Re: [RFC PATCH v12 18/33] KVM: x86/mmu: Handle page fault for private memory
From: Yan Zhao <hidden>
Date: 2023-09-15 06:14:41
Also in:
kvm, kvm-riscv, kvmarm, linux-arm-kernel, linux-fsdevel, linux-mips, linux-mm, linux-riscv, linuxppc-dev, lkml
On Wed, Sep 13, 2023 at 06:55:16PM -0700, Sean Christopherson wrote: ....
quoted hunk ↗ jump to hunk
+static void kvm_mmu_prepare_memory_fault_exit(struct kvm_vcpu *vcpu, + struct kvm_page_fault *fault) +{ + kvm_prepare_memory_fault_exit(vcpu, fault->gfn << PAGE_SHIFT, + PAGE_SIZE, fault->write, fault->exec, + fault->is_private); +} + +static int kvm_faultin_pfn_private(struct kvm_vcpu *vcpu, + struct kvm_page_fault *fault) +{ + int max_order, r; + + if (!kvm_slot_can_be_private(fault->slot)) { + kvm_mmu_prepare_memory_fault_exit(vcpu, fault); + return -EFAULT; + } + + r = kvm_gmem_get_pfn(vcpu->kvm, fault->slot, fault->gfn, &fault->pfn, + &max_order); + if (r) { + kvm_mmu_prepare_memory_fault_exit(vcpu, fault); + return r; + } + + fault->max_level = min(kvm_max_level_for_order(max_order), + fault->max_level); + fault->map_writable = !(fault->slot->flags & KVM_MEM_READONLY); + + return RET_PF_CONTINUE; +} + static int __kvm_faultin_pfn(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault) { struct kvm_memory_slot *slot = fault->slot;@@ -4293,6 +4356,14 @@ static int __kvm_faultin_pfn(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault return RET_PF_EMULATE; } + if (fault->is_private != kvm_mem_is_private(vcpu->kvm, fault->gfn)) {
In patch 21, fault->is_private is set as: ".is_private = kvm_mem_is_private(vcpu->kvm, cr2_or_gpa >> PAGE_SHIFT)", then, the inequality here means memory attribute has been updated after last check. So, why an exit to user space for converting is required instead of a mere retry? Or, is it because how .is_private is assigned in patch 21 is subjected to change in future?
quoted hunk ↗ jump to hunk
+ kvm_mmu_prepare_memory_fault_exit(vcpu, fault); + return -EFAULT; + } + + if (fault->is_private) + return kvm_faultin_pfn_private(vcpu, fault); + async = false; fault->pfn = __gfn_to_pfn_memslot(slot, fault->gfn, false, false, &async, fault->write, &fault->map_writable,@@ -7184,6 +7255,19 @@ void kvm_mmu_pre_destroy_vm(struct kvm *kvm) }