接前一篇文章：
上一回讲解了virtio balloon相关类所涉及的realize函数，如下表所示：
| realize函数 | parent_dc_realize函数 | |
| DeviceClass | virtio_pci_dc_realize | |
| PCIDeviceClass | virtio_pci_realize | |
| VirtioPCIClass | virtio_balloon_pci_realize | pci_qdev_realize |
本回继续接着讲。
再来回顾一下，virtio balloon PCI代理设备类型的初始化函数virtio_balloon_pci_class_init()，在hw/virtio/virtio-balloon-pci.c中，代码如下：
static void virtio_balloon_pci_class_init(ObjectClass *klass, void *data)
{
DeviceClass *dc = DEVICE_CLASS(klass);
VirtioPCIClass *k = VIRTIO_PCI_CLASS(klass);
PCIDeviceClass *pcidev_k = PCI_DEVICE_CLASS(klass);
k->realize = virtio_balloon_pci_realize;
set_bit(DEVICE_CATEGORY_MISC, dc->categories);
pcidev_k->vendor_id = PCI_VENDOR_ID_REDHAT_QUMRANET;
pcidev_k->device_id = PCI_DEVICE_ID_VIRTIO_BALLOON;
pcidev_k->revision = VIRTIO_PCI_ABI_VERSION;
pcidev_k->class_id = PCI_CLASS_OTHERS;
}device_set_realized函数在hw/virtio/virtio-balloon-pci.c中，代码如下：
static void device_set_realized(Object *obj, bool value, Error **errp)
{
DeviceState *dev = DEVICE(obj);
DeviceClass *dc = DEVICE_GET_CLASS(dev);
HotplugHandler *hotplug_ctrl;
BusState *bus;
NamedClockList *ncl;
Error *local_err = NULL;
bool unattached_parent = false;
static int unattached_count;
if (dev->hotplugged && !dc->hotpluggable) {
error_setg(errp, QERR_DEVICE_NO_HOTPLUG, object_get_typename(obj));
return;
}
if (value && !dev->realized) {
if (!check_only_migratable(obj, errp)) {
goto fail;
}
if (!obj->parent) {
gchar *name = g_strdup_printf("device[%d]", unattached_count++);
object_property_add_child(container_get(qdev_get_machine(),
"/unattached"),
name, obj);
unattached_parent = true;
g_free(name);
}
hotplug_ctrl = qdev_get_hotplug_handler(dev);
if (hotplug_ctrl) {
hotplug_handler_pre_plug(hotplug_ctrl, dev, &local_err);
if (local_err != NULL) {
goto fail;
}
}
if (dc->realize) {
dc->realize(dev, &local_err);
if (local_err != NULL) {
goto fail;
}
}
DEVICE_LISTENER_CALL(realize, Forward, dev);
/*
* always free/re-initialize here since the value cannot be cleaned up
* in device_unrealize due to its usage later on in the unplug path
*/
g_free(dev->canonical_path);
dev->canonical_path = object_get_canonical_path(OBJECT(dev));
QLIST_FOREACH(ncl, &dev->clocks, node) {
if (ncl->alias) {
continue;
} else {
clock_setup_canonical_path(ncl->clock);
}
}
if (qdev_get_vmsd(dev)) {
if (vmstate_register_with_alias_id(VMSTATE_IF(dev),
VMSTATE_INSTANCE_ID_ANY,
qdev_get_vmsd(dev), dev,
dev->instance_id_alias,
dev->alias_required_for_version,
&local_err) < 0) {
goto post_realize_fail;
}
}
/*
* Clear the reset state, in case the object was previously unrealized
* with a dirty state.
*/
resettable_state_clear(&dev->reset);
QLIST_FOREACH(bus, &dev->child_bus, sibling) {
if (!qbus_realize(bus, errp)) {
goto child_realize_fail;
}
}
if (dev->hotplugged) {
/*
* Reset the device, as well as its subtree which, at this point,
* should be realized too.
*/
resettable_assert_reset(OBJECT(dev), RESET_TYPE_COLD);
resettable_change_parent(OBJECT(dev), OBJECT(dev->parent_bus),
NULL);
resettable_release_reset(OBJECT(dev), RESET_TYPE_COLD);
}
dev->pending_deleted_event = false;
if (hotplug_ctrl) {
hotplug_handler_plug(hotplug_ctrl, dev, &local_err);
if (local_err != NULL) {
goto child_realize_fail;
}
}
qatomic_store_release(&dev->realized, value);
} else if (!value && dev->realized) {
/*
* Change the value so that any concurrent users are aware
* that the device is going to be unrealized
*
* TODO: change .realized property to enum that states
* each phase of the device realization/unrealization
*/
qatomic_set(&dev->realized, value);
/*
* Ensure that concurrent users see this update prior to
* any other changes done by unrealize.
