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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/export.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 <linux/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);
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_start_info->flags & SIF_VIRT_P2M_4TOOLS)
216                 return;
217 
218         /* Pre-initialize p2m_top_mfn to be completely missing */
219         if (p2m_top_mfn == NULL) {
220                 p2m_mid_missing_mfn = alloc_p2m_page();
221                 p2m_mid_mfn_init(p2m_mid_missing_mfn, p2m_missing);
222 
223                 p2m_top_mfn_p = alloc_p2m_page();
224                 p2m_top_mfn_p_init(p2m_top_mfn_p);
225 
226                 p2m_top_mfn = alloc_p2m_page();
227                 p2m_top_mfn_init(p2m_top_mfn);
228         } else {
229                 /* Reinitialise, mfn's all change after migration */
230                 p2m_mid_mfn_init(p2m_mid_missing_mfn, p2m_missing);
231         }
232 
233         for (pfn = 0; pfn < xen_max_p2m_pfn && pfn < MAX_P2M_PFN;
234              pfn += P2M_PER_PAGE) {
235                 topidx = p2m_top_index(pfn);
236                 mididx = p2m_mid_index(pfn);
237 
238                 mid_mfn_p = p2m_top_mfn_p[topidx];
239                 ptep = lookup_address((unsigned long)(xen_p2m_addr + pfn),
240                                       &level);
241                 BUG_ON(!ptep || level != PG_LEVEL_4K);
242                 mfn = pte_mfn(*ptep);
243                 ptep = (pte_t *)((unsigned long)ptep & ~(PAGE_SIZE - 1));
244 
245                 /* Don't bother allocating any mfn mid levels if
246                  * they're just missing, just update the stored mfn,
247                  * since all could have changed over a migrate.
248                  */
249                 if (ptep == p2m_missing_pte || ptep == p2m_identity_pte) {
250                         BUG_ON(mididx);
251                         BUG_ON(mid_mfn_p != p2m_mid_missing_mfn);
252                         p2m_top_mfn[topidx] = virt_to_mfn(p2m_mid_missing_mfn);
253                         pfn += (P2M_MID_PER_PAGE - 1) * P2M_PER_PAGE;
254                         continue;
255                 }
256 
257                 if (mid_mfn_p == p2m_mid_missing_mfn) {
258                         mid_mfn_p = alloc_p2m_page();
259                         p2m_mid_mfn_init(mid_mfn_p, p2m_missing);
260 
261                         p2m_top_mfn_p[topidx] = mid_mfn_p;
262                 }
263 
264                 p2m_top_mfn[topidx] = virt_to_mfn(mid_mfn_p);
265                 mid_mfn_p[mididx] = mfn;
266         }
267 }
268 
269 void xen_setup_mfn_list_list(void)
270 {
271         BUG_ON(HYPERVISOR_shared_info == &xen_dummy_shared_info);
272 
273         if (xen_start_info->flags & SIF_VIRT_P2M_4TOOLS)
274                 HYPERVISOR_shared_info->arch.pfn_to_mfn_frame_list_list = ~0UL;
275         else
276                 HYPERVISOR_shared_info->arch.pfn_to_mfn_frame_list_list =
277                         virt_to_mfn(p2m_top_mfn);
278         HYPERVISOR_shared_info->arch.max_pfn = xen_p2m_last_pfn;
279         HYPERVISOR_shared_info->arch.p2m_generation = 0;
280         HYPERVISOR_shared_info->arch.p2m_vaddr = (unsigned long)xen_p2m_addr;
281         HYPERVISOR_shared_info->arch.p2m_cr3 =
282                 xen_pfn_to_cr3(virt_to_mfn(swapper_pg_dir));
283 }
284 
285 /* Set up p2m_top to point to the domain-builder provided p2m pages */
286 void __init xen_build_dynamic_phys_to_machine(void)
287 {
288         unsigned long pfn;
289 
290         xen_p2m_addr = (unsigned long *)xen_start_info->mfn_list;
291         xen_p2m_size = ALIGN(xen_start_info->nr_pages, P2M_PER_PAGE);
292 
293         for (pfn = xen_start_info->nr_pages; pfn < xen_p2m_size; pfn++)
294                 xen_p2m_addr[pfn] = INVALID_P2M_ENTRY;
295 
296         xen_max_p2m_pfn = xen_p2m_size;
297 }
298 
299 #define P2M_TYPE_IDENTITY       0
300 #define P2M_TYPE_MISSING        1
301 #define P2M_TYPE_PFN            2
