@@ -1426,7 +1426,7 @@ static void update_memslots(struct kvm_memslots *slots,
 static int check_memory_region_flags(struct kvm *kvm,
 			     const struct kvm_userspace_memory_region_ext *mem)
 {
-	u32 valid_flags = 0;
+	u32 valid_flags = KVM_MEM_FD;
 
 	if (!kvm->dirty_log_unsupported)
 		valid_flags |= KVM_MEM_LOG_DIRTY_PAGES;

@@ -1604,10 +1604,20 @@ static int kvm_set_memslot(struct kvm *kvm,
 		kvm_copy_memslots(slots, __kvm_memslots(kvm, as_id));
 	}
 
+	if (mem->flags & KVM_MEM_FD && change == KVM_MR_CREATE) {
+		r = kvm_memfd_register(kvm, mem, new);
+		if (r)
+			goto out_slots;
+	}
+
 	r = kvm_arch_prepare_memory_region(kvm, new, mem, change);
 	if (r)
 		goto out_slots;
 
+	if (mem->flags & KVM_MEM_FD && (r || change == KVM_MR_DELETE)) {
+		kvm_memfd_unregister(kvm, new);
+	}
+
 	update_memslots(slots, new, change);
 	slots = install_new_memslots(kvm, as_id, slots);
 

@@ -1683,10 +1693,12 @@ int __kvm_set_memory_region(struct kvm *kvm,
 		return -EINVAL;
 	if (mem->guest_phys_addr & (PAGE_SIZE - 1))
 		return -EINVAL;
-	/* We can read the guest memory with __xxx_user() later on. */
 	if ((mem->userspace_addr & (PAGE_SIZE - 1)) ||
-	    (mem->userspace_addr != untagged_addr(mem->userspace_addr)) ||
-	     !access_ok((void __user *)(unsigned long)mem->userspace_addr,
+	    (mem->userspace_addr != untagged_addr(mem->userspace_addr)))
+		return -EINVAL;
+	/* We can read the guest memory with __xxx_user() later on. */
+	if (!(mem->flags & KVM_MEM_FD) &&
+	    !access_ok((void __user *)(unsigned long)mem->userspace_addr,
 			mem->memory_size))
 		return -EINVAL;
 	if (as_id >= KVM_ADDRESS_SPACE_NUM || id >= KVM_MEM_SLOTS_NUM)

@@ -1727,6 +1739,9 @@ int __kvm_set_memory_region(struct kvm *kvm,
 		new.dirty_bitmap = NULL;
 		memset(&new.arch, 0, sizeof(new.arch));
 	} else { /* Modify an existing slot. */
+		/* Private memslots are immutable, they can only be deleted. */
+		if (mem->flags & KVM_MEM_FD && mem->private_fd >= 0)
+			return -EINVAL;
 		if ((new.userspace_addr != old.userspace_addr) ||
 		    (new.npages != old.npages) ||
 		    ((new.flags ^ old.flags) & KVM_MEM_READONLY))