/* * Copyright (c) 2009, Microsoft Corporation. * * This program is free software; you can redistribute it and/or modify it * under the terms and conditions of the GNU General Public License, * version 2, as published by the Free Software Foundation. * * This program is distributed in the hope it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for * more details. * * You should have received a copy of the GNU General Public License along with * this program; if not, write to the Free Software Foundation, Inc., 59 Temple * Place - Suite 330, Boston, MA 02111-1307 USA. * * Authors: * Haiyang Zhang * Hank Janssen */ #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt #include #include #include #include #include #include #include #include #include #include "hyperv_vmbus.h" struct vmbus_channel_message_table_entry { enum vmbus_channel_message_type message_type; void (*message_handler)(struct vmbus_channel_message_header *msg); }; /** * vmbus_prep_negotiate_resp() - Create default response for Hyper-V Negotiate message * @icmsghdrp: Pointer to msg header structure * @icmsg_negotiate: Pointer to negotiate message structure * @buf: Raw buffer channel data * * @icmsghdrp is of type &struct icmsg_hdr. * @negop is of type &struct icmsg_negotiate. * Set up and fill in default negotiate response message. * * The fw_version specifies the framework version that * we can support and srv_version specifies the service * version we can support. * * Mainly used by Hyper-V drivers. */ bool vmbus_prep_negotiate_resp(struct icmsg_hdr *icmsghdrp, struct icmsg_negotiate *negop, u8 *buf, int fw_version, int srv_version) { int icframe_major, icframe_minor; int icmsg_major, icmsg_minor; int fw_major, fw_minor; int srv_major, srv_minor; int i; bool found_match = false; icmsghdrp->icmsgsize = 0x10; fw_major = (fw_version >> 16); fw_minor = (fw_version & 0xFFFF); srv_major = (srv_version >> 16); srv_minor = (srv_version & 0xFFFF); negop = (struct icmsg_negotiate *)&buf[ sizeof(struct vmbuspipe_hdr) + sizeof(struct icmsg_hdr)]; icframe_major = negop->icframe_vercnt; icframe_minor = 0; icmsg_major = negop->icmsg_vercnt; icmsg_minor = 0; /* * Select the framework version number we will * support. */ for (i = 0; i < negop->icframe_vercnt; i++) { if ((negop->icversion_data[i].major == fw_major) && (negop->icversion_data[i].minor == fw_minor)) { icframe_major = negop->icversion_data[i].major; icframe_minor = negop->icversion_data[i].minor; found_match = true; } } if (!found_match) goto fw_error; found_match = false; for (i = negop->icframe_vercnt; (i < negop->icframe_vercnt + negop->icmsg_vercnt); i++) { if ((negop->icversion_data[i].major == srv_major) && (negop->icversion_data[i].minor == srv_minor)) { icmsg_major = negop->icversion_data[i].major; icmsg_minor = negop->icversion_data[i].minor; found_match = true; } } /* * Respond with the framework and service * version numbers we can support. */ fw_error: if (!found_match) { negop->icframe_vercnt = 0; negop->icmsg_vercnt = 0; } else { negop->icframe_vercnt = 1; negop->icmsg_vercnt = 1; } negop->icversion_data[0].major = icframe_major; negop->icversion_data[0].minor = icframe_minor; negop->icversion_data[1].major = icmsg_major; negop->icversion_data[1].minor = icmsg_minor; return found_match; } EXPORT_SYMBOL_GPL(vmbus_prep_negotiate_resp); /* * alloc_channel - Allocate and initialize a vmbus channel object */ static struct vmbus_channel *alloc_channel(void) { static atomic_t chan_num = ATOMIC_INIT(0); struct vmbus_channel *channel; channel = kzalloc(sizeof(*channel), GFP_ATOMIC); if (!channel) return NULL; channel->id = atomic_inc_return(&chan_num); spin_lock_init(&channel->inbound_lock); spin_lock_init(&channel->lock); INIT_LIST_HEAD(&channel->sc_list); INIT_LIST_HEAD(&channel->percpu_list); channel->controlwq = alloc_workqueue("hv_vmbus_ctl/%d", WQ_MEM_RECLAIM, 1, channel->id); if (!channel->controlwq) { kfree(channel); return NULL; } return channel; } /* * release_hannel - Release the vmbus channel object itself */ static void release_channel(struct work_struct *work) { struct vmbus_channel *channel = container_of(work, struct vmbus_channel, work); destroy_workqueue(channel->controlwq); kfree(channel); } /* * free_channel - Release the resources used by the vmbus channel object */ static void free_channel(struct vmbus_channel *channel) { /* * We have to release the channel's workqueue/thread in the vmbus's * workqueue/thread context * ie we can't destroy ourselves. */ INIT_WORK(&channel->work, release_channel); queue_work(vmbus_connection.work_queue, &channel->work); } static void percpu_channel_enq(void *arg) { struct vmbus_channel *channel = arg; int cpu = smp_processor_id(); list_add_tail(&channel->percpu_list, &hv_context.percpu_list[cpu]); } static void percpu_channel_deq(void *arg) { struct vmbus_channel *channel = arg; list_del(&channel->percpu_list); } /* * vmbus_process_rescind_offer - * Rescind the offer by initiating a device removal */ static void vmbus_process_rescind_offer(struct work_struct *work) { struct vmbus_channel *channel = container_of(work, struct vmbus_channel, work); unsigned long flags; struct vmbus_channel *primary_channel; struct vmbus_channel_relid_released msg; struct device *dev; if (channel->device_obj) { dev = get_device(&channel->device_obj->device); if (dev) { vmbus_device_unregister(channel->device_obj); put_device(dev); } } memset(&msg, 0, sizeof(struct vmbus_channel_relid_released)); msg.child_relid = channel->offermsg.child_relid; msg.header.msgtype = CHANNELMSG_RELID_RELEASED; vmbus_post_msg(&msg, sizeof(struct vmbus_channel_relid_released)); if (channel->target_cpu != get_cpu()) { put_cpu(); smp_call_function_single(channel->target_cpu, percpu_channel_deq, channel, true); } else { percpu_channel_deq(channel); put_cpu(); } if (channel->primary_channel == NULL) { spin_lock_irqsave(&vmbus_connection.channel_lock, flags); list_del(&channel->listentry); spin_unlock_irqrestore(&vmbus_connection.channel_lock, flags); } else { primary_channel = channel->primary_channel; spin_lock_irqsave(&primary_channel->lock, flags); list_del(&channel->sc_list); spin_unlock_irqrestore(&primary_channel->lock, flags); } free_channel(channel); } void vmbus_free_channels(void) { struct vmbus_channel *channel; list_for_each_entry(channel, &vmbus_connection.chn_list, listentry) { vmbus_device_unregister(channel->device_obj); free_channel(channel); } } /* * vmbus_process_offer - Process the offer by creating a channel/device * associated with this offer */ static void vmbus_process_offer(struct work_struct *work) { struct vmbus_channel *newchannel = container_of(work, struct vmbus_channel, work); struct vmbus_channel *channel; bool fnew = true; bool enq = false; int ret; unsigned long flags; /* Make sure this is a new offer */ spin_lock_irqsave(&vmbus_connection.channel_lock, flags); list_for_each_entry(channel, &vmbus_connection.chn_list, listentry) { if (!uuid_le_cmp(channel->offermsg.offer.if_type, newchannel->offermsg.offer.if_type) && !uuid_le_cmp(channel->offermsg.offer.if_instance, newchannel->offermsg.offer.if_instance)) { fnew = false; break; } } if (fnew) { list_add_tail(&newchannel->listentry, &vmbus_connection.chn_list); enq = true; } spin_unlock_irqrestore(&vmbus_connection.channel_lock, flags); if (enq) { if (newchannel->target_cpu != get_cpu()) { put_cpu(); smp_call_function_single(newchannel->target_cpu, percpu_channel_enq, newchannel, true); } else { percpu_channel_enq(newchannel); put_cpu(); } } if (!fnew) { /* * Check to see if this is a sub-channel. */ if (newchannel->offermsg.offer.sub_channel_index != 0) { /* * Process the sub-channel. */ newchannel->primary_channel = channel; spin_lock_irqsave(&channel->lock, flags); list_add_tail(&newchannel->sc_list, &channel->sc_list); spin_unlock_irqrestore(&channel->lock, flags); if (newchannel->target_cpu != get_cpu()) { put_cpu(); smp_call_function_single(newchannel->target_cpu, percpu_channel_enq, newchannel, true); } else { percpu_channel_enq(newchannel); put_cpu(); } newchannel->state = CHANNEL_OPEN_STATE; if (channel->sc_creation_callback != NULL) channel->sc_creation_callback(newchannel); goto done_init_rescind; } goto err_free_chan; } /* * This state is used to indicate a successful open * so that when we do close the channel normally, we * can cleanup properly */ newchannel->state = CHANNEL_OPEN_STATE; /* * Start the process of binding this offer to the driver * We need to set the DeviceObject field before calling * vmbus_child_dev_add() */ newchannel->device_obj = vmbus_device_create( &newchannel->offermsg.offer.if_type, &newchannel->offermsg.offer.if_instance, newchannel); if (!newchannel->device_obj) goto err_free_chan; /* * Add the new device to the bus. This will kick off device-driver * binding which eventually invokes the device driver's AddDevice() * method. */ ret = vmbus_device_register(newchannel->device_obj); if (ret != 0) { pr_err("unable to add child device object (relid %d)\n", newchannel->offermsg.child_relid); spin_lock_irqsave(&vmbus_connection.channel_lock, flags); list_del(&newchannel->listentry); spin_unlock_irqrestore(&vmbus_connection.channel_lock, flags); kfree(newchannel->device_obj); goto err_free_chan; } done_init_rescind: spin_lock_irqsave(&newchannel->lock, flags); /* The next possible work is rescind handling */ INIT_WORK(&newchannel->work, vmbus_process_rescind_offer); /* Check if rescind offer was already received */ if (newchannel->rescind) queue_work(newchannel->controlwq, &newchannel->work); spin_unlock_irqrestore(&newchannel->lock, flags); return; err_free_chan: free_channel(newchannel); } enum { IDE = 0, SCSI, NIC, MAX_PERF_CHN, }; /* * This is an array of device_ids (device types) that are performance critical. * We attempt to distribute the interrupt load for these devices across * all available CPUs. */ static const struct hv_vmbus_device_id hp_devs[] = { /* IDE */ { HV_IDE_GUID, }, /* Storage - SCSI */ { HV_SCSI_GUID, }, /* Network */ { HV_NIC_GUID, }, /* NetworkDirect Guest RDMA */ { HV_ND_GUID, }, }; /* * We use this state to statically distribute the channel interrupt load. */ static u32 next_vp; /* * Starting with Win8, we can statically distribute the incoming * channel interrupt load by binding a channel to VCPU. We * implement here a simple round robin scheme for distributing * the interrupt load. * We will bind channels that are not performance critical to cpu 0 and * performance critical channels (IDE, SCSI and Network) will be uniformly * distributed across all available CPUs. */ static void init_vp_index(struct vmbus_channel *channel, const uuid_le *type_guid) { u32 cur_cpu; int i; bool perf_chn = false; u32 max_cpus = num_online_cpus(); for (i = IDE; i < MAX_PERF_CHN; i++) { if (!memcmp(type_guid->b, hp_devs[i].guid, sizeof(uuid_le))) { perf_chn = true; break; } } if ((vmbus_proto_version == VERSION_WS2008) || (vmbus_proto_version == VERSION_WIN7) || (!perf_chn)) { /* * Prior to win8, all channel interrupts are * delivered on cpu 0. * Also if the channel is not a performance critical * channel, bind it to cpu 0. */ channel->target_cpu = 0; channel->target_vp = 0; return; } cur_cpu = (++next_vp % max_cpus); channel->target_cpu = cur_cpu; channel->target_vp = hv_context.vp_index[cur_cpu]; } /* * vmbus_onoffer - Handler for channel offers from vmbus in parent partition. * */ static void vmbus_onoffer(struct vmbus_channel_message_header *hdr) { struct vmbus_channel_offer_channel *offer; struct vmbus_channel *newchannel; offer = (struct vmbus_channel_offer_channel *)hdr; /* Allocate the channel object and save this offer. */ newchannel = alloc_channel(); if (!newchannel) { pr_err("Unable to allocate