/* * Kernel-based Virtual Machine driver for Linux * * This module enables machines with Intel VT-x extensions to run virtual * machines without emulation or binary translation. * * MMU support * * Copyright (C) 2006 Qumranet, Inc. * Copyright 2010 Red Hat, Inc. and/or its affilates. * * Authors: * Yaniv Kamay * Avi Kivity * * This work is licensed under the terms of the GNU GPL, version 2. See * the COPYING file in the top-level directory. * */ /* * We need the mmu code to access both 32-bit and 64-bit guest ptes, * so the code in this file is compiled twice, once per pte size. */ #if PTTYPE == 64 #define pt_element_t u64 #define guest_walker guest_walker64 #define FNAME(name) paging##64_##name #define PT_BASE_ADDR_MASK PT64_BASE_ADDR_MASK #define PT_LVL_ADDR_MASK(lvl) PT64_LVL_ADDR_MASK(lvl) #define PT_LVL_OFFSET_MASK(lvl) PT64_LVL_OFFSET_MASK(lvl) #define PT_INDEX(addr, level) PT64_INDEX(addr, level) #define PT_LEVEL_MASK(level) PT64_LEVEL_MASK(level) #define PT_LEVEL_BITS PT64_LEVEL_BITS #ifdef CONFIG_X86_64 #define PT_MAX_FULL_LEVELS 4 #define CMPXCHG cmpxchg #else #define CMPXCHG cmpxchg64 #define PT_MAX_FULL_LEVELS 2 #endif #elif PTTYPE == 32 #define pt_element_t u32 #define guest_walker guest_walker32 #define FNAME(name) paging##32_##name #define PT_BASE_ADDR_MASK PT32_BASE_ADDR_MASK #define PT_LVL_ADDR_MASK(lvl) PT32_LVL_ADDR_MASK(lvl) #define PT_LVL_OFFSET_MASK(lvl) PT32_LVL_OFFSET_MASK(lvl) #define PT_INDEX(addr, level) PT32_INDEX(addr, level) #define PT_LEVEL_MASK(level) PT32_LEVEL_MASK(level) #define PT_LEVEL_BITS PT32_LEVEL_BITS #define PT_MAX_FULL_LEVELS 2 #define CMPXCHG cmpxchg #else #error Invalid PTTYPE value #endif #define gpte_to_gfn_lvl FNAME(gpte_to_gfn_lvl) #define gpte_to_gfn(pte) gpte_to_gfn_lvl((pte), PT_PAGE_TABLE_LEVEL) /* * The guest_walker structure emulates the behavior of the hardware page * table walker. */ struct guest_walker { int level; gfn_t table_gfn[PT_MAX_FULL_LEVELS]; pt_element_t ptes[PT_MAX_FULL_LEVELS]; pt_element_t prefetch_ptes[PTE_PREFETCH_NUM]; gpa_t pte_gpa[PT_MAX_FULL_LEVELS]; unsigned pt_access; unsigned pte_access; gfn_t gfn; u32 error_code; }; static gfn_t gpte_to_gfn_lvl(pt_element_t gpte, int lvl) { return (gpte & PT_LVL_ADDR_MASK(lvl)) >> PAGE_SHIFT; } static bool FNAME(cmpxchg_gpte)(struct kvm *kvm, gfn_t table_gfn, unsigned index, pt_element_t orig_pte, pt_element_t new_pte) { pt_element_t ret; pt_element_t *table; struct page *page; page = gfn_to_page(kvm, table_gfn); table = kmap_atomic(page, KM_USER0); ret = CMPXCHG(&table[index], orig_pte, new_pte); kunmap_atomic(table, KM_USER0); kvm_release_page_dirty(page); return (ret != orig_pte); } static unsigned FNAME(gpte_access)(struct kvm_vcpu *vcpu, pt_element_t gpte) { unsigned access; access = (gpte & (PT_WRITABLE_MASK | PT_USER_MASK)) | ACC_EXEC_MASK; #if PTTYPE == 64 if (is_nx(vcpu)) access &= ~(gpte >> PT64_NX_SHIFT); #endif return access; } /* * Fetch a guest pte for a guest virtual address */ static int FNAME(walk_addr)(struct guest_walker *walker, struct kvm_vcpu *vcpu, gva_t