virtio-rng: support multiple virtio-rng devices

Current hwrng core supports to register multiple hwrng devices,
and there is only one device really works in the same time.
QEMU alsu supports to have multiple virtio-rng backends.

This patch changes virtio-rng driver to support multiple
virtio-rng devices.

]# cat /sys/class/misc/hw_random/rng_available
virtio_rng.0 virtio_rng.1
]# cat /sys/class/misc/hw_random/rng_current
virtio_rng.0
]# echo -n virtio_rng.1 > /sys/class/misc/hw_random/rng_current
]# dd if=/dev/hwrng of=/dev/null

Signed-off-by: Amos Kong <akong@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

1 files changed, 63 insertions, 39 deletions

diff --git a/drivers/char/hw_random/virtio-rng.c b/drivers/char/hw_random/virtio-rng.c
index 2ce0e225e58c..12e242bbb0f5 100644
--- a/drivers/char/hw_random/virtio-rng.c
+++ b/drivers/char/hw_random/virtio-rng.c
@@ -25,88 +25,108 @@
 #include <linux/virtio_rng.h>
 #include <linux/module.h>
 
-static struct virtqueue *vq;
-static unsigned int data_avail;
-static DECLARE_COMPLETION(have_data);
-static bool busy;
+
+struct virtrng_info {
+        struct virtio_device *vdev;
+        struct hwrng hwrng;
+        struct virtqueue *vq;
+        unsigned int data_avail;
+        struct completion have_data;
+        bool busy;
+};
 
 static void random_recv_done(struct virtqueue *vq)
 {
+        struct virtrng_info *vi = vq->vdev->priv;
+
         /* We can get spurious callbacks, e.g. shared IRQs + virtio_pci. */
-        if (!virtqueue_get_buf(vq, &data_avail))
+        if (!virtqueue_get_buf(vi->vq, &vi->data_avail))
                 return;
 
-        complete(&have_data);
+        complete(&vi->have_data);
 }
 
 /* The host will fill any buffer we give it with sweet, sweet randomness. */
-static void register_buffer(u8 *buf, size_t size)
+static void register_buffer(struct virtrng_info *vi, u8 *buf, size_t size)
 {
         struct scatterlist sg;
 
         sg_init_one(&sg, buf, size);
 
         /* There should always be room for one buffer. */
-        virtqueue_add_inbuf(vq, &sg, 1, buf, GFP_KERNEL);
+        virtqueue_add_inbuf(vi->vq, &sg, 1, buf, GFP_KERNEL);
 
-        virtqueue_kick(vq);
+        virtqueue_kick(vi->vq);
 }
 
 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;
 
-        if (!busy) {
-                busy = true;
-                init_completion(&have_data);
-                register_buffer(buf, size);
+        if (!vi->busy) {
+                vi->busy = true;
+                init_completion(&vi->have_data);
+                register_buffer(vi, buf, size);
         }
 
         if (!wait)
                 return 0;
 
-        ret = wait_for_completion_killable(&have_data);
+        ret = wait_for_completion_killable(&vi->have_data);
         if (ret < 0)
                 return ret;
 
-        busy = false;
+        vi->busy = false;
 
-        return data_avail;
+        return vi->data_avail;
 }
 
 static void virtio_cleanup(struct hwrng *rng)
 {
-        if (busy)
-                wait_for_completion(&have_data);
-}
-
+        struct virtrng_info *vi = (struct virtrng_info *)rng->priv;
 
-static struct hwrng virtio_hwrng = {
-        .name           = "virtio",
-        .cleanup        = virtio_cleanup,
-        .read           = virtio_read,
-};
+        if (vi->busy)
+                wait_for_completion(&vi->have_data);
+}
 
 static int probe_common(struct virtio_device *vdev)
 {
-        int err;
+        int err, i;
+        struct virtrng_info *vi = NULL;
+
+        vi = kmalloc(sizeof(struct virtrng_info), GFP_KERNEL);
+        vi->hwrng.name = kmalloc(40, GFP_KERNEL);
+        init_completion(&vi->have_data);
+
+        vi->hwrng.read = virtio_read;
+        vi->hwrng.cleanup = virtio_cleanup;
+        vi->hwrng.priv = (unsigned long)vi;
+        vdev->priv = vi;
 
-        if (vq) {
-                /* We only support one device for now */
-                return -EBUSY;
-        }
         /* We expect a single virtqueue. */
-        vq = virtio_find_single_vq(vdev, random_recv_done, "input");
-        if (IS_ERR(vq)) {
-                err = PTR_ERR(vq);
-                vq = NULL;
+        vi->vq = virtio_find_single_vq(vdev, random_recv_done, "input");
+        if (IS_ERR(vi->vq)) {
+                err = PTR_ERR(vi->vq);
+                kfree(vi->hwrng.name);
+                vi->vq = NULL;
+                kfree(vi);
+                vi = NULL;
                 return err;
         }
 
-        err = hwrng_register(&virtio_hwrng);
+        i = 0;
+        do {
+                sprintf(vi->hwrng.name, "virtio_rng.%d", i++);
+                err = hwrng_register(&vi->hwrng);
+        } while (err == -EEXIST);
+
         if (err) {
                 vdev->config->del_vqs(vdev);
-                vq = NULL;
+                kfree(vi->hwrng.name);
+                vi->vq = NULL;
+                kfree(vi);
+                vi = NULL;
                 return err;
         }
 
@@ -115,11 +135,15 @@ static int probe_common(struct virtio_device *vdev)
 
 static void remove_common(struct virtio_device *vdev)
 {
+        struct virtrng_info *vi = vdev->priv;
         vdev->config->reset(vdev);
-        busy = false;
-        hwrng_unregister(&virtio_hwrng);
+        vi->busy = false;
+        hwrng_unregister(&vi->hwrng);
         vdev->config->del_vqs(vdev);
-        vq = NULL;
+        kfree(vi->hwrng.name);
+        vi->vq = NULL;
+        kfree(vi);
+        vi = NULL;
 }
 
 static int virtrng_probe(struct virtio_device *vdev)