/* * Xen leaves the responsibility for maintaining p2m mappings to the * guests themselves, but it must also access and update the p2m array * during suspend/resume when all the pages are reallocated. * * The p2m table is logically a flat array, but we implement it as a * three-level tree to allow the address space to be sparse. * * Xen * | * p2m_top p2m_top_mfn * / \ / \ * p2m_mid p2m_mid p2m_mid_mfn p2m_mid_mfn * / \ / \ / / * p2m p2m p2m p2m p2m p2m p2m ... * * The p2m_mid_mfn pages are mapped by p2m_top_mfn_p. * * The p2m_top and p2m_top_mfn levels are limited to 1 page, so the * maximum representable pseudo-physical address space is: * P2M_TOP_PER_PAGE * P2M_MID_PER_PAGE * P2M_PER_PAGE pages * * P2M_PER_PAGE depends on the architecture, as a mfn is always * unsigned long (8 bytes on 64-bit, 4 bytes on 32), leading to * 512 and 1024 entries respectively. * * In short, these structures contain the Machine Frame Number (MFN) of the PFN. * * However not all entries are filled with MFNs. Specifically for all other * leaf entries, or for the top root, or middle one, for which there is a void * entry, we assume it is "missing". So (for example) * pfn_to_mfn(0x90909090)=INVALID_P2M_ENTRY. * * We also have the possibility of setting 1-1 mappings on certain regions, so * that: * pfn_to_mfn(0xc0000)=0xc0000 * * The benefit of this is, that we can assume for non-RAM regions (think * PCI BARs, or ACPI spaces), we can create mappings easily b/c we * get the PFN value to match the MFN. * * For this to work efficiently we have one new page p2m_identity and * allocate (via reserved_brk) any other pages we need to cover the sides * (1GB or 4MB boundary violations). All entries in p2m_identity are set to * INVALID_P2M_ENTRY type (Xen toolstack only recognizes that and MFNs, * no other fancy value). * * On lookup we spot that the entry points to p2m_identity and return the * identity value instead of dereferencing and returning INVALID_P2M_ENTRY. * If the entry points to an allocated page, we just proceed as before and * return the PFN. If the PFN has IDENTITY_FRAME_BIT set we unmask that in * appropriate functions (pfn_to_mfn). * * The reason for having the IDENTITY_FRAME_BIT instead of just returning the * PFN is that we could find ourselves where pfn_to_mfn(pfn)==pfn for a * non-identity pfn. To protect ourselves against we elect to set (and get) the * IDENTITY_FRAME_BIT on all identity mapped PFNs. * * This simplistic diagram is used to explain the more subtle piece of code. * There is also a digram of the P2M at the end that can help. * Imagine your E820 looking as so: * * 1GB 2GB * /-------------------+---------\/----\ /----------\ /---+-----\ * | System RAM | Sys RAM ||ACPI| | reserved | | Sys RAM | * \-------------------+---------/\----/ \----------/ \---+-----/ * ^- 1029MB ^- 2001MB * * [1029MB = 263424 (0x40500), 2001MB = 512256 (0x7D100), * 2048MB = 524288 (0x80000)] * * And dom0_mem=max:3GB,1GB is passed in to the guest, meaning memory past 1GB * is actually not present (would have to kick the balloon driver to put it in). * * When we are told to set the PFNs for identity mapping (see patch: "xen/setup: * Set identity mapping for non-RAM E820 and E820 gaps.") we pass in the start * of the PFN and the end PFN (263424 and 512256 respectively). The first step * is to reserve_brk a top leaf page if the p2m[1] is missing. The top leaf page * covers 512^2 of page estate (1GB) and in case the start or end PFN is not * aligned on 512^2*PAGE_SIZE (1GB) we loop on aligned 1GB PFNs from start pfn * to end pfn. We reserve_brk top leaf pages if they are missing (means they * point to p2m_mid_missing). * * With the E820 example above, 263424 is not 1GB aligned so we allocate a * reserve_brk page which will cover the PFNs estate from 0x40000 to 