/* SPDX-License-Identifier: GPL-2.0-only */ /* * 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 affiliates. * * Authors: * Yaniv Kamay * Avi Kivity */ /* * The MMU needs to be able to access/walk 32-bit and 64-bit guest page tables, * as well as guest EPT tables, so the code in this file is compiled thrice, * once per guest PTE type. The per-type defines are #undef'd at the end. */ #if PTTYPE == 64 #define pt_element_t u64 #define guest_walker guest_walker64 #define FNAME(name) paging##64_##name #define PT_LEVEL_BITS 9 #define PT_GUEST_DIRTY_SHIFT PT_DIRTY_SHIFT #define PT_GUEST_ACCESSED_SHIFT PT_ACCESSED_SHIFT #define PT_HAVE_ACCESSED_DIRTY(mmu) true #ifdef CONFIG_X86_64 #define PT_MAX_FULL_LEVELS PT64_ROOT_MAX_LEVEL #else #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_LEVEL_BITS 10 #define PT_MAX_FULL_LEVELS 2 #define PT_GUEST_DIRTY_SHIFT PT_DIRTY_SHIFT #define PT_GUEST_ACCESSED_SHIFT PT_ACCESSED_SHIFT #define PT_HAVE_ACCESSED_DIRTY(mmu) true #define PT32_DIR_PSE36_SIZE 4 #define PT32_DIR_PSE36_SHIFT 13 #define PT32_DIR_PSE36_MASK \ (((1ULL << PT32_DIR_PSE36_SIZE) - 1) << PT32_DIR_PSE36_SHIFT) #elif PTTYPE == PTTYPE_EPT #define pt_element_t u64 #define guest_walker guest_walkerEPT #define FNAME(name) ept_##name #define PT_LEVEL_BITS 9 #define PT_GUEST_DIRTY_SHIFT 9 #define PT_GUEST_ACCESSED_SHIFT 8 #define PT_HAVE_ACCESSED_DIRTY(mmu) (!(mmu)->cpu_role.base.ad_disabled) #define PT_MAX_FULL_LEVELS PT64_ROOT_MAX_LEVEL #else #error Invalid PTTYPE value #endif /* Common logic, but per-type values. These also need to be undefined. */ #define PT_BASE_ADDR_MASK ((pt_element_t)(((1ULL << 52) - 1) & ~(u64)(PAGE_SIZE-1))) #define PT_LVL_ADDR_MASK(lvl) __PT_LVL_ADDR_MASK(PT_BASE_ADDR_MASK, lvl, PT_LEVEL_BITS) #define PT_LVL_OFFSET_MASK(lvl) __PT_LVL_OFFSET_MASK(PT_BASE_ADDR_MASK, lvl, PT_LEVEL_BITS) #define PT_INDEX(addr, lvl) __PT_INDEX(addr, lvl, PT_LEVEL_BITS) #define PT_GUEST_DIRTY_MASK (1 << PT_GUEST_DIRTY_SHIFT) #define PT_GUEST_ACCESSED_MASK (1 << PT_GUEST_ACCESSED_SHIFT) #define gpte_to_gfn_lvl FNAME(gpte_to_gfn_lvl) #define gpte_to_gfn(pte) gpte_to_gfn_lvl((pte), PG_LEVEL_4K) /* * The guest_walker structure emulates the behavior of the hardware page * table walker. */ struct guest_walker { int level; unsigned max_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]; pt_element_t __user *ptep_user[PT_MAX_FULL_LEVELS]; bool pte_writable[PT_MAX_FULL_LEVELS]; unsigned int pt_access[PT_MAX_FULL_LEVELS]; unsigned int pte_access; gfn_t gfn; struct x86_exception fault; }; #if PTTYPE == 32 static inline gfn_t pse36_gfn_delta(u32 gpte) { int shift = 32 - PT32_DIR_PSE36_SHIFT - PAGE_SHIFT; return (gpte & PT32_DIR_PSE36_MASK) << shift; } #endif static gfn_t gpte_to_gfn_lvl(pt_element_t gpte, int lvl) { return (gpte & PT_LVL_ADDR_MASK(lvl)) >> PAGE_SHIFT; } static inline void FNAME(protect_clean_gpte)(struct kvm_mmu *mmu, unsigned *access, unsigned gpte) { unsigned mask; /* dirty bit is not supported, so no need to track it */ if (!PT_HAVE_ACCESSED_DIRTY(mmu)) return; BUILD_BUG_ON(PT_WRITABLE_MASK != ACC_WRITE_MASK); mask = (unsigned)~ACC_WRITE_MASK; /* Allow write access to dirty gptes */ mask |= (gpte >> (PT_GUEST_DIRTY_SHIFT - PT_WRITABLE_SHIFT)) & PT_WRITABLE_MASK; *access &= mask; } static inline int FNAME(is_present_gpte)(unsigned long pte) { #if PTTYPE != PTTYPE_EPT return pte & PT_PRESENT_MASK; #else return pte & 7; #endif } static bool FNAME(is_bad_mt_xwr)(struct rsvd_bits_validate *rsvd_check, u64 gpte) { #if PTTYPE != PTTYPE_EPT return false; #else return __is_bad_mt_xwr(rsvd_check, gpte); #endif } static bool FNAME(is_rsvd_bits_set)(struct kvm_mmu *mmu, u64 gpte, int level) { return __is_rsvd_bits_set(&mmu->guest_rsvd_check, gpte, level) || FNAME(is_bad_mt_xwr)(&mmu->guest_rsvd_check, gpte); } static bool FNAME(prefetch_invalid_gpte)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp, u64 *spte, u64 gpte) { if (!FNAME(is_present_gpte)(gpte)) goto no_present; /* Prefetch only accessed entries (unless A/D bits are disabled). */ if (PT_HAVE_ACCESSED_DIRTY(vcpu->arch.mmu) && !(gpte & PT_GUEST_ACCESSED_MASK)) goto no_present; if (FNAME(is_rsvd_bits_set)(vcpu->arch.mmu, gpte, PG_LEVEL_4K)) goto no_present; return false; no_present: drop_spte(vcpu->kvm, spte); return true; } /* * For PTTYPE_EPT, a page table can be executable but not readable * on supported processors. Therefore, set_spte does not automatically * set bit 0 if execute only is supported. Here, we repurpose ACC_USER_MASK * to signify readability since it isn't used in the EPT case */ static inline unsigned FNAME(gpte_access)(u64 gpte) { unsigned access; #if PTTYPE == PTTYPE_EPT access = ((gpte & VMX_EPT_WRITABLE_MASK) ? ACC_WRITE_MASK : 0) | ((gpte & VMX_EPT_EXECUTABLE_MASK) ? ACC_EXEC_MASK : 0) | ((gpte & VMX_EPT_READABLE_MASK) ? ACC_USER_MASK : 0); #else BUILD_BUG_ON(ACC_EXEC_MASK != PT_PRESENT_MASK); BUILD_BUG_ON(ACC_EXEC_MASK != 1); access = gpte & (PT_WRITABLE_MASK | PT_USER_MASK | PT_PRESENT_MASK); /* Combine NX with P (which is set here) to get ACC_EXEC_MASK. */ access ^= (gpte >> PT64_NX_SHIFT); #endif return access; } static int FNAME(update_accessed_dirty_bits)(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu, struct guest_walker *walker, gpa_t addr, int write_fault) { unsigned level, index; pt_element_t pte, orig_pte; pt_element_t __user *ptep_user; gfn_t table_gfn; int ret; /* dirty/accessed bits are not supported, so no need to update them */ if (!PT_HAVE_ACCESSED_DIRTY(mmu)) return 0; for (level = walker->max_level; level >= walker->level; --level) { pte = orig_pte = walker->ptes[level - 1]; table_gfn = walker->table_gfn[level - 1]; ptep_user = walker->ptep_user[level - 1]; index = offset_in_page(ptep_user) / sizeof(pt_element_t); if (!(pte & PT_GUEST_ACCESSED_MASK)) { trace_kvm_mmu_set_accessed_bit(table_gfn, index, sizeof(pte)); pte |= PT_GUEST_ACCESSED_MASK; } if (level == walker->level && write_fault && !(pte & PT_GUEST_DIRTY_MASK)) { trace_kvm_mmu_set_dirty_bit(table_gfn, index, sizeof(pte)); #if PTTYPE == PTTYPE_EPT if (kvm_x86_ops.nested_ops->write_log_dirty(vcpu, addr)) return -EINVAL; #endif pte |= PT_GUEST_DIRTY_MASK; } if (pte == orig_pte) continue; /* * If the slot is read-only, simply do not process the accessed * and dirty bits. This is the correct thing to do if the slot * is ROM, and page tables in read-as-ROM/write-as-MMIO slots * are only supported if the accessed and dirty bits are already * set in the ROM (so that MMIO writes are never needed). * * Note that NPT does not allow this at all and faults, since * it always wants nested page table entries for the guest * page tables to be writable. And EPT works but will simply * overwrite the read-only memory to set the accessed and dirty * bits. */ if (unlikely(!walker->pte_writable[level - 1])) continue; ret = __try_cmpxchg_user(ptep_user, &orig_pte, pte, fault); if (ret) return ret; kvm_vcpu_mark_page_dirty(vcpu, table_gfn); walker->ptes[level - 1] = pte; } return 0; } static inline unsigned FNAME(gpte_pkeys)(struct kvm_vcpu *vcpu, u64 gpte) { unsigned pkeys = 0; #if