diff --git a/mm/shmem.c b/mm/shmem.c
index 54c213b7b42a..78d07299ef04 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -81,6 +81,7 @@ static struct vfsmount *shm_mnt;
 #include <linux/rmap.h>
 #include <linux/uuid.h>
 #include <linux/memfd.h>
+#include <linux/debugfs.h>
 
 #include <linux/uaccess.h>
 
@@ -3882,6 +3883,85 @@ int shmem_register_guest(struct inode *inode, void *owner,
 	return 0;
 }
 
+static void test_guest_invalidate_page_range(struct inode *inode, void *owner,
+					     pgoff_t start, pgoff_t end)
+{
+	/*
+	 * XXX: We can get here after the owner no longer exists. Need to check
+	 * somehow if the owner is still alive.
+	 */
+
+	printk("invalidate: %#lx-%#lx\n", start, end);
+}
+
+static const struct guest_ops guest_ops = {
+	.invalidate_page_range = test_guest_invalidate_page_range,
+};
+
+#define GUEST_MEM_REGISTER	_IOW('m', 1, int)
+#define GUEST_MEM_UNREGISTER	_IOW('m', 2, int)
+#define GUEST_MEM_GET_PFN	_IOW('m', 3, unsigned long)
+
+static long guest_mem_test_ioctl(struct file *file,
+				 unsigned int cmd, unsigned long arg)
+{
+	static struct file *memfd_file = NULL;
+	static const struct guest_mem_ops *guest_mem_ops = NULL;
+
+	switch (cmd) {
+	case GUEST_MEM_REGISTER: {
+		struct fd memfd = fdget(arg);
+
+		if (memfd_file)
+			return -EBUSY;
+
+		if (!memfd.file)
+			return -EINVAL;
+
+		memfd_file = memfd.file;
+		return memfd_register_guest(memfd_file->f_inode, file,
+					    &guest_ops, &guest_mem_ops);
+	}
+	case GUEST_MEM_UNREGISTER: {
+		if (!memfd_file)
+			return -EINVAL;
+
+		fput(memfd_file);
+		memfd_file = NULL;
+		guest_mem_ops = NULL;
+		return 0;
+	}
+	case GUEST_MEM_GET_PFN: {
+		unsigned long pfn;
+		printk("guest_mem_ops: %px\n", guest_mem_ops);
+		pfn = guest_mem_ops->get_lock_pfn(memfd_file->f_inode, 0);
+		printk("pfn: %#lx\n");
+		if (pfn < 0)
+			return pfn;
+		guest_mem_ops->put_unlock_pfn(pfn);
+		return 0;
+	}
+	default:
+		return -EINVAL;
+	}
+
+	return -EINVAL;
+}
+
+static const struct file_operations guest_mem_test_fops = {
+	.owner	 = THIS_MODULE,
+	.unlocked_ioctl = guest_mem_test_ioctl,
+	.llseek  = no_llseek,
+};
+
+static int __init guest_mem_test(void)
+{
+	debugfs_create_file("guest_mem_test", 0200, NULL, NULL,
+			    &guest_mem_test_fops);
+	return 0;
+}
+late_initcall(guest_mem_test);
+
 static const struct file_operations shmem_file_operations = {
 	.mmap		= shmem_mmap,
 	.get_unmapped_area = shmem_get_unmapped_area,