qemu qdev初步解析

[busuanzi] 2022-04-26

字数统计: 2.4k字 | 阅读时长≈ 13分

qdev初步解析

classDiagram

Object --|> DeviceState
DeviceState --|> USBDevice
USBDevice --|> USBRedirDevice

Object o-- ObjectClass
ObjectClass --|> DeviceClass
DeviceClass --|> USBDeviceClass

//hw/usb/redirect.c
static const TypeInfo usbredir_dev_info = {
    .name          = TYPE_USB_REDIR,
    .parent        = TYPE_USB_DEVICE,
    .instance_size = sizeof(USBRedirDevice),
    .class_init    = usbredir_class_initfn,
    .instance_init = usbredir_instance_init,
};

//hw/usb/bus.c
static const TypeInfo usb_device_type_info = {
    .name = TYPE_USB_DEVICE,
    .parent = TYPE_DEVICE,
    .instance_size = sizeof(USBDevice),
    .instance_init = usb_device_instance_init,
    .abstract = true,
    .class_size = sizeof(USBDeviceClass),
    .class_init = usb_device_class_init,
};
static void usb_device_instance_init(Object *obj)
{
    USBDevice *dev = USB_DEVICE(obj);
    USBDeviceClass *klass = USB_DEVICE_GET_CLASS(dev);

    if (klass->attached_settable) {
        object_property_add_bool(obj, "attached",
                                 usb_get_attached, usb_set_attached,
                                 NULL);
    } else {
        object_property_add_bool(obj, "attached",
                                 usb_get_attached, NULL,
                                 NULL);
    }
}

//hw/core/qdev.c
static const TypeInfo device_type_info = {
    .name = TYPE_DEVICE,
    .parent = TYPE_OBJECT,
    .instance_size = sizeof(DeviceState),
    .instance_init = device_initfn,
    .instance_post_init = device_post_init,
    .instance_finalize = device_finalize,
    .class_base_init = device_class_base_init,
    .class_init = device_class_init,
    .abstract = true,
    .class_size = sizeof(DeviceClass),
};
static void device_initfn(Object *obj)
{
    //...
    object_property_add_bool(obj, "realized",
                             device_get_realized, device_set_realized, NULL);
    object_property_add_bool(obj, "hotpluggable",
                             device_get_hotpluggable, NULL, NULL);
    object_property_add_bool(obj, "hotplugged",
                             device_get_hotplugged, NULL,
                             &error_abort);
    //...
}

//qom/object.c
static TypeInfo object_info = {
    .name = TYPE_OBJECT,
    .instance_size = sizeof(Object),
    .class_init = object_class_init,
    .abstract = true,
};

static void object_class_init(ObjectClass *klass, void *data)
{
    object_class_property_add_str(klass, "type", qdev_get_type,
                                  NULL, &error_abort);
}

继承关系一路找到object，并未发现“bus”属性

全局搜索，在下面文件中发现了bus属性

//blockdev.c
QemuOptsList qemu_legacy_drive_opts = {
    .name = "drive",
    .head = QTAILQ_HEAD_INITIALIZER(qemu_legacy_drive_opts.head),
    .desc = {
        {
            .name = "bus",
            .type = QEMU_OPT_NUMBER,
            .help = "bus number",
        }
    //...
    }
    //...
}

这里的bus是一个int类型，不是我们要找的结构

又在qdev-monitor.c中找到bus的相关代码，这里应该是我们要找的东西

//qdev-monitor.c
DeviceState *qdev_device_add(QemuOpts *opts, Error **errp)
{
    //...
    const char *driver, *path;
    DeviceState *dev;
    BusState *bus = NULL;
    //...
    path = qemu_opt_get(opts, "bus");
    if (path != NULL) {
        bus = qbus_find(path, errp);
        if (!bus) {
            error_setg(errp, "can not find bus for %s", driver);
            return NULL;
        }
        if (!object_dynamic_cast(OBJECT(bus), dc->bus_type)) {
            error_setg(errp, "Device '%s' can't go on %s bus",
                       driver, object_get_typename(OBJECT(bus)));
            return NULL;
        }
    }
    //...    
}
static BusState *qbus_find(const char *path, Error **errp)
{
    DeviceState *dev;
    BusState *bus;
    char elem[128];
    int pos, len;