channel object\n"); return; } /* * By default we setup state to enable batched * reading. A specific service can choose to * disable this prior to opening the channel. */ newchannel->batched_reading = true; /* * Setup state for signalling the host. */ newchannel->sig_event = (struct hv_input_signal_event *) (ALIGN((unsigned long) &newchannel->sig_buf, HV_HYPERCALL_PARAM_ALIGN)); newchannel->sig_event->connectionid.asu32 = 0; newchannel->sig_event->connectionid.u.id = VMBUS_EVENT_CONNECTION_ID; newchannel->sig_event->flag_number = 0; newchannel->sig_event->rsvdz = 0; if (vmbus_proto_version != VERSION_WS2008) { newchannel->is_dedicated_interrupt = (offer->is_dedicated_interrupt != 0); newchannel->sig_event->connectionid.u.id = offer->connection_id; } init_vp_index(newchannel, &offer->offer.if_type); memcpy(&newchannel->offermsg, offer, sizeof(struct vmbus_channel_offer_channel)); newchannel->monitor_grp = (u8)offer->monitorid / 32; newchannel->monitor_bit = (u8)offer->monitorid % 32; INIT_WORK(&newchannel->work, vmbus_process_offer); queue_work(newchannel->controlwq, &newchannel->work); } /* * vmbus_onoffer_rescind - Rescind offer handler. * * We queue a work item to process this offer synchronously */ static void vmbus_onoffer_rescind(struct vmbus_channel_message_header *hdr) { struct vmbus_channel_rescind_offer *rescind; struct vmbus_channel *channel; unsigned long flags; rescind = (struct vmbus_channel_rescind_offer *)hdr; channel = relid2channel(rescind->child_relid); if (channel == NULL) /* Just return here, no channel found */ return; spin_lock_irqsave(&channel->lock, flags); channel->rescind = true; /* * channel->work.func != vmbus_process_rescind_offer means we are still * processing offer request and the rescind offer processing should be * postponed. It will be done at the very end of vmbus_process_offer() * as rescind flag is being checked there. */ if (channel->work.func == vmbus_process_rescind_offer) /* work is initialized for vmbus_process_rescind_offer() from * vmbus_process_offer() where the channel got created */ queue_work(channel->controlwq, &channel->work); spin_unlock_irqrestore(&channel->lock, flags); } /* * vmbus_onoffers_delivered - * This is invoked when all offers have been delivered. * * Nothing to do here. */ static void vmbus_onoffers_delivered( struct vmbus_channel_message_header *hdr) { } /* * vmbus_onopen_result - Open result handler. * * This is invoked when we received a response to our channel open request. * Find the matching request, copy the response and signal the requesting * thread. */ static void vmbus_onopen_result(struct vmbus_channel_message_header *hdr) { struct vmbus_channel_open_result *result; struct vmbus_channel_msginfo *msginfo; struct vmbus_channel_message_header *requestheader; struct vmbus_channel_open_channel *openmsg; unsigned long flags; result = (struct vmbus_channel_open_result *)hdr; /* * Find the open msg, copy the result and signal/unblock the wait event */ spin_lock_irqsave(&vmbus_connection.channelmsg_lock, flags); list_for_each_entry(msginfo, &vmbus_connection.chn_msg_list, msglistentry) { requestheader = (struct vmbus_channel_message_header *)msginfo->msg; if (requestheader->msgtype == CHANNELMSG_OPENCHANNEL) { openmsg = (struct vmbus_channel_open_channel *)msginfo->msg; if (openmsg->child_relid == result->child_relid && openmsg->openid == result->openid) { memcpy(&msginfo->response.open_result, result, sizeof( struct vmbus_channel_open_result)); complete(&msginfo->waitevent); break; } } } spin_unlock_irqrestore(&vmbus_connection.channelmsg_lock, flags); } /* * vmbus_ongpadl_created - GPADL created handler. * * This is invoked when we received a response to our gpadl create request. * Find the matching request, copy the response and signal the requesting * thread. */ static void vmbus_ongpadl_created(struct vmbus_channel_message_header *hdr) { struct