0x80000. * Each entry in the allocate page is "missing" (points to p2m_missing). * * Next stage is to determine if we need to do a more granular boundary check * on the 4MB (or 2MB depending on architecture) off the start and end pfn's. * We check if the start pfn and end pfn violate that boundary check, and if * so reserve_brk a middle (p2m[x][y]) leaf page. This way we have a much finer * granularity of setting which PFNs are missing and which ones are identity. * In our example 263424 and 512256 both fail the check so we reserve_brk two * pages. Populate them with INVALID_P2M_ENTRY (so they both have "missing" * values) and assign them to p2m[1][2] and p2m[1][488] respectively. * * At this point we would at minimum reserve_brk one page, but could be up to * three. Each call to set_phys_range_identity has at maximum a three page * cost. If we were to query the P2M at this stage, all those entries from * start PFN through end PFN (so 1029MB -> 2001MB) would return * INVALID_P2M_ENTRY ("missing"). * * The next step is to walk from the start pfn to the end pfn setting * the IDENTITY_FRAME_BIT on each PFN. This is done in set_phys_range_identity. * If we find that the middle leaf is pointing to p2m_missing we can swap it * over to p2m_identity - this way covering 4MB (or 2MB) PFN space. At this * point we do not need to worry about boundary aligment (so no need to * reserve_brk a middle page, figure out which PFNs are "missing" and which * ones are identity), as that has been done earlier. If we find that the * middle leaf is not occupied by p2m_identity or p2m_missing, we dereference * that page (which covers 512 PFNs) and set the appropriate PFN with * IDENTITY_FRAME_BIT. In our example 263424 and 512256 end up there, and we * set from p2m[1][2][256->511] and p2m[1][488][0->256] with * IDENTITY_FRAME_BIT set. * * All other regions that are void (or not filled) either point to p2m_missing * (considered missing) or have the default value of INVALID_P2M_ENTRY (also * considered missing). In our case, p2m[1][2][0->255] and p2m[1][488][257->511] * contain the INVALID_P2M_ENTRY value and are considered "missing." * * This is what the p2m ends up looking (for the E820 above) with this * fabulous drawing: * * p2m /--------------\ * /-----\ | &mfn_list[0],| /-----------------\ * | 0 |------>| &mfn_list[1],| /---------------\ | ~0, ~0, .. | * |-----| | ..., ~0, ~0 | | ~0, ~0, [x]---+----->| IDENTITY [@256] | * | 1 |---\ \--------------/ | [p2m_identity]+\ | IDENTITY [@257] | * |-----| \ | [p2m_identity]+\\ | .... | * | 2 |--\ \-------------------->| ... | \\ \----------------/ * |-----| \ \---------------/ \\ * | 3 |\ \ \\ p2m_identity * |-----| \ \-------------------->/---------------\ /-----------------\ * | .. +->+ | [p2m_identity]+-->| ~0, ~0, ~0, ... | * \-----/ / | [p2m_identity]+-->| ..., ~0 | * / /---------------\ | .... | \-----------------/ * / | IDENTITY[@0] | /-+-[x], ~0, ~0.. | * / | IDENTITY[@256]|<----/ \---------------/ * / | ~0, ~0, .... | * | \---------------/ * | * p2m_mid_missing p2m_missing * /-----------------\ /------------\ * | [p2m_missing] +---->| ~0, ~0, ~0 | * | [p2m_missing] +---->| ..., ~0 | * \-----------------/ \------------/ * * where ~0 is INVALID_P2M_ENTRY. IDENTITY is (PFN | IDENTITY_BIT) */ #include #include #include #include #include #include #include #include #include #include #include #include #include "multicalls.h" #include "xen-ops.h" static void __init m2p_override_init(void); unsigned long xen_max_p2m_pfn __read_mostly; #define P2M_PER_PAGE (PAGE_SIZE / sizeof(unsigned long)) #define P2M_MID_PER_PAGE (PAGE_SIZE / sizeof(unsigned long *)) #define P2M_TOP_PER_PAGE (PAGE_SIZE / sizeof(unsigned long **)) #define MAX_P2M_PFN (P2M_TOP_PER_PAGE * P2M_MID_PER_PAGE * P2M_PER_PAGE) /* Placeholders for holes