Re: [Qemu-devel] [PATCH 2/2] VirtIO RNG

[Ian Molton]

>From 5f484301d73fa53009bbcd430f8ae85868b67772 Mon Sep 17 00:00:00 2001
From: Ian Molton <address@hidden>
Date: Tue, 17 Nov 2009 14:34:12 +0000
Subject: [PATCH 2/4] virtio: Add virtio-rng driver

        This patch adds support for virtio-rng. Data is read from a chardev and
can be either raw entropy or received via the EGD protocol.

Signed-off-by: Ian Molton <address@hidden>
---
 Makefile.target |    2 +-
 hw/pci.h        |    1 +
 hw/virtio-pci.c |   29 ++++++++
 hw/virtio-rng.c |  195
+++++++++++++++++++++++++++++++++++++++++++++++++++++++
 hw/virtio-rng.h |   19 ++++++
 hw/virtio.h     |    2 +
 rng.h           |   14 ++++
 7 files changed, 261 insertions(+), 1 deletions(-)
 create mode 100644 hw/virtio-rng.c
 create mode 100644 hw/virtio-rng.h
 create mode 100644 rng.h

diff --git a/Makefile.target b/Makefile.target
index 16ea443..2f9c929 100644
--- a/Makefile.target
+++ b/Makefile.target
@@ -166,7 +166,7 @@ obj-y += qemu-timer.o
 # virtio has to be here due to weird dependency between PCI and virtio-net.
 # need to fix this properly
 obj-y += virtio-blk.o virtio-balloon.o virtio-net.o virtio-serial-bus.o
-obj-y += rwhandler.o
+obj-y += virtio-rng.o rwhandler.o
 obj-$(CONFIG_KVM) += kvm.o kvm-all.o
 LIBS+=-lz

diff --git a/hw/pci.h b/hw/pci.h
index 20c670e..dc61cb5 100644
--- a/hw/pci.h
+++ b/hw/pci.h
@@ -69,6 +69,7 @@
 #define PCI_DEVICE_ID_VIRTIO_BLOCK       0x1001
 #define PCI_DEVICE_ID_VIRTIO_BALLOON     0x1002
 #define PCI_DEVICE_ID_VIRTIO_CONSOLE     0x1003
+#define PCI_DEVICE_ID_VIRTIO_RNG         0x1004

 #define FMT_PCIBUS                      PRIx64

diff --git a/hw/virtio-pci.c b/hw/virtio-pci.c
index 6eb19cd..bee3105 100644
--- a/hw/virtio-pci.c
+++ b/hw/virtio-pci.c
@@ -23,6 +23,7 @@
 #include "msix.h"
 #include "net.h"
 #include "block_int.h"
+#include "rng.h"
 #include "loader.h"

 /* from Linux's linux/virtio_pci.h */
@@ -95,6 +96,7 @@ typedef struct {
     uint32_t nvectors;
     BlockConf block;
     NICConf nic;
+    RNGConf rng;
     uint32_t host_features;
     /* Max. number of ports we can have for a the virtio-serial device */
     uint32_t max_virtserial_ports;
@@ -552,6 +554,21 @@ static int virtio_balloon_init_pci(PCIDevice *pci_dev)
     return 0;
 }