vmbus_channel_gpadl_created *gpadlcreated; struct vmbus_channel_msginfo *msginfo; struct vmbus_channel_message_header *requestheader; struct vmbus_channel_gpadl_header *gpadlheader; unsigned long flags; gpadlcreated = (struct vmbus_channel_gpadl_created *)hdr; /* * Find the establish msg, copy the result and signal/unblock the wait * event */ spin_lock_irqsave(&vmbus_connection.channelmsg_lock, flags); list_for_each_entry(msginfo, &vmbus_connection.chn_msg_list, msglistentry) { requestheader = (struct vmbus_channel_message_header *)msginfo->msg; if (requestheader->msgtype == CHANNELMSG_GPADL_HEADER) { gpadlheader = (struct vmbus_channel_gpadl_header *)requestheader; if ((gpadlcreated->child_relid == gpadlheader->child_relid) && (gpadlcreated->gpadl == gpadlheader->gpadl)) { memcpy(&msginfo->response.gpadl_created, gpadlcreated, sizeof( struct vmbus_channel_gpadl_created)); complete(&msginfo->waitevent); break; } } } spin_unlock_irqrestore(&vmbus_connection.channelmsg_lock, flags); } /* * vmbus_ongpadl_torndown - GPADL torndown handler. * * This is invoked when we received a response to our gpadl teardown request. * Find the matching request, copy the response and signal the requesting * thread. */ static void vmbus_ongpadl_torndown( struct vmbus_channel_message_header *hdr) { struct vmbus_channel_gpadl_torndown *gpadl_torndown; struct vmbus_channel_msginfo *msginfo; struct vmbus_channel_message_header *requestheader; struct vmbus_channel_gpadl_teardown *gpadl_teardown; unsigned long flags; gpadl_torndown = (struct vmbus_channel_gpadl_torndown *)hdr; /* * Find the open msg, copy the result and signal/unblock the wait event */ spin_lock_irqsave(&vmbus_connection.channelmsg_lock, flags); list_for_each_entry(msginfo, &vmbus_connection.chn_msg_list, msglistentry) { requestheader = (struct vmbus_channel_message_header *)msginfo->msg; if (requestheader->msgtype == CHANNELMSG_GPADL_TEARDOWN) { gpadl_teardown = (struct vmbus_channel_gpadl_teardown *)requestheader; if (gpadl_torndown->gpadl == gpadl_teardown->gpadl) { memcpy(&msginfo->response.gpadl_torndown, gpadl_torndown, sizeof( struct vmbus_channel_gpadl_torndown)); complete(&msginfo->waitevent); break; } } } spin_unlock_irqrestore(&vmbus_connection.channelmsg_lock, flags); } /* * vmbus_onversion_response - Version response handler * * This is invoked when we received a response to our initiate contact request. * Find the matching request, copy the response and signal the requesting * thread. */ static void vmbus_onversion_response( struct vmbus_channel_message_header *hdr) { struct vmbus_channel_msginfo *msginfo; struct vmbus_channel_message_header *requestheader; struct vmbus_channel_version_response *version_response; unsigned long flags; version_response = (struct vmbus_channel_version_response *)hdr; spin_lock_irqsave(&vmbus_connection.channelmsg_lock, flags); list_for_each_entry(msginfo, &vmbus_connection.chn_msg_list, msglistentry) { requestheader = (struct vmbus_channel_message_header *)msginfo->msg; if (requestheader->msgtype == CHANNELMSG_INITIATE_CONTACT) { memcpy(&msginfo->response.version_response, version_response, sizeof(struct vmbus_channel_version_response)); complete(&msginfo->waitevent); } } spin_unlock_irqrestore(&vmbus_connection.channelmsg_lock, flags); } /* Channel message dispatch table */ static struct vmbus_channel_message_table_entry channel_message_table[CHANNELMSG_COUNT] = { {CHANNELMSG_INVALID, NULL}, {CHANNELMSG_OFFERCHANNEL, vmbus_onoffer}, {CHANNELMSG_RESCIND_CHANNELOFFER, vmbus_onoffer_rescind}, {CHANNELMSG_REQUESTOFFERS, NULL}, {CHANNELMSG_ALLOFFERS_DELIVERED, vmbus_onoffers_delivered}, {CHANNELMSG_OPENCHANNEL, NULL}, {CHANNELMSG_OPENCHANNEL_RESULT, vmbus_onopen_result}, {CHANNELMSG_CLOSECHANNEL, NULL}, {CHANNELMSG_GPADL_HEADER, NULL}, {CHANNELMSG_GPADL_BODY, NULL}, {CHANNELMSG_GPADL_CREATED, vmbus_ongpadl_created}, {CHANNELMSG_GPADL_TEARDOWN, NULL}, {CHANNELMSG_GPADL_TORNDOWN, vmbus_ongpadl_torndown}, {CHANNELMSG_RELID_RELEASED, NULL}, {CHANNELMSG_INITIATE_CONTACT, NULL}, {CHANNELMSG_VERSION_RESPONSE, vmbus_onversion_response}, {CHANNELMSG_UNLOAD, NULL}, }; /* * vmbus_onmessage - Handler for channel protocol messages. * * This is invoked in the vmbus worker thread context. */ void vmbus_onmessage(void *context) { struct hv_message *msg = context; struct vmbus_channel_message_header *hdr; int size; hdr = (struct vmbus_channel_message_header *)msg->u.payload; size = msg->header.payload_size; if (hdr->msgtype >= CHANNELMSG_COUNT) { pr_err("Received invalid channel message type %d size %d\n", hdr->msgtype, size); print_hex_dump_bytes("", DUMP_PREFIX_NONE, (unsigned char *)msg->u.payload, size); return; } if (channel_message_table[hdr->msgtype].message_handler) channel_message_table[hdr->msgtype].message_handler(hdr); else pr_err("Unhandled channel message type %d\n", hdr->msgtype); } /* * vmbus_request_offers - Send a request to get all our pending offers. */ int vmbus_request_offers(void) { struct vmbus_channel_message_header *msg; struct vmbus_channel_msginfo *msginfo; int ret; unsigned long t; msginfo = kmalloc(sizeof(*msginfo) + sizeof(struct vmbus_channel_message_header), GFP_KERNEL); if (!msginfo) return -ENOMEM; init_completion(&msginfo->waitevent); msg = (struct vmbus_channel_message_header *)msginfo->msg; msg->msgtype = CHANNELMSG_REQUESTOFFERS; ret = vmbus_post_msg(msg, sizeof(struct vmbus_channel_message_header)); if (ret != 0) { pr_err("Unable to request offers - %d\n", ret); goto cleanup; } t = wait_for_completion_timeout(&msginfo->waitevent, 5*HZ); if (t == 0) { ret = -ETIMEDOUT; goto cleanup; } cleanup: kfree(msginfo); return ret; } /* * Retrieve the (sub) channel on which to send an outgoing request. * When a primary channel has multiple sub-channels, we choose a * channel whose VCPU binding is closest to the VCPU on which * this call is being made. */ struct vmbus_channel *vmbus_get_outgoing_channel(struct vmbus_channel *primary) { struct list_head *cur, *tmp; int cur_cpu; struct vmbus_channel *cur_channel; struct vmbus_channel *outgoing_channel = primary; int cpu_distance, new_cpu_distance; if (list_empty(&primary->sc_list)) return outgoing_channel; cur_cpu = hv_context.vp_index[get_cpu()]; put_cpu(); list_for_each_safe(cur, tmp, &primary->sc_list) { cur_channel = list_entry(cur, struct vmbus_channel, sc_list); if (cur_channel->state != CHANNEL_OPENED_STATE) continue; if (cur_channel->target_vp == cur_cpu) return cur_channel; cpu_distance = ((outgoing_channel->target_vp > cur_cpu) ? (outgoing_channel->target_vp - cur_cpu) : (cur_cpu - outgoing_channel->target_vp)); new_cpu_distance = ((cur_channel->target_vp > cur_cpu) ? (cur_channel->target_vp - cur_cpu) : (cur_cpu - cur_channel->target_vp)); if (cpu_distance < new_cpu_distance) continue; outgoing_channel = cur_channel; } return outgoing_channel; } EXPORT_SYMBOL_GPL(vmbus_get_outgoing_channel); static void invoke_sc_cb(struct vmbus_channel *primary_channel) { struct list_head *cur, *tmp; struct vmbus_channel *cur_channel; if (primary_channel->sc_creation_callback == NULL) return; list_for_each_safe(cur, tmp, &primary_channel->sc_list) { cur_channel = list_entry(cur, struct vmbus_channel, sc_list); primary_channel->sc_creation_callback(cur_channel); } } void vmbus_set_sc_create_callback(struct vmbus_channel *primary_channel, void (*sc_cr_cb)(struct vmbus_channel *new_sc)) { primary_channel->sc_creation_callback = sc_cr_cb; } EXPORT_SYMBOL_GPL(vmbus_set_sc_create_callback); bool vmbus_are_subchannels_present(struct vmbus_channel *primary) { bool ret; ret = !list_empty(&primary->sc_list); if (ret) { /* * Invoke the callback on sub-channel creation. * This will present a uniform interface to the * clients. */ invoke_sc_cb(primary); } return ret; } EXPORT_SYMBOL_GPL(vmbus_are_subchannels_present);