in the address space */ static RESERVE_BRK_ARRAY(unsigned long, p2m_missing, P2M_PER_PAGE); static RESERVE_BRK_ARRAY(unsigned long *, p2m_mid_missing, P2M_MID_PER_PAGE); static RESERVE_BRK_ARRAY(unsigned long, p2m_mid_missing_mfn, P2M_MID_PER_PAGE); static RESERVE_BRK_ARRAY(unsigned long **, p2m_top, P2M_TOP_PER_PAGE); static RESERVE_BRK_ARRAY(unsigned long, p2m_top_mfn, P2M_TOP_PER_PAGE); static RESERVE_BRK_ARRAY(unsigned long *, p2m_top_mfn_p, P2M_TOP_PER_PAGE); static RESERVE_BRK_ARRAY(unsigned long, p2m_identity, P2M_PER_PAGE); RESERVE_BRK(p2m_mid, PAGE_SIZE * (MAX_DOMAIN_PAGES / (P2M_PER_PAGE * P2M_MID_PER_PAGE))); RESERVE_BRK(p2m_mid_mfn, PAGE_SIZE * (MAX_DOMAIN_PAGES / (P2M_PER_PAGE * P2M_MID_PER_PAGE))); /* We might hit two boundary violations at the start and end, at max each * boundary violation will require three middle nodes. */ RESERVE_BRK(p2m_mid_identity, PAGE_SIZE * 2 * 3); static inline unsigned p2m_top_index(unsigned long pfn) { BUG_ON(pfn >= MAX_P2M_PFN); return pfn / (P2M_MID_PER_PAGE * P2M_PER_PAGE); } static inline unsigned p2m_mid_index(unsigned long pfn) { return (pfn / P2M_PER_PAGE) % P2M_MID_PER_PAGE; } static inline unsigned p2m_index(unsigned long pfn) { return pfn % P2M_PER_PAGE; } static void p2m_top_init(unsigned long ***top) { unsigned i; for (i = 0; i < P2M_TOP_PER_PAGE; i++) top[i] = p2m_mid_missing; } static void p2m_top_mfn_init(unsigned long *top) { unsigned i; for (i = 0; i < P2M_TOP_PER_PAGE; i++) top[i] = virt_to_mfn(p2m_mid_missing_mfn); } static void p2m_top_mfn_p_init(unsigned long **top) { unsigned i; for (i = 0; i < P2M_TOP_PER_PAGE; i++) top[i] = p2m_mid_missing_mfn; } static void p2m_mid_init(unsigned long **mid) { unsigned i; for (i = 0; i < P2M_MID_PER_PAGE; i++) mid[i] = p2m_missing; } static void p2m_mid_mfn_init(unsigned long *mid) { unsigned i; for (i = 0; i < P2M_MID_PER_PAGE; i++) mid[i] = virt_to_mfn(p2m_missing); } static void p2m_init(unsigned long *p2m) { unsigned i; for (i = 0; i < P2M_MID_PER_PAGE; i++) p2m[i] = INVALID_P2M_ENTRY; } /* * Build the parallel p2m_top_mfn and p2m_mid_mfn structures * * This is called both at boot time, and after resuming from suspend: * - At boot time we're called very early, and must use extend_brk() * to allocate memory. * * - After resume we're called from within stop_machine, but the mfn * tree should alreay be completely allocated. */ void __ref xen_build_mfn_list_list(void) { unsigned long pfn; /* Pre-initialize p2m_top_mfn to be completely missing */ if (p2m_top_mfn == NULL) { p2m_mid_missing_mfn = extend_brk(PAGE_SIZE, PAGE_SIZE); p2m_mid_mfn_init(p2m_mid_missing_mfn); p2m_top_mfn_p = extend_brk(PAGE_SIZE, PAGE_SIZE); p2m_top_mfn_p_init(p2m_top_mfn_p); p2m_top_mfn = extend_brk(PAGE_SIZE, PAGE_SIZE); p2m_top_mfn_init(p2m_top_mfn); } else { /* Reinitialise, mfn's all change after migration */ p2m_mid_mfn_init(p2m_mid_missing_mfn); } for (pfn = 0; pfn < xen_max_p2m_pfn; pfn += P2M_PER_PAGE) { unsigned topidx = p2m_top_index(pfn); unsigned mididx = p2m_mid_index(pfn); unsigned long **mid; unsigned long *mid_mfn_p; mid = p2m_top[topidx]; mid_mfn_p = p2m_top_mfn_p[topidx]; /* Don't bother allocating any mfn mid levels if * they're just missing, just update the stored mfn, * since all could have changed over a migrate. */ if (mid == p2m_mid_missing) { BUG_ON(mididx); BUG_ON(mid_mfn_p != p2m_mid_missing_mfn); p2m_top_mfn[topidx] = virt_to_mfn(p2m_mid_missing_mfn); pfn += (P2M_MID_PER_PAGE - 1) * P2M_PER_PAGE; continue; } if (mid_mfn_p == p2m_mid_missing_mfn) { /* * XXX boot-time only! We should never find * missing parts of the mfn tree after * runtime. extend_brk() will BUG if we call * it too late. */ mid_mfn_p = extend_brk(PAGE_SIZE, PAGE_SIZE); p2m_mid_mfn_init(mid_mfn_p); p2m_top_mfn_p[topidx] = mid_mfn_p; } p2m_top_mfn[topidx] = virt_to_mfn(mid_mfn_p); mid_mfn_p[mididx] = virt_to_mfn(mid[mididx]); } } void