302 #define P2M_TYPE_UNKNOWN        3
303 
304 static int xen_p2m_elem_type(unsigned long pfn)
305 {
306         unsigned long mfn;
307 
308         if (pfn >= xen_p2m_size)
309                 return P2M_TYPE_IDENTITY;
310 
311         mfn = xen_p2m_addr[pfn];
312 
313         if (mfn == INVALID_P2M_ENTRY)
314                 return P2M_TYPE_MISSING;
315 
316         if (mfn & IDENTITY_FRAME_BIT)
317                 return P2M_TYPE_IDENTITY;
318 
319         return P2M_TYPE_PFN;
320 }
321 
322 static void __init xen_rebuild_p2m_list(unsigned long *p2m)
323 {
324         unsigned int i, chunk;
325         unsigned long pfn;
326         unsigned long *mfns;
327         pte_t *ptep;
328         pmd_t *pmdp;
329         int type;
330 
331         p2m_missing = alloc_p2m_page();
332         p2m_init(p2m_missing);
333         p2m_identity = alloc_p2m_page();
334         p2m_init(p2m_identity);
335 
336         p2m_missing_pte = alloc_p2m_page();
337         paravirt_alloc_pte(&init_mm, __pa(p2m_missing_pte) >> PAGE_SHIFT);
338         p2m_identity_pte = alloc_p2m_page();
339         paravirt_alloc_pte(&init_mm, __pa(p2m_identity_pte) >> PAGE_SHIFT);
340         for (i = 0; i < PTRS_PER_PTE; i++) {
341                 set_pte(p2m_missing_pte + i,
342                         pfn_pte(PFN_DOWN(__pa(p2m_missing)), PAGE_KERNEL_RO));
343                 set_pte(p2m_identity_pte + i,
344                         pfn_pte(PFN_DOWN(__pa(p2m_identity)), PAGE_KERNEL_RO));
345         }
346 
347         for (pfn = 0; pfn < xen_max_p2m_pfn; pfn += chunk) {
348                 /*
349                  * Try to map missing/identity PMDs or p2m-pages if possible.
350                  * We have to respect the structure of the mfn_list_list
351                  * which will be built just afterwards.
352                  * Chunk size to test is one p2m page if we are in the middle
353                  * of a mfn_list_list mid page and the complete mid page area
354                  * if we are at index 0 of the mid page. Please note that a
355                  * mid page might cover more than one PMD, e.g. on 32 bit PAE
356                  * kernels.
357                  */
358                 chunk = (pfn & (P2M_PER_PAGE * P2M_MID_PER_PAGE - 1)) ?
359                         P2M_PER_PAGE : P2M_PER_PAGE * P2M_MID_PER_PAGE;
360 
361                 type = xen_p2m_elem_type(pfn);
362                 i = 0;
363                 if (type != P2M_TYPE_PFN)
364                         for (i = 1; i < chunk; i++)
365                                 if (xen_p2m_elem_type(pfn + i) != type)
366                                         break;
367                 if (i < chunk)
368                         /* Reset to minimal chunk size. */
369                         chunk = P2M_PER_PAGE;
370 
371                 if (type == P2M_TYPE_PFN || i < chunk) {
372                         /* Use initial p2m page contents. */
373 #ifdef CONFIG_X86_64
374                         mfns = alloc_p2m_page();
375                         copy_page(mfns, xen_p2m_addr + pfn);
376 #else
377                         mfns = xen_p2m_addr + pfn;
378 #endif
379                         ptep = populate_extra_pte((unsigned long)(p2m + pfn));
380                         set_pte(ptep,
381                                 pfn_pte(PFN_DOWN(__pa(mfns)), PAGE_KERNEL));
382                         continue;
383                 }
384 
385                 if (chunk == P2M_PER_PAGE) {
386                         /* Map complete missing or identity p2m-page. */
387                         mfns = (type == P2M_TYPE_MISSING) ?
388                                 p2m_missing : p2m_identity;
389                         ptep = populate_extra_pte((unsigned long)(p2m + pfn));
390                         set_pte(ptep,
391                                 pfn_pte(PFN_DOWN(__pa(mfns)), PAGE_KERNEL_RO));
392                         continue;
393                 }
394 
395                 /* Complete missing or identity PMD(s) can be mapped. */
396                 ptep = (type == P2M_TYPE_MISSING) ?
