diff options
Diffstat (limited to 'arch/x86/kvm/mmu/spte.c')
| -rw-r--r-- | arch/x86/kvm/mmu/spte.c | 253 |
1 files changed, 163 insertions, 90 deletions
diff --git a/arch/x86/kvm/mmu/spte.c b/arch/x86/kvm/mmu/spte.c index a5e014d7bc62..85a0473809b0 100644 --- a/arch/x86/kvm/mmu/spte.c +++ b/arch/x86/kvm/mmu/spte.c @@ -22,7 +22,9 @@ bool __read_mostly enable_mmio_caching = true; static bool __ro_after_init allow_mmio_caching; module_param_named(mmio_caching, enable_mmio_caching, bool, 0444); -EXPORT_SYMBOL_GPL(enable_mmio_caching); +EXPORT_SYMBOL_FOR_KVM_INTERNAL(enable_mmio_caching); + +bool __read_mostly kvm_ad_enabled; u64 __read_mostly shadow_host_writable_mask; u64 __read_mostly shadow_mmu_writable_mask; @@ -35,7 +37,6 @@ u64 __read_mostly shadow_mmio_value; u64 __read_mostly shadow_mmio_mask; u64 __read_mostly shadow_mmio_access_mask; u64 __read_mostly shadow_present_mask; -u64 __read_mostly shadow_memtype_mask; u64 __read_mostly shadow_me_value; u64 __read_mostly shadow_me_mask; u64 __read_mostly shadow_acc_track_mask; @@ -43,7 +44,25 @@ u64 __read_mostly shadow_acc_track_mask; u64 __read_mostly shadow_nonpresent_or_rsvd_mask; u64 __read_mostly shadow_nonpresent_or_rsvd_lower_gfn_mask; -u8 __read_mostly shadow_phys_bits; +static u8 __init kvm_get_host_maxphyaddr(void) +{ + /* + * boot_cpu_data.x86_phys_bits is reduced when MKTME or SME are detected + * in CPU detection code, but the processor treats those reduced bits as + * 'keyID' thus they are not reserved bits. Therefore KVM needs to look at + * the physical address bits reported by CPUID, i.e. the raw MAXPHYADDR, + * when reasoning about CPU behavior with respect to MAXPHYADDR. + */ + if (likely(boot_cpu_data.extended_cpuid_level >= 0x80000008)) + return cpuid_eax(0x80000008) & 0xff; + + /* + * Quite weird to have VMX or SVM but not MAXPHYADDR; probably a VM with + * custom CPUID. Proceed with whatever the kernel found since these features + * aren't virtualizable (SME/SEV also require CPUIDs higher than 0x80000008). + */ + return boot_cpu_data.x86_phys_bits; +} void __init kvm_mmu_spte_module_init(void) { @@ -55,6 +74,8 @@ void __init kvm_mmu_spte_module_init(void) * will change when the vendor module is (re)loaded. */ allow_mmio_caching = enable_mmio_caching; + + kvm_host.maxphyaddr = kvm_get_host_maxphyaddr(); } static u64 generation_mmio_spte_mask(u64 gen) @@ -74,8 +95,6 @@ u64 make_mmio_spte(struct kvm_vcpu *vcpu, u64 gfn, unsigned int access) u64 spte = generation_mmio_spte_mask(gen); u64 gpa = gfn << PAGE_SHIFT; - WARN_ON_ONCE(!vcpu->kvm->arch.shadow_mmio_value); - access &= shadow_mmio_access_mask; spte |= vcpu->kvm->arch.shadow_mmio_value | access; spte |= gpa | shadow_nonpresent_or_rsvd_mask; @@ -85,7 +104,7 @@ u64 make_mmio_spte(struct kvm_vcpu *vcpu, u64 gfn, unsigned int access) return spte; } -static bool kvm_is_mmio_pfn(kvm_pfn_t pfn) +static bool __kvm_is_mmio_pfn(kvm_pfn_t pfn) { if (pfn_valid(pfn)) return !is_zero_pfn(pfn) && PageReserved(pfn_to_page(pfn)) && @@ -106,42 +125,73 @@ static bool kvm_is_mmio_pfn(kvm_pfn_t pfn) E820_TYPE_RAM); } -/* - * Returns true if the SPTE has bits that may be set without holding mmu_lock. - * The caller is responsible for checking if