xen_setup_mfn_list_list(void) { BUG_ON(HYPERVISOR_shared_info == &xen_dummy_shared_info); HYPERVISOR_shared_info->arch.pfn_to_mfn_frame_list_list = virt_to_mfn(p2m_top_mfn); HYPERVISOR_shared_info->arch.max_pfn = xen_max_p2m_pfn; } /* Set up p2m_top to point to the domain-builder provided p2m pages */ void __init xen_build_dynamic_phys_to_machine(void) { unsigned long *mfn_list = (unsigned long *)xen_start_info->mfn_list; unsigned long max_pfn = min(MAX_DOMAIN_PAGES, xen_start_info->nr_pages); unsigned long pfn; xen_max_p2m_pfn = max_pfn; p2m_missing = extend_brk(PAGE_SIZE, PAGE_SIZE); p2m_init(p2m_missing); p2m_mid_missing = extend_brk(PAGE_SIZE, PAGE_SIZE); p2m_mid_init(p2m_mid_missing); p2m_top = extend_brk(PAGE_SIZE, PAGE_SIZE); p2m_top_init(p2m_top); p2m_identity = extend_brk(PAGE_SIZE, PAGE_SIZE); p2m_init(p2m_identity); /* * The domain builder gives us a pre-constructed p2m array in * mfn_list for all the pages initially given to us, so we just * need to graft that into our tree structure. */ for (pfn = 0; pfn < max_pfn; pfn += P2M_PER_PAGE) { unsigned topidx = p2m_top_index(pfn); unsigned mididx = p2m_mid_index(pfn); if (p2m_top[topidx] == p2m_mid_missing) { unsigned long **mid = extend_brk(PAGE_SIZE, PAGE_SIZE); p2m_mid_init(mid); p2m_top[topidx] = mid; } /* * As long as the mfn_list has enough entries to completely * fill a p2m page, pointing into the array is ok. But if * not the entries beyond the last pfn will be undefined. */ if (unlikely(pfn + P2M_PER_PAGE > max_pfn)) { unsigned long p2midx; p2midx = max_pfn % P2M_PER_PAGE; for ( ; p2midx < P2M_PER_PAGE; p2midx++) mfn_list[pfn + p2midx] = INVALID_P2M_ENTRY; } p2m_top[topidx][mididx] = &mfn_list[pfn]; } m2p_override_init(); } #ifdef CONFIG_X86_64 #include unsigned long __init xen_revector_p2m_tree(void) { unsigned long va_start; unsigned long va_end; unsigned long pfn; unsigned long *mfn_list = NULL; unsigned long size; va_start = xen_start_info->mfn_list; /*We copy in increments of P2M_PER_PAGE * sizeof(unsigned long), * so make sure it is rounded up to that */ size = PAGE_ALIGN(xen_start_info->nr_pages * sizeof(unsigned long)); va_end = va_start + size; /* If we were revectored already, don't do it again. */ if (va_start <= __START_KERNEL_map && va_start >= __PAGE_OFFSET) return 0; mfn_list = alloc_bootmem_align(size, PAGE_SIZE); if (!mfn_list) { pr_warn("Could not allocate space for a new P2M tree!\n"); return xen_start_info->mfn_list; } /* Fill it out with INVALID_P2M_ENTRY value */ memset(mfn_list, 0xFF, size); for (pfn = 0; pfn < ALIGN(MAX_DOMAIN_PAGES, P2M_PER_PAGE); pfn += P2M_PER_PAGE) { unsigned topidx = p2m_top_index(pfn); unsigned mididx; unsigned long *mid_p; if (!p2m_top[topidx]) continue; if (p2m_top[topidx] == p2m_mid_missing) continue; mididx = p2m_mid_index(pfn); mid_p = p2m_top[topidx][mididx]; if (!mid_p) continue; if ((mid_p == p2m_missing) || (mid_p == p2m_identity)) continue; if ((unsigned long)mid_p == INVALID_P2M_ENTRY) continue; /* The old va. Rebase it on mfn_list */ if (mid_p >= (unsigned long *)va_start && mid_p <= (unsigned long *)va_end) { unsigned long *new; new = &mfn_list[pfn]; copy_page(new, mid_p); p2m_top[topidx][mididx] = &mfn_list[pfn]; p2m_top_mfn_p[topidx][mididx] = virt_to_mfn(&mfn_list[pfn]); } /* This should be the leafs allocated for identity from _brk. */ } return (unsigned long)mfn_list; } #else unsigned long __init xen_revector_p2m_tree(void) { return 0; } #endif unsigned long get_phys_to_machine(unsigned long pfn) { unsigned topidx, mididx, idx; if (unlikely(pfn >= MAX_P2M_PFN)) return INVALID_P2M_ENTRY; topidx = p2m_top_index(pfn); mididx = p2m_mid_index(pfn); idx = p2m_index(pfn); /* * The INVALID_P2M_ENTRY is filled in both p2m_*identity * and