On Wed, Sep 13, 2023 at 06:55:16PM -0700, Sean Christopherson wrote:
....
> +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?
> + 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)
> }
>
