/* * 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 * * 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_BITS PT64_LEVEL_BITS #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 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_BITS PT32_LEVEL_BITS #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 CMPXCHG cmpxchg #elif PTTYPE == PTTYPE_EPT #define pt_element_t u64 #define guest_walker guest_walkerEPT #define FNAME(name) ept_##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_BITS PT64_LEVEL_BITS #define PT_GUEST_DIRTY_SHIFT 9 #define PT_GUEST_ACCESSED_SHIFT 8 #define PT_HAVE_ACCESSED_DIRTY(mmu) ((mmu)->ept_ad) #define CMPXCHG cmpxchg64 #define PT_MAX_FULL_LEVELS 4 #else #error Invalid PTTYPE value #endif #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), PT_PAGE_TABLE_LEVEL) /* * 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 pt_access; unsigned pte_access; gfn_t gfn; struct x86_exception fault; }; 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 int FNAME(cmpxchg_gpte)(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu, pt_element_t __user *ptep_user, unsigned index, pt_element_t orig_pte, pt_element_t new_pte) { int npages; pt_element_t ret; pt_element_t *table; struct page *page; npages = get_user_pages_fast((unsigned long)ptep_user, 1, FOLL_WRITE, &page); if (likely(npages == 1)) { table = kmap_atomic(page); ret = CMPXCHG(&table[index], orig_pte, new_pte); kunmap_atomic(table); kvm_release_page_dirty(page); } else { struct vm_area_struct *vma; unsigned long vaddr = (unsigned long)ptep_user & PAGE_MASK; unsigned long pfn; unsigned long paddr; down_read(¤t->mm->mmap_sem); vma = find_vma_intersection(current->mm, vaddr, vaddr + PAGE_SIZE); if (!vma || !(vma->vm_flags & VM_PFNMAP)) { up_read(¤t->mm->mmap_sem); return -EFAULT; } pfn = ((vaddr - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff; paddr = pfn << PAGE_SHIFT; table = memremap(paddr, PAGE_SIZE, MEMREMAP_WB); if (!table) { up_read(¤t->mm->mmap_sem); return -EFAULT; } ret = CMPXCHG(&table[index], orig_pte, new_pte); memunmap(table); up_read(¤t->mm->mmap_sem); } return (ret != orig_pte); } static bool FNAME(prefetch_invalid_gpte)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp, u64 *spte, u64 gpte) { if (is_rsvd_bits_set(vcpu->arch.mmu, gpte, PT_PAGE_TABLE_LEVEL)) goto no_present; if (!FNAME(is_present_gpte)(gpte)) goto no_present; /* if accessed bit is not supported prefetch non accessed gpte */ if (PT_HAVE_ACCESSED_DIRTY(vcpu->arch.mmu) && !(gpte & PT_GUEST_ACCESSED_MASK)) 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, 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_arch_write_log_dirty(vcpu)) 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 = FNAME(cmpxchg_gpte)(vcpu, mmu, ptep_user, index, orig_pte, pte); 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; } /* * Fetch a guest pte for a guest virtual address */ static int FNAME(walk_addr_generic)(struct guest_walker *walker, struct kvm_vcpu *vcpu, struct kvm_mmu *mmu, gva_t addr, u32 access) { int ret; pt_element_t pte; pt_element_t __user *uninitialized_var(ptep_user); gfn_t table_gfn; u64 pt_access, pte_access; unsigned index, accessed_dirty, pte_pkey; unsigned 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->root_level; pte = mmu->get_cr3(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 { gfn_t real_gfn; 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_gfn = mmu->translate_gpa(vcpu, 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_gfn == UNMAPPED_GVA)) return 0; real_gfn = gpa_to_gfn(real_gfn); host_addr = kvm_vcpu_gfn_to_hva_prot(vcpu, real_gfn, &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(__copy_from_user(&pte, ptep_user, sizeof(pte)))) 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(is_rsvd_bits_set(mmu, pte, walker->level))) { errcode = PFERR_RSVD_MASK | PFERR_PRESENT_MASK; goto error; } walker->ptes[walker->level - 1] = pte; } while (!