Re: [RFC v1 7/8] mshv: implement in-kernel device framework

On Fri, Jul 09, 2021 at 01:50:13PM +0000, Wei Liu wrote:

On Fri, Jul 09, 2021 at 02:02:04PM +0100, Matthew Wilcox wrote:

quoted

On Fri, Jul 09, 2021 at 11:43:38AM +0000, Wei Liu wrote:

quoted

+static long
+mshv_partition_ioctl_create_device(struct mshv_partition *partition,
+	void __user *user_args)
+{

[...]

quoted

+	mshv_partition_get(partition);
+	r = anon_inode_getfd(ops->name, &mshv_device_fops, dev, O_RDWR | O_CLOEXEC);
+	if (r < 0) {
+		mshv_partition_put_no_destroy(partition);
+		list_del(&dev->partition_node);
+		ops->destroy(dev);
+		goto out;
+	}
+
+	cd->fd = r;
+	r = 0;

Why return the fd in memory instead of returning the fd as the return
value from the ioctl?

quoted

+	if (copy_to_user(user_args, &tmp, sizeof(tmp))) {
+		r = -EFAULT;
+		goto out;
+	}

... this could then disappear.

Thanks for your comment, Matthew.

This is intentionally because I didn't want to deviate from KVM's API.
The fewer differences the better.

Then don't define your own structure.  Use theirs.