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Diffstat (limited to '')
| -rw-r--r-- | arch/x86/kvm/mmu/spte.c | 318 |
1 files changed, 318 insertions, 0 deletions
diff --git a/arch/x86/kvm/mmu/spte.c b/arch/x86/kvm/mmu/spte.c new file mode 100644 index 000000000..c51ad544f --- /dev/null +++ b/arch/x86/kvm/mmu/spte.c @@ -0,0 +1,318 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Kernel-based Virtual Machine driver for Linux + * + * Macros and functions to access KVM PTEs (also known as SPTEs) + * + * Copyright (C) 2006 Qumranet, Inc. + * Copyright 2020 Red Hat, Inc. and/or its affiliates. + */ + + +#include <linux/kvm_host.h> +#include "mmu.h" +#include "mmu_internal.h" +#include "x86.h" +#include "spte.h" + +#include <asm/e820/api.h> + +u64 __read_mostly shadow_nx_mask; +u64 __read_mostly shadow_x_mask; /* mutual exclusive with nx_mask */ +u64 __read_mostly shadow_user_mask; +u64 __read_mostly shadow_accessed_mask; +u64 __read_mostly shadow_dirty_mask; +u64 __read_mostly shadow_mmio_value; +u64 __read_mostly shadow_mmio_access_mask; +u64 __read_mostly shadow_present_mask; +u64 __read_mostly shadow_me_mask; +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 u64 generation_mmio_spte_mask(u64 gen) +{ + u64 mask; + + WARN_ON(gen & ~MMIO_SPTE_GEN_MASK); + BUILD_BUG_ON((MMIO_SPTE_GEN_HIGH_MASK | MMIO_SPTE_GEN_LOW_MASK) & SPTE_SPECIAL_MASK); + + mask = (gen << MMIO_SPTE_GEN_LOW_SHIFT) & MMIO_SPTE_GEN_LOW_MASK; + mask |= (gen << MMIO_SPTE_GEN_HIGH_SHIFT) & MMIO_SPTE_GEN_HIGH_MASK; + return mask; +} + +u64 make_mmio_spte(struct kvm_vcpu *vcpu, u64 gfn, unsigned int access) +{ + u64 gen = kvm_vcpu_memslots(vcpu)->generation & MMIO_SPTE_GEN_MASK; + u64 mask = generation_mmio_spte_mask(gen); + u64 gpa = gfn << PAGE_SHIFT; + + access &= shadow_mmio_access_mask; + mask |= shadow_mmio_value | access; + mask |= gpa | shadow_nonpresent_or_rsvd_mask; + mask |= (gpa & shadow_nonpresent_or_rsvd_mask) + << SHADOW_NONPRESENT_OR_RSVD_MASK_LEN; + + return mask; +} + +static bool kvm_is_mmio_pfn(kvm_pfn_t pfn) +{ + if (pfn_valid(pfn)) + return !is_zero_pfn(pfn) && PageReserved(pfn_to_page(pfn)) && + /* + * Some reserved pages, such as those from NVDIMM + * DAX devices, are not for MMIO, and can be mapped + * with cached memory type for better performance. + * However, the above check misconceives those pages + * as MMIO, and results in KVM mapping them with UC + * memory type, which would hurt the performance. + * Therefore, we check the host memory type in addition + * and only treat UC/UC-/WC pages as MMIO. + */ + (!pat_enabled() || pat_pfn_immune_to_uc_mtrr(pfn)); + + return !e820__mapped_raw_any(pfn_to_hpa(pfn), + pfn_to_hpa(pfn + 1) - 1, + E820_TYPE_RAM); +} + +int make_spte(struct kvm_vcpu *vcpu, unsigned int pte_access, int level, + gfn_t gfn, kvm_pfn_t pfn, u64 old_spte, bool speculative, + bool can_unsync, bool host_writable, bool ad_disabled, + u64 *new_spte) +{ + u64 spte = 0; + int ret = 0; + + if (ad_disabled) + spte |= SPTE_AD_DISABLED_MASK; + else if (kvm_vcpu_ad_need_write_protect(vcpu)) + spte |= SPTE_AD_WRPROT_ONLY_MASK; + + /* + * For the EPT case, shadow_present_mask is 0 if hardware + * supports exec-only page table entries. In that case, + * ACC_USER_MASK and shadow_user_mask are used to represent + * read access. See FNAME(gpte_access) in paging_tmpl.h. + */ + spte |= shadow_present_mask; + if (!speculative) + spte |= spte_shadow_accessed_mask(spte); + + if (level > PG_LEVEL_4K && (pte_access & ACC_EXEC_MASK) && + is_nx_huge_page_enabled()) { + pte_access &= ~ACC_EXEC_MASK; + } + + if (pte_access & ACC_EXEC_MASK) + spte |= shadow_x_mask; + else + spte |= shadow_nx_mask; + + if (pte_access & ACC_USER_MASK) + spte |= shadow_user_mask; + + if (level > PG_LEVEL_4K) + spte |= PT_PAGE_SIZE_MASK; + if (tdp_enabled) + spte |= kvm_x86_ops.get_mt_mask(vcpu, gfn, + kvm_is_mmio_pfn(pfn)); + + if (host_writable) + spte |= SPTE_HOST_WRITEABLE; + else + pte_access &= ~ACC_WRITE_MASK; + + if (!kvm_is_mmio_pfn(pfn)) + spte |= shadow_me_mask; + + spte |= (u64)pfn << PAGE_SHIFT; + + if (pte_access & ACC_WRITE_MASK) { + spte |= PT_WRITABLE_MASK | SPTE_MMU_WRITEABLE; + + /* + * Optimization: for pte sync, if spte was writable the hash + * lookup is unnecessary (and expensive). Write protection + * is responsibility of mmu_get_page / kvm_sync_page. + * Same reasoning can be applied to dirty page accounting. + */ + if (!can_unsync && is_writable_pte(old_spte)) + goto out; + + if (mmu_need_write_protect(vcpu, gfn, can_unsync)) { + pgprintk("%s: found shadow page for %llx, marking ro\n", + __func__, gfn); + ret |= SET_SPTE_WRITE_PROTECTED_PT; + pte_access &= ~ACC_WRITE_MASK; + spte &= ~(PT_WRITABLE_MASK | SPTE_MMU_WRITEABLE); + } + } + + if (pte_access & ACC_WRITE_MASK) + spte |= spte_shadow_dirty_mask(spte); + + if (speculative) + spte = mark_spte_for_access_track(spte); + +out: + *new_spte = spte; + return ret; +} + +u64 make_nonleaf_spte(u64 *child_pt, bool ad_disabled) +{ + u64 spte; + + spte = __pa(child_pt) | shadow_present_mask | PT_WRITABLE_MASK | + shadow_user_mask | shadow_x_mask | shadow_me_mask; + + if (ad_disabled) + spte |= SPTE_AD_DISABLED_MASK; + else + spte |= shadow_accessed_mask; + + return spte; +} + +u64 kvm_mmu_changed_pte_notifier_make_spte(u64 old_spte, kvm_pfn_t new_pfn) +{ + u64 new_spte; + + new_spte = old_spte & ~PT64_BASE_ADDR_MASK; + new_spte |= (u64)new_pfn << PAGE_SHIFT; + + new_spte &= ~PT_WRITABLE_MASK; + new_spte &= ~SPTE_HOST_WRITEABLE; + + new_spte = mark_spte_for_access_track(new_spte); + + return new_spte; +} + +static u8 kvm_get_shadow_phys_bits(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. + */ + 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; +} + +u64 mark_spte_for_access_track(u64 spte) +{ + if (spte_ad_enabled(spte)) + return spte & ~shadow_accessed_mask; + + if (is_access_track_spte(spte)) + return spte; + + /* + * Making an Access Tracking PTE will result in removal of write access + * from the PTE. So, verify that we will be able to restore the write + * access in