    /* find start element */
    if (path[0] == '/') {
        bus = sysbus_get_default();
        pos = 0;
    } else {
        if (sscanf(path, "%127[^/]%n", elem, &len) != 1) {
            assert(!path[0]);
            elem[0] = len = 0;
        }
        bus = qbus_find_recursive(sysbus_get_default(), elem, NULL);
        if (!bus) {
            error_setg(errp, "Bus '%s' not found", elem);
            return NULL;
        }
        pos = len;
    }
    //...
}

//sysbus_get_default 明显应该就是设备树的根了

然后用qbus_find_recursive递归查找节点

static BusState *qbus_find_recursive(BusState *bus, const char *name,
                                     const char *bus_typename)
{
    BusChild *kid;
    BusState *pick, *child, *ret;
    bool match;

    assert(name || bus_typename);
    if (name) {
        match = !strcmp(bus->name, name);
    } else {
        match = !!object_dynamic_cast(OBJECT(bus), bus_typename);
    }

    if (match && !qbus_is_full(bus)) {
        return bus;             /* root matches and isn't full */
    }

    pick = match ? bus : NULL;

    QTAILQ_FOREACH(kid, &bus->children, sibling) {
        DeviceState *dev = kid->child;
        QLIST_FOREACH(child, &dev->child_bus, sibling) {
            ret = qbus_find_recursive(child, name, bus_typename);
            if (ret && !qbus_is_full(ret)) {
                return ret;     /* a descendant matches and isn't full */
            }
            if (ret && !pick) {
                pick = ret;
            }
        }
    }

    /* root or a descendant matches, but is full */
    return pick;
}

可以看到，如果你没有设置id选项，设备就会随便给你一个名字device[n]

//调用顺序
//qdev_device_add->qdev_set_id
void qdev_set_id(DeviceState *dev, const char *id)
{
    if (id) {
        dev->id = id;
    }

    if (dev->id) {
        object_property_add_child(qdev_get_peripheral(), dev->id,
                                  OBJECT(dev), NULL);
    } else {
        static int anon_count;
        gchar *name = g_strdup_printf("device[%d]", anon_count++);
        object_property_add_child(qdev_get_peripheral_anon(), name,
                                  OBJECT(dev), NULL);
        g_free(name);
    }
}

看下面代码，不难看出，object的所有property均以数组的形式存在
你指定一个设备比如id=pci 那么它的实际id其实是pci.0
你再指定一个id为pci的设备，它不会产生冲突，反而会变成pci.1

//调用顺序
//object_property_add_child->object_property_add
ObjectProperty *
object_property_add(Object *obj, const char *name, const char *type,
                    ObjectPropertyAccessor *get,
                    ObjectPropertyAccessor *set,
                    ObjectPropertyRelease *release,
                    void *opaque, Error **errp)
{
    ObjectProperty *prop;
    size_t name_len = strlen(name);

    if (name_len >= 3 && !memcmp(name + name_len - 3, "[*]", 4)) {
        int i;
        ObjectProperty *ret;
        char *name_no_array = g_strdup(name);

        name_no_array[name_len - 3] = '\0';
        for (i = 0; ; ++i) {
            char *full_name = g_strdup_printf("%s[%d]", name_no_array, i);

            ret = object_property_add(obj, full_name, type, get, set,
                                      release, opaque, NULL);
            g_free(full_name);
            if (ret) {
                break;
            }
        }
        g_free(name_no_array);
        return ret;
    }

    if (object_property_find(obj, name, NULL) != NULL) {
        error_setg(errp, "attempt to add duplicate property '%s'"
                   " to object (type '%s')", name,
                   object_get_typename(obj));
        return NULL;
    }

    prop = g_malloc0(sizeof(*prop));

    prop->name = g_strdup(name);
    prop->type = g_strdup(type);

    prop->get = get;
    prop->set = set;
    prop->release = release;
    prop->opaque = opaque;

    g_hash_table_insert(obj->properties, prop->name, prop);
    return prop;
}

typedef struct Object Object;
struct Object
{
    /*< private >*/
    ObjectClass *class;
    ObjectFree *free;
    GHashTable *properties;
    uint32_t ref;
    Object *parent;
};