addr, int write_fault, int user_fault, int fetch_fault) { pt_element_t pte; gfn_t table_gfn; unsigned index, pt_access, uninitialized_var(pte_access); gpa_t pte_gpa; bool eperm, present, rsvd_fault; trace_kvm_mmu_pagetable_walk(addr, write_fault, user_fault, fetch_fault); walk: present = true; eperm = rsvd_fault = false; walker->level = vcpu->arch.mmu.root_level; pte = vcpu->arch.cr3; #if PTTYPE == 64 if (!is_long_mode(vcpu)) { pte = kvm_pdptr_read(vcpu, (addr >> 30) & 3); trace_kvm_mmu_paging_element(pte, walker->level); if (!is_present_gpte(pte)) { present = false; goto error; } --walker->level; } #endif ASSERT((!is_long_mode(vcpu) && is_pae(vcpu)) || (vcpu->arch.cr3 & CR3_NONPAE_RESERVED_BITS) == 0); pt_access = ACC_ALL; for (;;) { index = PT_INDEX(addr, walker->level); table_gfn = gpte_to_gfn(pte); pte_gpa = gfn_to_gpa(table_gfn); pte_gpa += index * sizeof(pt_element_t); walker->table_gfn[walker->level - 1] = table_gfn; walker->pte_gpa[walker->level - 1] = pte_gpa; if (kvm_read_guest(vcpu->kvm, pte_gpa, &pte, sizeof(pte))) { present = false; break; } trace_kvm_mmu_paging_element(pte, walker->level); if (!is_present_gpte(pte)) { present = false; break; } if (is_rsvd_bits_set(vcpu, pte, walker->level)) { rsvd_fault = true; break; } if (write_fault && !is_writable_pte(pte)) if (user_fault || is_write_protection(vcpu)) eperm = true; if (user_fault && !(pte & PT_USER_MASK)) eperm = true; #if PTTYPE == 64 if (fetch_fault && (pte & PT64_NX_MASK)) eperm = true; #endif if (!eperm && !rsvd_fault && !(pte & PT_ACCESSED_MASK)) { trace_kvm_mmu_set_accessed_bit(table_gfn, index, sizeof(pte)); if (FNAME(cmpxchg_gpte)(vcpu->kvm, table_gfn, index, pte, pte|PT_ACCESSED_MASK)) goto walk; mark_page_dirty(vcpu->kvm, table_gfn); pte |= PT_ACCESSED_MASK; } pte_access = pt_access & FNAME(gpte_access)(vcpu, pte); walker->ptes[walker->level - 1] = pte; if ((walker->level == PT_PAGE_TABLE_LEVEL) || ((walker->level == PT_DIRECTORY_LEVEL) && is_large_pte(pte) && (PTTYPE == 64 || is_pse(vcpu))) || ((walker->level == PT_PDPE_LEVEL) && is_large_pte(pte) && is_long_mode(vcpu))) { int lvl = walker->level; walker->gfn = gpte_to_gfn_lvl(pte, lvl); walker->gfn += (addr & PT_LVL_OFFSET_MASK(lvl)) >> PAGE_SHIFT; if (PTTYPE == 32 && walker->level == PT_DIRECTORY_LEVEL && is_cpuid_PSE36()) walker->gfn += pse36_gfn_delta(pte); break; } pt_access = pte_access; --walker->level; } if (!present || eperm || rsvd_fault) goto error; if (write_fault && !is_dirty_gpte(pte)) { bool ret; trace_kvm_mmu_set_dirty_bit(table_gfn, index, sizeof(pte)); ret = FNAME(cmpxchg_gpte)(vcpu->kvm, table_gfn, index, pte, pte|PT_DIRTY_MASK); if (ret) goto walk; mark_page_dirty(vcpu->kvm, table_gfn); pte |= PT_DIRTY_MASK; walker->ptes[walker->level - 1] = pte; } walker->pt_access = pt_access; walker->pte_access = pte_access; pgprintk("%s: pte %llx pte_access %x pt_access %x\n", __func__, (u64)pte, pte_access, pt_access); return 1; error: walker->error_code = 0; if (present) walker->error_code |= PFERR_PRESENT_MASK; if (write_fault) walker->error_code |= PFERR_WRITE_MASK; if (user_fault) walker->error_code |= PFERR_USER_MASK; if (fetch_fault && is_nx(vcpu)) walker->error_code |= PFERR_FETCH_MASK; if (rsvd_fault) walker->error_code |= PFERR_RSVD_MASK; trace_kvm_mmu_walker_error(walker->error_code); return 0; } static void FNAME(update_pte)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp, u64 *spte, const void *pte) { pt_element_t gpte; unsigned pte_access; pfn_t pfn; u64 new_spte; gpte = *(const pt_element_t *)pte; if (~gpte & (PT_PRESENT_MASK | PT_ACCESSED_MASK)) { if (!is_present_gpte(gpte)) { if (sp->unsync) new_spte = shadow_trap_nonpresent_pte; else new_spte = shadow_notrap_nonpresent_pte; __set_spte(spte, new_spte); } return; } pgprintk("%s: gpte %llx spte %p\n", __func__, (u64)gpte, spte); pte_access = sp->role.access & FNAME(gpte_access)(vcpu, gpte); if (gpte_to_gfn(gpte) != vcpu->arch.update_pte.gfn) return; pfn = vcpu->arch.update_pte.pfn; if (is_error_pfn(pfn)) return; if (mmu_notifier_retry(vcpu, vcpu->arch.update_pte.mmu_seq)) return; kvm_get_pfn(pfn); /* * we call mmu_set_spte() with reset_host_protection = true beacuse that * vcpu->arch.update_pte.pfn was fetched from get_user_pages(write = 1). */ mmu_set_spte(vcpu, spte, sp->role.access, pte_access, 0, 0, is_dirty_gpte(gpte), NULL, PT_PAGE_TABLE_LEVEL, gpte_to_gfn(gpte), pfn, true, true); } static bool FNAME(gpte_changed)(struct kvm_vcpu *vcpu, struct guest_walker *gw, int level) { pt_element_t curr_pte; gpa_t base_gpa, pte_gpa = gw->pte_gpa[level - 1]; u64 mask; int r, index; if (level == PT_PAGE_TABLE_LEVEL) { mask = PTE_PREFETCH_NUM * sizeof(pt_element_t) - 1; base_gpa = pte_gpa & ~mask; index = (pte_gpa - base_gpa) / sizeof(pt_element_t); r = kvm_read_guest_atomic(vcpu->kvm, base_gpa, gw->prefetch_ptes, sizeof(gw->prefetch_ptes)); curr_pte = gw->prefetch_ptes[index]; } else r = kvm_read_guest_atomic(vcpu->kvm, pte_gpa, &curr_pte, sizeof(curr_pte)); return r || curr_pte != gw->ptes[level - 1]; } static void FNAME(pte_prefetch)(struct kvm_vcpu *vcpu, struct guest_walker *gw, u64 *sptep) { struct kvm_mmu_page *sp; pt_element_t *gptep = gw->prefetch_ptes; u64 *spte; int i; sp = page_header(__pa(sptep)); if (sp->role.level > PT_PAGE_TABLE_LEVEL) return; if (sp->role.direct) return __direct_pte_prefetch(vcpu, sp, sptep); i = (sptep - sp->spt) & ~(PTE_PREFETCH_NUM - 1); spte = sp->spt + i; for (i = 0; i < PTE_PREFETCH_NUM; i++, spte++) { pt_element_t gpte; unsigned pte_access; gfn_t gfn; pfn_t pfn; bool dirty; if (spte == sptep) continue; if (*spte != shadow_trap_nonpresent_pte) continue; gpte = gptep[i]; if (!is_present_gpte(gpte) || is_rsvd_bits_set(vcpu, gpte, PT_PAGE_TABLE_LEVEL)) { if (!sp->unsync) __set_spte(spte, shadow_notrap_nonpresent_pte); continue; } if (!