diff options
Diffstat (limited to 'arch/x86/kvm/mmu.h')
| -rw-r--r-- | arch/x86/kvm/mmu.h | 77 |
1 files changed, 69 insertions, 8 deletions
diff --git a/arch/x86/kvm/mmu.h b/arch/x86/kvm/mmu.h index 29261527435..b982112d2ca 100644 --- a/arch/x86/kvm/mmu.h +++ b/arch/x86/kvm/mmu.h @@ -44,11 +44,17 @@ #define PT_DIRECTORY_LEVEL 2 #define PT_PAGE_TABLE_LEVEL 1 -#define PFERR_PRESENT_MASK (1U << 0) -#define PFERR_WRITE_MASK (1U << 1) -#define PFERR_USER_MASK (1U << 2) -#define PFERR_RSVD_MASK (1U << 3) -#define PFERR_FETCH_MASK (1U << 4) +#define PFERR_PRESENT_BIT 0 +#define PFERR_WRITE_BIT 1 +#define PFERR_USER_BIT 2 +#define PFERR_RSVD_BIT 3 +#define PFERR_FETCH_BIT 4 + +#define PFERR_PRESENT_MASK (1U << PFERR_PRESENT_BIT) +#define PFERR_WRITE_MASK (1U << PFERR_WRITE_BIT) +#define PFERR_USER_MASK (1U << PFERR_USER_BIT) +#define PFERR_RSVD_MASK (1U << PFERR_RSVD_BIT) +#define PFERR_FETCH_MASK (1U << PFERR_FETCH_BIT) int kvm_mmu_get_spte_hierarchy(struct kvm_vcpu *vcpu, u64 addr, u64 sptes[4]); void kvm_mmu_set_mmio_spte_mask(u64 mmio_mask); @@ -73,6 +79,8 @@ int handle_mmio_page_fault_common(struct kvm_vcpu *vcpu, u64 addr, bool direct); void kvm_init_shadow_mmu(struct kvm_vcpu *vcpu, struct kvm_mmu *context); void kvm_init_shadow_ept_mmu(struct kvm_vcpu *vcpu, struct kvm_mmu *context, bool execonly); +void update_permission_bitmask(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu, + bool ept); static inline unsigned int kvm_mmu_available_pages(struct kvm *kvm) { @@ -96,6 +104,39 @@ static inline int is_present_gpte(unsigned long pte) return pte & PT_PRESENT_MASK; } +/* + * Currently, we have two sorts of write-protection, a) the first one + * write-protects guest page to sync the guest modification, b) another one is + * used to sync dirty bitmap when we do KVM_GET_DIRTY_LOG. The differences + * between these two sorts are: + * 1) the first case clears SPTE_MMU_WRITEABLE bit. + * 2) the first case requires flushing tlb immediately avoiding corrupting + * shadow page table between all vcpus so it should be in the protection of + * mmu-lock. And the another case does not need to flush tlb until returning + * the dirty bitmap to userspace since it only write-protects the page + * logged in the bitmap, that means the page in the dirty bitmap is not + * missed, so it can flush tlb out of mmu-lock. + * + * So, there is the problem: the first case can meet the corrupted tlb caused + * by another case which write-protects pages but without flush tlb + * immediately. In order to making the first case be aware this problem we let + * it flush tlb if we try to write-protect a spte whose SPTE_MMU_WRITEABLE bit + * is set, it works since another case never touches SPTE_MMU_WRITEABLE bit. + * + * Anyway, whenever a spte is updated (only permission and status bits are + * changed) we need to check whether the spte with SPTE_MMU_WRITEABLE becomes + * readonly, if that happens, we need to flush tlb. Fortunately, + * mmu_spte_update() has already handled it perfectly. + * + * The rules to use SPTE_MMU_WRITEABLE and PT_WRITABLE_MASK: + * - if we want to see if it has writable tlb entry or if the spte can be + * writable on the mmu mapping, check SPTE_MMU_WRITEABLE, this is the most + * case, otherwise + * - if we fix page fault on the spte or do write-protection by dirty logging, + * check PT_WRITABLE_MASK. + * + * TODO: introduce APIs to split these two cases. + */ static inline int is_writable_pte(unsigned long pte) { return pte & PT_WRITABLE_MASK; @@ -110,10 +151,30 @@ static inline bool is_write_protection(struct kvm_vcpu *vcpu) * Will a fault with a given page-fault error code (pfec) cause a permission * fault with the given access (in ACC_* format)? */ -static inline bool permission_fault(struct kvm_mmu *mmu, unsigned pte_access, - unsigned pfec) +static inline bool permission_fault(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu, + unsigned pte_access, unsigned pfec) { - return (mmu->permissions[pfec >> 1] >> pte_access) & 1; + int cpl = kvm_x86_ops->get_cpl(vcpu); + unsigned long rflags = kvm_x86_ops->get_rflags(vcpu); + + /* + * If CPL < 3, SMAP prevention are disabled if EFLAGS.AC = 1. + * + * If CPL = 3, SMAP applies to all supervisor-mode data accesses + * (these are implicit supervisor accesses) regardless of the value + * of EFLAGS.AC. + * + * This computes (cpl < 3) && (rflags & X86_EFLAGS_AC), leaving + * the result in X86_EFLAGS_AC. We then insert it in place of + * the PFERR_RSVD_MASK bit; this bit will always be zero in pfec, + * but it will be one in index if SMAP checks are being overridden. + * It is important to keep this branchless. + */ + unsigned long smap = (cpl - 3) & (rflags & X86_EFLAGS_AC); + int index = (pfec >> 1) + + (smap >> (X86_EFLAGS_AC_BIT - PFERR_RSVD_BIT + 1)); + + return (mmu->permissions[index] >> pte_access) & 1; } void kvm_mmu_invalidate_zap_all_pages(struct kvm *kvm); |