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->pt_access = FNAME(gpte_access)(pt_access ^ walk_nx_mask); 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 && walker->level == PT_DIRECTORY_LEVEL && is_cpuid_PSE36()) gfn += pse36_gfn_delta(pte); real_gpa = mmu->translate_gpa(vcpu, gfn_to_gpa(gfn), access, &walker->fault); if (real_gpa == UNMAPPED_GVA) 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, 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); return 1; error: errcode |= write_fault | user_fault; if (fetch_fault && (mmu->nx || kvm_read_cr4_bits(vcpu, X86_CR4_SMEP))) 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 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 &= 0x180; 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; vcpu->arch.exit_qualification |= (pte_access & 0x7) << 3; } #endif walker->fault.address = addr; walker->fault.nested_page_fault = mmu != vcpu->arch.walk_mmu; trace_kvm_mmu_walker_error(walker->fault.error_code); return 0; } static int FNAME(walk_addr)(struct guest_walker *walker, struct kvm_vcpu *vcpu, gva_t addr, u32 access) { return FNAME(walk_addr_generic)(walker, vcpu, vcpu->arch.mmu, addr, access); } #if PTTYPE != PTTYPE_EPT static int FNAME(walk_addr_nested)(struct guest_walker *walker, struct kvm_vcpu *vcpu, gva_t addr, u32 access) { return FNAME(walk_addr_generic)(walker, vcpu, &vcpu->arch.nested_mmu, addr, access); } #endif static bool FNAME(prefetch_gpte)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp, u64 *spte, pt_element_t gpte, bool no_dirty_log) { 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); pfn = pte_prefetch_gfn_to_pfn(vcpu, gfn, no_dirty_log && (pte_access & ACC_WRITE_MASK)); if (is_error_pfn(pfn)) return false; /* * we call mmu_set_spte() with host_writable = true because * pte_prefetch_gfn_to_pfn always gets a writable pfn. */ mmu_set_spte(vcpu, spte, pte_access, 0, PT_PAGE_TABLE_LEVEL, gfn, pfn, true, true); kvm_release_pfn_clean(pfn); return true; } static void FNAME(update_pte)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp, u64 *spte, const void *pte) { pt_element_t gpte = *(const pt_element_t *)pte; FNAME(prefetch_gpte)(vcpu, sp, spte, gpte, false); } 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_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 = 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++) { 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, gva_t addr, struct guest_walker *gw, int write_fault, int hlevel, kvm_pfn_t pfn, bool map_writable, bool prefault) { struct kvm_mmu_page *sp = NULL; struct kvm_shadow_walk_iterator it; unsigned direct_access, access = gw->pt_access; int top_level, ret; direct_access = gw->pte_access; 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; if (!VALID_PAGE(vcpu->arch.mmu->root_hpa)) 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; clear_sp_write_flooding_count(it.sptep); 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); } /* * 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(vcpu, it.sptep, sp); } for (; shadow_walk_okay(&it) && it.level > hlevel; shadow_walk_next(&it)) { gfn_t direct_gfn; clear_sp_write_flooding_count(it.sptep); 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); link_shadow_page(vcpu, it.sptep, sp); } clear_sp_write_flooding_count(it.sptep); ret = mmu_set_spte(vcpu, it.sptep, gw->pte_access, write_fault, it.level, gw->gfn, pfn, prefault, map_writable); 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, int 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_write_protection(vcpu) && !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, gva_t addr, u32 error_code, bool prefault) { int write_fault = error_code & PFERR_WRITE_MASK; int user_fault = error_code & PFERR_USER_MASK; struct guest_walker walker; int r; kvm_pfn_t pfn; int level = PT_PAGE_TABLE_LEVEL; bool force_pt_level = false; unsigned long mmu_seq; bool map_writable, is_self_change_mapping; pgprintk("%s: addr %lx err %x\n", __func__, addr, error_code); r = mmu_topup_memory_caches(vcpu); if (r) return r; /* * If PFEC.RSVD is set, this is a shadow page fault. * The bit needs to be cleared before walking guest page tables. */ error_code &= ~PFERR_RSVD_MASK; /* * Look up the guest pte for the faulting address. */ r = FNAME(walk_addr)(&walker, vcpu, addr, error_code); /* * The page is not mapped by the guest. Let the guest handle it. */ if (!r) { pgprintk("%s: guest page fault\n", __func__); if (!prefault) inject_page_fault(vcpu, &walker.fault); return RET_PF_RETRY; } if (page_fault_handle_page_track(vcpu, error_code, walker.gfn)) { shadow_page_table_clear_flood(vcpu, addr); return RET_PF_EMULATE; } vcpu->arch.write_fault_to_shadow_pgtable = false; is_self_change_mapping = FNAME(is_self_change_mapping)(vcpu, &walker, user_fault, &vcpu->arch.write_fault_to_shadow_pgtable); if (walker.level >= PT_DIRECTORY_LEVEL && !is_self_change_mapping) { level = mapping_level(vcpu, walker.gfn, &force_pt_level); if (likely(!force_pt_level)) { level = min(walker.level, level); walker.gfn = walker.gfn & ~(KVM_PAGES_PER_HPAGE(level) - 1); } } else force_pt_level = true; mmu_seq = vcpu->kvm->mmu_notifier_seq; smp_rmb(); if (try_async_pf(vcpu, prefault, walker.gfn, addr, &pfn, write_fault, &map_writable)) return RET_PF_RETRY; if (handle_abnormal_pfn(vcpu, addr, walker.gfn, pfn, walker.pte_access, &r)) 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 (write_fault && !