// file bootdevice.c

void device_add_bootindex_property(Object *obj, int32_t *bootindex,
                                   const char *name, const char *suffix,
                                   DeviceState *dev, Error **errp);


ObjectProperty *
object_property_add(Object *obj, const char *name, const char *type,
                    ObjectPropertyAccessor *get,
                    ObjectPropertyAccessor *set,
                    ObjectPropertyRelease *release,
                    void *opaque, Error **errp);

关于addr
经过一系列转化后，变成两部分保存在devfn中

一部分是pci的slot 在前5位保存，最大1f(0-31),对应硬件设备的插槽
一部分是FUN，后3位保存,最大值7（0-7）
通过和名为slot_reserved_mask的bitmap比较确认空闲与否

如果默认没有填写，会从前往后依次尝试

static Property pci_props[] = {
    DEFINE_PROP_PCI_DEVFN("addr", PCIDevice, devfn, -1)
    //...
};

#define PCI_SLOT(devfn)         (((devfn) >> 3) & 0x1f)
#define PCI_FUNC(devfn)         ((devfn) & 0x07)

static bool pci_bus_devfn_reserved(PCIBus *bus, int devfn)
{
    return bus->slot_reserved_mask & (1UL << PCI_SLOT(devfn));
}

static bool pci_bus_devfn_reserved(PCIBus *bus, int devfn)
{
    return bus->slot_reserved_mask & (1UL << PCI_SLOT(devfn));
}

这里的devfn就是addr

static PCIDevice *do_pci_register_device(PCIDevice *pci_dev,
                                         const char *name, int devfn,
                                         Error **errp)
{
    PCIDeviceClass *pc = PCI_DEVICE_GET_CLASS(pci_dev);
    PCIConfigReadFunc *config_read = pc->config_read;
    PCIConfigWriteFunc *config_write = pc->config_write;
    Error *local_err = NULL;
    DeviceState *dev = DEVICE(pci_dev);
    PCIBus *bus = pci_get_bus(pci_dev);

    /* Only pci bridges can be attached to extra PCI root buses */
    if (pci_bus_is_root(bus) && bus->parent_dev && !pc->is_bridge) {
        error_setg(errp,
                   "PCI: Only PCI/PCIe bridges can be plugged into %s",
                    bus->parent_dev->name);
        return NULL;
    }

    if (devfn < 0) {
        for(devfn = bus->devfn_min ; devfn < ARRAY_SIZE(bus->devices);
            devfn += PCI_FUNC_MAX) {
            if (pci_bus_devfn_available(bus, devfn) &&
                   !pci_bus_devfn_reserved(bus, devfn)) {
                goto found;
            }
        }
        error_setg(errp, "PCI: no slot/function available for %s, all in use "
                   "or reserved", name);
        return NULL;
    found: ;
    } else if (pci_bus_devfn_reserved(bus, devfn)) {
        error_setg(errp, "PCI: slot %d function %d not available for %s,"
                   " reserved",
                   PCI_SLOT(devfn), PCI_FUNC(devfn), name);
        return NULL;
    } else if (!pci_bus_devfn_available(bus, devfn)) {
        error_setg(errp, "PCI: slot %d function %d not available for %s,"
                   " in use by %s",
                   PCI_SLOT(devfn), PCI_FUNC(devfn), name,
                   bus->devices[devfn]->name);
        return NULL;
    } else if (dev->hotplugged &&
               pci_get_function_0(pci_dev)) {
        error_setg(errp, "PCI: slot %d function 0 already ocuppied by %s,"
                   " new func %s cannot be exposed to guest.",
                   PCI_SLOT(pci_get_function_0(pci_dev)->devfn),
                   pci_get_function_0(pci_dev)->name,
                   name);