PTTYPE == 64 pte_t pte = {.pte = gpte}; pkeys = pte_flags_pkey(pte_flags(pte)); #endif return pkeys; } static inline bool FNAME(is_last_gpte)(struct kvm_mmu *mmu, unsigned int level, unsigned int gpte) { /* * For EPT and PAE paging (both variants), bit 7 is either reserved at * all level or indicates a huge page (ignoring CR3/EPTP). In either * case, bit 7 being set terminates the walk. */ #if PTTYPE == 32 /* * 32-bit paging requires special handling because bit 7 is ignored if * CR4.PSE=0, not reserved. Clear bit 7 in the gpte if the level is * greater than the last level for which bit 7 is the PAGE_SIZE bit. * * The RHS has bit 7 set iff level < (2 + PSE). If it is clear, bit 7 * is not reserved and does not indicate a large page at this level, * so clear PT_PAGE_SIZE_MASK in gpte if that is the case. */ gpte &= level - (PT32_ROOT_LEVEL + mmu->cpu_role.ext.cr4_pse); #endif /* * PG_LEVEL_4K always terminates. The RHS has bit 7 set * iff level <= PG_LEVEL_4K, which for our purpose means * level == PG_LEVEL_4K; set PT_PAGE_SIZE_MASK in gpte then. */ gpte |= level - PG_LEVEL_4K - 1; return gpte & PT_PAGE_SIZE_MASK; } /* * Fetch a guest pte for a guest virtual address, or for an L2's GPA. */ static int FNAME(walk_addr_generic)(struct guest_walker *walker, struct kvm_vcpu *vcpu, struct kvm_mmu *mmu, gpa_t addr, u64 access) { int ret; pt_element_t pte; pt_element_t __user *ptep_user; gfn_t table_gfn; u64 pt_access, pte_access; unsigned index, accessed_dirty, pte_pkey; u64 nested_access; gpa_t pte_gpa; bool have_ad; int offset; u64 walk_nx_mask = 0; const int write_fault = access & PFERR_WRITE_MASK; const int user_fault = access & PFERR_USER_MASK; const int fetch_fault = access & PFERR_FETCH_MASK; u16 errcode = 0; gpa_t real_gpa; gfn_t gfn; trace_kvm_mmu_pagetable_walk(addr, access); retry_walk: walker->level = mmu->cpu_role.base.level; pte = mmu->get_guest_pgd(vcpu); have_ad = PT_HAVE_ACCESSED_DIRTY(mmu); #if PTTYPE == 64 walk_nx_mask = 1ULL << PT64_NX_SHIFT; if (walker->level == PT32E_ROOT_LEVEL) { pte = mmu->get_pdptr(vcpu, (addr >> 30) & 3); trace_kvm_mmu_paging_element(pte, walker->level); if (!FNAME(is_present_gpte)(pte)) goto error; --walker->level; } #endif walker->max_level = walker->level; ASSERT(!(is_long_mode(vcpu) && !is_pae(vcpu))); /* * FIXME: on Intel processors, loads of the PDPTE registers for PAE paging * by the MOV to CR instruction are treated as reads and do not cause the * processor to set the dirty flag in any EPT paging-structure entry. */ nested_access = (have_ad ? PFERR_WRITE_MASK : 0) | PFERR_USER_MASK; pte_access = ~0; ++walker->level; do { unsigned long host_addr; pt_access = pte_access; --walker->level; index = PT_INDEX(addr, walker->level); table_gfn = gpte_to_gfn(pte); offset = index * sizeof(pt_element_t); pte_gpa = gfn_to_gpa(table_gfn) + offset; BUG_ON(walker->level < 1); walker->table_gfn[walker->level - 1] = table_gfn; walker->pte_gpa[walker->level - 1] = pte_gpa; real_gpa = kvm_translate_gpa(vcpu, mmu, gfn_to_gpa(table_gfn), nested_access, &walker->fault); /* * FIXME: This can happen if emulation (for of an INS/OUTS * instruction) triggers a nested page fault. The exit * qualification / exit info field will incorrectly have * "guest page access" as the nested page fault's cause, * instead of "guest page structure access". To fix this, * the x86_exception struct should be augmented with enough * information to fix the exit_qualification or exit_info_1 * fields. */ if (unlikely(real_gpa == INVALID_GPA)) return 0; host_addr = kvm_vcpu_gfn_to_hva_prot(vcpu, gpa_to_gfn(real_gpa), &walker->pte_writable[walker->level - 1]); if (unlikely(kvm_is_error_hva(host_addr))) goto error; ptep_user = (pt_element_t __user *)((void *)host_addr + offset); if (unlikely(__get_user(pte, ptep_user))) goto error; walker->ptep_user[walker->level - 1] = ptep_user; trace_kvm_mmu_paging_element(pte, walker->level); /* * Inverting the NX it lets us AND it like other * permission bits. */ pte_access = pt_access & (pte ^ walk_nx_mask); if (unlikely(!FNAME(is_present_gpte)(pte))) goto error; if (unlikely(FNAME(is_rsvd_bits_set)(mmu, pte, walker->level))) { errcode = PFERR_RSVD_MASK | PFERR_PRESENT_MASK; goto error; } walker->ptes[walker->level - 1] = pte; /* Convert to ACC_*_MASK flags for struct guest_walker. */ walker->pt_access[walker->level - 1] = FNAME(gpte_access)(pt_access ^ walk_nx_mask); } while (!FNAME(is_last_gpte)(mmu, walker->level, pte)); pte_pkey = FNAME(gpte_pkeys)(vcpu, pte); accessed_dirty = have_ad ? pte_access & PT_GUEST_ACCESSED_MASK : 0; /* Convert to ACC_*_MASK flags for struct guest_walker. */ walker->pte_access = FNAME(gpte_access)(pte_access ^ walk_nx_mask); errcode = permission_fault(vcpu, mmu, walker->pte_access, pte_pkey, access); if (unlikely(errcode)) goto error; gfn = gpte_to_gfn_lvl(pte, walker->level); gfn += (addr & PT_LVL_OFFSET_MASK(walker->level)) >> PAGE_SHIFT; #if PTTYPE == 32 if (walker->level > PG_LEVEL_4K && is_cpuid_PSE36()) gfn += pse36_gfn_delta(pte); #endif real_gpa = kvm_translate_gpa(vcpu, mmu, gfn_to_gpa(gfn), access, &walker->fault); if (real_gpa == INVALID_GPA) return 0; walker->gfn = real_gpa >> PAGE_SHIFT; if (!write_fault) FNAME(protect_clean_gpte)(mmu, &walker->pte_access, pte); else /* * On a write fault, fold the dirty bit into accessed_dirty. * For modes without A/D bits support accessed_dirty will be * always clear. */ accessed_dirty &= pte >> (PT_GUEST_DIRTY_SHIFT - PT_GUEST_ACCESSED_SHIFT); if (unlikely(!accessed_dirty)) { ret = FNAME(update_accessed_dirty_bits)(vcpu, mmu, walker, addr, write_fault); if (unlikely(ret < 0)) goto error; else if (ret) goto retry_walk; } pgprintk("%s: pte %llx pte_access %x pt_access %x\n", __func__, (u64)pte, walker->pte_access, walker->pt_access[walker->level - 1]); return 1; error: errcode |= write_fault | user_fault; if (fetch_fault && (is_efer_nx(mmu) || is_cr4_smep(mmu))) errcode |= PFERR_FETCH_MASK; walker->fault.vector = PF_VECTOR; walker->fault.error_code_valid = true; walker->fault.error_code = errcode; #if PTTYPE == PTTYPE_EPT /* * Use PFERR_RSVD_MASK in error_code to tell if EPT * misconfiguration requires to be injected. The detection is * done by is_rsvd_bits_set() above. * * We set up the value of exit_qualification to inject: * [2:0] - Derive from the access bits. The exit_qualification might be * out of date if it is serving an EPT misconfiguration. * [5:3] - Calculated by the page walk of the guest EPT page tables * [7:8] - Derived from [7:8] of real exit_qualification * * The other bits are set to 0. */ if (!