(gpte & PT_ACCESSED_MASK)) continue; pte_access = sp->role.access & FNAME(gpte_access)(vcpu, gpte); gfn = gpte_to_gfn(gpte); dirty = is_dirty_gpte(gpte); pfn = pte_prefetch_gfn_to_pfn(vcpu, gfn, (pte_access & ACC_WRITE_MASK) && dirty); if (is_error_pfn(pfn)) { kvm_release_pfn_clean(pfn); break; } mmu_set_spte(vcpu, spte, sp->role.access, pte_access, 0, 0, dirty, NULL, PT_PAGE_TABLE_LEVEL, gfn, pfn, true, true); } } /* * Fetch a shadow pte for a specific level in the paging hierarchy. */ static u64 *FNAME(fetch)(struct kvm_vcpu *vcpu, gva_t addr, struct guest_walker *gw, int user_fault, int write_fault, int hlevel, int *ptwrite, pfn_t pfn) { unsigned access = gw->pt_access; struct kvm_mmu_page *sp = NULL; bool dirty = is_dirty_gpte(gw->ptes[gw->level - 1]); int top_level; unsigned direct_access; struct kvm_shadow_walk_iterator it; if (!is_present_gpte(gw->ptes[gw->level - 1])) return NULL; direct_access = gw->pt_access & gw->pte_access; if (!dirty) direct_access &= ~ACC_WRITE_MASK; top_level = vcpu->arch.mmu.root_level; if (top_level == PT32E_ROOT_LEVEL) top_level = PT32_ROOT_LEVEL; /* * Verify that the top-level gpte is still there. Since the page * is a root page, it is either write protected (and cannot be * changed from now on) or it is invalid (in which case, we don't * really care if it changes underneath us after this point). */ if (FNAME(gpte_changed)(vcpu, gw, top_level)) goto out_gpte_changed; for (shadow_walk_init(&it, vcpu, addr); shadow_walk_okay(&it) && it.level > gw->level; shadow_walk_next(&it)) { gfn_t table_gfn; drop_large_spte(vcpu, it.sptep); sp = NULL; if (!is_shadow_present_pte(*it.sptep)) { table_gfn = gw->table_gfn[it.level - 2]; sp = kvm_mmu_get_page(vcpu, table_gfn, addr, it.level-1, false, access, it.sptep); } /* * Verify that the gpte in the page we've just write * protected is still there. */ if (FNAME(gpte_changed)(vcpu, gw, it.level - 1)) goto out_gpte_changed; if (sp) link_shadow_page(it.sptep, sp); } for (; shadow_walk_okay(&it) && it.level > hlevel; shadow_walk_next(&it)) { gfn_t direct_gfn; validate_direct_spte(vcpu, it.sptep, direct_access); drop_large_spte(vcpu, it.sptep); if (is_shadow_present_pte(*it.sptep)) continue; direct_gfn = gw->gfn & ~(KVM_PAGES_PER_HPAGE(it.level) - 1); sp = kvm_mmu_get_page(vcpu, direct_gfn, addr, it.level-1, true, direct_access, it.sptep); link_shadow_page(it.sptep, sp); } mmu_set_spte(vcpu, it.sptep, access, gw->pte_access & access, user_fault, write_fault, dirty, ptwrite, it.level, gw->gfn, pfn, false, true); FNAME(pte_prefetch)(vcpu, gw, it.sptep); return it.sptep; out_gpte_changed: if (sp) kvm_mmu_put_page(sp, it.sptep); kvm_release_pfn_clean(pfn); return NULL; } /* * Page fault handler. There are several causes for a page fault: * - there is no shadow pte for the guest pte * - write access through a shadow pte marked read only so that we can set * the dirty bit * - write access to a shadow pte marked read only so we can update the page * dirty bitmap, when userspace requests it * - mmio access; in this case we will never install a present shadow pte * - normal guest page fault due to the guest pte marked not present, not * writable, or not executable * * Returns: 1 if we need to emulate the instruction, 0 otherwise, or * a negative value on error. */ static int FNAME(page_fault)(struct kvm_vcpu *vcpu, gva_t addr, u32 error_code) { int