1 files changed, 33 insertions, 10 deletions

diff --git a/drivers/char/hw_random/virtio-rng.c b/drivers/char/hw_random/virtio-rng.c
index a90001e02bf7..208c547dcac1 100644
--- a/drivers/char/hw_random/virtio-rng.c
+++ b/drivers/char/hw_random/virtio-rng.c
@@ -18,13 +18,20 @@ static DEFINE_IDA(rng_index_ida);
 struct virtrng_info {
 	struct hwrng hwrng;
 	struct virtqueue *vq;
-	struct completion have_data;
 	char name[25];
-	unsigned int data_avail;
 	int index;
 	bool busy;
 	bool hwrng_register_done;
 	bool hwrng_removed;
+	/* data transfer */
+	struct completion have_data;
+	unsigned int data_avail;
+	/* minimal size returned by rng_buffer_size() */
+#if SMP_CACHE_BYTES < 32
+	u8 data[32];
+#else
+	u8 data[SMP_CACHE_BYTES];
+#endif
 };
 
 static void random_recv_done(struct virtqueue *vq)
@@ -39,14 +46,14 @@ static void random_recv_done(struct virtqueue *vq)
 }
 
 /* The host will fill any buffer we give it with sweet, sweet randomness. */
-static void register_buffer(struct virtrng_info *vi, u8 *buf, size_t size)
+static void register_buffer(struct virtrng_info *vi)
 {
 	struct scatterlist sg;
 
-	sg_init_one(&sg, buf, size);
+	sg_init_one(&sg, vi->data, sizeof(vi->data));
 
 	/* There should always be room for one buffer. */
-	virtqueue_add_inbuf(vi->vq, &sg, 1, buf, GFP_KERNEL);
+	virtqueue_add_inbuf(vi->vq, &sg, 1, vi->data, GFP_KERNEL);
 
 	virtqueue_kick(vi->vq);
 }
@@ -55,6 +62,8 @@ 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;
+	unsigned int chunk;
+	size_t read;
 
 	if (vi->hwrng_removed)
 		return -ENODEV;
@@ -62,19 +71,33 @@ static int virtio_read(struct hwrng *rng, void *buf, size_t size, bool wait)
 	if (!vi->busy) {
 		vi->busy = true;
 		reinit_completion(&vi->have_data);
-		register_buffer(vi, buf, size);
+		register_buffer(vi);
 	}
 
 	if (!wait)
 		return 0;
 
-	ret = wait_for_completion_killable(&vi->have_data);
-	if (ret < 0)
-		return ret;
+	read = 0;
+	while (size != 0) {
+		ret = wait_for_completion_killable(&vi->have_data);
+		if (ret < 0)
+			return ret;
+
+		chunk = min_t(unsigned int, size, vi->data_avail);
+		memcpy(buf + read, vi->data, chunk);
+		read += chunk;
+		size -= chunk;
+		vi->data_avail = 0;
+
+		if (size != 0) {
+			reinit_completion(&vi->have_data);
+			register_buffer(vi);
+		}
+	}
 
 	vi->busy = false;
 
-	return vi->data_avail;
+	return read;
 }
 
 static void virtio_cleanup(struct hwrng *rng)