in p2m_*missing, so returning the INVALID_P2M_ENTRY * would be wrong. */ if (p2m_top[topidx][mididx] == p2m_identity) return IDENTITY_FRAME(pfn); return p2m_top[topidx][mididx][idx]; } EXPORT_SYMBOL_GPL(get_phys_to_machine); static void *alloc_p2m_page(void) { return (void *)__get_free_page(GFP_KERNEL | __GFP_REPEAT); } static void free_p2m_page(void *p) { free_page((unsigned long)p); } /* * Fully allocate the p2m structure for a given pfn. We need to check * that both the top and mid levels are allocated, and make sure the * parallel mfn tree is kept in sync. We may race with other cpus, so * the new pages are installed with cmpxchg; if we lose the race then * simply free the page we allocated and use the one that's there. */ static bool alloc_p2m(unsigned long pfn) { unsigned topidx, mididx; unsigned long ***top_p, **mid; unsigned long *top_mfn_p, *mid_mfn; topidx = p2m_top_index(pfn); mididx = p2m_mid_index(pfn); top_p = &p2m_top[topidx]; mid = *top_p; if (mid == p2m_mid_missing) { /* Mid level is missing, allocate a new one */ mid = alloc_p2m_page(); if (!mid) return false; p2m_mid_init(mid); if (cmpxchg(top_p, p2m_mid_missing, mid) != p2m_mid_missing) free_p2m_page(mid); } top_mfn_p = &p2m_top_mfn[topidx]; mid_mfn = p2m_top_mfn_p[topidx]; BUG_ON(virt_to_mfn(mid_mfn) != *top_mfn_p); if (mid_mfn == p2m_mid_missing_mfn) { /* Separately check the mid mfn level */ unsigned long missing_mfn; unsigned long mid_mfn_mfn; mid_mfn = alloc_p2m_page(); if (!mid_mfn) return false; p2m_mid_mfn_init(mid_mfn); missing_mfn = virt_to_mfn(p2m_mid_missing_mfn); mid_mfn_mfn = virt_to_mfn(mid_mfn); if (cmpxchg(top_mfn_p, missing_mfn, mid_mfn_mfn) != missing_mfn) free_p2m_page(mid_mfn); else p2m_top_mfn_p[topidx] = mid_mfn; } if (p2m_top[topidx][mididx] == p2m_identity || p2m_top[topidx][mididx] == p2m_missing) { /* p2m leaf page is missing */ unsigned long *p2m; unsigned long *p2m_orig = p2m_top[topidx][mididx]; p2m = alloc_p2m_page(); if (!p2m) return false; p2m_init(p2m); if (cmpxchg(&mid[mididx], p2m_orig, p2m) != p2m_orig) free_p2m_page(p2m); else mid_mfn[mididx] = virt_to_mfn(p2m); } return true; } static bool __init early_alloc_p2m_middle(unsigned long pfn, bool check_boundary) { unsigned topidx, mididx, idx; unsigned long *p2m; unsigned long *mid_mfn_p; topidx = p2m_top_index(pfn); mididx = p2m_mid_index(pfn); idx = p2m_index(pfn); /* Pfff.. No boundary cross-over, lets get out. */ if (!idx && check_boundary) return false; WARN(p2m_top[topidx][mididx] == p2m_identity, "P2M[%d][%d] == IDENTITY, should be MISSING (or alloced)!\n", topidx, mididx); /* * Could be done by xen_build_dynamic_phys_to_machine.. */ if (p2m_top[topidx][mididx] != p2m_missing) return false; /* Boundary cross-over for the edges: */ p2m = extend_brk(PAGE_SIZE, PAGE_SIZE); p2m_init(p2m); p2m_top[topidx][mididx] = p2m; /* For save/restore we need to MFN of the P2M saved */ mid_mfn_p = p2m_top_mfn_p[topidx]; WARN(mid_mfn_p[mididx] != virt_to_mfn(p2m_missing), "P2M_TOP_P[%d][%d] != MFN of p2m_missing!\n", topidx, mididx); mid_mfn_p[mididx] = virt_to_mfn(p2m); return true; } static bool __init early_alloc_p2m(unsigned long pfn) { unsigned topidx = p2m_top_index(pfn); unsigned long *mid_mfn_p; unsigned long **mid; mid = p2m_top[topidx]; mid_mfn_p = p2m_top_mfn_p[topidx]; if (mid == p2m_mid_missing) { mid = extend_brk(PAGE_SIZE, PAGE_SIZE); p2m_mid_init(mid); p2m_top[topidx] = mid; BUG_ON(mid_mfn_p != p2m_mid_missing_mfn); } /* And the save/restore P2M tables.. */ if (mid_mfn_p == p2m_mid_missing_mfn) { mid_mfn_p = extend_brk(PAGE_SIZE, PAGE_SIZE); p2m_mid_mfn_init(mid_mfn_p); p2m_top_mfn_p[topidx] = mid_mfn_p; p2m_top_mfn[topidx] = virt_to_mfn(mid_mfn_p); /* Note: we don't set mid_mfn_p[midix] here, * look in early_alloc_p2m_middle */ } return true; } bool __init early_set_phys_to_machine(unsigned long pfn, unsigned long mfn) { if (unlikely(!