE * P2M_PER_PAGE pages
 23  *
 24  * P2M_PER_PAGE depends on the architecture, as a mfn is always
 25  * unsigned long (8 bytes on 64-bit, 4 bytes on 32), leading to
 26  * 512 and 1024 entries respectively.
 27  *
 28  * In short, these structures contain the Machine Frame Number (MFN) of the PFN.
 29  *
 30  * However not all entries are filled with MFNs. Specifically for all other
 31  * leaf entries, or for the top  root, or middle one, for which there is a void
 32  * entry, we assume it is  "missing". So (for example)
 33  *  pfn_to_mfn(0x90909090)=INVALID_P2M_ENTRY.
 34  * We have a dedicated page p2m_missing with all entries being
 35  * INVALID_P2M_ENTRY. This page may be referenced multiple times in the p2m
 36  * list/tree in case there are multiple areas with P2M_PER_PAGE invalid pfns.
 37  *
 38  * We also have the possibility of setting 1-1 mappings on certain regions, so
 39  * that:
 40  *  pfn_to_mfn(0xc0000)=0xc0000
 41  *
 42  * The benefit of this is, that we can assume for non-RAM regions (think
 43  * PCI BARs, or ACPI spaces), we can create mappings easily because we
 44  * get the PFN value to match the MFN.
 45  *
 46  * For this to work efficiently we have one new page p2m_identity. All entries
 47  * in p2m_identity are set to INVALID_P2M_ENTRY type (Xen toolstack only
 48  * recognizes that and MFNs, no other fancy value).
 49  *
 50  * On lookup we spot that the entry points to p2m_identity and return the
 51  * identity value instead of dereferencing and returning INVALID_P2M_ENTRY.
 52  * If the entry points to an allocated page, we just proceed as before and
 53  * return the PFN. If the PFN has IDENTITY_FRAME_BIT set we unmask that in
 54  * appropriate functions (pfn_to_mfn).
 55  *
 56  * The reason for having the IDENTITY_FRAME_BIT instead of just returning the
 57  * PFN is that we could find ourselves where pfn_to_mfn(pfn)==pfn for a
 58  * non-identity pfn. To protect ourselves against we elect to set (and get) the
 59  * IDENTITY_FRAME_BIT on all identity mapped PFNs.
 60  */
 61 
 62 #include <linux/init.h>
 63 #include <linux/module.h>
 64 #include <linux/list.h>
 65 #include <linux/hash.h>
 66 #include <linux/sched.h>
 67 #include <linux/seq_file.h>
 68 #include <linux/bootmem.h>
 69 #include <linux/slab.h>
 70 #include <linux/vmalloc.h>
 71 
 72 #include <asm/cache.h>
 73 #include <asm/setup.h>
 74 #include <asm/uaccess.h>
 75 
 76 #include <asm/xen/page.h>
 77 #include <asm/xen/hypercall.h>
 78 #include <asm/xen/hypervisor.h>
 79 #include <xen/balloon.h>
 80 #include <xen/grant_table.h>
 81 
 82 #include "multicalls.h"
 83 #include "xen-ops.h"
 84 
 85 #define P2M_MID_PER_PAGE        (PAGE_SIZE / sizeof(unsigned long *))
 86 #define P2M_TOP_PER_PAGE        (PAGE_SIZE / sizeof(unsigned long **))
 87 
 88 #define MAX_P2M_PFN     (P2M_TOP_PER_PAGE * P2M_MID_PER_PAGE * P2M_PER_PAGE)
 89 
 90 #define PMDS_PER_MID_PAGE       (P2M_MID_PER_PAGE / PTRS_PER_PTE)
 91 
 92 unsigned long *xen_p2m_addr __read_mostly;
 93 EXPORT_SYMBOL_GPL(xen_p2m_addr);
 94 unsigned long xen_p2m_size __read_mostly;
 95 EXPORT_SYMBOL_GPL(xen_p2m_size);
 96 unsigned long xen_max_p2m_pfn __read_mostly;
 97 EXPORT_SYMBOL_GPL(xen_max_p2m_pfn);
 98 
 99 #ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG_LIMIT
100 #define P2M_LIMIT CONFIG_XEN_BALLOON_MEMORY_HOTPLUG_LIMIT
101 #else
102 #define P2M_LIMIT 0
103 #endif
104 
105 static DEFINE_SPINLOCK(p2m_update_lock);
106 
107 static unsigned long *p2m_mid_missing_mfn;
108 static unsigned long *p2m_top_mfn;
109 static unsigned long **p2m_top_mfn_p;
110 static unsigned long *p2m_missing;
111 static unsigned long *p2m_identity;
112 static pte_t *p2m_missing_pte;
113 static pte_t *p2m_identity_pte;
114 
115 /*
116  * Hint at last populated PFN.
