Re: [Qemu-devel] [RFC PATCH 1/3] virtio-bus : Introduce VirtioBus.

[Peter Maydell]

On 16 November 2012 15:35,  <address@hidden> wrote:
> From: KONRAD Frederic <address@hidden>

You forgot to CC enough people...

> This patch create a new VirtioBus, which can be added to Virtio transports 
> like
> virtio-pci, virtio-mmio,...
>
> One VirtIODevice can be connected to this device, like virtio-blk in the 3rd
> patch.
>
> The VirtioBus shares through a VirtioBusInfo structure :
>
>     * two callbacks with the transport : init_cb and exit_cb, which must be
>       called by the VirtIODevice, after the initialization and before the
>       destruction, to put the right PCI IDs and/or stop the event fd.
>
>     * a VirtIOBindings structure.
>
> Signed-off-by: KONRAD Frederic <address@hidden>
> ---
>  hw/Makefile.objs |   1 +
>  hw/virtio-bus.c  | 111 
> +++++++++++++++++++++++++++++++++++++++++++++++++++++++
>  hw/virtio-bus.h  |  49 ++++++++++++++++++++++++
>  3 files changed, 161 insertions(+)
>  create mode 100644 hw/virtio-bus.c
>  create mode 100644 hw/virtio-bus.h
>
> diff --git a/hw/Makefile.objs b/hw/Makefile.objs
> index af4ab0c..1b25d77 100644
> --- a/hw/Makefile.objs
> +++ b/hw/Makefile.objs
> @@ -1,6 +1,7 @@
>  common-obj-y = usb/ ide/
>  common-obj-y += loader.o
>  common-obj-$(CONFIG_VIRTIO) += virtio-console.o
> +common-obj-$(CONFIG_VIRTIO) += virtio-bus.o
>  common-obj-$(CONFIG_VIRTIO_PCI) += virtio-pci.o
>  common-obj-y += fw_cfg.o
>  common-obj-$(CONFIG_PCI) += pci.o pci_bridge.o pci_bridge_dev.o
> diff --git a/hw/virtio-bus.c b/hw/virtio-bus.c
> new file mode 100644
> index 0000000..b2e7e9c
> --- /dev/null
> +++ b/hw/virtio-bus.c
> @@ -0,0 +1,111 @@
> +/*
> + * VirtioBus
> + *
> + *  Copyright (C) 2012 : GreenSocs Ltd
> + *      http://www.greensocs.com/ , email: address@hidden
> + *
> + *  Developed by :
> + *  Frederic Konrad   <address@hidden>
> + *
> + * This work is licensed under the terms of the GNU GPL, version 2.  See
> + * the COPYING file in the top-level directory.

Unless you copied this code from an existing v2-only file, preferred
license for new code is v2-or-any-later-version.

> + */
> +
> +#include "hw.h"
> +#include "qemu-error.h"
> +#include "qdev.h"
> +#include "virtio-bus.h"
> +#include "virtio.h"
> +
> +#define DEBUG_VIRTIO_BUS
> +
> +#ifdef DEBUG_VIRTIO_BUS
> +
> +#define DPRINTF(fmt, ...) \
> +do { printf("virtio_bus: " fmt , ## __VA_ARGS__); } while (0)
> +#else
> +#define DPRINTF(fmt, ...) do {} while (0)
> +#endif
> +
> +static char *virtio_bus_get_fw_dev_path(DeviceState *dev);

Is this function necessary? I think your implementation
is doing the same as the default.

> +static void virtio_bus_class_init(ObjectClass *klass, void *data)
> +{
> +    BusClass *k = BUS_CLASS(klass);
> +    k->get_fw_dev_path = virtio_bus_get_fw_dev_path;
> +}
> +
> +static const TypeInfo virtio_bus_info = {
> +    .name = TYPE_VIRTIO_BUS,
> +    .parent = TYPE_BUS,
> +    .instance_size = sizeof(VirtioBus),
> +    .class_init = virtio_bus_class_init,
> +};
> +
> +/* VirtioBus */
> +
> +static int next_virtio_bus;
> +
> +/* Create a virtio bus, and attach to transport.  */
> +void virtio_bus_new(VirtioBus *bus, DeviceState *host,
> +                    const VirtioBusInfo *info)
> +{
> +    /*
> +     * Setting name to NULL return always "virtio.0"
> +     * as bus name in info qtree.
> +     */
> +    char *bus_name = g_strdup_printf("%s.%d", BUS_NAME, next_virtio_bus);
> +    qbus_create_inplace(&bus->qbus, TYPE_VIRTIO_BUS, host, bus_name);
> +    bus->busnr = next_virtio_bus++;

This looks suspicious to me -- is keeping a count of the global
bus number really the right way to do this?

