diff options
Diffstat (limited to 'drivers/char/hw_random/virtio-rng.c')
| -rw-r--r-- | drivers/char/hw_random/virtio-rng.c | 69 |
1 files changed, 45 insertions, 24 deletions
diff --git a/drivers/char/hw_random/virtio-rng.c b/drivers/char/hw_random/virtio-rng.c index 208c547dcac1..3a194eb3ce8a 100644 --- a/drivers/char/hw_random/virtio-rng.c +++ b/drivers/char/hw_random/virtio-rng.c @@ -4,6 +4,7 @@ * Copyright (C) 2007, 2008 Rusty Russell IBM Corporation */ +#include <asm/barrier.h> #include <linux/err.h> #include <linux/hw_random.h> #include <linux/scatterlist.h> @@ -20,12 +21,12 @@ struct virtrng_info { struct virtqueue *vq; char name[25]; int index; - bool busy; bool hwrng_register_done; bool hwrng_removed; /* data transfer */ struct completion have_data; unsigned int data_avail; + unsigned int data_idx; /* minimal size returned by rng_buffer_size() */ #if SMP_CACHE_BYTES < 32 u8 data[32]; @@ -37,19 +38,23 @@ struct virtrng_info { static void random_recv_done(struct virtqueue *vq) { struct virtrng_info *vi = vq->vdev->priv; + unsigned int len; /* We can get spurious callbacks, e.g. shared IRQs + virtio_pci. */ - if (!virtqueue_get_buf(vi->vq, &vi->data_avail)) + if (!virtqueue_get_buf(vi->vq, &len)) return; + smp_store_release(&vi->data_avail, len); complete(&vi->have_data); } -/* The host will fill any buffer we give it with sweet, sweet randomness. */ -static void register_buffer(struct virtrng_info *vi) +static void request_entropy(struct virtrng_info *vi) { struct scatterlist sg; + reinit_completion(&vi->have_data); + vi->data_idx = 0; + sg_init_one(&sg, vi->data, sizeof(vi->data)); /* There should always be room for one buffer. */ @@ -58,6 +63,18 @@ static void register_buffer(struct virtrng_info *vi) virtqueue_kick(vi->vq); } +static unsigned int copy_data(struct virtrng_info *vi, void *buf, + unsigned int size) +{ + size = min_t(unsigned int, size, vi->data_avail); + memcpy(buf, vi->data + vi->data_idx, size); + vi->data_idx += size; + vi->data_avail -= size; + if (vi->data_avail == 0) + request_entropy(vi); + return size; +} + static int virtio_read(struct hwrng *rng, void *buf, size_t size, bool wait) { int ret; @@ -68,35 +85,37 @@ static int virtio_read(struct hwrng *rng, void *buf, size_t size, bool wait) if (vi->hwrng_removed) return -ENODEV; - if (!vi->busy) { - vi->busy = true; - reinit_completion(&vi->have_data); - register_buffer(vi); + read = 0; + + /* copy available data */ + if (smp_load_acquire(&vi->data_avail)) { + chunk = copy_data(vi, buf, size); + size -= chunk; + read += chunk; } if (!wait) - return 0; + return read; - read = 0; + /* We have already copied available entropy, + * so either size is 0 or data_avail is 0 + */ while (size != 0) { + /* data_avail is 0 but a request is pending */ ret = wait_for_completion_killable(&vi->have_data); if (ret < 0) return ret; + /* if vi->data_avail is 0, we have been interrupted + * by a cleanup, but buffer stays in the queue + */ + if (vi->data_avail == 0) + return read; - chunk = min_t(unsigned int, size, vi->data_avail); - memcpy(buf + read, vi->data, chunk); - read += chunk; + chunk = copy_data(vi, buf + read, size); size -= chunk; - vi->data_avail = 0; - - if (size != 0) { - reinit_completion(&vi->have_data); - register_buffer(vi); - } + read += chunk; } - vi->busy = false; - return read; } @@ -104,8 +123,7 @@ static void virtio_cleanup(struct hwrng *rng) { struct virtrng_info *vi = (struct virtrng_info *)rng->priv; - if (vi->busy) - wait_for_completion(&vi->have_data); + complete(&vi->have_data); } static int probe_common(struct virtio_device *vdev) @@ -141,6 +159,9 @@ static int probe_common(struct virtio_device *vdev) goto err_find; } + /* we always have a pending entropy request */ + request_entropy(vi); + return 0; err_find: @@ -156,9 +177,9 @@ static void remove_common(struct virtio_device *vdev) vi->hwrng_removed = true; vi->data_avail = 0; + vi->data_idx = 0; complete(&vi->have_data); vdev->config->reset(vdev); - vi->busy = false; if (vi->hwrng_register_done) hwrng_unregister(&vi->hwrng); vdev->config->del_vqs(vdev); |