+static int virtio_rng_init_pci(PCIDevice *pci_dev)
+{
+    VirtIOPCIProxy *proxy = DO_UPCAST(VirtIOPCIProxy, pci_dev, pci_dev);
+    VirtIODevice *vdev;
+
+    vdev = virtio_rng_init(&pci_dev->qdev, &proxy->rng);
+    virtio_init_pci(proxy, vdev,
+                    PCI_VENDOR_ID_REDHAT_QUMRANET,
+                    PCI_DEVICE_ID_VIRTIO_RNG,
+                    PCI_CLASS_OTHERS,
+                    0x00);
+
+    return 0;
+}
+
 static PCIDeviceInfo virtio_info[] = {
     {
         .qdev.name = "virtio-blk-pci",
@@ -606,6 +623,18 @@ static PCIDeviceInfo virtio_info[] = {
         },
         .qdev.reset = virtio_pci_reset,
     },{
+        .qdev.name = "virtio-rng-pci",
+        .qdev.size = sizeof(VirtIOPCIProxy),
+        .init      = virtio_rng_init_pci,
+        .exit      = virtio_exit_pci,
+        .qdev.props = (Property[]) {
+            DEFINE_PROP_CHR("chardev",     VirtIOPCIProxy, rng.chrdev),
+            DEFINE_PROP_SIZE("rate",       VirtIOPCIProxy, rng.rate, 0),
+            DEFINE_PROP_STRING("protocol", VirtIOPCIProxy, rng.proto),
+            DEFINE_PROP_END_OF_LIST(),
+        },
+        .qdev.reset = virtio_pci_reset,
+    },{
         /* end of list */
     }
 };
diff --git a/hw/virtio-rng.c b/hw/virtio-rng.c
new file mode 100644
index 0000000..154ea76
--- /dev/null
+++ b/hw/virtio-rng.c
@@ -0,0 +1,195 @@
+/*
+ * Virtio RNG Device
+ *
+ * Copyright Collabora 2009
+ *
+ * Authors:
+ *  Ian Molton <address@hidden>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2.  See
+ * the COPYING file in the top-level directory.
+ *
+ */
+
+#include "hw.h"
+#include "qemu-char.h"
+#include "virtio.h"
+#include "virtio-rng.h"
+#include "rng.h"
+#include <sys/time.h>
+
+typedef struct VirtIORng
+{
+    VirtIODevice vdev;
+    VirtQueue *vq;
+    CharDriverState *chr;
+    struct timeval last;
+    int rate;
+    int egd;
+    int entropy_remaining;
+    int pool;
+} VirtIORng;
+
+/* Maximum size of the buffer the guest expects */
+#define BUFF_MAX 64
+
+/* EGD protocol - we only use this command */
+#define EGD_READ_BLOCK 0x2
+
+#define EGD_MAX_BLOCK_SIZE 255
+#define EGD_MAX_REQUESTS 3
+#define EGD_MAX_POOL_SIZE (EGD_MAX_BLOCK_SIZE * (EGD_MAX_REQUESTS-1))
+
+static inline void req_entropy(VirtIORng *s)
+{
+    static const unsigned char entropy_rq[2] = { EGD_READ_BLOCK,
+                                                 EGD_MAX_BLOCK_SIZE };
+    if (s->egd) {
+        /* Let the socket buffer up the incoming data for us. Max block
size
+           for EGD protocol is (stupidly) 255, so make sure we always
have a
+           block pending for performance. We can have 3 outstanding
buffers */
+        if (s->pool <= EGD_MAX_POOL_SIZE) {
+            s->chr->chr_write(s->chr, entropy_rq, sizeof(entropy_rq));
+            s->pool += EGD_MAX_BLOCK_SIZE;
+        }
+    } else {
+        s->pool = BUFF_MAX;
+    }
+}
+
+static int vrng_can_read(void *opaque)
+{
+    VirtIORng *s = (VirtIORng *) opaque;
+    struct timeval now, d;
+    int max_entropy;
+
+    if (!virtio_queue_ready(s->vq) ||
+        !(s->vdev.status & VIRTIO_CONFIG_S_DRIVER_OK) ||
+        virtio_queue_empty(s->vq))
+        return 0;
+
+    req_entropy(s);
+
+    if (s->rate) {
+        qemu_gettimeofday(&now);
+        timersub(&now, &s->last, &d);
+        if (d.tv_sec * 1000000 + d.tv_usec > 1000000) {
+            s->entropy_remaining = s->rate;
+            s->last = now;
+        }
+        max_entropy = MIN(s->pool, s->entropy_remaining);
+    } else {
+        max_entropy = s->pool;
+    }
+
+    /* current implementations have a 64 byte buffer.
+     * We fall back to a one byte per read if there is not enough room.
+     */
+    max_entropy = MIN(max_entropy, BUFF_MAX);
+    if (max_entropy) {
+        if (virtqueue_avail_bytes(s->vq, max_entropy, 0))
+            return max_entropy;
+        if (virtqueue_avail_bytes(s->vq, 1, 0))
+            return 1;
+    }