*/
smp_wmb();
QLIST_FOREACH(bus, &dev->child_bus, sibling) {
qbus_unrealize(bus);
}
if (qdev_get_vmsd(dev)) {
vmstate_unregister(VMSTATE_IF(dev), qdev_get_vmsd(dev), dev);
}
if (dc->unrealize) {
dc->unrealize(dev);
}
dev->pending_deleted_event = true;
DEVICE_LISTENER_CALL(unrealize, Reverse, dev);
}
assert(local_err == NULL);
return;
child_realize_fail:
QLIST_FOREACH(bus, &dev->child_bus, sibling) {
qbus_unrealize(bus);
}
if (qdev_get_vmsd(dev)) {
vmstate_unregister(VMSTATE_IF(dev), qdev_get_vmsd(dev), dev);
}
post_realize_fail:
g_free(dev->canonical_path);
dev->canonical_path = NULL;
if (dc->unrealize) {
dc->unrealize(dev);
}
fail:
error_propagate(errp, local_err);
if (unattached_parent) {
/*
* Beware, this doesn't just revert
* object_property_add_child(), it also runs bus_remove()!
*/
object_unparent(OBJECT(dev));
unattached_count--;
}
}设置virtio PCI代理设备的realize属性时，device_set_realized函数中会首先调用DeviceClass->realize函数指针所指向的函数，也就是virtio_pci_dc_realize函数。代码片段如下：
if (dc->realize) {
dc->realize(dev, &local_err);
if (local_err != NULL) {
goto fail;
}
}virtio_pci_dc_realize函数在hw/virtio/virtio-pci.c中，代码如下：
static void virtio_pci_dc_realize(DeviceState *qdev, Error **errp)
{
VirtioPCIClass *vpciklass = VIRTIO_PCI_GET_CLASS(qdev);
VirtIOPCIProxy *proxy = VIRTIO_PCI(qdev);
PCIDevice *pci_dev = &proxy->pci_dev;
if (!(proxy->flags & VIRTIO_PCI_FLAG_DISABLE_PCIE) &&
virtio_pci_modern(proxy)) {
pci_dev->cap_present |= QEMU_PCI_CAP_EXPRESS;
}
vpciklass->parent_dc_realize(qdev, errp);
}virtio_pci_dc_realize函数中会调用VirtioPCIClass->parent_dc_realize，也就是pci_qdev_realize函数。在pci_qdev_realize函数中会调用PCIDeviceClass的realize函数指针所指向的函数，也就是virtio_pci_realize函数。virtio_pci_realize函数在hw/virtio/virtio-pci.c中，代码如下：
static void virtio_pci_realize(PCIDevice *pci_dev, Error **errp)
{
VirtIOPCIProxy *proxy = VIRTIO_PCI(pci_dev);
VirtioPCIClass *k = VIRTIO_PCI_GET_CLASS(pci_dev);
bool pcie_port = pci_bus_is_express(pci_get_bus(pci_dev)) &&
!pci_bus_is_root(pci_get_bus(pci_dev));
if (kvm_enabled() && !kvm_has_many_ioeventfds()) {
proxy->flags &= ~VIRTIO_PCI_FLAG_USE_IOEVENTFD;
}
/* fd-based ioevents can't be synchronized in record/replay */
if (replay_mode != REPLAY_MODE_NONE) {
proxy->flags &= ~VIRTIO_PCI_FLAG_USE_IOEVENTFD;
}
/*
* virtio pci bar layout used by default.
* subclasses can re-arrange things if needed.
