diff options
Diffstat (limited to 'kernel/arch/x86/kvm/paging_tmpl.h')
| -rw-r--r-- | kernel/arch/x86/kvm/paging_tmpl.h | 1011 |
1 files changed, 1011 insertions, 0 deletions
diff --git a/kernel/arch/x86/kvm/paging_tmpl.h b/kernel/arch/x86/kvm/paging_tmpl.h new file mode 100644 index 000000000..6e6d115fe --- /dev/null +++ b/kernel/arch/x86/kvm/paging_tmpl.h @@ -0,0 +1,1011 @@ +/* + * 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 <yaniv@qumranet.com> + * Avi Kivity <avi@qumranet.com> + * + * 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. + */ + +/* + * This is used to catch non optimized PT_GUEST_(DIRTY|ACCESS)_SHIFT macro + * uses for EPT without A/D paging type. + */ +extern u64 __pure __using_nonexistent_pte_bit(void) + __compiletime_error("wrong use of PT_GUEST_(DIRTY|ACCESS)_SHIFT"); + +#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_ACCESSED_MASK PT_ACCESSED_MASK + #define PT_GUEST_DIRTY_MASK PT_DIRTY_MASK + #define PT_GUEST_DIRTY_SHIFT PT_DIRTY_SHIFT + #define PT_GUEST_ACCESSED_SHIFT PT_ACCESSED_SHIFT + #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_ACCESSED_MASK PT_ACCESSED_MASK + #define PT_GUEST_DIRTY_MASK PT_DIRTY_MASK + #define PT_GUEST_DIRTY_SHIFT PT_DIRTY_SHIFT + #define PT_GUEST_ACCESSED_SHIFT PT_ACCESSED_SHIFT + #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_ACCESSED_MASK 0 + #define PT_GUEST_DIRTY_MASK 0 + #define PT_GUEST_DIRTY_SHIFT __using_nonexistent_pte_bit() + #define PT_GUEST_ACCESSED_SHIFT __using_nonexistent_pte_bit() + #define CMPXCHG cmpxchg64 + #define PT_MAX_FULL_LEVELS 4 +#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; + 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)(unsigned *access, unsigned gpte) +{ + unsigned mask; + + /* dirty bit is not supported, so no need to track it */ + if (!PT_GUEST_DIRTY_MASK) + 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 bool FNAME(is_rsvd_bits_set)(struct kvm_mmu *mmu, u64 gpte, int level) +{ + int bit7 = (gpte >> 7) & 1, low6 = gpte & 0x3f; + + return (gpte & mmu->rsvd_bits_mask[bit7][level-1]) | + ((mmu->bad_mt_xwr & (1ull << low6)) != 0); +} + +static inline int FNAME(is_present_gpte)(unsigned long pte) +{ +#if PTTYPE != PTTYPE_EPT + return is_present_gpte(pte); +#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, 1, &page); + /* Check if the user is doing something meaningless. */ + if (unlikely(npages != 1)) + return -EFAULT; + + table = kmap_atomic(page); + ret = CMPXCHG(&table[index], orig_pte, new_pte); + kunmap_atomic(table); + + kvm_release_page_dirty(page); + + return (ret != orig_pte); +} + +static bool FNAME(prefetch_invalid_gpte)(struct kvm_vcpu *vcpu, + struct kvm_mmu_page *sp, u64 *spte, + u64 gpte) +{ + if (FNAME(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_GUEST_ACCESSED_MASK && !(gpte & PT_GUEST_ACCESSED_MASK)) + goto no_present; + + return false; + +no_present: + drop_spte(vcpu->kvm, spte); + return true; +} + +static inline unsigned FNAME(gpte_access)(struct kvm_vcpu *vcpu, 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) | + ACC_USER_MASK; +#else + access = (gpte & (PT_WRITABLE_MASK | PT_USER_MASK)) | 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_GUEST_DIRTY_MASK) + 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)); + 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; + + mark_page_dirty(vcpu->kvm, table_gfn); + walker->ptes[level] = pte; + } + return 0; +} + +/* + * 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; + unsigned index, pt_access, pte_access, accessed_dirty; + gpa_t pte_gpa; + int offset; + 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); + +#if PTTYPE == 64 + 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))); + + accessed_dirty = PT_GUEST_ACCESSED_MASK; + pt_access = pte_access = ACC_ALL; + ++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; + 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), + PFERR_USER_MASK|PFERR_WRITE_MASK, + &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 = gfn_to_hva_prot(vcpu->kvm, 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); + + 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; + } + + accessed_dirty &= pte; + pte_access = pt_access & FNAME(gpte_access)(vcpu, pte); + + walker->ptes[walker->level - 1] = pte; + } while (!is_last_gpte(mmu, walker->level, pte)); + + if (unlikely(permission_fault(vcpu, mmu, pte_access, access))) { + errcode |= PFERR_PRESENT_MASK; + 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)(&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; + } + + 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: + 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 [2:0] of real exit_qualification at EPT violation + * [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 &= 0x187; + vcpu->arch.exit_qualification |= ((pt_access & pte) & 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; + 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)(vcpu, gpte); + FNAME(protect_clean_gpte)(&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, NULL, PT_PAGE_TABLE_LEVEL, + gfn, pfn, true, true); + + 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_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++) { + 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, + 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, emulate = 0; + + 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, 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, PT_GUEST_ACCESSED_MASK); + } + + 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, it.sptep); + link_shadow_page(it.sptep, sp, PT_GUEST_ACCESSED_MASK); + } + + clear_sp_write_flooding_count(it.sptep); + mmu_set_spte(vcpu, it.sptep, gw->pte_access, write_fault, &emulate, + it.level, gw->gfn, pfn, prefault, map_writable); + FNAME(pte_prefetch)(vcpu, gw, it.sptep); + + return emulate; + +out_gpte_changed: + if (sp) + kvm_mmu_put_page(sp, it.sptep); + kvm_release_pfn_clean(pfn); + return 0; +} + + /* + * 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; + pfn_t pfn; + int level = PT_PAGE_TABLE_LEVEL; + int force_pt_level; + unsigned long mmu_seq; + bool map_writable, is_self_change_mapping; + + pgprintk("%s: addr %lx err %x\n", __func__, addr, error_code); + + if (unlikely(error_code & PFERR_RSVD_MASK)) { + r = handle_mmio_page_fault(vcpu, addr, error_code, + mmu_is_nested(vcpu)); + if (likely(r != RET_MMIO_PF_INVALID)) + return r; + + /* + * page fault with PFEC.RSVD = 1 is caused by shadow + * page fault, should not be used to walk guest page + * table. + */ + error_code &= ~PFERR_RSVD_MASK; + }; + + 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, 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 0; + } + + 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) + force_pt_level = mapping_level_dirty_bitmap(vcpu, walker.gfn) + || is_self_change_mapping; + else + force_pt_level = 1; + if (!force_pt_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(); + + if (try_async_pf(vcpu, prefault, walker.gfn, addr, &pfn, write_fault, + &map_writable)) + return 0; + + if (handle_abnormal_pfn(vcpu, mmu_is_nested(vcpu) ? 0 : 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; + } + + 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); + make_mmu_pages_available(vcpu); + 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); + spin_unlock(&vcpu->kvm->mmu_lock); + + return r; + +out_unlock: + spin_unlock(&vcpu->kvm->mmu_lock); + kvm_release_pfn_clean(pfn); + return 0; +} + +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) +{ + 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(vcpu->arch.mmu.root_hpa)) { + WARN_ON(1); + return; + } + + 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)) { + 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(vcpu->kvm); + + if (!rmap_can_add(vcpu)) + break; + + if (kvm_read_guest_atomic(vcpu->kvm, 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; + + /* 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_read_guest_atomic(vcpu->kvm, pte_gpa, &gpte, + sizeof(pt_element_t))) + return -EINVAL; + + if (FNAME(prefetch_invalid_gpte)(vcpu, sp, &sp->spt[i], gpte)) { + vcpu->kvm->tlbs_dirty++; + continue; + } + + gfn = gpte_to_gfn(gpte); + pte_access = sp->role.access; + pte_access &= FNAME(gpte_access)(vcpu, gpte); + FNAME(protect_clean_gpte)(&pte_access, gpte); + + if (sync_mmio_spte(vcpu->kvm, &sp->spt[i], gfn, pte_access, + &nr_present)) + continue; + + if (gfn != sp->gfns[i]) { + drop_spte(vcpu->kvm, &sp->spt[i]); + vcpu->kvm->tlbs_dirty++; + continue; + } + + nr_present++; + + host_writable = sp->spt[i] & SPTE_HOST_WRITEABLE; + + set_spte(vcpu, &sp->spt[i], pte_access, + PT_PAGE_TABLE_LEVEL, gfn, + spte_to_pfn(sp->spt[i]), true, false, + host_writable); + } + + 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 |