the SPTE is shadow-present, and - * for determining whether or not the caller cares about non-leaf SPTEs. - */ -bool spte_has_volatile_bits(u64 spte) +static bool kvm_is_mmio_pfn(kvm_pfn_t pfn, int *is_host_mmio) { /* - * Always atomically update spte if it can be updated - * out of mmu-lock, it can ensure dirty bit is not lost, - * also, it can help us to get a stable is_writable_pte() - * to ensure tlb flush is not missed. + * Determining if a PFN is host MMIO is relative expensive. Cache the + * result locally (in the sole caller) to avoid doing the full query + * multiple times when creating a single SPTE. */ + if (*is_host_mmio < 0) + *is_host_mmio = __kvm_is_mmio_pfn(pfn); + + return *is_host_mmio; +} + +static void kvm_track_host_mmio_mapping(struct kvm_vcpu *vcpu) +{ + struct kvm_mmu_page *root = root_to_sp(vcpu->arch.mmu->root.hpa); + + if (root) + WRITE_ONCE(root->has_mapped_host_mmio, true); + else + WRITE_ONCE(vcpu->kvm->arch.has_mapped_host_mmio, true); + + /* + * Force vCPUs to exit and flush CPU buffers if the vCPU is using the + * affected root(s). + */ + kvm_make_all_cpus_request(vcpu->kvm, KVM_REQ_OUTSIDE_GUEST_MODE); +} + +/* + * Returns true if the SPTE needs to be updated atomically due to having bits + * that may be changed without holding mmu_lock, and for which KVM must not + * lose information. E.g. KVM must not drop Dirty bit information. The caller + * is responsible for checking if the SPTE is shadow-present, and for + * determining whether or not the caller cares about non-leaf SPTEs. + */ +bool spte_needs_atomic_update(u64 spte) +{ + /* SPTEs can be made Writable bit by KVM's fast page fault handler. */ if (!is_writable_pte(spte) && is_mmu_writable_spte(spte)) return true; - if (is_access_track_spte(spte)) + /* + * A/D-disabled SPTEs can be access-tracked by aging, and access-tracked + * SPTEs can be restored by KVM's fast page fault handler. + */ + if (!spte_ad_enabled(spte)) return true; - if (spte_ad_enabled(spte)) { - if (!(spte & shadow_accessed_mask) || - (is_writable_pte(spte) && !(spte & shadow_dirty_mask))) - return true; - } - - return false; + /* + * Dirty and Accessed bits can be set by the CPU. Ignore the Accessed + * bit, as KVM tolerates false negatives/positives, e.g. KVM doesn't + * invalidate TLBs when aging SPTEs, and so it's safe to clobber the + * Accessed bit (and rare in practice). + */ + return is_writable_pte(spte) && !(spte & shadow_dirty_mask); } bool make_spte(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp, const struct kvm_memory_slot *slot, unsigned int pte_access, gfn_t gfn, kvm_pfn_t pfn, - u64 old_spte, bool prefetch, bool can_unsync, + u64 old_spte, bool prefetch, bool synchronizing, bool host_writable, u64 *new_spte) { int level = sp->role.level; u64 spte = SPTE_MMU_PRESENT_MASK; + int is_host_mmio = -1; bool wrprot = false; /* @@ -154,12 +204,12 @@ bool make_spte(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp, if (sp->role.ad_disabled) spte |= SPTE_TDP_AD_DISABLED; - else if (kvm_mmu_page_ad_need_write_protect(sp)) + else if (kvm_mmu_page_ad_need_write_protect(vcpu->kvm, sp)) spte |= SPTE_TDP_AD_WRPROT_ONLY; spte |= shadow_present_mask; - if (!prefetch) - spte |= spte_shadow_accessed_mask(spte); + if (!prefetch || synchronizing) + spte |= shadow_accessed_mask; /* * For simplicity, enforce the NX huge page mitigation even if not @@ -189,74 +239,77 @@ bool make_spte(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp, if (level > PG_LEVEL_4K) spte |= PT_PAGE_SIZE_MASK; - if (shadow_memtype_mask) - spte |= static_call(kvm_x86_get_mt_mask)(vcpu, gfn, - kvm_is_mmio_pfn(pfn)); + if (kvm_x86_ops.get_mt_mask) + spte |= kvm_x86_call(get_mt_mask)(vcpu, gfn, + kvm_is_mmio_pfn(pfn, &is_host_mmio)); if (host_writable) spte |= shadow_host_writable_mask; else pte_access &= ~ACC_WRITE_MASK; - if (shadow_me_value && !kvm_is_mmio_pfn(pfn)) + if (shadow_me_value && !kvm_is_mmio_pfn(pfn, &is_host_mmio)) spte |= shadow_me_value; spte |= (u64)pfn << PAGE_SHIFT; if (pte_access & ACC_WRITE_MASK) { - spte |= PT_WRITABLE_MASK | shadow_mmu_writable_mask; - - /* - * Optimization: for pte sync, if spte was writable the hash - * lookup is unnecessary (and expensive). Write protection - * is responsibility of kvm_mmu_get_page / kvm_mmu_sync_roots. - * Same reasoning can be applied to dirty page accounting. - */ - if (is_writable_pte(old_spte)) - goto out; - /* * Unsync shadow pages that are reachable by the new, writable * SPTE. Write-protect the SPTE if the page can't be unsync'd, * e.g. it's write-tracked (upper-level SPs) or has one or more * shadow pages and unsync'ing pages is not allowed. + * + * When overwriting an existing leaf SPTE, and the old SPTE was + * writable, skip trying to unsync shadow pages as any relevant + * shadow pages must already be unsync, i.e. the hash lookup is + * unnecessary (and expensive). Note, this relies on KVM not + * changing PFNs without first zapping the old SPTE, which is + * guaranteed by both the shadow MMU and the TDP MMU. */ - if (mmu_try_to_unsync_pages(vcpu->kvm, slot, gfn, can_unsync, prefetch)) { + if ((!is_last_spte(old_spte, level) || !is_writable_pte(old_spte)) && + mmu_try_to_unsync_pages(vcpu->kvm, slot, gfn, synchronizing, prefetch)) wrprot = true; - pte_access &= ~ACC_WRITE_MASK; - spte &= ~(PT_WRITABLE_MASK | shadow_mmu_writable_mask); - } + else + spte |= PT_WRITABLE_MASK | shadow_mmu_writable_mask | + shadow_dirty_mask; } - if (pte_access & ACC_WRITE_MASK) - spte |= spte_shadow_dirty_mask(spte); - -out: - if (prefetch) + if (prefetch && !synchronizing) spte = mark_spte_for_access_track(spte); WARN_ONCE(is_rsvd_spte(&vcpu->arch.mmu->shadow_zero_check, spte, level), "spte = 0x%llx, level = %d, rsvd bits = 0x%llx", spte, level, get_rsvd_bits(&vcpu->arch.mmu->shadow_zero_check, spte, level)); + /* + * Mark the memslot dirty *after* modifying it for access tracking. + * Unlike folios, memslots can be safely marked dirty out of mmu_lock, + * i.e. in the fast page fault handler. + */ if ((spte & PT_WRITABLE_MASK) && kvm_slot_dirty_track_enabled(slot)) { /* Enforced by kvm_mmu_hugepage_adjust. */ WARN_ON_ONCE(level > PG_LEVEL_4K); mark_page_dirty_in_slot(vcpu->kvm, slot, gfn); } + if (cpu_feature_enabled(X86_FEATURE_CLEAR_CPU_BUF_VM_MMIO) && + !kvm_vcpu_can_access_host_mmio(vcpu) && + kvm_is_mmio_pfn(pfn, &is_host_mmio)) + kvm_track_host_mmio_mapping(vcpu); + *new_spte = spte; return