(walker.pte_access & ACC_WRITE_MASK) && !is_write_protection(vcpu) && !user_fault && !is_noslot_pfn(pfn)) { 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 (kvm_read_cr4_bits(vcpu, X86_CR4_SMEP)) walker.pte_access &= ~ACC_EXEC_MASK; } r = RET_PF_RETRY; spin_lock(&vcpu->kvm->mmu_lock); if (mmu_notifier_retry(vcpu->kvm, mmu_seq)) goto out_unlock; kvm_mmu_audit(vcpu, AUDIT_PRE_PAGE_FAULT); if (make_mmu_pages_available(vcpu) < 0) goto out_unlock; if (!force_pt_level) transparent_hugepage_adjust(vcpu, &walker.gfn, &pfn, &level); r = FNAME(fetch)(vcpu, addr, &walker, write_fault, level, pfn, map_writable, prefault); ++vcpu->stat.pf_fixed; kvm_mmu_audit(vcpu, AUDIT_POST_PAGE_FAULT); out_unlock: spin_unlock(&vcpu->kvm->mmu_lock); kvm_release_pfn_clean(pfn); return r; } static gpa_t FNAME(get_level1_sp_gpa)(struct kvm_mmu_page *sp) { int offset = 0; WARN_ON(sp->role.level != PT_PAGE_TABLE_LEVEL); if (PTTYPE == 32) offset = sp->role.quadrant << PT64_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; 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); if (!VALID_PAGE(root_hpa)) { WARN_ON(1); return; } spin_lock(&vcpu->kvm->mmu_lock); for_each_shadow_entry_using_root(vcpu, root_hpa, gva, iterator) { level = iterator.level; sptep = iterator.sptep; sp = page_header(__pa(sptep)); if (is_last_spte(*sptep, level)) { pt_element_t gpte; gpa_t pte_gpa; if (!sp->unsync) break; pte_gpa = FNAME(get_level1_sp_gpa)(sp); pte_gpa += (sptep - sp->spt) * sizeof(pt_element_t); if (mmu_page_zap_pte(vcpu->kvm, sp, sptep)) kvm_flush_remote_tlbs_with_address(vcpu->kvm, sp->gfn, KVM_PAGES_PER_HPAGE(sp->role.level)); if (!rmap_can_add(vcpu)) break; if (kvm_vcpu_read_guest_atomic(vcpu, pte_gpa, &gpte, sizeof(pt_element_t))) break; FNAME(update_pte)(vcpu, sp, sptep, &gpte); } if (!is_shadow_present_pte(*sptep) || !sp->unsync_children) break; } spin_unlock(&vcpu->kvm->mmu_lock); } static gpa_t FNAME(gva_to_gpa)(struct kvm_vcpu *vcpu, gva_t vaddr, u32 access, struct x86_exception *exception) { struct guest_walker walker; gpa_t gpa = UNMAPPED_GVA; int r; r = FNAME(walk_addr)(&walker, vcpu, vaddr, access); if (r) { gpa = gfn_to_gpa(walker.gfn); gpa |= vaddr & ~PAGE_MASK; } else if (exception) *exception = walker.fault; return gpa; } #if PTTYPE != PTTYPE_EPT static gpa_t FNAME(gva_to_gpa_nested)(struct kvm_vcpu *vcpu, gva_t vaddr, u32 access, struct x86_exception *exception) { struct guest_walker walker; gpa_t gpa = UNMAPPED_GVA; int r; r = FNAME(walk_addr_nested)(&walker, vcpu, vaddr, access); if (r) { gpa = gfn_to_gpa(walker.gfn); gpa |= vaddr & ~PAGE_MASK; } else if (exception) *exception = walker.fault; return gpa; } #endif /* * 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. * * Note: * We should flush all tlbs if spte is dropped even though guest is * responsible for it. Since if we don't, kvm_mmu_notifier_invalidate_page * and kvm_mmu_notifier_invalidate_range_start detect the mapping page isn't * used by guest then tlbs are not flushed, so guest is allowed to access the * freed pages. * And we increase kvm->tlbs_dirty to delay tlbs flush in this case. */ static int FNAME(sync_page)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp) { int i, nr_present = 0; bool host_writable; gpa_t first_pte_gpa; int set_spte_ret = 0; /* direct kvm_mmu_page can not be unsync. */ BUG_ON(sp->role.direct); first_pte_gpa = FNAME(get_level1_sp_gpa)(sp); for (i = 0; i < PT64_ENT_PER_PAGE; i++) { 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 0; if (FNAME(prefetch_invalid_gpte)(vcpu, sp, &sp->spt[i], gpte)) { /* * Update spte before increasing tlbs_dirty to make * sure no tlb flush is lost after spte is zapped; see * the comments in kvm_flush_remote_tlbs(). */ smp_wmb(); vcpu->kvm->tlbs_dirty++; 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, &nr_present)) continue; if (gfn != sp->gfns[i]) { drop_spte(vcpu->kvm, &sp->spt[i]); /* * The same as above where we are doing * prefetch_invalid_gpte(). */ smp_wmb(); vcpu->kvm->tlbs_dirty++; continue; } nr_present++; host_writable = sp->spt[i] & SPTE_HOST_WRITEABLE; set_spte_ret |= set_spte(vcpu, &sp->spt[i], pte_access, PT_PAGE_TABLE_LEVEL, gfn, spte_to_pfn(sp->spt[i]), true, false, host_writable); } if (set_spte_ret & SET_SPTE_NEED_REMOTE_TLB_FLUSH) kvm_flush_remote_tlbs(vcpu->kvm); return nr_present; } #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 CMPXCHG #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