write_fault = error_code & PFERR_WRITE_MASK; int user_fault = error_code & PFERR_USER_MASK; int fetch_fault = error_code & PFERR_FETCH_MASK; struct guest_walker walker; u64 *sptep; int write_pt = 0; int r; pfn_t pfn; int level = PT_PAGE_TABLE_LEVEL; unsigned long mmu_seq; pgprintk("%s: addr %lx err %x\n", __func__, addr, error_code); r = mmu_topup_memory_caches(vcpu); if (r) return r; /* * Look up the guest pte for the faulting address. */ r = FNAME(walk_addr)(&walker, vcpu, addr, write_fault, user_fault, fetch_fault); /* * The page is not mapped by the guest. Let the guest handle it. */ if (!r) { pgprintk("%s: guest page fault\n", __func__); inject_page_fault(vcpu, addr, walker.error_code); vcpu->arch.last_pt_write_count = 0; /* reset fork detector */ return 0; } if (walker.level >= PT_DIRECTORY_LEVEL) { level = min(walker.level, mapping_level(vcpu, walker.gfn)); walker.gfn = walker.gfn & ~(KVM_PAGES_PER_HPAGE(level) - 1); } mmu_seq = vcpu->kvm->mmu_notifier_seq; smp_rmb(); pfn = gfn_to_pfn(vcpu->kvm, walker.gfn); /* mmio */ if (is_error_pfn(pfn)) return kvm_handle_bad_page(vcpu->kvm, walker.gfn, pfn); spin_lock(&vcpu->kvm->mmu_lock); if (mmu_notifier_retry(vcpu, mmu_seq)) goto out_unlock; kvm_mmu_audit(vcpu, "pre page fault"); kvm_mmu_free_some_pages(vcpu); sptep = FNAME(fetch)(vcpu, addr, &walker, user_fault, write_fault, level, &write_pt, pfn); (void)sptep; pgprintk("%s: shadow pte %p %llx ptwrite %d\n", __func__, sptep, *sptep, write_pt); if (!write_pt) vcpu->arch.last_pt_write_count = 0; /* reset fork detector */ ++vcpu->stat.pf_fixed; kvm_mmu_audit(vcpu, "post page fault (fixed)"); spin_unlock(&vcpu->kvm->mmu_lock); return write_pt; out_unlock: spin_unlock(&vcpu->kvm->mmu_lock); kvm_release_pfn_clean(pfn); return 0; } static void FNAME(invlpg)(struct kvm_vcpu *vcpu, gva_t gva) { struct kvm_shadow_walk_iterator iterator; struct kvm_mmu_page *sp; gpa_t pte_gpa = -1; int level; u64 *sptep; int need_flush = 0; spin_lock(&vcpu->kvm->mmu_lock); for_each_shadow_entry(vcpu, gva, iterator) { level = iterator.level; sptep = iterator.sptep; sp = page_header(__pa(sptep)); if (is_last_spte(*sptep, level)) { int offset, shift; if (!sp->unsync) break; shift = PAGE_SHIFT - (PT_LEVEL_BITS - PT64_LEVEL_BITS) * level; offset = sp->role.quadrant << shift; pte_gpa = (sp->gfn << PAGE_SHIFT) + offset; pte_gpa += (sptep - sp->spt) * sizeof(pt_element_t); if (is_shadow_present_pte(*sptep)) { if (is_large_pte(*sptep)) --vcpu->kvm->stat.lpages; drop_spte(vcpu->kvm, sptep, shadow_trap_nonpresent_pte); need_flush = 1; } else __set_spte(sptep, shadow_trap_nonpresent_pte); break; } if (!is_shadow_present_pte(*sptep) || !sp->unsync_children) break; } if (need_flush) kvm_flush_remote_tlbs(vcpu->kvm); atomic_inc(&vcpu->kvm->arch.invlpg_counter); spin_unlock(&vcpu->kvm->mmu_lock); if (pte_gpa == -1) return; if (mmu_topup_memory_caches(vcpu)) return; kvm_mmu_pte_write(vcpu, pte_gpa, NULL, sizeof(pt_element_t), 0); } static gpa_t FNAME(gva_to_gpa)(struct kvm_vcpu *vcpu, gva_t vaddr, u32 access, u32 *error) { struct guest_walker walker; gpa_t gpa = UNMAPPED_GVA; int r; r = FNAME(walk_addr)(&walker, vcpu, vaddr, !!