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WSL2-Linux-Kernel
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WSL2-Linux-Kernel/drivers/hv/channel_mgmt.c

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// SPDX-License-Identifier: GPL-2.0-only
/*
* Copyright (c) 2009, Microsoft Corporation.
*
* Authors:
* Haiyang Zhang <haiyangz@microsoft.com>
* Hank Janssen <hjanssen@microsoft.com>
*/
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/kernel.h>
#include <linux/interrupt.h>
#include <linux/sched.h>
#include <linux/wait.h>
#include <linux/mm.h>
#include <linux/slab.h>
#include <linux/list.h>
#include <linux/module.h>
#include <linux/completion.h>
#include <linux/delay.h>
#include <linux/cpu.h>
#include <linux/hyperv.h>
#include <asm/mshyperv.h>
#include <linux/sched/isolation.h>
#include "hyperv_vmbus.h"
static void init_vp_index(struct vmbus_channel *channel);
const struct vmbus_device vmbus_devs[] = {
/* IDE */
{ .dev_type = HV_IDE,
HV_IDE_GUID,
.perf_device = true,
.allowed_in_isolated = false,
},
/* SCSI */
{ .dev_type = HV_SCSI,
HV_SCSI_GUID,
.perf_device = true,
.allowed_in_isolated = true,
},
/* Fibre Channel */
{ .dev_type = HV_FC,
HV_SYNTHFC_GUID,
.perf_device = true,
.allowed_in_isolated = false,
},
/* Synthetic NIC */
{ .dev_type = HV_NIC,
HV_NIC_GUID,
.perf_device = true,
.allowed_in_isolated = true,
},
/* Network Direct */
{ .dev_type = HV_ND,
HV_ND_GUID,
.perf_device = true,
.allowed_in_isolated = false,
},
/* PCIE */
{ .dev_type = HV_PCIE,
HV_PCIE_GUID,
.perf_device = false,
.allowed_in_isolated = false,
},
/* Synthetic Frame Buffer */
{ .dev_type = HV_FB,
HV_SYNTHVID_GUID,
.perf_device = false,
.allowed_in_isolated = false,
},
/* Synthetic Keyboard */
{ .dev_type = HV_KBD,
HV_KBD_GUID,
.perf_device = false,
.allowed_in_isolated = false,
},
/* Synthetic MOUSE */
{ .dev_type = HV_MOUSE,
HV_MOUSE_GUID,
.perf_device = false,
.allowed_in_isolated = false,
},
/* KVP */
{ .dev_type = HV_KVP,
HV_KVP_GUID,
.perf_device = false,
.allowed_in_isolated = false,
},
/* Time Synch */
{ .dev_type = HV_TS,
HV_TS_GUID,
.perf_device = false,
.allowed_in_isolated = true,
},
/* Heartbeat */
{ .dev_type = HV_HB,
HV_HEART_BEAT_GUID,
.perf_device = false,
.allowed_in_isolated = true,
},
/* Shutdown */
{ .dev_type = HV_SHUTDOWN,
HV_SHUTDOWN_GUID,
.perf_device = false,
.allowed_in_isolated = true,
},
/* File copy */
{ .dev_type = HV_FCOPY,
HV_FCOPY_GUID,
.perf_device = false,
.allowed_in_isolated = false,
},
/* Backup */
{ .dev_type = HV_BACKUP,
HV_VSS_GUID,
.perf_device = false,
.allowed_in_isolated = false,
},
/* Dynamic Memory */
{ .dev_type = HV_DM,
HV_DM_GUID,
.perf_device = false,
.allowed_in_isolated = false,
},
/* Unknown GUID */
{ .dev_type = HV_UNKNOWN,
.perf_device = false,
.allowed_in_isolated = false,
},
};
static const struct {
guid_t guid;
} vmbus_unsupported_devs[] = {
{ HV_AVMA1_GUID },
{ HV_AVMA2_GUID },
{ HV_RDV_GUID },
{ HV_IMC_GUID },
};
/*
* The rescinded channel may be blocked waiting for a response from the host;
* take care of that.