+    return 0;
+}
+
+static void vrng_read(void *opaque, const uint8_t *buf, int size)
+{
+    VirtIORng *s = (VirtIORng *) opaque;
+    VirtQueueElement elem;
+    int offset = 0;
+
+    /* The current kernel implementation has only one outstanding input
+     * buffer of 64 bytes.
+     */
+    while (offset < size) {
+        int i = 0;
+        if (!virtqueue_pop(s->vq, &elem))
+                break;
+        while (offset < size && i < elem.in_num) {
+            int len = MIN(elem.in_sg[i].iov_len, size - offset);
+            memcpy(elem.in_sg[i].iov_base, buf + offset, len);
+            offset += len;
+            i++;
+        }
+        virtqueue_push(s->vq, &elem, size);
+    }
+
+    if (s->rate)
+        s->entropy_remaining -= size;
+    s->pool -= size;
+
+    virtio_notify(&s->vdev, s->vq);
+}
+
+static void vrng_event(void *opaque, int event)
+{
+
+}
+
+
+
+static void virtio_rng_handle(VirtIODevice *vdev, VirtQueue *vq)
+{
+    /* Nothing to do - we push data when its available */
+}
+
+static uint32_t virtio_rng_get_features(VirtIODevice *vdev, uint32_t
features)
+{
+    return 0;
+}
+
+static void virtio_rng_save(QEMUFile *f, void *opaque)
+{
+    VirtIORng *s = opaque;
+
+    virtio_save(&s->vdev, f);
+}
+
+static int virtio_rng_load(QEMUFile *f, void *opaque, int version_id)
+{
+    VirtIORng *s = opaque;
+
+    if (version_id != 1)
+        return -EINVAL;
+
+    virtio_load(&s->vdev, f);
+    return 0;
+}
+
+VirtIODevice *virtio_rng_init(DeviceState *dev, RNGConf *rngdev)
+{
+    VirtIORng *s;
+    s = (VirtIORng *)virtio_common_init("virtio-rng",
+                                            VIRTIO_ID_RNG,
+                                            0, sizeof(VirtIORng));
+
+    if (!s)
+        return NULL;
+
+    s->vdev.get_features = virtio_rng_get_features;
+
+    s->vq = virtio_add_queue(&s->vdev, 128, virtio_rng_handle);
+    s->chr = rngdev->chrdev;
+    s->rate = rngdev->rate;
+    gettimeofday(&s->last, NULL);
+
+    if(rngdev->proto && !strncmp(rngdev->proto, "egd", 3))
+        s->egd = 1;
+
+#ifdef DEBUG
+    printf("entropy being read from %s", rngdev->chrdev->label);
+    if(s->rate)
+        printf(" at %d bytes/sec max.", s->rate);
+    printf(" protocol: %s\n", s->egd?"egd":"raw");
+#endif
+
+    qemu_chr_add_handlers(s->chr, vrng_can_read, vrng_read, vrng_event, s);
+
+    register_savevm("virtio-rng", -1, 1, virtio_rng_save,
virtio_rng_load, s);
+
+    return &s->vdev;
+}
+
diff --git a/hw/virtio-rng.h b/hw/virtio-rng.h
new file mode 100644
index 0000000..bc4d2d8
--- /dev/null
+++ b/hw/virtio-rng.h
@@ -0,0 +1,19 @@
+/*
+ * Virtio RNG Support
+ *
+ * Copyright Collabora 2009
+ *
+ * Authors:
+ *  Ian Molton <address@hidden>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2.  See
+ * the COPYING file in the top-level directory.
+ *
+ */
+#ifndef _QEMU_VIRTIO_RNG_H
+#define _QEMU_VIRTIO_RNG_H
+
+/* The ID for virtio console */
+#define VIRTIO_ID_RNG 4
+
+#endif
diff --git a/hw/virtio.h b/hw/virtio.h
index 3baa2a3..749b2a6 100644
--- a/hw/virtio.h
+++ b/hw/virtio.h
@@ -16,6 +16,7 @@

 #include "hw.h"
 #include "net.h"
+#include "rng.h"
 #include "qdev.h"
 #include "sysemu.h"
 #include "block_int.h"
@@ -174,6 +175,7 @@ VirtIODevice *virtio_blk_init(DeviceState *dev,
BlockConf *conf);
 VirtIODevice *virtio_net_init(DeviceState *dev, NICConf *conf);
 VirtIODevice *virtio_serial_init(DeviceState *dev, uint32_t max_nr_ports);
 VirtIODevice *virtio_balloon_init(DeviceState *dev);
+VirtIODevice *virtio_rng_init(DeviceState *dev, RNGConf *rngdev);

 void virtio_net_exit(VirtIODevice *vdev);

diff --git a/rng.h b/rng.h
new file mode 100644
index 0000000..14ae7e0
--- /dev/null
+++ b/rng.h
@@ -0,0 +1,14 @@
+#ifndef QEMU_RNG_H
+#define QEMU_RNG_H
+
+#include "qemu-option.h"
+
+/* qdev rng properties */
+
+typedef struct RNGConf {
+    CharDriverState *chrdev;
+    uint64_t rate;
+    char *proto;
+} RNGConf;
+
+#endif
-- 
1.7.0.3