__set_phys_to_machine(pfn, mfn))) { if (!early_alloc_p2m(pfn)) return false; if (!early_alloc_p2m_middle(pfn, false /* boundary crossover OK!*/)) return false; if (!__set_phys_to_machine(pfn, mfn)) return false; } return true; } unsigned long __init set_phys_range_identity(unsigned long pfn_s, unsigned long pfn_e) { unsigned long pfn; if (unlikely(pfn_s >= MAX_P2M_PFN || pfn_e >= MAX_P2M_PFN)) return 0; if (unlikely(xen_feature(XENFEAT_auto_translated_physmap))) return pfn_e - pfn_s; if (pfn_s > pfn_e) return 0; for (pfn = (pfn_s & ~(P2M_MID_PER_PAGE * P2M_PER_PAGE - 1)); pfn < ALIGN(pfn_e, (P2M_MID_PER_PAGE * P2M_PER_PAGE)); pfn += P2M_MID_PER_PAGE * P2M_PER_PAGE) { WARN_ON(!early_alloc_p2m(pfn)); } early_alloc_p2m_middle(pfn_s, true); early_alloc_p2m_middle(pfn_e, true); for (pfn = pfn_s; pfn < pfn_e; pfn++) if (!__set_phys_to_machine(pfn, IDENTITY_FRAME(pfn))) break; if (!WARN((pfn - pfn_s) != (pfn_e - pfn_s), "Identity mapping failed. We are %ld short of 1-1 mappings!\n", (pfn_e - pfn_s) - (pfn - pfn_s))) printk(KERN_DEBUG "1-1 mapping on %lx->%lx\n", pfn_s, pfn); return pfn - pfn_s; } /* Try to install p2m mapping; fail if intermediate bits missing */ bool __set_phys_to_machine(unsigned long pfn, unsigned long mfn) { unsigned topidx, mididx, idx; if (unlikely(xen_feature(XENFEAT_auto_translated_physmap))) { BUG_ON(pfn != mfn && mfn != INVALID_P2M_ENTRY); return true; } if (unlikely(pfn >= MAX_P2M_PFN)) { BUG_ON(mfn != INVALID_P2M_ENTRY); return true; } topidx = p2m_top_index(pfn); mididx = p2m_mid_index(pfn); idx = p2m_index(pfn); /* For sparse holes were the p2m leaf has real PFN along with * PCI holes, stick in the PFN as the MFN value. */ if (mfn != INVALID_P2M_ENTRY && (mfn & IDENTITY_FRAME_BIT)) { if (p2m_top[topidx][mididx] == p2m_identity) return true; /* Swap over from MISSING to IDENTITY if needed. */ if (p2m_top[topidx][mididx] == p2m_missing) { WARN_ON(cmpxchg(&p2m_top[topidx][mididx], p2m_missing, p2m_identity) != p2m_missing); return true; } } if (p2m_top[topidx][mididx] == p2m_missing) return mfn == INVALID_P2M_ENTRY; p2m_top[topidx][mididx][idx] = mfn; return true; } bool set_phys_to_machine(unsigned long pfn, unsigned long mfn) { if (unlikely(!__set_phys_to_machine(pfn, mfn))) { if (!alloc_p2m(pfn)) return false; if (!__set_phys_to_machine(pfn, mfn)) return false; } return true; } #define M2P_OVERRIDE_HASH_SHIFT 10 #define M2P_OVERRIDE_HASH (1 << M2P_OVERRIDE_HASH_SHIFT) static RESERVE_BRK_ARRAY(struct list_head, m2p_overrides, M2P_OVERRIDE_HASH); static DEFINE_SPINLOCK(m2p_override_lock); static void __init m2p_override_init(void) { unsigned i; m2p_overrides = extend_brk(sizeof(*m2p_overrides) * M2P_OVERRIDE_HASH, sizeof(unsigned long)); for (i = 0; i < M2P_OVERRIDE_HASH; i++) INIT_LIST_HEAD(&m2p_overrides[i]); } static unsigned long mfn_hash(unsigned long mfn) { return hash_long(mfn, M2P_OVERRIDE_HASH_SHIFT); } /* Add an MFN override for a particular page */ int m2p_add_override(unsigned long mfn, struct page *page, struct gnttab_map_grant_ref *kmap_op) { unsigned long flags; unsigned long pfn; unsigned long uninitialized_var(address); unsigned level; pte_t *ptep = NULL; int ret = 0; pfn = page_to_pfn(page); if (!PageHighMem(page)) { address = (unsigned long)__va(pfn << PAGE_SHIFT); ptep = lookup_address(address, &level); if (WARN(ptep == NULL || level != PG_LEVEL_4K, "m2p_add_override: pfn %lx not mapped", pfn)) return -EINVAL; } WARN_ON(PagePrivate(page)); SetPagePrivate(page); set_page_private(page, mfn); page->index = pfn_to_mfn(pfn); if (unlikely(!set_phys_to_machine(pfn, FOREIGN_FRAME(mfn)))) return -ENOMEM; if (kmap_op != NULL) { if (!PageHighMem(page)) { struct multicall_space mcs = xen_mc_entry(sizeof(*kmap_op)); MULTI_grant_table_op(mcs.mc, GNTTABOP_map_grant_ref, kmap_op, 