*/
static void vmbus_rescind_cleanup(struct vmbus_channel *channel)
{
struct vmbus_channel_msginfo *msginfo;
unsigned long flags;
spin_lock_irqsave(&vmbus_connection.channelmsg_lock, flags);
channel->rescind = true;
list_for_each_entry(msginfo, &vmbus_connection.chn_msg_list,
msglistentry) {
if (msginfo->waiting_channel == channel) {
complete(&msginfo->waitevent);
break;
}
}
spin_unlock_irqrestore(&vmbus_connection.channelmsg_lock, flags);
}
static bool is_unsupported_vmbus_devs(const guid_t *guid)
{
int i;
for (i = 0; i < ARRAY_SIZE(vmbus_unsupported_devs); i++)
if (guid_equal(guid, &vmbus_unsupported_devs[i].guid))
return true;
return false;
}
static u16 hv_get_dev_type(const struct vmbus_channel *channel)
{
const guid_t *guid = &channel->offermsg.offer.if_type;
u16 i;
if (is_hvsock_channel(channel) || is_unsupported_vmbus_devs(guid))
return HV_UNKNOWN;
for (i = HV_IDE; i < HV_UNKNOWN; i++) {
if (guid_equal(guid, &vmbus_devs[i].guid))
return i;
}
pr_info("Unknown GUID: %pUl\n", guid);
return i;
}
/**
* vmbus_prep_negotiate_resp() - Create default response for Negotiate message
* @icmsghdrp: Pointer to msg header structure
* @buf: Raw buffer channel data
* @buflen: Length of the raw buffer channel data.
* @fw_version: The framework versions we can support.
* @fw_vercnt: The size of @fw_version.
* @srv_version: The service versions we can support.
* @srv_vercnt: The size of @srv_version.
* @nego_fw_version: The selected framework version.
* @nego_srv_version: The selected service version.
*
* Note: Versions are given in decreasing order.
*
* Set up and fill in default negotiate response message.
* Mainly used by Hyper-V drivers.
*/
bool vmbus_prep_negotiate_resp(struct icmsg_hdr *icmsghdrp, u8 *buf,
u32 buflen, const int *fw_version, int fw_vercnt,
const int *srv_version, int srv_vercnt,
int *nego_fw_version, int *nego_srv_version)
{
int icframe_major, icframe_minor;
int icmsg_major, icmsg_minor;
int fw_major, fw_minor;
int srv_major, srv_minor;
int i, j;
bool found_match = false;
struct icmsg_negotiate *negop;
/* Check that there's enough space for icframe_vercnt, icmsg_vercnt */
if (buflen < ICMSG_HDR + offsetof(struct icmsg_negotiate, reserved)) {
pr_err_ratelimited("Invalid icmsg negotiate\n");
return false;
}
icmsghdrp->icmsgsize = 0x10;
negop = (struct icmsg_negotiate *)&buf[ICMSG_HDR];
icframe_major = negop->icframe_vercnt;
icframe_minor = 0;
icmsg_major = negop->icmsg_vercnt;
icmsg_minor = 0;
/* Validate negop packet */
if (icframe_major > IC_VERSION_NEGOTIATION_MAX_VER_COUNT ||
icmsg_major > IC_VERSION_NEGOTIATION_MAX_VER_COUNT ||
ICMSG_NEGOTIATE_PKT_SIZE(icframe_major, icmsg_major) > buflen) {
pr_err_ratelimited("Invalid icmsg negotiate - icframe_major: %u, icmsg_major: %u\n",
icframe_major, icmsg_major);
goto fw_error;
}
/*
* Select the framework version number we will
* support.
*/
for (i = 0; i < fw_vercnt; i++) {
fw_major = (fw_version[i] >> 16);
fw_minor = (fw_version[i] & 0xFFFF);
for (j = 0; j < negop->icframe_vercnt; j++) {
if ((negop->icversion_data[j].major == fw_major) &&
(negop->icversion_data[j].minor == fw_minor)) {
icframe_major = negop->icversion_data[j].major;
icframe_minor = negop->icversion_data[j].minor;
found_match = true;
break;
}
}
if (found_match)
break;
}
if (!found_match)
goto fw_error;
found_match = false;
for (i = 0; i < srv_vercnt; i++) {
srv_major = (srv_version[i] >> 16);
srv_minor = (srv_version[i] & 0xFFFF);
for (j = negop->icframe_vercnt;
(j < negop->icframe_vercnt + negop->icmsg_vercnt);
j++) {
if ((negop->icversion_data[j].major == srv_major) &&
(negop->icversion_data[j].minor == srv_minor)) {
icmsg_major = negop->icversion_data[j].major;
icmsg_minor = negop->icversion_data[j].minor;
found_match = true;
break;
}
}
if (found_match)
break;
}
/*
* 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;
}
if (nego_fw_version)
*nego_fw_version = (icframe_major << 16) | icframe_minor;
if (nego_srv_version)
*nego_srv_version = (icmsg_major << 16) | icmsg_minor;
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)
{
struct vmbus_channel *channel;
channel = kzalloc(sizeof(*channel), GFP_ATOMIC);
if (!channel)
return NULL;
spin_lock_init(&channel->sched_lock);
init_completion(&channel->rescind_event);
INIT_LIST_HEAD(&channel->sc_list);
tasklet_init(&channel->callback_event,
vmbus_on_event, (unsigned long)channel);
hv_ringbuffer_pre_init(channel);
return channel;
}
/*
* free_channel - Release the resources used by the vmbus channel object
*/
static void free_channel(struct vmbus_channel *channel)
{
tasklet_kill(&channel->callback_event);
vmbus_remove_channel_attr_group(channel);
kobject_put(&channel->kobj);
}
void vmbus_channel_map_relid(struct vmbus_channel *channel)
{
if (WARN_ON(channel->offermsg.child_relid >= MAX_CHANNEL_RELIDS))
return;
/*
* The mapping of the channel's relid is visible from the CPUs that
* execute vmbus_chan_sched() by the time that vmbus_chan_sched() will
* execute:
*
* (a) In the "normal (i.e., not resuming from hibernation)" path,
* the full barrier in virt_store_mb() guarantees that the store
* is propagated to all CPUs before the add_channel_work work
* is queued. In turn, add_channel_work is queued before the
* channel's ring buffer is allocated/initialized and the
* OPENCHANNEL message for the channel is sent in vmbus_open().