397                         p2m_missing_pte : p2m_identity_pte;
398                 for (i = 0; i < PMDS_PER_MID_PAGE; i++) {
399                         pmdp = populate_extra_pmd(
400                                 (unsigned long)(p2m + pfn) + i * PMD_SIZE);
401                         set_pmd(pmdp, __pmd(__pa(ptep) | _KERNPG_TABLE));
402                 }
403         }
404 }
405 
406 void __init xen_vmalloc_p2m_tree(void)
407 {
408         static struct vm_struct vm;
409         unsigned long p2m_limit;
410 
411         xen_p2m_last_pfn = xen_max_p2m_pfn;
412 
413         p2m_limit = (phys_addr_t)P2M_LIMIT * 1024 * 1024 * 1024 / PAGE_SIZE;
414         vm.flags = VM_ALLOC;
415         vm.size = ALIGN(sizeof(unsigned long) * max(xen_max_p2m_pfn, p2m_limit),
416                         PMD_SIZE * PMDS_PER_MID_PAGE);
417         vm_area_register_early(&vm, PMD_SIZE * PMDS_PER_MID_PAGE);
418         pr_notice("p2m virtual area at %p, size is %lx\n", vm.addr, vm.size);
419 
420         xen_max_p2m_pfn = vm.size / sizeof(unsigned long);
421 
422         xen_rebuild_p2m_list(vm.addr);
423 
424         xen_p2m_addr = vm.addr;
425         xen_p2m_size = xen_max_p2m_pfn;
426 
427         xen_inv_extra_mem();
428 }
429 
430 unsigned long get_phys_to_machine(unsigned long pfn)
431 {
432         pte_t *ptep;
433         unsigned int level;
434 
435         if (unlikely(pfn >= xen_p2m_size)) {
436                 if (pfn < xen_max_p2m_pfn)
437                         return xen_chk_extra_mem(pfn);
438 
439                 return IDENTITY_FRAME(pfn);
440         }
441 
442         ptep = lookup_address((unsigned long)(xen_p2m_addr + pfn), &level);
443         BUG_ON(!ptep || level != PG_LEVEL_4K);
444 
445         /*
446          * The INVALID_P2M_ENTRY is filled in both p2m_*identity
447          * and in p2m_*missing, so returning the INVALID_P2M_ENTRY
448          * would be wrong.
449          */
450         if (pte_pfn(*ptep) == PFN_DOWN(__pa(p2m_identity)))
451                 return IDENTITY_FRAME(pfn);
452 
453         return xen_p2m_addr[pfn];
454 }
455 EXPORT_SYMBOL_GPL(get_phys_to_machine);
456 
457 /*
458  * Allocate new pmd(s). It is checked whether the old pmd is still in place.
459  * If not, nothing is changed. This is okay as the only reason for allocating
460  * a new pmd is to replace p2m_missing_pte or p2m_identity_pte by a individual
461  * pmd. In case of PAE/x86-32 there are multiple pmds to allocate!
462  */
463 static pte_t *alloc_p2m_pmd(unsigned long addr, pte_t *pte_pg)
464 {
465         pte_t *ptechk;
466         pte_t *pte_newpg[PMDS_PER_MID_PAGE];
467         pmd_t *pmdp;
468         unsigned int level;
469         unsigned long flags;
470         unsigned long vaddr;
471         int i;
472 
473         /* Do all allocations first to bail out in error case. */
474         for (i = 0; i < PMDS_PER_MID_PAGE; i++) {
475                 pte_newpg[i] = alloc_p2m_page();
476                 if (!pte_newpg[i]) {
477                         for (i--; i >= 0; i--)
478                                 free_p2m_page(pte_newpg[i]);
479 
480                         return NULL;
481                 }
482         }
483 
484         vaddr = addr & ~(PMD_SIZE * PMDS_PER_MID_PAGE - 1);
485 
486         for (i = 0; i < PMDS_PER_MID_PAGE; i++) {
487                 copy_page(pte_newpg[i], pte_pg);
488                 paravirt_alloc_pte(&init_mm, __pa(pte_newpg[i]) >> PAGE_SHIFT);
489 
490                 pmdp = lookup_pmd_address(vaddr);
491                 BUG_ON(!pmdp);
492 
493                 spin_lock_irqsave(&p2m_update_lock, flags);
494 
495                 ptechk = lookup_address(vaddr, &level);
496                 if (ptechk == pte_pg) {
497                         HYPERVISOR_shared_info->arch.p2m_generation++;
498                         wmb(); /* Tools are synchronizing via p2m_generation. */
499                         set_pmd(pmdp,
500                                 __pmd(__pa(pte_newpg[i]) | _KERNPG_TABLE));
501                         wmb(); /* Tools are synchronizing via p2m_generation. */
502                         HYPERVISOR_shared_info->arch.p2m_generation++;
503                         pte_newpg[i] = NULL;
504                 }
505 
506                 spin_unlock_irqrestore(&p2m_update_lock, flags);
507 
508                 if (pte_newpg[i]) {
509                         paravirt_release_pte(__pa(pte_newpg[i]) >> PAGE_SHIFT);
510                         free_p2m_page(pte_newpg[i]);
511                 }
512 
513                 vaddr += PMD_SIZE;
514         }
515 
516         return lookup_address(addr, &level);
517 }
518 
519 /*
520  * Fully allocate the p2m structure for a given pfn.  We need to check
521  * that both the top and mid levels are allocated, and make sure the
522  * parallel mfn tree is kept in sync.  We may race with other cpus, so
523  * the new pages are installed with cmpxchg; if we lose the race then
524  * simply free the page we allocated and use the one that's there.