wrprot; } -static u64 make_spte_executable(u64 spte) +static u64 modify_spte_protections(u64 spte, u64 set, u64 clear) { bool is_access_track = is_access_track_spte(spte); if (is_access_track) spte = restore_acc_track_spte(spte); - spte &= ~shadow_nx_mask; - spte |= shadow_x_mask; + KVM_MMU_WARN_ON(set & clear); + spte = (spte | set) & ~clear; if (is_access_track) spte = mark_spte_for_access_track(spte); @@ -264,6 +317,16 @@ static u64 make_spte_executable(u64 spte) return spte; } +static u64 make_spte_executable(u64 spte) +{ + return modify_spte_protections(spte, shadow_x_mask, shadow_nx_mask); +} + +static u64 make_spte_nonexecutable(u64 spte) +{ + return modify_spte_protections(spte, shadow_nx_mask, shadow_x_mask); +} + /* * Construct an SPTE that maps a sub-page of the given huge page SPTE where * `index` identifies which sub-page. @@ -271,18 +334,12 @@ static u64 make_spte_executable(u64 spte) * This is used during huge page splitting to build the SPTEs that make up the * new page table. */ -u64 make_huge_page_split_spte(struct kvm *kvm, u64 huge_spte, union kvm_mmu_page_role role, - int index) +u64 make_small_spte(struct kvm *kvm, u64 huge_spte, + union kvm_mmu_page_role role, int index) { - u64 child_spte; - - if (WARN_ON_ONCE(!is_shadow_present_pte(huge_spte))) - return 0; + u64 child_spte = huge_spte; - if (WARN_ON_ONCE(!is_large_pte(huge_spte))) - return 0; - - child_spte = huge_spte; + KVM_BUG_ON(!is_shadow_present_pte(huge_spte) || !is_large_pte(huge_spte), kvm); /* * The child_spte already has the base address of the huge page being @@ -306,6 +363,26 @@ u64 make_huge_page_split_spte(struct kvm *kvm, u64 huge_spte, union kvm_mmu_page return child_spte; } +u64 make_huge_spte(struct kvm *kvm, u64 small_spte, int level) +{ + u64 huge_spte; + + KVM_BUG_ON(!is_shadow_present_pte(small_spte) || level == PG_LEVEL_4K, kvm); + + huge_spte = small_spte | PT_PAGE_SIZE_MASK; + + /* + * huge_spte already has the address of the sub-page being collapsed + * from small_spte, so just clear the lower address bits to create the + * huge page address. + */ + huge_spte &= KVM_HPAGE_MASK(level) | ~PAGE_MASK; + + if (is_nx_huge_page_enabled(kvm)) + huge_spte = make_spte_nonexecutable(huge_spte); + + return huge_spte; +} u64 make_nonleaf_spte(u64 *child_pt, bool ad_disabled) { @@ -338,7 +415,7 @@ u64 mark_spte_for_access_track(u64 spte) spte |= (spte & SHADOW_ACC_TRACK_SAVED_BITS_MASK) << SHADOW_ACC_TRACK_SAVED_BITS_SHIFT; - spte &= ~shadow_acc_track_mask; + spte &= ~(shadow_acc_track_mask | shadow_accessed_mask); return spte; } @@ -377,13 +454,13 @@ void kvm_mmu_set_mmio_spte_mask(u64 mmio_value, u64 mmio_mask, u64 access_mask) mmio_value = 0; /* - * The masked MMIO value must obviously match itself and a removed SPTE - * must not get a false positive. Removed SPTEs and MMIO SPTEs should - * never collide as MMIO must set some RWX bits, and removed SPTEs must + * The masked MMIO value must obviously match itself and a frozen SPTE + * must not get a false positive. Frozen SPTEs and MMIO SPTEs should + * never collide as MMIO must set some RWX bits, and frozen SPTEs must * not set any RWX bits. */ if (WARN_ON((mmio_value & mmio_mask) != mmio_value) || - WARN_ON(mmio_value && (REMOVED_SPTE & mmio_mask) == mmio_value)) + WARN_ON(mmio_value && (FROZEN_SPTE & mmio_mask) == mmio_value)) mmio_value = 0; if (!mmio_value) @@ -393,7 +470,13 @@ void kvm_mmu_set_mmio_spte_mask(u64 mmio_value, u64 mmio_mask, u64 access_mask) shadow_mmio_mask = mmio_mask; shadow_mmio_access_mask = access_mask; } -EXPORT_SYMBOL_GPL(kvm_mmu_set_mmio_spte_mask); +EXPORT_SYMBOL_FOR_KVM_INTERNAL(kvm_mmu_set_mmio_spte_mask); + +void kvm_mmu_set_mmio_spte_value(struct kvm *kvm, u64 mmio_value) +{ + kvm->arch.shadow_mmio_value = mmio_value; +} +EXPORT_SYMBOL_FOR_KVM_INTERNAL(kvm_mmu_set_mmio_spte_value); void kvm_mmu_set_me_spte_mask(u64 me_value, u64 me_mask) { @@ -404,25 +487,21 @@ void kvm_mmu_set_me_spte_mask(u64 me_value, u64 me_mask) shadow_me_value = me_value; shadow_me_mask = me_mask; } -EXPORT_SYMBOL_GPL(kvm_mmu_set_me_spte_mask); +EXPORT_SYMBOL_FOR_KVM_INTERNAL(kvm_mmu_set_me_spte_mask); void kvm_mmu_set_ept_masks(bool has_ad_bits, bool has_exec_only) { + kvm_ad_enabled = has_ad_bits; + shadow_user_mask = VMX_EPT_READABLE_MASK; - shadow_accessed_mask = has_ad_bits ? VMX_EPT_ACCESS_BIT : 0ull; - shadow_dirty_mask = has_ad_bits ? VMX_EPT_DIRTY_BIT : 0ull; + shadow_accessed_mask = VMX_EPT_ACCESS_BIT; + shadow_dirty_mask = VMX_EPT_DIRTY_BIT; shadow_nx_mask = 0ull; shadow_x_mask = VMX_EPT_EXECUTABLE_MASK; /* VMX_EPT_SUPPRESS_VE_BIT is needed for W or X violation. */ shadow_present_mask = (has_exec_only ? 0ull : VMX_EPT_READABLE_MASK) | VMX_EPT_SUPPRESS_VE_BIT; - /* - * EPT overrides the host MTRRs, and so KVM must program the desired - * memtype directly into the SPTEs. Note, this mask is just the mask - * of all bits that factor into the memtype, the actual memtype must be - * dynamically calculated, e.g. to ensure host MMIO is mapped UC. - */ - shadow_memtype_mask = VMX_EPT_MT_MASK | VMX_EPT_IPAT_BIT; + shadow_acc_track_mask = VMX_EPT_RWX_MASK; shadow_host_writable_mask = EPT_SPTE_HOST_WRITABLE; shadow_mmu_writable_mask = EPT_SPTE_MMU_WRITABLE; @@ -434,14 +513,14 @@ void kvm_mmu_set_ept_masks(bool has_ad_bits, bool has_exec_only) kvm_mmu_set_mmio_spte_mask(VMX_EPT_MISCONFIG_WX_VALUE, VMX_EPT_RWX_MASK | VMX_EPT_SUPPRESS_VE_BIT, 0); } -EXPORT_SYMBOL_GPL(kvm_mmu_set_ept_masks); +EXPORT_SYMBOL_FOR_KVM_INTERNAL(kvm_mmu_set_ept_masks); void kvm_mmu_reset_all_pte_masks(void) { u8 low_phys_bits; u64 mask; - shadow_phys_bits = kvm_get_shadow_phys_bits(); + kvm_ad_enabled = true; /* * If the CPU has 46 or less physical address bits, then set an @@ -474,12 +553,6 @@ void kvm_mmu_reset_all_pte_masks(void) shadow_x_mask = 0; shadow_present_mask = PT_PRESENT_MASK; - /* - * For shadow paging and NPT, KVM uses PAT entry '0' to encode WB - * memtype in the SPTEs, i.e. relies on host MTRRs to provide the - * correct memtype (WB is the "weakest" memtype). - */ - shadow_memtype_mask = 0; shadow_acc_track_mask = 0; shadow_me_mask = 0; shadow_me_value = 0; @@ -494,7 +567,7 @@ void kvm_mmu_reset_all_pte_masks(void) * 52-bit physical addresses then there are no reserved PA bits in the * PTEs and so the reserved PA approach must be disabled. */ - if (shadow_phys_bits < 52) + if (kvm_host.maxphyaddr < 52) mask = BIT_ULL(51) | PT_PRESENT_MASK; else mask = 0; |