* Hyper-V won't start sending the interrupts for the channel
* before the OPENCHANNEL message is acked. The memory barrier
* in vmbus_chan_sched() -> sync_test_and_clear_bit() ensures
* that vmbus_chan_sched() must find the channel's relid in
* recv_int_page before retrieving the channel pointer from the
* array of channels.
*
* (b) In the "resuming from hibernation" path, the virt_store_mb()
* guarantees that the store is propagated to all CPUs before
* the VMBus connection is marked as ready for the resume event
* (cf. check_ready_for_resume_event()). The interrupt handler
* of the VMBus driver and vmbus_chan_sched() can not run before
* vmbus_bus_resume() has completed execution (cf. resume_noirq).
*/
virt_store_mb(
vmbus_connection.channels[channel->offermsg.child_relid],
channel);
}
void vmbus_channel_unmap_relid(struct vmbus_channel *channel)
{
if (WARN_ON(channel->offermsg.child_relid >= MAX_CHANNEL_RELIDS))
return;
WRITE_ONCE(
vmbus_connection.channels[channel->offermsg.child_relid],
NULL);
}
static void vmbus_release_relid(u32 relid)
{
struct vmbus_channel_relid_released msg;
int ret;
memset(&msg, 0, sizeof(struct vmbus_channel_relid_released));
msg.child_relid = relid;
msg.header.msgtype = CHANNELMSG_RELID_RELEASED;
ret = vmbus_post_msg(&msg, sizeof(struct vmbus_channel_relid_released),
true);
trace_vmbus_release_relid(&msg, ret);
}
void hv_process_channel_removal(struct vmbus_channel *channel)
{
lockdep_assert_held(&vmbus_connection.channel_mutex);
BUG_ON(!channel->rescind);
/*
* hv_process_channel_removal() could find INVALID_RELID only for
* hv_sock channels. See the inline comments in vmbus_onoffer().
*/
WARN_ON(channel->offermsg.child_relid == INVALID_RELID &&
!is_hvsock_channel(channel));
/*
* Upon suspend, an in-use hv_sock channel is removed from the array of
* channels and the relid is invalidated. After hibernation, when the
* user-space application destroys the channel, it's unnecessary and
* unsafe to remove the channel from the array of channels. See also
* the inline comments before the call of vmbus_release_relid() below.
*/
if (channel->offermsg.child_relid != INVALID_RELID)
vmbus_channel_unmap_relid(channel);
if (channel->primary_channel == NULL)
list_del(&channel->listentry);
else
list_del(&channel->sc_list);
/*
* If this is a "perf" channel, updates the hv_numa_map[] masks so that
* init_vp_index() can (re-)use the CPU.
*/
if (hv_is_perf_channel(channel))
hv_clear_allocated_cpu(channel->target_cpu);
/*
* Upon suspend, an in-use hv_sock channel is marked as "rescinded" and
* the relid is invalidated; after hibernation, when the user-space app
* destroys the channel, the relid is INVALID_RELID, and in this case
* it's unnecessary and unsafe to release the old relid, since the same
* relid can refer to a completely different channel now.
