1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * Kernel-based Virtual Machine driver for Linux 4 * 5 * Macros and functions to access KVM PTEs (also known as SPTEs) 6 * 7 * Copyright (C) 2006 Qumranet, Inc. 8 * Copyright 2020 Red Hat, Inc. and/or its affiliates. 9 */ 10 11 12 #include <linux/kvm_host.h> 13 #include "mmu.h" 14 #include "mmu_internal.h" 15 #include "x86.h" 16 #include "spte.h" 17 18 #include <asm/e820/api.h> 19 20 u64 __read_mostly shadow_nx_mask; 21 u64 __read_mostly shadow_x_mask; /* mutual exclusive with nx_mask */ 22 u64 __read_mostly shadow_user_mask; 23 u64 __read_mostly shadow_accessed_mask; 24 u64 __read_mostly shadow_dirty_mask; 25 u64 __read_mostly shadow_mmio_value; 26 u64 __read_mostly shadow_mmio_access_mask; 27 u64 __read_mostly shadow_present_mask; 28 u64 __read_mostly shadow_me_mask; 29 u64 __read_mostly shadow_acc_track_mask; 30 31 u64 __read_mostly shadow_nonpresent_or_rsvd_mask; 32 u64 __read_mostly shadow_nonpresent_or_rsvd_lower_gfn_mask; 33 34 u8 __read_mostly shadow_phys_bits; 35 36 static u64 generation_mmio_spte_mask(u64 gen) 37 { 38 u64 mask; 39 40 WARN_ON(gen & ~MMIO_SPTE_GEN_MASK); 41 BUILD_BUG_ON((MMIO_SPTE_GEN_HIGH_MASK | MMIO_SPTE_GEN_LOW_MASK) & SPTE_SPECIAL_MASK); 42 43 mask = (gen << MMIO_SPTE_GEN_LOW_START) & MMIO_SPTE_GEN_LOW_MASK; 44 mask |= (gen << MMIO_SPTE_GEN_HIGH_START) & MMIO_SPTE_GEN_HIGH_MASK; 45 return mask; 46 } 47 48 u64 make_mmio_spte(struct kvm_vcpu *vcpu, u64 gfn, unsigned int access) 49 { 50 u64 gen = kvm_vcpu_memslots(vcpu)->generation & MMIO_SPTE_GEN_MASK; 51 u64 mask = generation_mmio_spte_mask(gen); 52 u64 gpa = gfn << PAGE_SHIFT; 53 54 access &= shadow_mmio_access_mask; 55 mask |= shadow_mmio_value | access; 56 mask |= gpa | shadow_nonpresent_or_rsvd_mask; 57 mask |= (gpa & shadow_nonpresent_or_rsvd_mask) 58 << SHADOW_NONPRESENT_OR_RSVD_MASK_LEN; 59 60 return mask; 61 } 62 63 static bool kvm_is_mmio_pfn(kvm_pfn_t pfn) 64 { 65 if (pfn_valid(pfn)) 66 return !is_zero_pfn(pfn) && PageReserved(pfn_to_page(pfn)) && 67 /* 68 * Some reserved pages, such as those from NVDIMM 69 * DAX devices, are not for MMIO, and can be mapped 70 * with cached memory type for better performance. 71 * However, the above check misconceives those pages 72 * as MMIO, and results in KVM mapping them with UC 73 * memory type, which would hurt the performance. 74 * Therefore, we check the host memory type in addition 75 * and only treat UC/UC-/WC pages as MMIO. 76 */ 77 (!pat_enabled() || pat_pfn_immune_to_uc_mtrr(pfn)); 78 79 return !e820__mapped_raw_any(pfn_to_hpa(pfn), 80 pfn_to_hpa(pfn + 1) - 1, 81 E820_TYPE_RAM); 82 } 83 84 int make_spte(struct kvm_vcpu *vcpu, unsigned int pte_access, int level, 85 gfn_t gfn, kvm_pfn_t pfn, u64 old_spte, bool speculative, 86 bool can_unsync, bool host_writable, bool ad_disabled, 87 u64 *new_spte) 88 { 89 u64 spte = 0; 90 int ret = 0; 91 92 if (ad_disabled) 93 spte |= SPTE_AD_DISABLED_MASK; 94 else if (kvm_vcpu_ad_need_write_protect(vcpu)) 95 spte |= SPTE_AD_WRPROT_ONLY_MASK; 96 97 /* 98 * For the EPT case, shadow_present_mask is 0 if hardware 99 * supports exec-only page table entries. In that case, 100 * ACC_USER_MASK and shadow_user_mask are used to represent 101 * read access. See FNAME(gpte_access) in paging_tmpl.h. 102 */ 103 spte |= shadow_present_mask; 104 if (!speculative) 105 spte |= spte_shadow_accessed_mask(spte); 106 107 if (level > PG_LEVEL_4K && (pte_access & ACC_EXEC_MASK) && 108 is_nx_huge_page_enabled()) { 109 pte_access &= ~ACC_EXEC_MASK; 110 } 111 112 if (pte_access & ACC_EXEC_MASK) 113 spte |= shadow_x_mask; 114 else 115 spte |= shadow_nx_mask; 116 117 if (pte_access & ACC_USER_MASK) 118 spte |= shadow_user_mask; 119 120 if (level > PG_LEVEL_4K) 121 spte |= PT_PAGE_SIZE_MASK; 122 if (tdp_enabled) 123 spte |= kvm_x86_ops.get_mt_mask(vcpu, gfn, 124 kvm_is_mmio_pfn(pfn)); 125 126 if (host_writable) 127 spte |= SPTE_HOST_WRITEABLE; 128 else 129 pte_access &= ~ACC_WRITE_MASK; 130 131 if (!kvm_is_mmio_pfn(pfn)) 132 spte |= shadow_me_mask; 133 134 spte |= (u64)pfn << PAGE_SHIFT; 135 136 if (pte_access & ACC_WRITE_MASK) { 137 spte |= PT_WRITABLE_MASK | SPTE_MMU_WRITEABLE; 138 139 /* 140 * Optimization: for pte sync, if spte was writable the hash 141 * lookup is unnecessary (and expensive). Write protection 142 * is responsibility of mmu_get_page / kvm_sync_page. 143 * Same reasoning can be applied to dirty page accounting. 144 */ 145 if (!can_unsync && is_writable_pte(old_spte)) 146 goto out; 147 148 if (mmu_need_write_protect(vcpu, gfn, can_unsync)) { 149 pgprintk("%s: found shadow page for %llx, marking ro\n", 150 __func__, gfn); 151 ret |= SET_SPTE_WRITE_PROTECTED_PT; 152 pte_access &= ~ACC_WRITE_MASK; 153 spte &= ~(PT_WRITABLE_MASK | SPTE_MMU_WRITEABLE); 154 } 155 } 156 157 if (pte_access & ACC_WRITE_MASK) 158 spte |= spte_shadow_dirty_mask(spte); 159 160 if (speculative) 161 spte = mark_spte_for_access_track(spte); 162 163 out: 164 *new_spte = spte; 165 return ret; 166 } 167 168 u64 make_nonleaf_spte(u64 *child_pt, bool ad_disabled) 169 { 170 u64 spte; 171 172 spte = __pa(child_pt) | shadow_present_mask | PT_WRITABLE_MASK | 173 shadow_user_mask | shadow_x_mask | shadow_me_mask; 174 175 if (ad_disabled) 176 spte |= SPTE_AD_DISABLED_MASK; 177 else 178 spte |= shadow_accessed_mask; 179 180 return spte; 181 } 182 183 u64 kvm_mmu_changed_pte_notifier_make_spte(u64 old_spte, kvm_pfn_t new_pfn) 184 { 185 u64 new_spte; 186 187 new_spte = old_spte & ~PT64_BASE_ADDR_MASK; 188 new_spte |= (u64)new_pfn << PAGE_SHIFT; 189 190 new_spte &= ~PT_WRITABLE_MASK; 191 new_spte &= ~SPTE_HOST_WRITEABLE; 192 193 new_spte = mark_spte_for_access_track(new_spte); 194 195 return new_spte; 196 } 197 198 static u8 kvm_get_shadow_phys_bits(void) 199 { 200 /* 201 * boot_cpu_data.x86_phys_bits is reduced when MKTME or SME are detected 202 * in CPU detection code, but the processor treats those reduced bits as 203 * 'keyID' thus they are not reserved bits. Therefore KVM needs to look at 204 * the physical address bits reported by CPUID. 205 */ 206 if (likely(boot_cpu_data.extended_cpuid_level >= 0x80000008)) 207 return cpuid_eax(0x80000008) & 0xff; 208 209 /* 210 * Quite weird to have VMX or SVM but not MAXPHYADDR; probably a VM with 211 * custom CPUID. Proceed with whatever the kernel found since these features 212 * aren't virtualizable (SME/SEV also require CPUIDs higher than 0x80000008). 