(errcode & PFERR_RSVD_MASK)) { vcpu->arch.exit_qualification &= (EPT_VIOLATION_GVA_IS_VALID | EPT_VIOLATION_GVA_TRANSLATED); if (write_fault) vcpu->arch.exit_qualification |= EPT_VIOLATION_ACC_WRITE; if (user_fault) vcpu->arch.exit_qualification |= EPT_VIOLATION_ACC_READ; if (fetch_fault) vcpu->arch.exit_qualification |= EPT_VIOLATION_ACC_INSTR; /* * Note, pte_access holds the raw RWX bits from the EPTE, not * ACC_*_MASK flags! */ vcpu->arch.exit_qualification |= (pte_access & VMX_EPT_RWX_MASK) << EPT_VIOLATION_RWX_SHIFT; } #endif walker->fault.address = addr; walker->fault.nested_page_fault = mmu != vcpu->arch.walk_mmu; walker->fault.async_page_fault = false; trace_kvm_mmu_walker_error(walker->fault.error_code); return 0; } static int FNAME(walk_addr)(struct guest_walker *walker, struct kvm_vcpu *vcpu, gpa_t addr, u64 access) { return FNAME(walk_addr_generic)(walker, vcpu, vcpu->arch.mmu, addr, access); } static bool FNAME(prefetch_gpte)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp, u64 *spte, pt_element_t gpte, bool no_dirty_log) { struct kvm_memory_slot *slot; unsigned pte_access; gfn_t gfn; kvm_pfn_t pfn; if (FNAME(prefetch_invalid_gpte)(vcpu, sp, spte, gpte)) return false; pgprintk("%s: gpte %llx spte %p\n", __func__, (u64)gpte, spte); gfn = gpte_to_gfn(gpte); pte_access = sp->role.access & FNAME(gpte_access)(gpte); FNAME(protect_clean_gpte)(vcpu->arch.mmu, &pte_access, gpte); slot = gfn_to_memslot_dirty_bitmap(vcpu, gfn, no_dirty_log && (pte_access & ACC_WRITE_MASK)); if (!slot) return false; pfn = gfn_to_pfn_memslot_atomic(slot, gfn); if (is_error_pfn(pfn)) return false; mmu_set_spte(vcpu, slot, spte, pte_access, gfn, pfn, NULL); kvm_release_pfn_clean(pfn); return 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 == PG_LEVEL_4K) { 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_vcpu_read_guest_atomic(vcpu, base_gpa, gw->prefetch_ptes, sizeof(gw->prefetch_ptes)); curr_pte = gw->prefetch_ptes[index]; } else r = kvm_vcpu_read_guest_atomic(vcpu, 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 = sptep_to_sp(sptep); if (sp->role.level > PG_LEVEL_4K) return; /* * If addresses are being invalidated, skip prefetching to avoid * accidentally prefetching those addresses. */ if (unlikely(vcpu->kvm->mmu_invalidate_in_progress)) return; if (sp->role.direct) return __direct_pte_prefetch(vcpu, sp, sptep); i = spte_index(sptep) & ~(PTE_PREFETCH_NUM - 1); spte = sp->spt + i; for (i = 0; i < PTE_PREFETCH_NUM; i++, spte++) { if (spte == sptep) continue; if (is_shadow_present_pte(*spte)) continue; if (!FNAME(prefetch_gpte)(vcpu, sp, spte, gptep[i], true)) break; } } /* * Fetch a shadow pte for a specific level in the paging hierarchy. * If the guest tries to write a write-protected page, we need to * emulate this operation, return 1 to indicate this case. */ static int FNAME(fetch)(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault, struct guest_walker *gw) { struct kvm_mmu_page *sp = NULL; struct kvm_shadow_walk_iterator it; unsigned int direct_access, access; int top_level, ret; gfn_t base_gfn = fault->gfn; WARN_ON_ONCE(gw->gfn != base_gfn); direct_access = gw->pte_access; top_level = vcpu->arch.mmu->cpu_role.base.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; if (WARN_ON(!VALID_PAGE(vcpu->arch.mmu->root.hpa))) goto out_gpte_changed; for_each_shadow_entry(vcpu, fault->addr, it) { gfn_t table_gfn; clear_sp_write_flooding_count(it.sptep); if (it.level == gw->level) break; table_gfn = gw->table_gfn[it.level - 2]; access = gw->pt_access[it.level - 2]; sp = kvm_mmu_get_child_sp(vcpu, it.sptep, table_gfn, false, access); if (sp != ERR_PTR(-EEXIST)) { /* * We must synchronize the pagetable before linking it * because the guest doesn't need to flush tlb when * the gpte is changed from non-present to present. * Otherwise, the guest may use the wrong mapping. * * For PG_LEVEL_4K, kvm_mmu_get_page() has already * synchronized it transiently via kvm_sync_page(). * * For higher level pagetable, we synchronize it via * the slower mmu_sync_children(). If it needs to * break, some progress has been made; return * RET_PF_RETRY and retry on the next #PF. * KVM_REQ_MMU_SYNC is not necessary but it * expedites the process. */ if (sp->unsync_children && mmu_sync_children(vcpu, sp, false)) return RET_PF_RETRY; } /* * 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 != ERR_PTR(-EEXIST)) link_shadow_page(vcpu, it.sptep, sp); } kvm_mmu_hugepage_adjust(vcpu, fault); trace_kvm_mmu_spte_requested(fault); for (; shadow_walk_okay(&it); shadow_walk_next(&it)) { /* * We cannot overwrite existing page tables with an NX * large page, as the leaf could be executable. */ if (fault->nx_huge_page_workaround_enabled) disallowed_hugepage_adjust(fault, *it.sptep, it.level); base_gfn = gfn_round_for_level(fault->gfn, it.level); if (it.level == fault->goal_level) break; validate_direct_spte(vcpu, it.sptep, direct_access); sp = kvm_mmu_get_child_sp(vcpu, it.sptep, base_gfn, true, direct_access); if (sp == ERR_PTR(-EEXIST)) continue; link_shadow_page(vcpu, it.sptep, sp); if (fault->huge_page_disallowed) account_nx_huge_page(vcpu->kvm, sp, fault->req_level >= it.level); } if (WARN_ON_ONCE(it.level != fault->goal_level)) return -EFAULT; ret = mmu_set_spte(vcpu, fault->slot, it.sptep, gw->pte_access, base_gfn, fault->pfn, fault); if (ret == RET_PF_SPURIOUS) return ret; FNAME(pte_prefetch)(vcpu, gw, it.sptep); return ret; out_gpte_changed: return RET_PF_RETRY; } /* * To see whether the mapped gfn can write its page table in the current * mapping. * * It is the helper function of FNAME(page_fault). When guest uses large page * size to map the writable gfn which is used as current page table, we should * force kvm to use small page size to map it because new shadow page will be * created when kvm establishes shadow page table that stop kvm using large * page size. Do it early can avoid unnecessary #PF and emulation. * * @write_fault_to_shadow_pgtable will return true if the fault gfn is * currently used as its page table. * * Note: the PDPT page table is not checked for PAE-32 bit guest. It is ok * since the PDPT is always shadowed, that means, we can not use large page * size to map the gfn which is used as PDPT. */ static bool FNAME(is_self_change_mapping)(struct kvm_vcpu *vcpu, struct guest_walker *walker, bool user_fault, bool *write_fault_to_shadow_pgtable) { int level; gfn_t mask = ~(KVM_PAGES_PER_HPAGE(walker->level) - 1); bool self_changed = false; if (!(walker->pte_access & ACC_WRITE_MASK || (!is_cr0_wp(vcpu->arch.mmu) && !user_fault))) return false; for (level = walker->level; level <= walker->max_level; level++) { gfn_t gfn = walker->gfn ^ walker->table_gfn[level - 1]; self_changed |= !(gfn & mask); *write_fault_to_shadow_pgtable |= !gfn; } return self_changed; } /* * 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, struct kvm_page_fault *fault) { struct guest_walker walker; int r; bool is_self_change_mapping; pgprintk("%s: addr %lx err %x\n", __func__, fault->addr, fault->error_code); WARN_ON_ONCE(fault->is_tdp); /* * Look up the guest pte for the faulting address. * If PFEC.RSVD is set, this is a shadow page fault. * The bit needs to be cleared before walking guest page tables. */ r = FNAME(walk_addr)(&walker, vcpu, fault->addr, fault->error_code & ~PFERR_RSVD_MASK); /* * The page is not mapped by the guest. Let the guest handle it. */ if (!r) { pgprintk("%s: guest page fault\n", __func__); if (!fault->prefetch) kvm_inject_emulated_page_fault(vcpu, &walker.fault); return RET_PF_RETRY; } fault->gfn = walker.gfn; fault->slot = kvm_vcpu_gfn_to_memslot(vcpu, fault->gfn); if (page_fault_handle_page_track(vcpu, fault)) { shadow_page_table_clear_flood(vcpu, fault->addr); return RET_PF_EMULATE; } r = mmu_topup_memory_caches(vcpu, true); if (r) return r; vcpu->arch.write_fault_to_shadow_pgtable = false; is_self_change_mapping = FNAME(is_self_change_mapping)(vcpu, &walker, fault->user, &vcpu->arch.write_fault_to_shadow_pgtable); if (is_self_change_mapping) fault->max_level = PG_LEVEL_4K; else fault->max_level = walker.level; r = kvm_faultin_pfn(vcpu, fault, walker.pte_access); if (r != RET_PF_CONTINUE) return r; /* * Do not change pte_access if the pfn is a mmio page, otherwise * we will cache the incorrect access into mmio spte. */ if (fault->write && !(walker.pte_access & ACC_WRITE_MASK) && !is_cr0_wp(vcpu->arch.mmu) && !fault->user && fault->slot) { walker.pte_access |= ACC_WRITE_MASK; walker.pte_access &= ~ACC_USER_MASK; /* * If we converted a user page to a kernel page, * so that the kernel can write to it when cr0.wp=0, * then we should prevent the kernel from executing it * if SMEP is enabled. */ if (is_cr4_smep(vcpu->arch.mmu)) walker.pte_access &= ~ACC_EXEC_MASK; } r = RET_PF_RETRY; write_lock(&vcpu->kvm->mmu_lock); if (is_page_fault_stale(vcpu, fault)) goto out_unlock; r = make_mmu_pages_available(vcpu); if (r) goto out_unlock; r = FNAME(fetch)(vcpu, fault, &walker); out_unlock: write_unlock(&vcpu->kvm->mmu_lock); kvm_release_pfn_clean(fault->pfn); return r; } static gpa_t FNAME(get_level1_sp_gpa)(struct kvm_mmu_page *sp) { int offset = 0; WARN_ON(sp->role.level != PG_LEVEL_4K); if (PTTYPE == 32) offset = sp->role.quadrant << SPTE_LEVEL_BITS; return gfn_to_gpa(sp->gfn) + offset * sizeof(pt_element_t); } static void FNAME(invlpg)(struct kvm_vcpu *vcpu, gva_t gva, hpa_t root_hpa) { struct kvm_shadow_walk_iterator iterator; struct kvm_mmu_page *sp; u64 old_spte; int level; u64 *sptep; vcpu_clear_mmio_info(vcpu, gva); /* * No need to check return value here, rmap_can_add() can * help us to skip pte prefetch later. */ mmu_topup_memory_caches(vcpu, true); if (!VALID_PAGE(root_hpa)) { WARN_ON(1); return; } write_lock(&vcpu->kvm->mmu_lock); for_each_shadow_entry_using_root(vcpu, root_hpa, gva, iterator) { level = iterator.level; sptep = iterator.sptep; sp = sptep_to_sp(sptep); old_spte = *sptep; if (is_last_spte(old_spte, level)) { pt_element_t gpte; gpa_t pte_gpa; if (!sp->unsync) break; pte_gpa = FNAME(get_level1_sp_gpa)(sp); pte_gpa += spte_index(sptep) * sizeof(pt_element_t); mmu_page_zap_pte(vcpu->kvm, sp, sptep, NULL); if (is_shadow_present_pte(old_spte)) kvm_flush_remote_tlbs_sptep(vcpu->kvm, sptep); if (!rmap_can_add(vcpu)) break; if (kvm_vcpu_read_guest_atomic(vcpu, pte_gpa, &gpte, sizeof(pt_element_t))) break; FNAME(prefetch_gpte)(vcpu, sp, sptep, gpte, false); } if (!sp->unsync_children) break; } write_unlock(&vcpu->kvm->mmu_lock); } /* Note, @addr is a GPA when gva_to_gpa() translates an L2 GPA to an L1 GPA. */ static gpa_t FNAME(gva_to_gpa)(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu, gpa_t addr, u64 access, struct x86_exception *exception) { struct guest_walker walker; gpa_t gpa = INVALID_GPA; int r; #ifndef CONFIG_X86_64 /* A 64-bit GVA should be impossible on 32-bit KVM. */ WARN_ON_ONCE((addr >> 32) && mmu == vcpu->arch.walk_mmu); #endif r = FNAME(walk_addr_generic)(&walker, vcpu, mmu, addr, access); if (r) { gpa = gfn_to_gpa(walker.gfn); gpa |= addr & ~PAGE_MASK; } else if (exception) *exception = walker.fault; return gpa; } /* * Using the information in sp->shadowed_translation (kvm_mmu_page_get_gfn()) 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. * * Returns * < 0: the sp should be zapped * 0: the sp is synced and no tlb flushing is required * > 0: the sp is synced and tlb flushing is required */ static int FNAME(sync_page)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp) { union kvm_mmu_page_role root_role = vcpu->arch.mmu->root_role; int i; bool host_writable; gpa_t first_pte_gpa; bool flush = false; /* * Ignore various flags when verifying that it's safe to sync a shadow * page using the current MMU context. * * - level: not part of the overall MMU role and will never match as the MMU's * level tracks the root level * - access: updated based on the new guest PTE * - quadrant: not part of the overall MMU role (similar to level) */ const union kvm_mmu_page_role sync_role_ign = { .level = 0xf, .access = 0x7, .quadrant = 0x3, .passthrough = 0x1, }; /* * Direct pages can never be unsync, and KVM should never attempt to * sync a shadow page for a different MMU context, e.g. if the role * differs then the memslot lookup (SMM vs. non-SMM) will be bogus, the * reserved bits checks will be wrong, etc... */ if (WARN_ON_ONCE(sp->role.direct || (sp->role.word ^ root_role.word) & ~sync_role_ign.word)) return -1; first_pte_gpa = FNAME(get_level1_sp_gpa)(sp); for (i = 0; i < SPTE_ENT_PER_PAGE; i++) { u64 *sptep, spte; struct kvm_memory_slot *slot; unsigned pte_access; pt_element_t gpte; gpa_t pte_gpa; gfn_t gfn; if (!sp->spt[i]) continue; pte_gpa = first_pte_gpa + i * sizeof(pt_element_t); if (kvm_vcpu_read_guest_atomic(vcpu, pte_gpa, &gpte, sizeof(pt_element_t))) return -1; if (FNAME(prefetch_invalid_gpte)(vcpu, sp, &sp->spt[i], gpte)) { flush = true; continue; } gfn = gpte_to_gfn(gpte); pte_access = sp->role.access; pte_access &= FNAME(gpte_access)(gpte); FNAME(protect_clean_gpte)(vcpu->arch.mmu, &pte_access, gpte); if (sync_mmio_spte(vcpu, &sp->spt[i], gfn, pte_access)) continue; /* * Drop the SPTE if the new protections would result in a RWX=0 * SPTE or if the gfn is changing. The RWX=0 case only affects * EPT with execute-only support, i.e. EPT without an effective * "present" bit, as all other paging modes will create a * read-only SPTE if pte_access is zero. */ if ((!pte_access && !shadow_present_mask) || gfn != kvm_mmu_page_get_gfn(sp, i)) { drop_spte(vcpu->kvm, &sp->spt[i]); flush = true; continue; } /* Update the shadowed access bits in case they changed. */ kvm_mmu_page_set_access(sp, i, pte_access); sptep = &sp->spt[i]; spte = *sptep; host_writable = spte & shadow_host_writable_mask; slot = kvm_vcpu_gfn_to_memslot(vcpu, gfn); make_spte(vcpu, sp, slot, pte_access, gfn, spte_to_pfn(spte), spte, true, false, host_writable, &spte); flush |= mmu_spte_update(sptep, spte); } /* * Note, any flush is purely for KVM's correctness, e.g. when dropping * an existing SPTE or clearing W/A/D bits to ensure an mmu_notifier * unmap or dirty logging event doesn't fail to flush. The guest is * responsible for flushing the TLB to ensure any changes in protection * bits are recognized, i.e. until the guest flushes or page faults on * a relevant address, KVM is architecturally allowed to let vCPUs use * cached translations with the old protection bits. */ return flush; } #undef pt_element_t #undef guest_walker #undef FNAME #undef PT_BASE_ADDR_MASK #undef PT_INDEX #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 PT_GUEST_ACCESSED_MASK #undef PT_GUEST_DIRTY_MASK #undef PT_GUEST_DIRTY_SHIFT #undef PT_GUEST_ACCESSED_SHIFT #undef PT_HAVE_ACCESSED_DIRTY