525  */
526 int xen_alloc_p2m_entry(unsigned long pfn)
527 {
528         unsigned topidx;
529         unsigned long *top_mfn_p, *mid_mfn;
530         pte_t *ptep, *pte_pg;
531         unsigned int level;
532         unsigned long flags;
533         unsigned long addr = (unsigned long)(xen_p2m_addr + pfn);
534         unsigned long p2m_pfn;
535 
536         ptep = lookup_address(addr, &level);
537         BUG_ON(!ptep || level != PG_LEVEL_4K);
538         pte_pg = (pte_t *)((unsigned long)ptep & ~(PAGE_SIZE - 1));
539 
540         if (pte_pg == p2m_missing_pte || pte_pg == p2m_identity_pte) {
541                 /* PMD level is missing, allocate a new one */
542                 ptep = alloc_p2m_pmd(addr, pte_pg);
543                 if (!ptep)
544                         return -ENOMEM;
545         }
546 
547         if (p2m_top_mfn && pfn < MAX_P2M_PFN) {
548                 topidx = p2m_top_index(pfn);
549                 top_mfn_p = &p2m_top_mfn[topidx];
550                 mid_mfn = READ_ONCE(p2m_top_mfn_p[topidx]);
551 
552                 BUG_ON(virt_to_mfn(mid_mfn) != *top_mfn_p);
553 
554                 if (mid_mfn == p2m_mid_missing_mfn) {
555                         /* Separately check the mid mfn level */
556                         unsigned long missing_mfn;
557                         unsigned long mid_mfn_mfn;
558                         unsigned long old_mfn;
559 
560                         mid_mfn = alloc_p2m_page();
561                         if (!mid_mfn)
562                                 return -ENOMEM;
563 
564                         p2m_mid_mfn_init(mid_mfn, p2m_missing);
565 
566                         missing_mfn = virt_to_mfn(p2m_mid_missing_mfn);
567                         mid_mfn_mfn = virt_to_mfn(mid_mfn);
568                         old_mfn = cmpxchg(top_mfn_p, missing_mfn, mid_mfn_mfn);
569                         if (old_mfn != missing_mfn) {
570                                 free_p2m_page(mid_mfn);
571                                 mid_mfn = mfn_to_virt(old_mfn);
572                         } else {
573                                 p2m_top_mfn_p[topidx] = mid_mfn;
574                         }
575                 }
576         } else {
577                 mid_mfn = NULL;
578         }
579 
580         p2m_pfn = pte_pfn(READ_ONCE(*ptep));
581         if (p2m_pfn == PFN_DOWN(__pa(p2m_identity)) ||
582             p2m_pfn == PFN_DOWN(__pa(p2m_missing))) {
583                 /* p2m leaf page is missing */
584                 unsigned long *p2m;
585 
586                 p2m = alloc_p2m_page();
587                 if (!p2m)
588                         return -ENOMEM;
589 
590                 if (p2m_pfn == PFN_DOWN(__pa(p2m_missing)))
591                         p2m_init(p2m);
592                 else
593                         p2m_init_identity(p2m, pfn & ~(P2M_PER_PAGE - 1));
594 
595                 spin_lock_irqsave(&p2m_update_lock, flags);
596 
597                 if (pte_pfn(*ptep) == p2m_pfn) {
598                         HYPERVISOR_shared_info->arch.p2m_generation++;
599                         wmb(); /* Tools are synchronizing via p2m_generation. */
600                         set_pte(ptep,
601                                 pfn_pte(PFN_DOWN(__pa(p2m)), PAGE_KERNEL));
602                         wmb(); /* Tools are synchronizing via p2m_generation. */
603                         HYPERVISOR_shared_info->arch.p2m_generation++;
604                         if (mid_mfn)
605                                 mid_mfn[p2m_mid_index(pfn)] = virt_to_mfn(p2m);
606                         p2m = NULL;
607                 }
608 
609                 spin_unlock_irqrestore(&p2m_update_lock, flags);