*
* region 0 -- virtio legacy io bar
* region 1 -- msi-x bar
* region 2 -- virtio modern io bar (off by default)
* region 4+5 -- virtio modern memory (64bit) bar
*
*/
proxy->legacy_io_bar_idx = 0;
proxy->msix_bar_idx = 1;
proxy->modern_io_bar_idx = 2;
proxy->modern_mem_bar_idx = 4;
proxy->common.offset = 0x0;
proxy->common.size = 0x1000;
proxy->common.type = VIRTIO_PCI_CAP_COMMON_CFG;
proxy->isr.offset = 0x1000;
proxy->isr.size = 0x1000;
proxy->isr.type = VIRTIO_PCI_CAP_ISR_CFG;
proxy->device.offset = 0x2000;
proxy->device.size = 0x1000;
proxy->device.type = VIRTIO_PCI_CAP_DEVICE_CFG;
proxy->notify.offset = 0x3000;
proxy->notify.size = virtio_pci_queue_mem_mult(proxy) * VIRTIO_QUEUE_MAX;
proxy->notify.type = VIRTIO_PCI_CAP_NOTIFY_CFG;
proxy->notify_pio.offset = 0x0;
proxy->notify_pio.size = 0x4;
proxy->notify_pio.type = VIRTIO_PCI_CAP_NOTIFY_CFG;
/* subclasses can enforce modern, so do this unconditionally */
memory_region_init(&proxy->modern_bar, OBJECT(proxy), "virtio-pci",
/* PCI BAR regions must be powers of 2 */
pow2ceil(proxy->notify.offset + proxy->notify.size));
if (proxy->disable_legacy == ON_OFF_AUTO_AUTO) {
proxy->disable_legacy = pcie_port ? ON_OFF_AUTO_ON : ON_OFF_AUTO_OFF;
}
if (!virtio_pci_modern(proxy) && !virtio_pci_legacy(proxy)) {
error_setg(errp, "device cannot work as neither modern nor legacy mode"
" is enabled");
error_append_hint(errp, "Set either disable-modern or disable-legacy"
" to off\n");
return;
}
if (pcie_port && pci_is_express(pci_dev)) {
int pos;
uint16_t last_pcie_cap_offset = PCI_CONFIG_SPACE_SIZE;
pos = pcie_endpoint_cap_init(pci_dev, 0);
assert(pos > 0);
pos = pci_add_capability(pci_dev, PCI_CAP_ID_PM, 0,
PCI_PM_SIZEOF, errp);
if (pos < 0) {
return;
}
pci_dev->exp.pm_cap = pos;
/*
* Indicates that this function complies with revision 1.2 of the
* PCI Power Management Interface Specification.
*/
pci_set_word(pci_dev->config + pos + PCI_PM_PMC, 0x3);
if (proxy->flags & VIRTIO_PCI_FLAG_AER) {
pcie_aer_init(pci_dev, PCI_ERR_VER, last_pcie_cap_offset,
PCI_ERR_SIZEOF, NULL);
last_pcie_cap_offset += PCI_ERR_SIZEOF;
}
if (proxy->flags & VIRTIO_PCI_FLAG_INIT_DEVERR) {
/* Init error enabling flags */
pcie_cap_deverr_init(pci_dev);
}
if (proxy->flags & VIRTIO_PCI_FLAG_INIT_LNKCTL) {
/* Init Link Control Register */
pcie_cap_lnkctl_init(pci_dev);
}
if (proxy->flags & VIRTIO_PCI_FLAG_INIT_PM) {
/* Init Power Management Control Register */
pci_set_word(pci_dev->wmask + pos + PCI_PM_CTRL,
PCI_PM_CTRL_STATE_MASK);
}
if (proxy->flags & VIRTIO_PCI_FLAG_ATS) {
pcie_ats_init(pci_dev, last_pcie_cap_offset,
proxy->flags & VIRTIO_PCI_FLAG_ATS_PAGE_ALIGNED);
last_pcie_cap_offset += PCI_EXT_CAP_ATS_SIZEOF;
}
if (proxy->flags & VIRTIO_PCI_FLAG_INIT_FLR) {
/* Set Function Level Reset capability bit */
pcie_cap_flr_init(pci_dev);
}
} else {
/*
* make future invocations of pci_is_express() return false
* and pci_config_size() return PCI_CONFIG_SPACE_SIZE.
*/
pci_dev->cap_present &= ~QEMU_PCI_CAP_EXPRESS;
}
virtio_pci_bus_new(&proxy->bus, sizeof(proxy->bus), proxy);
if (k->realize) {
k->realize(proxy, errp);
}
}
在这个函数的最后会调用VirtioPCIClass的realize函数指针所指向的函数，也就是virtio_balloon_pci_realize函数。代码片段如下：
static void virtio_pci_realize(PCIDevice *pci_dev, Error **errp)
{
VirtIOPCIProxy *proxy = VIRTIO_PCI(pci_dev);
VirtioPCIClass *k = VIRTIO_PCI_GET_CLASS(pci_dev);
……
if (k->realize) {
k->realize(proxy, errp);
}
}