117  *
118  * Used to set HYPERVISOR_shared_info->arch.max_pfn so the toolstack
119  * can avoid scanning the whole P2M (which may be sized to account for
120  * hotplugged memory).
121  */
122 static unsigned long xen_p2m_last_pfn;
123 
124 static inline unsigned p2m_top_index(unsigned long pfn)
125 {
126         BUG_ON(pfn >= MAX_P2M_PFN);
127         return pfn / (P2M_MID_PER_PAGE * P2M_PER_PAGE);
128 }
129 
130 static inline unsigned p2m_mid_index(unsigned long pfn)
131 {
132         return (pfn / P2M_PER_PAGE) % P2M_MID_PER_PAGE;
133 }
134 
135 static inline unsigned p2m_index(unsigned long pfn)
136 {
137         return pfn % P2M_PER_PAGE;
138 }
139 
140 static void p2m_top_mfn_init(unsigned long *top)
141 {
142         unsigned i;
143 
144         for (i = 0; i < P2M_TOP_PER_PAGE; i++)
145                 top[i] = virt_to_mfn(p2m_mid_missing_mfn);
146 }
147 
148 static void p2m_top_mfn_p_init(unsigned long **top)
149 {
150         unsigned i;
151 
152         for (i = 0; i < P2M_TOP_PER_PAGE; i++)
153                 top[i] = p2m_mid_missing_mfn;
154 }
155 
156 static void p2m_mid_mfn_init(unsigned long *mid, unsigned long *leaf)
157 {
158         unsigned i;
159 
160         for (i = 0; i < P2M_MID_PER_PAGE; i++)
161                 mid[i] = virt_to_mfn(leaf);
162 }
163 
164 static void p2m_init(unsigned long *p2m)
165 {
166         unsigned i;
167 
168         for (i = 0; i < P2M_PER_PAGE; i++)
169                 p2m[i] = INVALID_P2M_ENTRY;
170 }
171 
172 static void p2m_init_identity(unsigned long *p2m, unsigned long pfn)
173 {
174         unsigned i;
175 
176         for (i = 0; i < P2M_PER_PAGE; i++)
177                 p2m[i] = IDENTITY_FRAME(pfn + i);
178 }
179 
180 static void * __ref alloc_p2m_page(void)
181 {
182         if (unlikely(!slab_is_available()))
183                 return alloc_bootmem_align(PAGE_SIZE, PAGE_SIZE);
184 
185         return (void *)__get_free_page(GFP_KERNEL | __GFP_REPEAT);
186 }
187 
188 static void __ref free_p2m_page(void *p)
189 {
190         if (unlikely(!slab_is_available())) {
191                 free_bootmem((unsigned long)p, PAGE_SIZE);
192                 return;
193         }
194 
195         free_page((unsigned long)p);
196 }
197 
198 /*
199  * Build the parallel p2m_top_mfn and p2m_mid_mfn structures
200  *
201  * This is called both at boot time, and after resuming from suspend:
202  * - At boot time we're called rather early, and must use alloc_bootmem*()
203  *   to allocate memory.
204  *
205  * - After resume we're called from within stop_machine, but the mfn
206  *   tree should already be completely allocated.