(access & PFERR_WRITE_MASK), !!(access & PFERR_USER_MASK), !!(access & PFERR_FETCH_MASK)); if (r) { gpa = gfn_to_gpa(walker.gfn); gpa |= vaddr & ~PAGE_MASK; } else if (error) *error = walker.error_code; return gpa; } static void FNAME(prefetch_page)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp) { int i, j, offset, r; pt_element_t pt[256 / sizeof(pt_element_t)]; gpa_t pte_gpa; if (sp->role.direct || (PTTYPE == 32 && sp->role.level > PT_PAGE_TABLE_LEVEL)) { nonpaging_prefetch_page(vcpu, sp); return; } pte_gpa = gfn_to_gpa(sp->gfn); if (PTTYPE == 32) { offset = sp->role.quadrant << PT64_LEVEL_BITS; pte_gpa += offset * sizeof(pt_element_t); } for (i = 0; i < PT64_ENT_PER_PAGE; i += ARRAY_SIZE(pt)) { r = kvm_read_guest_atomic(vcpu->kvm, pte_gpa, pt, sizeof pt); pte_gpa += ARRAY_SIZE(pt) * sizeof(pt_element_t); for (j = 0; j < ARRAY_SIZE(pt); ++j) if (r || is_present_gpte(pt[j])) sp->spt[i+j] = shadow_trap_nonpresent_pte; else sp->spt[i+j] = shadow_notrap_nonpresent_pte; } } /* * Using the cached information from sp->gfns is safe because: * - The spte has a reference to the struct page, so the pfn for a given gfn * can't change unless all sptes pointing to it are nuked first. */ static int FNAME(sync_page)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp, bool clear_unsync) { int i, offset, nr_present; bool reset_host_protection; gpa_t first_pte_gpa; offset = nr_present = 0; /* direct kvm_mmu_page can not be unsync. */ BUG_ON(sp->role.direct); if (PTTYPE == 32) offset = sp->role.quadrant << PT64_LEVEL_BITS; first_pte_gpa = gfn_to_gpa(sp->gfn) + offset * sizeof(pt_element_t); for (i = 0; i < PT64_ENT_PER_PAGE; i++) { unsigned pte_access; pt_element_t gpte; gpa_t pte_gpa; gfn_t gfn; if (!is_shadow_present_pte(sp->spt[i])) continue; pte_gpa = first_pte_gpa + i * sizeof(pt_element_t); if (kvm_read_guest_atomic(vcpu->kvm, pte_gpa, &gpte, sizeof(pt_element_t))) return -EINVAL; gfn = gpte_to_gfn(gpte); if (is_rsvd_bits_set(vcpu, gpte, PT_PAGE_TABLE_LEVEL) || gfn != sp->gfns[i] || !is_present_gpte(gpte) || !(gpte & PT_ACCESSED_MASK)) { u64 nonpresent; if (is_present_gpte(gpte) || !clear_unsync) nonpresent = shadow_trap_nonpresent_pte; else nonpresent = shadow_notrap_nonpresent_pte; drop_spte(vcpu->kvm, &sp->spt[i], nonpresent); continue; } nr_present++; pte_access = sp->role.access & FNAME(gpte_access)(vcpu, gpte); if (!(sp->spt[i] & SPTE_HOST_WRITEABLE)) { pte_access &= ~ACC_WRITE_MASK; reset_host_protection = 0; } else { reset_host_protection = 1; } set_spte(vcpu, &sp->spt[i], pte_access, 0, 0, is_dirty_gpte(gpte), PT_PAGE_TABLE_LEVEL, gfn, spte_to_pfn(sp->spt[i]), true, false, reset_host_protection); } return !nr_present; } #undef pt_element_t #undef guest_walker #undef FNAME #undef PT_BASE_ADDR_MASK #undef PT_INDEX #undef PT_LEVEL_MASK #undef PT_LVL_ADDR_MASK #undef PT_LVL_OFFSET_MASK #undef PT_LEVEL_BITS #undef PT_MAX_FULL_LEVELS #undef gpte_to_gfn #undef gpte_to_gfn_lvl #undef CMPXCHG