1 files changed, 79 insertions, 2 deletions

diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c
index 7d85cc33c0bb..08a6bc7d25b6 100644
--- a/virt/kvm/guest_memfd.c
+++ b/virt/kvm/guest_memfd.c
@@ -312,7 +312,74 @@ static pgoff_t kvm_gmem_get_index(struct kvm_memory_slot *slot, gfn_t gfn)
 	return gfn - slot->base_gfn + slot->gmem.pgoff;
 }
 
+static bool kvm_gmem_supports_mmap(struct inode *inode)
+{
+	const u64 flags = (u64)inode->i_private;
+
+	return flags & GUEST_MEMFD_FLAG_MMAP;
+}
+
+static vm_fault_t kvm_gmem_fault_user_mapping(struct vm_fault *vmf)
+{
+	struct inode *inode = file_inode(vmf->vma->vm_file);
+	struct folio *folio;
+	vm_fault_t ret = VM_FAULT_LOCKED;
+
+	if (((loff_t)vmf->pgoff << PAGE_SHIFT) >= i_size_read(inode))
+		return VM_FAULT_SIGBUS;
+
+	folio = kvm_gmem_get_folio(inode, vmf->pgoff);
+	if (IS_ERR(folio)) {
+		int err = PTR_ERR(folio);
+
+		if (err == -EAGAIN)
+			return VM_FAULT_RETRY;
+
+		return vmf_error(err);
+	}
+
+	if (WARN_ON_ONCE(folio_test_large(folio))) {
+		ret = VM_FAULT_SIGBUS;
+		goto out_folio;
+	}
+
+	if (!folio_test_uptodate(folio)) {
+		clear_highpage(folio_page(folio, 0));
+		kvm_gmem_mark_prepared(folio);
+	}
+
+	vmf->page = folio_file_page(folio, vmf->pgoff);
+
+out_folio:
+	if (ret != VM_FAULT_LOCKED) {
+		folio_unlock(folio);
+		folio_put(folio);
+	}
+
+	return ret;
+}
+
+static const struct vm_operations_struct kvm_gmem_vm_ops = {
+	.fault = kvm_gmem_fault_user_mapping,
+};
+
+static int kvm_gmem_mmap(struct file *file, struct vm_area_struct *vma)
+{
+	if (!kvm_gmem_supports_mmap(file_inode(file)))
+		return -ENODEV;
+
+	if ((vma->vm_flags & (VM_SHARED | VM_MAYSHARE)) !=
+	    (VM_SHARED | VM_MAYSHARE)) {
+		return -EINVAL;
+	}
+
+	vma->vm_ops = &kvm_gmem_vm_ops;
+
+	return 0;
+}
+
 static struct file_operations kvm_gmem_fops = {
+	.mmap		= kvm_gmem_mmap,
 	.open		= generic_file_open,
 	.release	= kvm_gmem_release,
 	.fallocate	= kvm_gmem_fallocate,
@@ -391,6 +458,11 @@ static const struct inode_operations kvm_gmem_iops = {
 	.setattr	= kvm_gmem_setattr,
 };
 
+bool __weak kvm_arch_supports_gmem_mmap(struct kvm *kvm)
+{
+	return true;
+}
+
 static int __kvm_gmem_create(struct kvm *kvm, loff_t size, u64 flags)
 {
 	const char *anon_name = "[kvm-gmem]";
@@ -452,6 +524,9 @@ int kvm_gmem_create(struct kvm *kvm, struct kvm_create_guest_memfd *args)
 	u64 flags = args->flags;
 	u64 valid_flags = 0;
 
+	if (kvm_arch_supports_gmem_mmap(kvm))
+		valid_flags |= GUEST_MEMFD_FLAG_MMAP;
+
 	if (flags & ~valid_flags)
 		return -EINVAL;
 
@@ -508,6 +583,8 @@ int kvm_gmem_bind(struct kvm *kvm, struct kvm_memory_slot *slot,
 	 */
 	WRITE_ONCE(slot->gmem.file, file);
 	slot->gmem.pgoff = start;
+	if (kvm_gmem_supports_mmap(inode))
+		slot->flags |= KVM_MEMSLOT_GMEM_ONLY;
 
 	xa_store_range(&gmem->bindings, start, end - 1, slot, GFP_KERNEL);
 	filemap_invalidate_unlock(inode->i_mapping);
@@ -627,7 +704,7 @@ out:
 }
 EXPORT_SYMBOL_GPL(kvm_gmem_get_pfn);
 
-#ifdef CONFIG_KVM_GENERIC_PRIVATE_MEM
+#ifdef CONFIG_HAVE_KVM_ARCH_GMEM_POPULATE
 long kvm_gmem_populate(struct kvm *kvm, gfn_t start_gfn, void __user *src, long npages,
 		       kvm_gmem_populate_cb post_populate, void *opaque)
 {
@@ -643,7 +720,7 @@ long kvm_gmem_populate(struct kvm *kvm, gfn_t start_gfn, void __user *src, long
 		return -EINVAL;
 
 	slot = gfn_to_memslot(kvm, start_gfn);
-	if (!kvm_slot_can_be_private(slot))
+	if (!kvm_slot_has_gmem(slot))
 		return -EINVAL;
 
 	file = kvm_gmem_get_file(slot);