> +    bus->info = info;
> +    /* no hotplug for the moment ? */
> +    bus->qbus.allow_hotplug = 0;

Correct -- we don't need to hotplug the virtio backend.

> +    bus->bus_in_use = false;
> +    DPRINTF("bus %s created\n", bus_name);
> +}
> +
> +/* Bind the VirtIODevice to the VirtioBus. */
> +void virtio_bus_bind_device(VirtioBus *bus)
> +{
> +    assert(bus != NULL);
> +    assert(bus->vdev != NULL);
> +    virtio_bind_device(bus->vdev, &(bus->info->virtio_bindings),
> +                       bus->qbus.parent);

This looks wrong -- virtio_bind_device() is part of the
old-style transport API.

> +}
> +
> +/* This must be called to when the VirtIODevice init */
> +int virtio_bus_init_cb(VirtioBus *bus, VirtIODevice *vdev)
> +{
> +    if (bus->bus_in_use == true) {
> +        error_report("%s in use.\n", bus->qbus.name);
> +        return -1;
> +    }
> +    assert(bus->info->init_cb != NULL);
> +    /* keep the VirtIODevice in the VirtioBus */
> +    bus->vdev = vdev;

This shouldn't be happening here, it should happen as
part of plugging the device into the bus.

> +    bus->info->init_cb(bus->qbus.parent);
> +
> +    bus->bus_in_use = true;
> +    return 0;
> +}
> +
> +/* This must be called when the VirtIODevice exit */
> +void virtio_bus_exit_cb(VirtioBus *bus)
> +{
> +    assert(bus->info->exit_cb != NULL);
> +    bus->info->exit_cb(bus->qbus.parent);
> +    bus->bus_in_use = false;
> +}

These shouldn't be necessary -- the VirtioDevice should
have a pointer to the VirtioBus and can just invoke the
init/exit callbacks directly.

> +
> +static char *virtio_bus_get_fw_dev_path(DeviceState *dev)
> +{
> +    return g_strdup_printf("%s", qdev_fw_name(dev));
> +}
> +
> +
> +static void virtio_register_types(void)
> +{
> +    type_register_static(&virtio_bus_info);
> +}
> +
> +type_init(virtio_register_types)
> diff --git a/hw/virtio-bus.h b/hw/virtio-bus.h
> new file mode 100644
> index 0000000..6ea5035
> --- /dev/null
> +++ b/hw/virtio-bus.h
> @@ -0,0 +1,49 @@
> +/*
> + * VirtioBus
> + *
> + *  Copyright (C) 2012 : GreenSocs Ltd
> + *      http://www.greensocs.com/ , email: address@hidden
> + *
> + *  Developed by :
> + *  Frederic Konrad   <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 _VIRTIO_BUS_H_
> +#define _VIRTIO_BUS_H_

Leading underscores are reserved by the C standard. VIRTIO_BUS_H will
do fine.

> +
> +#include "qdev.h"
> +#include "sysemu.h"
> +#include "virtio.h"
> +
> +#define TYPE_VIRTIO_BUS "VIRTIO"

Type names are generally "virtio-bus" by convention.

> +#define BUS_NAME "virtio"

I don't think you want this.


> +typedef struct VirtioBus VirtioBus;
> +typedef struct VirtioBusInfo VirtioBusInfo;
> +
> +struct VirtioBusInfo {
> +    void (*init_cb)(DeviceState *dev);
> +    void (*exit_cb)(DeviceState *dev);
> +    VirtIOBindings virtio_bindings;

This doesn't look right -- VirtIOBindings is the
old-style way for the transport to specify a bunch
of function pointers for its specific implementation.
Those function pointers should probably just be in
the VirtioBus struct.

> +};

I was just talking to Anthony on IRC and he said SCSIBusInfo
is really kind of a historical accident. So we can just fold
this struct into VirtioBus. Sorry for misleading you earlier.

> +struct VirtioBus {
> +    BusState qbus;
> +    int busnr;

Why does the bus need to know what number it is?

> +    bool bus_in_use;
> +    uint16_t pci_device_id;
> +    uint16_t pci_class;

This shouldn't be here -- VirtioBus should be transport
independent, so no PCI related info.

> +    VirtIODevice *vdev;

This could use a comment saying that we only ever have one
child device on the bus.

> +    const VirtioBusInfo *info;
> +};
> +
> +void virtio_bus_new(VirtioBus *bus, DeviceState *host,
> +                    const VirtioBusInfo *info);
> +void virtio_bus_bind_device(VirtioBus *bus);
> +int virtio_bus_init_cb(VirtioBus *bus, VirtIODevice *dev);
> +void virtio_bus_exit_cb(VirtioBus *bus);
> +
> +#endif
> --
> 1.7.11.7

-- PMM