[Qemu-devel] [PATCH] virtio-rng: support multiple virtio-rng devices

[Amos Kong]

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 <address@hidden>
---
 drivers/char/hw_random/virtio-rng.c | 102 ++++++++++++++++++++++--------------
 include/linux/hw_random.h           |   2 +-
 2 files changed, 64 insertions(+), 40 deletions(-)

diff --git a/drivers/char/hw_random/virtio-rng.c 
b/drivers/char/hw_random/virtio-rng.c
index 2ce0e22..12e242b 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)
diff --git a/include/linux/hw_random.h b/include/linux/hw_random.h
index b4b0eef..02d9c87 100644
--- a/include/linux/hw_random.h
+++ b/include/linux/hw_random.h
@@ -31,7 +31,7 @@
  * @priv:              Private data, for use by the RNG driver.
  */
 struct hwrng {
-       const char *name;
+       char *name;
        int (*init)(struct hwrng *rng);
        void (*cleanup)(struct hwrng *rng);
        int (*data_present)(struct hwrng *rng, int wait);
-- 
1.9.0