213 */ 214 return boot_cpu_data.x86_phys_bits; 215 } 216 217 u64 mark_spte_for_access_track(u64 spte) 218 { 219 if (spte_ad_enabled(spte)) 220 return spte & ~shadow_accessed_mask; 221 222 if (is_access_track_spte(spte)) 223 return spte; 224 225 /* 226 * Making an Access Tracking PTE will result in removal of write access 227 * from the PTE. So, verify that we will be able to restore the write 228 * access in the fast page fault path later on. 229 */ 230 WARN_ONCE((spte & PT_WRITABLE_MASK) && 231 !spte_can_locklessly_be_made_writable(spte), 232 "kvm: Writable SPTE is not locklessly dirty-trackable\n"); 233 234 WARN_ONCE(spte & (SHADOW_ACC_TRACK_SAVED_BITS_MASK << 235 SHADOW_ACC_TRACK_SAVED_BITS_SHIFT), 236 "kvm: Access Tracking saved bit locations are not zero\n"); 237 238 spte |= (spte & SHADOW_ACC_TRACK_SAVED_BITS_MASK) << 239 SHADOW_ACC_TRACK_SAVED_BITS_SHIFT; 240 spte &= ~shadow_acc_track_mask; 241 242 return spte; 243 } 244 245 void kvm_mmu_set_mmio_spte_mask(u64 mmio_value, u64 access_mask) 246 { 247 BUG_ON((u64)(unsigned)access_mask != access_mask); 248 WARN_ON(mmio_value & (shadow_nonpresent_or_rsvd_mask << SHADOW_NONPRESENT_OR_RSVD_MASK_LEN)); 249 WARN_ON(mmio_value & shadow_nonpresent_or_rsvd_lower_gfn_mask); 250 shadow_mmio_value = mmio_value | SPTE_MMIO_MASK; 251 shadow_mmio_access_mask = access_mask; 252 } 253 EXPORT_SYMBOL_GPL(kvm_mmu_set_mmio_spte_mask); 254 255 /* 256 * Sets the shadow PTE masks used by the MMU. 257 * 258 * Assumptions: 259 * - Setting either @accessed_mask or @dirty_mask requires setting both 260 * - At least one of @accessed_mask or @acc_track_mask must be set 261 */ 262 void kvm_mmu_set_mask_ptes(u64 user_mask, u64 accessed_mask, 263 u64 dirty_mask, u64 nx_mask, u64 x_mask, u64 p_mask, 264 u64 acc_track_mask, u64 me_mask) 265 { 266 BUG_ON(!dirty_mask != !accessed_mask); 267 BUG_ON(!accessed_mask && !acc_track_mask); 268 BUG_ON(acc_track_mask & SPTE_SPECIAL_MASK); 269 270 shadow_user_mask = user_mask; 271 shadow_accessed_mask = accessed_mask; 272 shadow_dirty_mask = dirty_mask; 273 shadow_nx_mask = nx_mask; 274 shadow_x_mask = x_mask; 275 shadow_present_mask = p_mask; 276 shadow_acc_track_mask = acc_track_mask; 277 shadow_me_mask = me_mask; 278 } 279 EXPORT_SYMBOL_GPL(kvm_mmu_set_mask_ptes); 280 281 void kvm_mmu_reset_all_pte_masks(void) 282 { 283 u8 low_phys_bits; 284 285 shadow_user_mask = 0; 286 shadow_accessed_mask = 0; 287 shadow_dirty_mask = 0; 288 shadow_nx_mask = 0; 289 shadow_x_mask = 0; 290 shadow_present_mask = 0; 291 shadow_acc_track_mask = 0; 292 293 shadow_phys_bits = kvm_get_shadow_phys_bits(); 294 295 /* 296 * If the CPU has 46 or less physical address bits, then set an 297 * appropriate mask to guard against L1TF attacks. Otherwise, it is 298 * assumed that the CPU is not vulnerable to L1TF. 299 * 300 * Some Intel CPUs address the L1 cache using more PA bits than are 301 * reported by CPUID. Use the PA width of the L1 cache when possible 302 * to achieve more effective mitigation, e.g. if system RAM overlaps 303 * the most significant bits of legal physical address space. 304 */ 305 shadow_nonpresent_or_rsvd_mask = 0; 306 low_phys_bits = boot_cpu_data.x86_phys_bits; 307 if (boot_cpu_has_bug(X86_BUG_L1TF) && 308 !WARN_ON_ONCE(boot_cpu_data.x86_cache_bits >= 309 52 - SHADOW_NONPRESENT_OR_RSVD_MASK_LEN)) { 310 low_phys_bits = boot_cpu_data.x86_cache_bits 311 - SHADOW_NONPRESENT_OR_RSVD_MASK_LEN; 312 shadow_nonpresent_or_rsvd_mask = 313 rsvd_bits(low_phys_bits, boot_cpu_data.x86_cache_bits - 1); 314 } 315 316 shadow_nonpresent_or_rsvd_lower_gfn_mask = 317 GENMASK_ULL(low_phys_bits - 1, PAGE_SHIFT); 318 } 319