It is more cleaner if we can update pte_access fist then set spte according to pte_access, also introduce gfn_need_write_protect to check whether the gfn need to be write-protected
Signed-off-by: Xiao Guangrong <[email protected]> --- arch/x86/kvm/mmu.c | 109 ++++++++++++++++++++++++++++++++-------------------- 1 files changed, 67 insertions(+), 42 deletions(-) diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c index 4ea731e..49957df 100644 --- a/arch/x86/kvm/mmu.c +++ b/arch/x86/kvm/mmu.c @@ -2329,6 +2329,63 @@ static int mmu_need_write_protect(struct kvm_vcpu *vcpu, gfn_t gfn, return 0; } +static bool gfn_need_write_protect(struct kvm_vcpu *vcpu, u64 *sptep, + int level, gfn_t gfn, bool can_unsync) +{ + /* + * 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(*sptep)) + return false; + + if ((level > PT_PAGE_TABLE_LEVEL && + has_wrprotected_page(vcpu->kvm, gfn, level)) || + mmu_need_write_protect(vcpu, gfn, can_unsync)) + return true; + + return false; +} + +/* The return value indicates whether the @gfn need to be write protected. */ +static bool vcpu_adjust_access(struct kvm_vcpu *vcpu, u64 *sptep, + unsigned *pte_access, int user_fault, + int write_fault, int level, gfn_t gfn, + bool can_unsync, bool host_writable) +{ + bool ret = false; + unsigned access = *pte_access; + + if (!host_writable) + access &= ~ACC_WRITE_MASK; + + if (!(access & ACC_WRITE_MASK) && (!vcpu->arch.mmu.direct_map && + write_fault && !is_write_protection(vcpu) && !user_fault)) { + access |= ACC_WRITE_MASK; + 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)) + access &= ~ACC_EXEC_MASK; + } + + if ((access & ACC_WRITE_MASK) && + gfn_need_write_protect(vcpu, sptep, level, gfn, can_unsync)) { + access &= ~ACC_WRITE_MASK; + ret = true; + } + + *pte_access = access; + return ret; +} + static int set_spte(struct kvm_vcpu *vcpu, u64 *sptep, unsigned pte_access, int user_fault, int write_fault, int level, @@ -2341,6 +2398,9 @@ static int set_spte(struct kvm_vcpu *vcpu, u64 *sptep, if (set_mmio_spte(sptep, gfn, pfn, pte_access)) return 0; + ret = vcpu_adjust_access(vcpu, sptep, &pte_access, user_fault, + write_fault, level, gfn, can_unsync, host_writable); + spte = PT_PRESENT_MASK; if (!speculative) spte |= shadow_accessed_mask; @@ -2353,61 +2413,26 @@ static int set_spte(struct kvm_vcpu *vcpu, u64 *sptep, if (pte_access & ACC_USER_MASK) spte |= shadow_user_mask; + if (pte_access & ACC_WRITE_MASK) { + spte |= PT_WRITABLE_MASK; + spte |= SPTE_MMU_WRITEABLE; + } + if (level > PT_PAGE_TABLE_LEVEL) 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; spte |= (u64)pfn << PAGE_SHIFT; - if ((pte_access & ACC_WRITE_MASK) - || (!vcpu->arch.mmu.direct_map && write_fault - && !is_write_protection(vcpu) && !user_fault)) { - spte |= PT_WRITABLE_MASK | SPTE_MMU_WRITEABLE; - - if (!vcpu->arch.mmu.direct_map - && !(pte_access & ACC_WRITE_MASK)) { - spte &= ~PT_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)) - spte |= PT64_NX_MASK; - } - - /* - * 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(*sptep)) - goto set_pte; - - if ((level > PT_PAGE_TABLE_LEVEL && - has_wrprotected_page(vcpu->kvm, gfn, level)) || - mmu_need_write_protect(vcpu, gfn, can_unsync)) { - pgprintk("%s: found shadow page for %llx, marking ro\n", - __func__, gfn); - ret = 1; - pte_access &= ~ACC_WRITE_MASK; - spte &= ~(PT_WRITABLE_MASK | SPTE_MMU_WRITEABLE); - } - } - - if (pte_access & ACC_WRITE_MASK) + if (is_writable_pte(spte)) mark_page_dirty(vcpu->kvm, gfn); -set_pte: if (mmu_spte_update(sptep, spte)) kvm_flush_remote_tlbs(vcpu->kvm); return ret; -- 1.7.7.6 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