610 
611                 if (p2m)
612                         free_p2m_page(p2m);
613         }
614 
615         /* Expanded the p2m? */
616         if (pfn > xen_p2m_last_pfn) {
617                 xen_p2m_last_pfn = pfn;
618                 HYPERVISOR_shared_info->arch.max_pfn = xen_p2m_last_pfn;
619         }
620 
621         return 0;
622 }
623 EXPORT_SYMBOL(xen_alloc_p2m_entry);
624 
625 unsigned long __init set_phys_range_identity(unsigned long pfn_s,
626                                       unsigned long pfn_e)
627 {
628         unsigned long pfn;
629 
630         if (unlikely(pfn_s >= xen_p2m_size))
631                 return 0;
632 
633         if (pfn_s > pfn_e)
634                 return 0;
635 
636         if (pfn_e > xen_p2m_size)
637                 pfn_e = xen_p2m_size;
638 
639         for (pfn = pfn_s; pfn < pfn_e; pfn++)
640                 xen_p2m_addr[pfn] = IDENTITY_FRAME(pfn);
641 
642         return pfn - pfn_s;
643 }
644 
645 bool __set_phys_to_machine(unsigned long pfn, unsigned long mfn)
646 {
647         pte_t *ptep;
648         unsigned int level;
649 
650         if (unlikely(pfn >= xen_p2m_size)) {
651                 BUG_ON(mfn != INVALID_P2M_ENTRY);
652                 return true;
653         }
654 
655         /*
656          * The interface requires atomic updates on p2m elements.
657          * xen_safe_write_ulong() is using __put_user which does an atomic
658          * store via asm().
659          */
660         if (likely(!xen_safe_write_ulong(xen_p2m_addr + pfn, mfn)))
661                 return true;
662 
663         ptep = lookup_address((unsigned long)(xen_p2m_addr + pfn), &level);
664         BUG_ON(!ptep || level != PG_LEVEL_4K);
665 
666         if (pte_pfn(*ptep) == PFN_DOWN(__pa(p2m_missing)))
667                 return mfn == INVALID_P2M_ENTRY;
668 
669         if (pte_pfn(*ptep) == PFN_DOWN(__pa(p2m_identity)))
670                 return mfn == IDENTITY_FRAME(pfn);
671 
672         return false;
673 }
674 
675 bool set_phys_to_machine(unsigned long pfn, unsigned long mfn)
676 {
677         if (unlikely(!__set_phys_to_machine(pfn, mfn))) {
678                 int ret;
679 
680                 ret = xen_alloc_p2m_entry(pfn);
681                 if (ret < 0)
682                         return false;
683 
684                 return __set_phys_to_machine(pfn, mfn);
685         }
686 
687         return true;
688 }
689 
690 int set_foreign_p2m_mapping(struct gnttab_map_grant_ref *map_ops,
691                             struct gnttab_map_grant_ref *kmap_ops,
692                             struct page **pages, unsigned int count)
693 {
694         int i, ret = 0;
695         pte_t *pte;
696 
697         if (xen_feature(XENFEAT_auto_translated_physmap))
698                 return 0;
699 
700         if (kmap_ops) {
701                 ret = HYPERVISOR_grant_table_op(GNTTABOP_map_grant_ref,
702                                                 kmap_ops, count);
703                 if (ret)
704                         goto out;
705         }
706 
707         for (i = 0; i < count; i++) {
708                 unsigned long mfn, pfn;
709 
710                 /* Do not add to override if the map failed. */
711                 if (map_ops[i].status)
712                         continue;
713 
714                 if (map_ops[i].flags & GNTMAP_contains_pte) {
715                         pte = (pte_t *)(mfn_to_virt(PFN_DOWN(map_ops[i].host_addr)) +
716                                 (map_ops[i].host_addr & ~PAGE_MASK));
717                         mfn = pte_mfn(*pte);
718                 } else {
719                         mfn = PFN_DOWN(map_ops[i].dev_bus_addr);
