virtio-rng: hardware random number generator device

The Linux kernel already has a virtio-rng driver, this is the device
implementation.

When the guest asks for entropy from the virtio hwrng, it puts a buffer
in the vq.  We then put entropy into that buffer, and push it back to
the guest.

Signed-off-by: Amit Shah <amit.shah@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
---
aliguori: converted to new RngBackend interface
aliguori: remove entropy needed event
aliguori: fix migration

1 files changed, 211 insertions, 0 deletions

diff --git a/hw/virtio-rng.c b/hw/virtio-rng.c
new file mode 100644
index 0000000..b7fb5e9
--- /dev/null
+++ b/hw/virtio-rng.c
@@ -0,0 +1,211 @@
+/*
+ * A virtio device implementing a hardware random number generator.
+ *
+ * Copyright 2012 Red Hat, Inc.
+ * Copyright 2012 Amit Shah <amit.shah@redhat.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or
+ * (at your option) any later version.  See the COPYING file in the
+ * top-level directory.
+ */
+
+#include "iov.h"
+#include "qdev.h"
+#include "virtio.h"
+#include "virtio-rng.h"
+#include "qemu/rng.h"
+
+typedef struct VirtIORNG {
+    VirtIODevice vdev;
+
+    DeviceState *qdev;
+
+    /* Only one vq - guest puts buffer(s) on it when it needs entropy */
+    VirtQueue *vq;
+    VirtQueueElement elem;
+
+    /* Config data for the device -- currently only chardev */
+    VirtIORNGConf *conf;
+
+    /* Whether we've popped a vq element into 'elem' above */
+    bool popped;
+
+    RngBackend *rng;
+} VirtIORNG;
+
+static bool is_guest_ready(VirtIORNG *vrng)
+{
+    if (virtio_queue_ready(vrng->vq)
+        && (vrng->vdev.status & VIRTIO_CONFIG_S_DRIVER_OK)) {
+        return true;
+    }
+    return false;
+}
+
+static size_t pop_an_elem(VirtIORNG *vrng)
+{
+    size_t size;
+
+    if (!vrng->popped && !virtqueue_pop(vrng->vq, &vrng->elem)) {
+        return 0;
+    }
+    vrng->popped = true;
+
+    size = iov_size(vrng->elem.in_sg, vrng->elem.in_num);
+    return size;
+}
+
+/* Send data from a char device over to the guest */
+static void chr_read(void *opaque, const void *buf, size_t size)
+{
+    VirtIORNG *vrng = opaque;
+    size_t len;
+    int offset;
+
+    if (!is_guest_ready(vrng)) {
+        return;
+    }
+
+    offset = 0;
+    while (offset < size) {
+        if (!pop_an_elem(vrng)) {
+            break;
+        }
+        len = iov_from_buf(vrng->elem.in_sg, vrng->elem.in_num,
+                           0, buf + offset, size - offset);
+        offset += len;
+
+        virtqueue_push(vrng->vq, &vrng->elem, len);
+        vrng->popped = false;
+    }
+    virtio_notify(&vrng->vdev, vrng->vq);
+
+    /*
+     * Lastly, if we had multiple elems queued by the guest, and we
+     * didn't have enough data to fill them all, indicate we want more
+     * data.
+     */
+    len = pop_an_elem(vrng);
+    if (len) {
+        rng_backend_request_entropy(vrng->rng, size, chr_read, vrng);
+    }
+}
+
+static void handle_input(VirtIODevice *vdev, VirtQueue *vq)
+{
+    VirtIORNG *vrng = DO_UPCAST(VirtIORNG, vdev, vdev);
+    size_t size;
+
+    size = pop_an_elem(vrng);
+    if (size) {
+        rng_backend_request_entropy(vrng->rng, size, chr_read, vrng);
+    }
+}
+
+static uint32_t get_features(VirtIODevice *vdev, uint32_t f)
+{
+    return f;
+}
+
+static void virtio_rng_save(QEMUFile *f, void *opaque)
+{
+    VirtIORNG *vrng = opaque;
+
+    virtio_save(&vrng->vdev, f);
+
+    qemu_put_byte(f, vrng->popped);
+    if (vrng->popped) {
+        int i;
+
+        qemu_put_be32(f, vrng->elem.index);
+
+        qemu_put_be32(f, vrng->elem.in_num);
+        for (i = 0; i < vrng->elem.in_num; i++) {
+            qemu_put_be64(f, vrng->elem.in_addr[i]);
+        }
+
+        qemu_put_be32(f, vrng->elem.out_num);
+        for (i = 0; i < vrng->elem.out_num; i++) {
+            qemu_put_be64(f, vrng->elem.out_addr[i]);
+        }
+    }
+}
+
+static int virtio_rng_load(QEMUFile *f, void *opaque, int version_id)
+{
+    VirtIORNG *vrng = opaque;
+
+    if (version_id != 1) {
+        return -EINVAL;
+    }
+    virtio_load(&vrng->vdev, f);
+
+    vrng->popped = qemu_get_byte(f);
+    if (vrng->popped) {
+        int i;
+
+        vrng->elem.index = qemu_get_be32(f);
+
+        vrng->elem.in_num = qemu_get_be32(f);
+        g_assert(vrng->elem.in_num < VIRTQUEUE_MAX_SIZE);
+        for (i = 0; i < vrng->elem.in_num; i++) {
+            vrng->elem.in_addr[i] = qemu_get_be64(f);
+        }
+
+        vrng->elem.out_num = qemu_get_be32(f);
+        g_assert(vrng->elem.out_num < VIRTQUEUE_MAX_SIZE);
+        for (i = 0; i < vrng->elem.out_num; i++) {
+            vrng->elem.out_addr[i] = qemu_get_be64(f);
+        }
+
+        virtqueue_map_sg(vrng->elem.in_sg, vrng->elem.in_addr,
+                         vrng->elem.in_num, 1);
+        virtqueue_map_sg(vrng->elem.out_sg, vrng->elem.out_addr,
+                         vrng->elem.out_num, 0);
+    }
+    return 0;
+}
+
+VirtIODevice *virtio_rng_init(DeviceState *dev, VirtIORNGConf *conf)
+{
+    VirtIORNG *vrng;
+    VirtIODevice *vdev;
+    Error *local_err = NULL;
+
+    vdev = virtio_common_init("virtio-rng", VIRTIO_ID_RNG, 0,
+                              sizeof(VirtIORNG));
+
+    vrng = DO_UPCAST(VirtIORNG, vdev, vdev);
+
+    vrng->rng = conf->rng;
+    if (vrng->rng == NULL) {
+        qerror_report(QERR_INVALID_PARAMETER_VALUE, "rng", "a valid object");
+        return NULL;
+    }
+
+    rng_backend_open(vrng->rng, &local_err);
+    if (local_err) {
+        qerror_report_err(local_err);
+        error_free(local_err);
+        return NULL;
+    }
+
+    vrng->vq = virtio_add_queue(vdev, 8, handle_input);
+    vrng->vdev.get_features = get_features;
+
+    vrng->qdev = dev;
+    vrng->conf = conf;
+    vrng->popped = false;
+    register_savevm(dev, "virtio-rng", -1, 1, virtio_rng_save,
+                    virtio_rng_load, vrng);
+
+    return vdev;
+}
+
+void virtio_rng_exit(VirtIODevice *vdev)
+{
+    VirtIORNG *vrng = DO_UPCAST(VirtIORNG, vdev, vdev);
+
+    unregister_savevm(vrng->qdev, "virtio-rng", vrng);
+    virtio_cleanup(vdev);
+}