207  */
208 void __ref xen_build_mfn_list_list(void)
209 {
210         unsigned long pfn, mfn;
211         pte_t *ptep;
212         unsigned int level, topidx, mididx;
213         unsigned long *mid_mfn_p;
214 
215         if (xen_feature(XENFEAT_auto_translated_physmap) ||
216             xen_start_info->flags & SIF_VIRT_P2M_4TOOLS)
217                 return;
218 
219         /* Pre-initialize p2m_top_mfn to be completely missing */
220         if (p2m_top_mfn == NULL) {
221                 p2m_mid_missing_mfn = alloc_p2m_page();
222                 p2m_mid_mfn_init(p2m_mid_missing_mfn, p2m_missing);
223 
224                 p2m_top_mfn_p = alloc_p2m_page();
225                 p2m_top_mfn_p_init(p2m_top_mfn_p);
226 
227                 p2m_top_mfn = alloc_p2m_page();
228                 p2m_top_mfn_init(p2m_top_mfn);
229         } else {
230                 /* Reinitialise, mfn's all change after migration */
231                 p2m_mid_mfn_init(p2m_mid_missing_mfn, p2m_missing);
232         }
233 
234         for (pfn = 0; pfn < xen_max_p2m_pfn && pfn < MAX_P2M_PFN;
235              pfn += P2M_PER_PAGE) {
236                 topidx = p2m_top_index(pfn);
237                 mididx = p2m_mid_index(pfn);
238 
239                 mid_mfn_p = p2m_top_mfn_p[topidx];
240                 ptep = lookup_address((unsigned long)(xen_p2m_addr + pfn),
241                                       &level);
242                 BUG_ON(!ptep || level != PG_LEVEL_4K);
243                 mfn = pte_mfn(*ptep);
244                 ptep = (pte_t *)((unsigned long)ptep & ~(PAGE_SIZE - 1));
245 
246                 /* Don't bother allocating any mfn mid levels if
247                  * they're just missing, just update the stored mfn,
248                  * since all could have changed over a migrate.
249                  */
250                 if (ptep == p2m_missing_pte || ptep == p2m_identity_pte) {
251                         BUG_ON(mididx);
252                         BUG_ON(mid_mfn_p != p2m_mid_missing_mfn);
253                         p2m_top_mfn[topidx] = virt_to_mfn(p2m_mid_missing_mfn);
254                         pfn += (P2M_MID_PER_PAGE - 1) * P2M_PER_PAGE;
255                         continue;
256                 }
257 
258                 if (mid_mfn_p == p2m_mid_missing_mfn) {
259                         mid_mfn_p = alloc_p2m_page();
260                         p2m_mid_mfn_init(mid_mfn_p, p2m_missing);
261 
262                         p2m_top_mfn_p[topidx] = mid_mfn_p;
263                 }
264 
265                 p2m_top_mfn[topidx] = virt_to_mfn(mid_mfn_p);
266                 mid_mfn_p[mididx] = mfn;
267         }
268 }
269 
270 void xen_setup_mfn_list_list(void)
271 {
272         if (xen_feature(XENFEAT_auto_translated_physmap))
273                 return;
274 
275         BUG_ON(HYPERVISOR_shared_info == &xen_dummy_shared_info);
276 
277         if (xen_start_info->flags & SIF_VIRT_P2M_4TOOLS)
278                 HYPERVISOR_shared_info->arch.pfn_to_mfn_frame_list_list = ~0UL;
279         else
280                 HYPERVISOR_shared_info->arch.pfn_to_mfn_frame_list_list =
281                         virt_to_mfn(p2m_top_mfn);
282         HYPERVISOR_shared_info->arch.max_pfn = xen_p2m_last_pfn;
283         HYPERVISOR_shared_info->arch.p2m_generation = 0;
284         HYPERVISOR_shared_info->arch.p2m_vaddr = (unsigned long)xen_p2m_addr;
285         HYPERVISOR_shared_info->arch.p2m_cr3 =
286                 xen_pfn_to_cr3(virt_to_mfn(swapper_pg_dir));
287 }
288 
289 /* Set up p2m_top to point to the domain-builder provided p2m pages */
290 void __init xen_build_dynamic_phys_to_machine(void)
291 {
292         unsigned long pfn;
293 
294          if (xen_feature(XENFEAT_auto_translated_physmap))
295                 return;
296 
297         xen_p2m_addr = (unsigned long *)xen_start_info->mfn_list;
298         xen_p2m_size = ALIGN(xen_start_info->nr_pages, P2M_PER_PAGE);
299 
300         for (pfn = xen_start_info->nr_pages; pfn < xen_p2m_size; pfn++)
301                 xen_p2m_addr[pfn] = INVALID_P2M_ENTRY;
302 
303         xen_max_p2m_pfn = xen_p2m_size;
304 }
305 
306 #define P2M_TYPE_IDENTITY       0