1); xen_mc_issue(PARAVIRT_LAZY_MMU); } /* let's use dev_bus_addr to record the old mfn instead */ kmap_op->dev_bus_addr = page->index; page->index = (unsigned long) kmap_op; } spin_lock_irqsave(&m2p_override_lock, flags); list_add(&page->lru, &m2p_overrides[mfn_hash(mfn)]); spin_unlock_irqrestore(&m2p_override_lock, flags); /* p2m(m2p(mfn)) == mfn: the mfn is already present somewhere in * this domain. Set the FOREIGN_FRAME_BIT in the p2m for the other * pfn so that the following mfn_to_pfn(mfn) calls will return the * pfn from the m2p_override (the backend pfn) instead. * We need to do this because the pages shared by the frontend * (xen-blkfront) can be already locked (lock_page, called by * do_read_cache_page); when the userspace backend tries to use them * with direct_IO, mfn_to_pfn returns the pfn of the frontend, so * do_blockdev_direct_IO is going to try to lock the same pages * again resulting in a deadlock. * As a side effect get_user_pages_fast might not be safe on the * frontend pages while they are being shared with the backend, * because mfn_to_pfn (that ends up being called by GUPF) will * return the backend pfn rather than the frontend pfn. */ ret = __get_user(pfn, &machine_to_phys_mapping[mfn]); if (ret == 0 && get_phys_to_machine(pfn) == mfn) set_phys_to_machine(pfn, FOREIGN_FRAME(mfn)); return 0; } EXPORT_SYMBOL_GPL(m2p_add_override); int m2p_remove_override(struct page *page, bool clear_pte) { unsigned long flags; unsigned long mfn; unsigned long pfn; unsigned long uninitialized_var(address); unsigned level; pte_t *ptep = NULL; int ret = 0; pfn = page_to_pfn(page); mfn = get_phys_to_machine(pfn); if (mfn == INVALID_P2M_ENTRY || !(mfn & FOREIGN_FRAME_BIT)) return -EINVAL; if (!PageHighMem(page)) { address = (unsigned long)__va(pfn << PAGE_SHIFT); ptep = lookup_address(address, &level); if (WARN(ptep == NULL || level != PG_LEVEL_4K, "m2p_remove_override: pfn %lx not mapped", pfn)) return -EINVAL; } spin_lock_irqsave(&m2p_override_lock, flags); list_del(&page->lru); spin_unlock_irqrestore(&m2p_override_lock, flags); WARN_ON(!PagePrivate(page)); ClearPagePrivate(page); if (clear_pte) { struct gnttab_map_grant_ref *map_op = (struct gnttab_map_grant_ref *) page->index; set_phys_to_machine(pfn, map_op->dev_bus_addr); if (!PageHighMem(page)) { struct multicall_space mcs; struct gnttab_unmap_grant_ref *unmap_op; /* * It might be that we queued all the m2p grant table * hypercalls in a multicall, then m2p_remove_override * get called before the multicall has actually been * issued. In this case handle is going to -1 because * it hasn't been modified yet. */ if (map_op->handle == -1) xen_mc_flush(); /* * Now if map_op->handle is negative it means that the * hypercall actually returned an error. */ if (map_op->handle == GNTST_general_error) { printk(KERN_WARNING "m2p_remove_override: " "pfn %lx mfn %lx, failed to modify kernel mappings", pfn, mfn); return -1; } mcs = xen_mc_entry( sizeof(struct gnttab_unmap_grant_ref)); unmap_op = mcs.args; unmap_op->host_addr = map_op->host_addr; unmap_op->handle = map_op->handle; unmap_op->dev_bus_addr = 0; MULTI_grant_table_op(mcs.mc, GNTTABOP_unmap_grant_ref, unmap_op, 1); xen_mc_issue(PARAVIRT_LAZY_MMU); set_pte_at(&init_mm, address, ptep, pfn_pte(pfn, PAGE_KERNEL)); __flush_tlb_single(address); map_op->host_addr = 0; } } else set_phys_to_machine(pfn, page->index); /* p2m(m2p(mfn)) == FOREIGN_FRAME(mfn): the mfn is already present * somewhere in this domain, even before being added to the * m2p_override (see comment above in m2p_add_override). * If there are no other entries in the m2p_override corresponding * to this mfn, then remove the FOREIGN_FRAME_BIT from the p2m for * the original pfn (the one shared by the frontend): the backend * cannot