       return NULL;
    }

    pci_dev->devfn = devfn;
    pci_dev->requester_id_cache = pci_req_id_cache_get(pci_dev);
    pstrcpy(pci_dev->name, sizeof(pci_dev->name), name);

    memory_region_init(&pci_dev->bus_master_container_region, OBJECT(pci_dev),
                       "bus master container", UINT64_MAX);
    address_space_init(&pci_dev->bus_master_as,
                       &pci_dev->bus_master_container_region, pci_dev->name);

    if (qdev_hotplug) {
        pci_init_bus_master(pci_dev);
    }
    pci_dev->irq_state = 0;
    pci_config_alloc(pci_dev);

    pci_config_set_vendor_id(pci_dev->config, pc->vendor_id);
    pci_config_set_device_id(pci_dev->config, pc->device_id);
    pci_config_set_revision(pci_dev->config, pc->revision);
    pci_config_set_class(pci_dev->config, pc->class_id);

    if (!pc->is_bridge) {
        if (pc->subsystem_vendor_id || pc->subsystem_id) {
            pci_set_word(pci_dev->config + PCI_SUBSYSTEM_VENDOR_ID,
                         pc->subsystem_vendor_id);
            pci_set_word(pci_dev->config + PCI_SUBSYSTEM_ID,
                         pc->subsystem_id);
        } else {
            pci_set_default_subsystem_id(pci_dev);
        }
    } else {
        /* subsystem_vendor_id/subsystem_id are only for header type 0 */
        assert(!pc->subsystem_vendor_id);
        assert(!pc->subsystem_id);
    }
    pci_init_cmask(pci_dev);
    pci_init_wmask(pci_dev);
    pci_init_w1cmask(pci_dev);
    if (pc->is_bridge) {
        pci_init_mask_bridge(pci_dev);
    }
    pci_init_multifunction(bus, pci_dev, &local_err);
    if (local_err) {
        error_propagate(errp, local_err);
        do_pci_unregister_device(pci_dev);
        return NULL;
    }

    if (!config_read)
        config_read = pci_default_read_config;
    if (!config_write)
        config_write = pci_default_write_config;
    pci_dev->config_read = config_read;
    pci_dev->config_write = config_write;
    bus->devices[devfn] = pci_dev;
    pci_dev->version_id = 2; /* Current pci device vmstate version */
    return pci_dev;
}

关于masterbus字段，我们看以下下面这段代码
没有配置masterbus，直接使用usb_register_port在bus（pci）上注册
如果使用了，则使用usb_register_companion注册共用port

static void usb_uhci_common_realize(PCIDevice *dev, Error **errp)
{
    //...
    if (s->masterbus) {
        USBPort *ports[NB_PORTS];
        for(i = 0; i < NB_PORTS; i++) {
            ports[i] = &s->ports[i].port;
        }
        usb_register_companion(s->masterbus, ports, NB_PORTS,
                               s->firstport, s, &uhci_port_ops,
                               USB_SPEED_MASK_LOW | USB_SPEED_MASK_FULL,
                               &err);
        if (err) {
            error_propagate(errp, err);
            return;
        }
    } else {
        usb_bus_new(&s->bus, sizeof(s->bus), &uhci_bus_ops, DEVICE(dev));
        for (i = 0; i < NB_PORTS; i++) {
            usb_register_port(&s->bus, &s->ports[i].port, s, i, &uhci_port_ops,
                              USB_SPEED_MASK_LOW | USB_SPEED_MASK_FULL);
        }
    }
}

//hw/usb/bus.c
void usb_register_port(USBBus *bus, USBPort *port, void *opaque, int index,
                       USBPortOps *ops, int speedmask)
{
    usb_fill_port(port, opaque, index, ops, speedmask);
    QTAILQ_INSERT_TAIL(&bus->free, port, next);
    bus->nfree++;
}

void usb_register_companion(const char *masterbus, USBPort *ports[],
                            uint32_t portcount, uint32_t firstport,
                            void *opaque, USBPortOps *ops, int speedmask,
                            Error **errp)
{
    USBBus *bus;
    int i;