307 #define P2M_TYPE_MISSING        1
308 #define P2M_TYPE_PFN            2
309 #define P2M_TYPE_UNKNOWN        3
310 
311 static int xen_p2m_elem_type(unsigned long pfn)
312 {
313         unsigned long mfn;
314 
315         if (pfn >= xen_p2m_size)
316                 return P2M_TYPE_IDENTITY;
317 
318         mfn = xen_p2m_addr[pfn];
319 
320         if (mfn == INVALID_P2M_ENTRY)
321                 return P2M_TYPE_MISSING;
322 
323         if (mfn & IDENTITY_FRAME_BIT)
324                 return P2M_TYPE_IDENTITY;
325 
326         return P2M_TYPE_PFN;
327 }
328 
329 static void __init xen_rebuild_p2m_list(unsigned long *p2m)
330 {
331         unsigned int i, chunk;
332         unsigned long pfn;
333         unsigned long *mfns;
334         pte_t *ptep;
335         pmd_t *pmdp;
336         int type;
337 
338         p2m_missing = alloc_p2m_page();
339         p2m_init(p2m_missing);
340         p2m_identity = alloc_p2m_page();
341         p2m_init(p2m_identity);
342 
343         p2m_missing_pte = alloc_p2m_page();
344         paravirt_alloc_pte(&init_mm, __pa(p2m_missing_pte) >> PAGE_SHIFT);
345         p2m_identity_pte = alloc_p2m_page();
346         paravirt_alloc_pte(&init_mm, __pa(p2m_identity_pte) >> PAGE_SHIFT);
347         for (i = 0; i < PTRS_PER_PTE; i++) {
348                 set_pte(p2m_missing_pte + i,
349                         pfn_pte(PFN_DOWN(__pa(p2m_missing)), PAGE_KERNEL_RO));
350                 set_pte(p2m_identity_pte + i,
351                         pfn_pte(PFN_DOWN(__pa(p2m_identity)), PAGE_KERNEL_RO));
352         }
353 
354         for (pfn = 0; pfn < xen_max_p2m_pfn; pfn += chunk) {
355                 /*
356                  * Try to map missing/identity PMDs or p2m-pages if possible.
357                  * We have to respect the structure of the mfn_list_list
358                  * which will be built just afterwards.
359                  * Chunk size to test is one p2m page if we are in the middle
360                  * of a mfn_list_list mid page and the complete mid page area
361                  * if we are at index 0 of the mid page. Please note that a
362                  * mid page might cover more than one PMD, e.g. on 32 bit PAE
363                  * kernels.
364                  */
365                 chunk = (pfn & (P2M_PER_PAGE * P2M_MID_PER_PAGE - 1)) ?
366                         P2M_PER_PAGE : P2M_PER_PAGE * P2M_MID_PER_PAGE;
367 
368                 type = xen_p2m_elem_type(pfn);
369                 i = 0;
370                 if (type != P2M_TYPE_PFN)
371                         for (i = 1; i < chunk; i++)
372                                 if (xen_p2m_elem_type(pfn + i) != type)
373                                         break;
374                 if (i < chunk)
375                         /* Reset to minimal chunk size. */
376                         chunk = P2M_PER_PAGE;
377 
378                 if (type == P2M_TYPE_PFN || i < chunk) {
379                         /* Use initial p2m page contents. */
380 #ifdef CONFIG_X86_64
381                         mfns = alloc_p2m_page();
382                         copy_page(mfns, xen_p2m_addr + pfn);
383 #else
384                         mfns = xen_p2m_addr + pfn;
385 #endif
386                         ptep = populate_extra_pte((unsigned long)(p2m + pfn));
387                         set_pte(ptep,
388                                 pfn_pte(PFN_DOWN(__pa(mfns)), PAGE_KERNEL));
389                         continue;
390                 }
391 
392                 if (chunk == P2M_PER_PAGE) {
393                         /* Map complete missing or identity p2m-page. */
394                         mfns = (type == P2M_TYPE_MISSING) ?
395                                 p2m_missing : p2m_identity;
396                         ptep = populate_extra_pte((unsigned long)(p2m + pfn));
397                         set_pte(ptep,
398                                 pfn_pte(PFN_DOWN(__pa(mfns)), PAGE_KERNEL_RO));
399                         continue;
400                 }
401 
402                 /* Complete missing or identity PMD(s) can be mapped. */
403                 ptep = (type == P2M_TYPE_MISSING) ?