do any IO on this page anymore because it has been * unshared. Removing the FOREIGN_FRAME_BIT from the p2m entry of * the original pfn causes mfn_to_pfn(mfn) to return the frontend * pfn again. */ mfn &= ~FOREIGN_FRAME_BIT; ret = __get_user(pfn, &machine_to_phys_mapping[mfn]); if (ret == 0 && get_phys_to_machine(pfn) == FOREIGN_FRAME(mfn) && m2p_find_override(mfn) == NULL) set_phys_to_machine(pfn, mfn); return 0; } EXPORT_SYMBOL_GPL(m2p_remove_override); struct page *m2p_find_override(unsigned long mfn) { unsigned long flags; struct list_head *bucket = &m2p_overrides[mfn_hash(mfn)]; struct page *p, *ret; ret = NULL; spin_lock_irqsave(&m2p_override_lock, flags); list_for_each_entry(p, bucket, lru) { if (page_private(p) == mfn) { ret = p; break; } } spin_unlock_irqrestore(&m2p_override_lock, flags); return ret; } unsigned long m2p_find_override_pfn(unsigned long mfn, unsigned long pfn) { struct page *p = m2p_find_override(mfn); unsigned long ret = pfn; if (p) ret = page_to_pfn(p); return ret; } EXPORT_SYMBOL_GPL(m2p_find_override_pfn); #ifdef CONFIG_XEN_DEBUG_FS #include #include "debugfs.h" static int p2m_dump_show(struct seq_file *m, void *v) { static const char * const level_name[] = { "top", "middle", "entry", "abnormal", "error"}; #define TYPE_IDENTITY 0 #define TYPE_MISSING 1 #define TYPE_PFN 2 #define TYPE_UNKNOWN 3 static const char * const type_name[] = { [TYPE_IDENTITY] = "identity", [TYPE_MISSING] = "missing", [TYPE_PFN] = "pfn", [TYPE_UNKNOWN] = "abnormal"}; unsigned long pfn, prev_pfn_type = 0, prev_pfn_level = 0; unsigned int uninitialized_var(prev_level); unsigned int uninitialized_var(prev_type); if (!p2m_top) return 0; for (pfn = 0; pfn < MAX_DOMAIN_PAGES; pfn++) { unsigned topidx = p2m_top_index(pfn); unsigned mididx = p2m_mid_index(pfn); unsigned idx = p2m_index(pfn); unsigned lvl, type; lvl = 4; type = TYPE_UNKNOWN; if (p2m_top[topidx] == p2m_mid_missing) { lvl = 0; type = TYPE_MISSING; } else if (p2m_top[topidx] == NULL) { lvl = 0; type = TYPE_UNKNOWN; } else if (p2m_top[topidx][mididx] == NULL) { lvl = 1; type = TYPE_UNKNOWN; } else if (p2m_top[topidx][mididx] == p2m_identity) { lvl = 1; type = TYPE_IDENTITY; } else if (p2m_top[topidx][mididx] == p2m_missing) { lvl = 1; type = TYPE_MISSING; } else if (p2m_top[topidx][mididx][idx] == 0) { lvl = 2; type = TYPE_UNKNOWN; } else if (p2m_top[topidx][mididx][idx] == IDENTITY_FRAME(pfn)) { lvl = 2; type = TYPE_IDENTITY; } else if (p2m_top[topidx][mididx][idx] == INVALID_P2M_ENTRY) { lvl = 2; type = TYPE_MISSING; } else if (p2m_top[topidx][mididx][idx] == pfn) { lvl = 2; type = TYPE_PFN; } else if (p2m_top[topidx][mididx][idx] != pfn) { lvl = 2; type = TYPE_PFN; } if (pfn == 0) { prev_level = lvl; prev_type = type; } if (pfn == MAX_DOMAIN_PAGES-1) { lvl = 3; type = TYPE_UNKNOWN; } if (prev_type != type) { seq_printf(m, " [0x%lx->0x%lx] %s\n", prev_pfn_type, pfn, type_name[prev_type]); prev_pfn_type = pfn; prev_type = type; } if (prev_level != lvl) { seq_printf(m, " [0x%lx->0x%lx] level %s\n", prev_pfn_level, pfn, level_name[prev_level]); prev_pfn_level = pfn; prev_level = lvl; } } return 0; #undef TYPE_IDENTITY #undef TYPE_MISSING #undef TYPE_PFN #undef TYPE_UNKNOWN } static int p2m_dump_open(struct inode *inode, struct file *filp) { return single_open(filp, p2m_dump_show, NULL); } static const struct file_operations p2m_dump_fops = { .open = p2m_dump_open, .read = seq_read, .llseek = seq_lseek, .release = single_release, }; static struct dentry *d_mmu_debug; static int __init xen_p2m_debugfs(void) { struct dentry *d_xen = xen_init_debugfs(); if (d_xen == NULL) return -ENOMEM; d_mmu_debug = debugfs_create_dir("mmu", d_xen); debugfs_create_file("p2m", 0600, d_mmu_debug, NULL, &p2m_dump_fops); return 0; } fs_initcall(xen_p2m_debugfs); #endif /* CONFIG_XEN_DEBUG_FS */