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

[Rusty Russell]

Amos Kong <address@hidden> writes:
> 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.

I never thought anyone would want multiple RNG devices, as it doesn't
seem to make sense.

But why not?

Applied,
Rusty.

>
> ]# 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