404                         p2m_missing_pte : p2m_identity_pte;
405                 for (i = 0; i < PMDS_PER_MID_PAGE; i++) {
406                         pmdp = populate_extra_pmd(
407                                 (unsigned long)(p2m + pfn) + i * PMD_SIZE);
408                         set_pmd(pmdp, __pmd(__pa(ptep) | _KERNPG_TABLE));
409                 }
410         }
411 }
412 
413 void __init xen_vmalloc_p2m_tree(void)
414 {
415         static struct vm_struct vm;
416         unsigned long p2m_limit;
417 
418         xen_p2m_last_pfn = xen_max_p2m_pfn;
419 
420         p2m_limit = (phys_addr_t)P2M_LIMIT * 1024 * 1024 * 1024 / PAGE_SIZE;
421         vm.flags = VM_ALLOC;
422         vm.size = ALIGN(sizeof(unsigned long) * max(xen_max_p2m_pfn, p2m_limit),
423                         PMD_SIZE * PMDS_PER_MID_PAGE);
424         vm_area_register_early(&vm, PMD_SIZE * PMDS_PER_MID_PAGE);
425         pr_notice("p2m virtual area at %p, size is %lx\n", vm.addr, vm.size);
426 
427         xen_max_p2m_pfn = vm.size / sizeof(unsigned long);
428 
429         xen_rebuild_p2m_list(vm.addr);
430 
431         xen_p2m_addr = vm.addr;
432         xen_p2m_size = xen_max_p2m_pfn;
433 
434         xen_inv_extra_mem();
435 }
436 
437 unsigned long get_phys_to_machine(unsigned long pfn)
438 {
439         pte_t *ptep;
440         unsigned int level;
441 
442         if (unlikely(pfn >= xen_p2m_size)) {
443                 if (pfn < xen_max_p2m_pfn)
444                         return xen_chk_extra_mem(pfn);
445 
446                 return IDENTITY_FRAME(pfn);
447         }
448 
449         ptep = lookup_address((unsigned long)(xen_p2m_addr + pfn), &level);
450         BUG_ON(!ptep || level != PG_LEVEL_4K);
451 
452         /*
453          * The INVALID_P2M_ENTRY is filled in both p2m_*identity
454          * and in p2m_*missing, so returning the INVALID_P2M_ENTRY
455          * would be wrong.
456          */
457         if (pte_pfn(*ptep) == PFN_DOWN(__pa(p2m_identity)))
458                 return IDENTITY_FRAME(pfn);
459 
460         return xen_p2m_addr[pfn];
461 }
462 EXPORT_SYMBOL_GPL(get_phys_to_machine);
463 
464 /*
465  * Allocate new pmd(s). It is checked whether the old pmd is still in place.
466  * If not, nothing is changed. This is okay as the only reason for allocating
467  * a new pmd is to replace p2m_missing_pte or p2m_identity_pte by a individual
468  * pmd. In case of PAE/x86-32 there are multiple pmds to allocate!
469  */
470 static pte_t *alloc_p2m_pmd(unsigned long addr, pte_t *pte_pg)
471 {
472         pte_t *ptechk;
473         pte_t *pte_newpg[PMDS_PER_MID_PAGE];
474         pmd_t *pmdp;
475         unsigned int level;
476         unsigned long flags;
477         unsigned long vaddr;
478         int i;
479 
480         /* Do all allocations first to bail out in error case. */
481         for (i = 0; i < PMDS_PER_MID_PAGE; i++) {
482                 pte_newpg[i] = alloc_p2m_page();
483                 if (!pte_newpg[i]) {
484                         for (i--; i >= 0; i--)
485                                 free_p2m_page(pte_newpg[i]);
486 
487                         return NULL;
488                 }
489         }
490 
491         vaddr = addr & ~(PMD_SIZE * PMDS_PER_MID_PAGE - 1);
492 
493         for (i = 0; i < PMDS_PER_MID_PAGE; i++) {
494                 copy_page(pte_newpg[i], pte_pg);
495                 paravirt_alloc_pte(&init_mm, __pa(pte_newpg[i]) >> PAGE_SHIFT);
496 
497                 pmdp = lookup_pmd_address(vaddr);
498                 BUG_ON(!pmdp);
499 
500                 spin_lock_irqsave(&p2m_update_lock, flags);
501 
502                 ptechk = lookup_address(vaddr, &level);
503                 if (ptechk == pte_pg) {
504                         HYPERVISOR_shared_info->arch.p2m_generation++;
505                         wmb(); /* Tools are synchronizing via p2m_generation. */
506                         set_pmd(pmdp,
507                                 __pmd(__pa(pte_newpg[i]) | _KERNPG_TABLE));
508                         wmb(); /* Tools are synchronizing via p2m_generation. */
509                         HYPERVISOR_shared_info->arch.p2m_generation++;
510                         pte_newpg[i] = NULL;
511                 }
512 
513                 spin_unlock_irqrestore(&p2m_update_lock, flags);
514 
515                 if (pte_newpg[i]) {
516                         paravirt_release_pte(__pa(pte_newpg[i]) >> PAGE_SHIFT);
517                         free_p2m_page(pte_newpg[i]);
518                 }
519 
520                 vaddr += PMD_SIZE;
521         }
522 
523         return lookup_address(addr, &level);
524 }
525 
526 /*
527  * Fully allocate the p2m structure for a given pfn.  We need to check
528  * that both the top and mid levels are allocated, and make sure the
529  * parallel mfn tree is kept in sync.  We may race with other cpus, so
530  * the new pages are installed with cmpxchg; if we lose the race then
531  * simply free the page we allocated and use the one that's there.