    QTAILQ_FOREACH(bus, &busses, next) {
        if (strcmp(bus->qbus.name, masterbus) == 0) {
            break;
        }
    }

    if (!bus) {
        error_setg(errp, "USB bus '%s' not found", masterbus);
        return;
    }
    if (!bus->ops->register_companion) {
        error_setg(errp, "Can't use USB bus '%s' as masterbus,"
                   " it doesn't support companion controllers",
                   masterbus);
        return;
    }

    for (i = 0; i < portcount; i++) {
        usb_fill_port(ports[i], opaque, i, ops, speedmask);
    }

    bus->ops->register_companion(bus, ports, portcount, firstport, errp);
}

在被共用的USB设备上（这里指ehci），除了定义自己的ports之外，还定义了一个USBPort*的公用指针数组
,然后在注册时，把共用的PORT放在这个指针上

ehci自己的realize函数，则把所有端口都注册到bus总线上
这里的bus总线，是usbbus，通过usb_bus_new函数创建
每个主控驱动独立使用时，都会创建一个，复用则不会

    USBPort ports[NB_PORTS];
    USBPort *companion_ports[NB_PORTS];
//...
static void ehci_register_companion(USBBus *bus, USBPort *ports[],
                                    uint32_t portcount, uint32_t firstport,
                                    Error **errp)
{
    EHCIState *s = container_of(bus, EHCIState, bus);
    uint32_t i;

    if (firstport + portcount > NB_PORTS) {
        error_setg(errp, "firstport must be between 0 and %u",
                   NB_PORTS - portcount);
        return;
    }

    for (i = 0; i < portcount; i++) {
        if (s->companion_ports[firstport + i]) {
            error_setg(errp, "firstport %u asks for ports %u-%u,"
                       " but port %u has a companion assigned already",
                       firstport, firstport, firstport + portcount - 1,
                       firstport + i);
            return;
        }
    }

    for (i = 0; i < portcount; i++) {
        s->companion_ports[firstport + i] = ports[i];
        s->ports[firstport + i].speedmask |=
            USB_SPEED_MASK_LOW | USB_SPEED_MASK_FULL;
        /* Ensure devs attached before the initial reset go to the companion */
        s->portsc[firstport + i] = PORTSC_POWNER;
    }

    s->companion_count++;
    s->caps[0x05] = (s->companion_count << 4) | portcount;
}

qemu的设备结构，基本上是Device-Bus-Device-Bus这样的
添加Device的时候，在指定的Bus上加入Device.id[{x}]
而添加Bus的时候，如果不指定名字，名字自动设置为Device.id.{x}

static void qbus_realize(BusState *bus, DeviceState *parent, const char *name)
{
    const char *typename = object_get_typename(OBJECT(bus));
    BusClass *bc;
    int i, bus_id;

    bus->parent = parent;

    if (name) {
        bus->name = g_strdup(name);
    } else if (bus->parent && bus->parent->id) {
        /* parent device has id -> use it plus parent-bus-id for bus name */
        bus_id = bus->parent->num_child_bus;
        bus->name = g_strdup_printf("%s.%d", bus->parent->id, bus_id);
    } else {
        /* no id -> use lowercase bus type plus global bus-id for bus name */
        bc = BUS_GET_CLASS(bus);
        bus_id = bc->automatic_ids++;
        bus->name = g_strdup_printf("%s.%d", typename, bus_id);
        for (i = 0; bus->name[i]; i++) {
            bus->name[i] = qemu_tolower(bus->name[i]);
        }
    }

    if (bus->parent) {
        QLIST_INSERT_HEAD(&bus->parent->child_bus, bus, sibling);
        bus->parent->num_child_bus++;
        object_property_add_child(OBJECT(bus->parent), bus->name, OBJECT(bus), NULL);
        object_unref(OBJECT(bus));
    } else {
        /* The only bus without a parent is the main system bus */
        assert(bus == sysbus_get_default());
    }
}

本文作者： crazyboy
本文链接： http://crazyboy.www.crazyboy.info/blog/blog/2022/04/26/it/linux/qemu/qemu-device/
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