Re: [Qemu-devel] [PATCH 4/5] virtio: Add virtio-rng driver

[Anthony Liguori <anthony@codemonkey.ws>]

On 02/01/2010 07:34 AM, Ian Molton wrote:
> 	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<ian.molton@collabora.co.uk>
> ---
>   Makefile.target |    2 +-
>   hw/pci.h        |    1 +
>   hw/virtio-pci.c |   27 +++++++
>   hw/virtio-rng.c |  202 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
>   hw/virtio-rng.h |   19 +++++
>   hw/virtio.h     |    2 +
>   rng.h           |   18 +++++
>   7 files changed, 270 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 5c0ef1f..21d28f4 100644
> --- a/Makefile.target
> +++ b/Makefile.target
> @@ -172,7 +172,7 @@ ifdef CONFIG_SOFTMMU
>   obj-y = vl.o async.o monitor.o pci.o pci_host.o pcie_host.o machine.o gdbstub.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-pci.o virtio-serial-bus.o
> +obj-y += virtio-blk.o virtio-balloon.o virtio-net.o virtio-pci.o virtio-serial-bus.o virtio-rng.o
>   obj-$(CONFIG_KVM) += kvm.o kvm-all.o
>   obj-$(CONFIG_ISA_MMIO) += isa_mmio.o
>   LIBS+=-lz
> diff --git a/hw/pci.h b/hw/pci.h
> index 8b511d2..77cb543 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
>
>   typedef uint64_t pcibus_t;
>   #define FMT_PCIBUS                      PRIx64
> diff --git a/hw/virtio-pci.c b/hw/virtio-pci.c
> index 709d13e..f057388 100644
> --- a/hw/virtio-pci.c
> +++ b/hw/virtio-pci.c
> @@ -22,6 +22,7 @@
>   #include "sysemu.h"
>   #include "msix.h"
>   #include "net.h"
> +#include "rng.h"
>   #include "loader.h"
>
>   /* from Linux's linux/virtio_pci.h */
> @@ -94,6 +95,7 @@ typedef struct {
>       uint32_t nvectors;
>       DriveInfo *dinfo;
>       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;
> @@ -550,6 +552,21 @@ 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,
>    

Gerd (or the right person at Red Hat) needs to Ack the assignment of 
this PCI device id.

> +                    PCI_CLASS_OTHERS,
> +                    0x00);
> +
> +    return 0;
> +}
> +
>   static PCIDeviceInfo virtio_info[] = {
>       {
>           .qdev.name = "virtio-blk-pci",
> @@ -603,6 +620,16 @@ 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_RNG_PROPERTIES(VirtIOPCIProxy, rng),
>    

I don't see any reason to use a define here.

> +            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..d8cbb74
> --- /dev/null
> +++ b/hw/virtio-rng.c
> @@ -0,0 +1,202 @@
> +/*
> + * Virtio RNG Device
> + *
> + * Copyright Collabora 2009
> + *
> + * Authors:
> + *  Ian Molton<ian.molton@collabora.co.uk>
> + *
> + * 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) {
>    

Coding style is off here (newline between ) and { ).

> +    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) {
> +        gettimeofday(&now, NULL);
> +        timersub(&now,&s->last,&d);
>    

Can't call gettimeofday directly.  You have to use qemu_gettimeofday().  
But it would be better to not rely on gettimeofday and instead make use 
of the rt_clock.
> +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;
> +}
>
>    

This doesn't look correct to me.  There is absolutely no state 
maintained by the virtio-rng backend?  I find that hard to believe.

Regards,

Anthony Liguori