532  */
533 int xen_alloc_p2m_entry(unsigned long pfn)
534 {
535         unsigned topidx;
536         unsigned long *top_mfn_p, *mid_mfn;
537         pte_t *ptep, *pte_pg;
538         unsigned int level;
539         unsigned long flags;
540         unsigned long addr = (unsigned long)(xen_p2m_addr + pfn);
541         unsigned long p2m_pfn;
542 
543         if (xen_feature(XENFEAT_auto_translated_physmap))
544                 return 0;
545 
546         ptep = lookup_address(addr, &level);
547         BUG_ON(!ptep || level != PG_LEVEL_4K);
548         pte_pg = (pte_t *)((unsigned long)ptep & ~(PAGE_SIZE - 1));
549 
550         if (pte_pg == p2m_missing_pte || pte_pg == p2m_identity_pte) {
551                 /* PMD level is missing, allocate a new one */
552                 ptep = alloc_p2m_pmd(addr, pte_pg);
553                 if (!ptep)
554                         return -ENOMEM;
555         }
556 
557         if (p2m_top_mfn && pfn < MAX_P2M_PFN) {
558                 topidx = p2m_top_index(pfn);
559                 top_mfn_p = &p2m_top_mfn[topidx];
560                 mid_mfn = ACCESS_ONCE(p2m_top_mfn_p[topidx]);
561 
562                 BUG_ON(virt_to_mfn(mid_mfn) != *top_mfn_p);
563 
564                 if (mid_mfn == p2m_mid_missing_mfn) {
565                         /* Separately check the mid mfn level */
566                         unsigned long missing_mfn;
567                         unsigned long mid_mfn_mfn;
568                         unsigned long old_mfn;
569 
570                         mid_mfn = alloc_p2m_page();
571                         if (!mid_mfn)
572                                 return -ENOMEM;
573 
574                         p2m_mid_mfn_init(mid_mfn, p2m_missing);
575 
576                         missing_mfn = virt_to_mfn(p2m_mid_missing_mfn);
577                         mid_mfn_mfn = virt_to_mfn(mid_mfn);
578                         old_mfn = cmpxchg(top_mfn_p, missing_mfn, mid_mfn_mfn);
579                         if (old_mfn != missing_mfn) {
580                                 free_p2m_page(mid_mfn);
581                                 mid_mfn = mfn_to_virt(old_mfn);
582                         } else {
583                                 p2m_top_mfn_p[topidx] = mid_mfn;
584                         }
585                 }
586         } else {
587                 mid_mfn = NULL;
588         }
589 
590         p2m_pfn = pte_pfn(READ_ONCE(*ptep));
591         if (p2m_pfn == PFN_DOWN(__pa(p2m_identity)) ||
592             p2m_pfn == PFN_DOWN(__pa(p2m_missing))) {
593                 /* p2m leaf page is missing */
594                 unsigned long *p2m;
595 
596                 p2m = alloc_p2m_page();
597                 if (!p2m)
598                         return -ENOMEM;
599 
600                 if (p2m_pfn == PFN_DOWN(__pa(p2m_missing)))
601                         p2m_init(p2m);
602                 else
603                         p2m_init_identity(p2m, pfn & ~(P2M_PER_PAGE - 1));
604 
605                 spin_lock_irqsave(&p2m_update_lock, flags);
606 
607                 if (pte_pfn(*ptep) == p2m_pfn) {
608                         HYPERVISOR_shared_info->arch.p2m_generation++;
609                         wmb(); /* Tools are synchronizing via p2m_generation. */
610                         set_pte(ptep,
611                                 pfn_pte(PFN_DOWN(__pa(p2m)), PAGE_KERNEL));
612                         wmb(); /* Tools are synchronizing via p2m_generation. */
613                         HYPERVISOR_shared_info->arch.p2m_generation++;
614                         if (mid_mfn)
615                                 mid_mfn[p2m_mid_index(pfn)] = virt_to_mfn(p2m);
616                         p2m = NULL;
617                 }
618 
619                 spin_unlock_irqrestore(&p2m_update_lock, flags);
620 