*/
if (channel->offermsg.child_relid != INVALID_RELID)
vmbus_release_relid(channel->offermsg.child_relid);
free_channel(channel);
}
void vmbus_free_channels(void)
{
struct vmbus_channel *channel, *tmp;
list_for_each_entry_safe(channel, tmp, &vmbus_connection.chn_list,
listentry) {
/* hv_process_channel_removal() needs this */
channel->rescind = true;
vmbus_device_unregister(channel->device_obj);
}
}
/* Note: the function can run concurrently for primary/sub channels. */
static void vmbus_add_channel_work(struct work_struct *work)
{
struct vmbus_channel *newchannel =
container_of(work, struct vmbus_channel, add_channel_work);
struct vmbus_channel *primary_channel = newchannel->primary_channel;
int ret;
/*
* 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;
if (primary_channel != NULL) {
/* newchannel is a sub-channel. */
struct hv_device *dev = primary_channel->device_obj;
if (vmbus_add_channel_kobj(dev, newchannel))
goto err_deq_chan;
if (primary_channel->sc_creation_callback != NULL)
primary_channel->sc_creation_callback(newchannel);
newchannel->probe_done = true;
return;
}
/*
* Start the process of binding the primary channel to the driver
*/
newchannel->device_obj = vmbus_device_create(
&newchannel->offermsg.offer.if_type,
&newchannel->offermsg.offer.if_instance,
newchannel);
if (!newchannel->device_obj)
goto err_deq_chan;
newchannel->device_obj->device_id = newchannel->device_id;
/*
* 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);
kfree(newchannel->device_obj);
goto err_deq_chan;
}
newchannel->probe_done = true;
return;
err_deq_chan:
mutex_lock(&vmbus_connection.channel_mutex);
/*
* We need to set the flag, otherwise
* vmbus_onoffer_rescind() can be blocked.
*/
newchannel->probe_done = true;
if (primary_channel == NULL)
list_del(&newchannel->listentry);
else
list_del(&newchannel->sc_list);
/* vmbus_process_offer() has mapped the channel. */
vmbus_channel_unmap_relid(newchannel);
mutex_unlock(&vmbus_connection.channel_mutex);
vmbus_release_relid(newchannel->offermsg.child_relid);
free_channel(newchannel);
}
/*
* vmbus_process_offer - Process the offer by creating a channel/device
* associated with this offer
*/
static void vmbus_process_offer(struct vmbus_channel *newchannel)
{
struct vmbus_channel *channel;
struct workqueue_struct *wq;
bool fnew = true;
/*
* Synchronize vmbus_process_offer() and CPU hotplugging:
*
* CPU1 CPU2
*
* [vmbus_process_offer()] [Hot removal of the CPU]
*
* CPU_READ_LOCK CPUS_WRITE_LOCK
* LOAD cpu_online_mask SEARCH chn_list
* STORE target_cpu LOAD target_cpu
* INSERT chn_list STORE cpu_online_mask
* CPUS_READ_UNLOCK CPUS_WRITE_UNLOCK
*
* Forbids: CPU1's LOAD from *not* seing CPU2's STORE &&
* CPU2's SEARCH from *not* seeing CPU1's INSERT
*
* Forbids: CPU2's SEARCH from seeing CPU1's INSERT &&
* CPU2's LOAD from *not* seing CPU1's STORE
*/
cpus_read_lock();
/*
* Serializes the modifications of the chn_list list as well as
* the accesses to next_numa_node_id in init_vp_index().
*/
mutex_lock(&vmbus_connection.channel_mutex);
list_for_each_entry(channel, &vmbus_connection.chn_list, listentry) {
if (guid_equal(&channel->offermsg.offer.if_type,
&newchannel->offermsg.offer.if_type) &&
guid_equal(&channel->offermsg.offer.if_instance,
&newchannel->offermsg.offer.if_instance)) {
fnew = false;
newchannel->primary_channel = channel;
break;
}
}
init_vp_index(newchannel);
/* Remember the channels that should be cleaned up upon suspend. */
if (is_hvsock_channel(newchannel) || is_sub_channel(newchannel))
atomic_inc(&vmbus_connection.nr_chan_close_on_suspend);
/*
* Now that we have acquired the channel_mutex,
* we can release the potentially racing rescind thread.
*/
atomic_dec(&vmbus_connection.offer_in_progress);
if (fnew) {
list_add_tail(&newchannel->listentry,
&vmbus_connection.chn_list);
} else {
/*
* Check to see if this is a valid sub-channel.
*/
if (newchannel->offermsg.offer.sub_channel_index == 0) {
mutex_unlock(&vmbus_connection.channel_mutex);
cpus_read_unlock();
/*
* Don't call free_channel(), because newchannel->kobj
* is not initialized yet.
