Revert "hwrng: virtio - ensure reads happen after successful probe"

This reverts commit e052dbf554.

Now that we use the virtio ->scan() function to register with the hwrng
core, we will not get read requests till probe is successfully finished.

So revert the workaround we had in place to refuse read requests while
we were not yet setup completely.

Signed-off-by: Amit Shah <amit.shah@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

drivers/char/hw_random/core.c

@@ -68,12 +68,6 @@ static void add_early_randomness(struct hwrng *rng)
 	unsigned char bytes[16];
 	int bytes_read;
 
-	/*
-	 * Currently only virtio-rng cannot return data during device
-	 * probe, and that's handled in virtio-rng.c itself.  If there
-	 * are more such devices, this call to rng_get_data can be
-	 * made conditional here instead of doing it per-device.
-	 */
 	bytes_read = rng_get_data(rng, bytes, sizeof(bytes), 1);
 	if (bytes_read > 0)
 		add_device_randomness(bytes, bytes_read);

drivers/char/hw_random/virtio-rng.c

@@ -38,7 +38,6 @@ struct virtrng_info {
 	bool hwrng_register_done;
 };
 
-static bool probe_done;
 
 static void random_recv_done(struct virtqueue *vq)
 {
@@ -69,13 +68,6 @@ static int virtio_read(struct hwrng *rng, void *buf, size_t size, bool wait)
 	int ret;
 	struct virtrng_info *vi = (struct virtrng_info *)rng->priv;
 
-	/*
-	 * Don't ask host for data till we're setup.  This call can
-	 * happen during hwrng_register(), after commit d9e7972619.
-	 */
-	if (unlikely(!probe_done))
-		return 0;
-
 	if (!vi->busy) {
 		vi->busy = true;
 		init_completion(&vi->have_data);
@@ -137,7 +129,6 @@ static int probe_common(struct virtio_device *vdev)
 		return err;
 	}
 
-	probe_done = true;
 	return 0;
 }