621                 if (p2m)
622                         free_p2m_page(p2m);
623         }
624 
625         /* Expanded the p2m? */
626         if (pfn > xen_p2m_last_pfn) {
627                 xen_p2m_last_pfn = pfn;
628                 HYPERVISOR_shared_info->arch.max_pfn = xen_p2m_last_pfn;
629         }
630 
631         return 0;
632 }
633 EXPORT_SYMBOL(xen_alloc_p2m_entry);
634 
635 unsigned long __init set_phys_range_identity(unsigned long pfn_s,
636                                       unsigned long pfn_e)
637 {
638         unsigned long pfn;
639 
640         if (unlikely(pfn_s >= xen_p2m_size))
641                 return 0;
642 
643         if (unlikely(xen_feature(XENFEAT_auto_translated_physmap)))
644                 return pfn_e - pfn_s;
645 
646         if (pfn_s > pfn_e)
647                 return 0;
648 
649         if (pfn_e > xen_p2m_size)
650                 pfn_e = xen_p2m_size;
651 
652         for (pfn = pfn_s; pfn < pfn_e; pfn++)
653                 xen_p2m_addr[pfn] = IDENTITY_FRAME(pfn);
654 
655         return pfn - pfn_s;
656 }
657 
658 bool __set_phys_to_machine(unsigned long pfn, unsigned long mfn)
659 {
660         pte_t *ptep;
661         unsigned int level;
662 
663         /* don't track P2M changes in autotranslate guests */
664         if (unlikely(xen_feature(XENFEAT_auto_translated_physmap)))
665                 return true;
666 
667         if (unlikely(pfn >= xen_p2m_size)) {
668                 BUG_ON(mfn != INVALID_P2M_ENTRY);
669                 return true;
670         }
671 
672         /*
673          * The interface requires atomic updates on p2m elements.
674          * xen_safe_write_ulong() is using __put_user which does an atomic
675          * store via asm().
676          */
677         if (likely(!xen_safe_write_ulong(xen_p2m_addr + pfn, mfn)))
678                 return true;
679 
680         ptep = lookup_address((unsigned long)(xen_p2m_addr + pfn), &level);
681         BUG_ON(!ptep || level != PG_LEVEL_4K);
682 
683         if (pte_pfn(*ptep) == PFN_DOWN(__pa(p2m_missing)))
684                 return mfn == INVALID_P2M_ENTRY;
685 
686         if (pte_pfn(*ptep) == PFN_DOWN(__pa(p2m_identity)))
687                 return mfn == IDENTITY_FRAME(pfn);
688 
689         return false;
690 }
691 
692 bool set_phys_to_machine(unsigned long pfn, unsigned long mfn)
693 {
694         if (unlikely(!__set_phys_to_machine(pfn, mfn))) {
695                 int ret;
696 
697                 ret = xen_alloc_p2m_entry(pfn);
698                 if (ret < 0)
699                         return false;
700 
701                 return __set_phys_to_machine(pfn, mfn);
702         }
703 
704         return true;
705 }
706 
707 int set_foreign_p2m_mapping(struct gnttab_map_grant_ref *map_ops,
708                             struct gnttab_map_grant_ref *kmap_ops,
709                             struct page **pages, unsigned int count)
710 {
711         int i, ret = 0;
712         pte_t *pte;
713 
714         if (xen_feature(XENFEAT_auto_translated_physmap))
715                 return 0;
716 
717         if (kmap_ops) {
718                 ret = HYPERVISOR_grant_table_op(GNTTABOP_map_grant_ref,
719                                                 kmap_ops, count);
720                 if (ret)
721                         goto out;
722         }
723 
724         for (i = 0; i < count; i++) {
725                 unsigned long mfn, pfn;
726 
727                 /* Do not add to override if the map failed. */
728                 if (map_ops[i].status)
729                         continue;
730 
731                 if (map_ops[i].flags & GNTMAP_contains_pte) {
732                         pte = (pte_t *)(mfn_to_virt(PFN_DOWN(map_ops[i].host_addr)) +
733                                 (map_ops[i].host_addr & ~PAGE_MASK));