720                 }
721                 pfn = page_to_pfn(pages[i]);
722 
723                 WARN(pfn_to_mfn(pfn) != INVALID_P2M_ENTRY, "page must be ballooned");
724 
725                 if (unlikely(!set_phys_to_machine(pfn, FOREIGN_FRAME(mfn)))) {
726                         ret = -ENOMEM;
727                         goto out;
728                 }
729         }
730 
731 out:
732         return ret;
733 }
734 EXPORT_SYMBOL_GPL(set_foreign_p2m_mapping);
735 
736 int clear_foreign_p2m_mapping(struct gnttab_unmap_grant_ref *unmap_ops,
737                               struct gnttab_unmap_grant_ref *kunmap_ops,
738                               struct page **pages, unsigned int count)
739 {
740         int i, ret = 0;
741 
742         if (xen_feature(XENFEAT_auto_translated_physmap))
743                 return 0;
744 
745         for (i = 0; i < count; i++) {
746                 unsigned long mfn = __pfn_to_mfn(page_to_pfn(pages[i]));
747                 unsigned long pfn = page_to_pfn(pages[i]);
748 
749                 if (mfn == INVALID_P2M_ENTRY || !(mfn & FOREIGN_FRAME_BIT)) {
750                         ret = -EINVAL;
751                         goto out;
752                 }
753 
754                 set_phys_to_machine(pfn, INVALID_P2M_ENTRY);
755         }
756         if (kunmap_ops)
757                 ret = HYPERVISOR_grant_table_op(GNTTABOP_unmap_grant_ref,
758                                                 kunmap_ops, count);
759 out:
760         return ret;
761 }
762 EXPORT_SYMBOL_GPL(clear_foreign_p2m_mapping);
763 
764 #ifdef CONFIG_XEN_DEBUG_FS
765 #include <linux/debugfs.h>
766 #include "debugfs.h"
767 static int p2m_dump_show(struct seq_file *m, void *v)
768 {
769         static const char * const type_name[] = {
770                                 [P2M_TYPE_IDENTITY] = "identity",
771                                 [P2M_TYPE_MISSING] = "missing",
772                                 [P2M_TYPE_PFN] = "pfn",
773                                 [P2M_TYPE_UNKNOWN] = "abnormal"};
774         unsigned long pfn, first_pfn;
775         int type, prev_type;
776 
777         prev_type = xen_p2m_elem_type(0);
778         first_pfn = 0;
779 
780         for (pfn = 0; pfn < xen_p2m_size; pfn++) {
781                 type = xen_p2m_elem_type(pfn);
782                 if (type != prev_type) {
783                         seq_printf(m, " [0x%lx->0x%lx] %s\n", first_pfn, pfn,
784                                    type_name[prev_type]);
785                         prev_type = type;
786                         first_pfn = pfn;
787                 }
788         }
789         seq_printf(m, " [0x%lx->0x%lx] %s\n", first_pfn, pfn,
790                    type_name[prev_type]);
791         return 0;
792 }
793 
794 static int p2m_dump_open(struct inode *inode, struct file *filp)
795 {
796         return single_open(filp, p2m_dump_show, NULL);
797 }
798 
799 static const struct file_operations p2m_dump_fops = {
800         .open           = p2m_dump_open,
801         .read           = seq_read,
802         .llseek         = seq_lseek,
803         .release        = single_release,
804 };
805 
806 static struct dentry *d_mmu_debug;
807 
808 static int __init xen_p2m_debugfs(void)
809 {
810         struct dentry *d_xen = xen_init_debugfs();
811 
812         if (d_xen == NULL)
813                 return -ENOMEM;
814 
815         d_mmu_debug = debugfs_create_dir("mmu", d_xen);
816 
817         debugfs_create_file("p2m", 0600, d_mmu_debug, NULL, &p2m_dump_fops);
818         return 0;
819 }
820 fs_initcall(xen_p2m_debugfs);
821 #endif /* CONFIG_XEN_DEBUG_FS */
822 

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