the fast page fault path later on. + */ + WARN_ONCE((spte & PT_WRITABLE_MASK) && + !spte_can_locklessly_be_made_writable(spte), + "kvm: Writable SPTE is not locklessly dirty-trackable\n"); + + WARN_ONCE(spte & (SHADOW_ACC_TRACK_SAVED_BITS_MASK << + SHADOW_ACC_TRACK_SAVED_BITS_SHIFT), + "kvm: Access Tracking saved bit locations are not zero\n"); + + spte |= (spte & SHADOW_ACC_TRACK_SAVED_BITS_MASK) << + SHADOW_ACC_TRACK_SAVED_BITS_SHIFT; + spte &= ~shadow_acc_track_mask; + + return spte; +} + +void kvm_mmu_set_mmio_spte_mask(u64 mmio_value, u64 access_mask) +{ + BUG_ON((u64)(unsigned)access_mask != access_mask); + WARN_ON(mmio_value & (shadow_nonpresent_or_rsvd_mask << SHADOW_NONPRESENT_OR_RSVD_MASK_LEN)); + WARN_ON(mmio_value & shadow_nonpresent_or_rsvd_lower_gfn_mask); + shadow_mmio_value = mmio_value | SPTE_MMIO_MASK; + shadow_mmio_access_mask = access_mask; +} +EXPORT_SYMBOL_GPL(kvm_mmu_set_mmio_spte_mask); + +/* + * Sets the shadow PTE masks used by the MMU. + * + * Assumptions: + * - Setting either @accessed_mask or @dirty_mask requires setting both + * - At least one of @accessed_mask or @acc_track_mask must be set + */ +void kvm_mmu_set_mask_ptes(u64 user_mask, u64 accessed_mask, + u64 dirty_mask, u64 nx_mask, u64 x_mask, u64 p_mask, + u64 acc_track_mask, u64 me_mask) +{ + BUG_ON(!dirty_mask != !accessed_mask); + BUG_ON(!accessed_mask && !acc_track_mask); + BUG_ON(acc_track_mask & SPTE_SPECIAL_MASK); + + shadow_user_mask = user_mask; + shadow_accessed_mask = accessed_mask; + shadow_dirty_mask = dirty_mask; + shadow_nx_mask = nx_mask; + shadow_x_mask = x_mask; + shadow_present_mask = p_mask; + shadow_acc_track_mask = acc_track_mask; + shadow_me_mask = me_mask; +} +EXPORT_SYMBOL_GPL(kvm_mmu_set_mask_ptes); + +void kvm_mmu_reset_all_pte_masks(void) +{ + u8 low_phys_bits; + + shadow_user_mask = 0; + shadow_accessed_mask = 0; + shadow_dirty_mask = 0; + shadow_nx_mask = 0; + shadow_x_mask = 0; + shadow_present_mask = 0; + shadow_acc_track_mask = 0; + + shadow_phys_bits = kvm_get_shadow_phys_bits(); + + /* + * If the CPU has 46 or less physical address bits, then set an + * appropriate mask to guard against L1TF attacks. Otherwise, it is + * assumed that the CPU is not vulnerable to L1TF. + * + * Some Intel CPUs address the L1 cache using more PA bits than are + * reported by CPUID. Use the PA width of the L1 cache when possible + * to achieve more effective mitigation, e.g. if system RAM overlaps + * the most significant bits of legal physical address space. + */ + shadow_nonpresent_or_rsvd_mask = 0; + low_phys_bits = boot_cpu_data.x86_phys_bits; + if (boot_cpu_has_bug(X86_BUG_L1TF) && + !WARN_ON_ONCE(boot_cpu_data.x86_cache_bits >= + 52 - SHADOW_NONPRESENT_OR_RSVD_MASK_LEN)) { + low_phys_bits = boot_cpu_data.x86_cache_bits + - SHADOW_NONPRESENT_OR_RSVD_MASK_LEN; + shadow_nonpresent_or_rsvd_mask = + rsvd_bits(low_phys_bits, boot_cpu_data.x86_cache_bits - 1); + } + + shadow_nonpresent_or_rsvd_lower_gfn_mask = + GENMASK_ULL(low_phys_bits - 1, PAGE_SHIFT); +} |