734                         mfn = pte_mfn(*pte);
735                 } else {
736                         mfn = PFN_DOWN(map_ops[i].dev_bus_addr);
737                 }
738                 pfn = page_to_pfn(pages[i]);
739 
740                 WARN(pfn_to_mfn(pfn) != INVALID_P2M_ENTRY, "page must be ballooned");
741 
742                 if (unlikely(!set_phys_to_machine(pfn, FOREIGN_FRAME(mfn)))) {
743                         ret = -ENOMEM;
744                         goto out;
745                 }
746         }
747 
748 out:
749         return ret;
750 }
751 EXPORT_SYMBOL_GPL(set_foreign_p2m_mapping);
752 
753 int clear_foreign_p2m_mapping(struct gnttab_unmap_grant_ref *unmap_ops,
754                               struct gnttab_unmap_grant_ref *kunmap_ops,
755                               struct page **pages, unsigned int count)
756 {
757         int i, ret = 0;
758 
759         if (xen_feature(XENFEAT_auto_translated_physmap))
760                 return 0;
761 
762         for (i = 0; i < count; i++) {
763                 unsigned long mfn = __pfn_to_mfn(page_to_pfn(pages[i]));
764                 unsigned long pfn = page_to_pfn(pages[i]);
765 
766                 if (mfn == INVALID_P2M_ENTRY || !(mfn & FOREIGN_FRAME_BIT)) {
767                         ret = -EINVAL;
768                         goto out;
769                 }
770 
771                 set_phys_to_machine(pfn, INVALID_P2M_ENTRY);
772         }
773         if (kunmap_ops)
774                 ret = HYPERVISOR_grant_table_op(GNTTABOP_unmap_grant_ref,
775                                                 kunmap_ops, count);
776 out:
777         return ret;
778 }
779 EXPORT_SYMBOL_GPL(clear_foreign_p2m_mapping);
780 
781 #ifdef CONFIG_XEN_DEBUG_FS
782 #include <linux/debugfs.h>
783 #include "debugfs.h"
784 static int p2m_dump_show(struct seq_file *m, void *v)
785 {
786         static const char * const type_name[] = {
787                                 [P2M_TYPE_IDENTITY] = "identity",
788                                 [P2M_TYPE_MISSING] = "missing",
789                                 [P2M_TYPE_PFN] = "pfn",
790                                 [P2M_TYPE_UNKNOWN] = "abnormal"};
791         unsigned long pfn, first_pfn;
792         int type, prev_type;
793 
794         prev_type = xen_p2m_elem_type(0);
795         first_pfn = 0;
796 
797         for (pfn = 0; pfn < xen_p2m_size; pfn++) {
798                 type = xen_p2m_elem_type(pfn);
799                 if (type != prev_type) {
800                         seq_printf(m, " [0x%lx->0x%lx] %s\n", first_pfn, pfn,
801                                    type_name[prev_type]);
802                         prev_type = type;
803                         first_pfn = pfn;
804                 }
805         }
806         seq_printf(m, " [0x%lx->0x%lx] %s\n", first_pfn, pfn,
807                    type_name[prev_type]);
808         return 0;
809 }
810 
811 static int p2m_dump_open(struct inode *inode, struct file *filp)
812 {
813         return single_open(filp, p2m_dump_show, NULL);
814 }
815 
816 static const struct file_operations p2m_dump_fops = {
817         .open           = p2m_dump_open,
818         .read           = seq_read,
819         .llseek         = seq_lseek,
820         .release        = single_release,
821 };
822 
823 static struct dentry *d_mmu_debug;
824 
825 static int __init xen_p2m_debugfs(void)
826 {
827         struct dentry *d_xen = xen_init_debugfs();
828 
829         if (d_xen == NULL)
830                 return -ENOMEM;
831 
832         d_mmu_debug = debugfs_create_dir("mmu", d_xen);
833 
834         debugfs_create_file("p2m", 0600, d_mmu_debug, NULL, &p2m_dump_fops);
835         return 0;
836 }
837 fs_initcall(xen_p2m_debugfs);
838 #endif /* CONFIG_XEN_DEBUG_FS */
839 

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