*/
kfree(newchannel);
WARN_ON_ONCE(1);
return;
}
/*
* Process the sub-channel.
*/
list_add_tail(&newchannel->sc_list, &channel->sc_list);
}
vmbus_channel_map_relid(newchannel);
mutex_unlock(&vmbus_connection.channel_mutex);
cpus_read_unlock();
/*
* vmbus_process_offer() mustn't call channel->sc_creation_callback()
* directly for sub-channels, because sc_creation_callback() ->
* vmbus_open() may never get the host's response to the
* OPEN_CHANNEL message (the host may rescind a channel at any time,
* e.g. in the case of hot removing a NIC), and vmbus_onoffer_rescind()
* may not wake up the vmbus_open() as it's blocked due to a non-zero
* vmbus_connection.offer_in_progress, and finally we have a deadlock.
*
* The above is also true for primary channels, if the related device
* drivers use sync probing mode by default.
*
* And, usually the handling of primary channels and sub-channels can
* depend on each other, so we should offload them to different
* workqueues to avoid possible deadlock, e.g. in sync-probing mode,
* NIC1's netvsc_subchan_work() can race with NIC2's netvsc_probe() ->
* rtnl_lock(), and causes deadlock: the former gets the rtnl_lock
* and waits for all the sub-channels to appear, but the latter
* can't get the rtnl_lock and this blocks the handling of
* sub-channels.
*/
INIT_WORK(&newchannel->add_channel_work, vmbus_add_channel_work);
wq = fnew ? vmbus_connection.handle_primary_chan_wq :
vmbus_connection.handle_sub_chan_wq;
queue_work(wq, &newchannel->add_channel_work);
}
/*
* Check if CPUs used by other channels of the same device.
* It should only be called by init_vp_index().
*/
static bool hv_cpuself_used(u32 cpu, struct vmbus_channel *chn)
{
struct vmbus_channel *primary = chn->primary_channel;
struct vmbus_channel *sc;
lockdep_assert_held(&vmbus_connection.channel_mutex);
if (!primary)
return false;
if (primary->target_cpu == cpu)
return true;
list_for_each_entry(sc, &primary->sc_list, sc_list)
if (sc != chn && sc->target_cpu == cpu)
return true;
return false;
}
/*
* We use this state to statically distribute the channel interrupt load.
*/
static int next_numa_node_id;
/*
* We can statically distribute the incoming channel interrupt load
* by binding a channel to VCPU.
*
* For non-performance critical channels we assign the VMBUS_CONNECT_CPU.
* Performance critical channels will be distributed evenly among all
* the available NUMA nodes. Once the node is assigned, we will assign
* the CPU based on a simple round robin scheme.
*/
static void init_vp_index(struct vmbus_channel *channel)
{
bool perf_chn = hv_is_perf_channel(channel);
u32 i, ncpu = num_online_cpus();
cpumask_var_t available_mask;
struct cpumask *allocated_mask;
const struct cpumask *hk_mask = housekeeping_cpumask(HK_TYPE_MANAGED_IRQ);
u32 target_cpu;
int numa_node;
if (!perf_chn ||
!alloc_cpumask_var(&available_mask, GFP_KERNEL) ||
cpumask_empty(hk_mask)) {
/*
* If the channel is not a performance critical
* channel, bind it to VMBUS_CONNECT_CPU.
* In case alloc_cpumask_var() fails, bind it to
* VMBUS_CONNECT_CPU.
* If all the cpus are isolated, bind it to
* VMBUS_CONNECT_CPU.
*/
channel->target_cpu = VMBUS_CONNECT_CPU;
if (perf_chn)
hv_set_allocated_cpu(VMBUS_CONNECT_CPU);
return;
}
for (i = 1; i <= ncpu + 1; i++) {
while (true) {
numa_node = next_numa_node_id++;
if (numa_node == nr_node_ids) {
next_numa_node_id = 0;
continue;
}
if (cpumask_empty(cpumask_of_node(numa_node)))
continue;
break;
}
allocated_mask = &hv_context.hv_numa_map[numa_node];
retry:
cpumask_xor(available_mask, allocated_mask, cpumask_of_node(numa_node));
cpumask_and(available_mask, available_mask, hk_mask);
if (cpumask_empty(available_mask)) {
/*
* We have cycled through all the CPUs in the node;
* reset the allocated map.
*/
cpumask_clear(allocated_mask);
goto retry;
}
target_cpu = cpumask_first(available_mask);
cpumask_set_cpu(target_cpu, allocated_mask);
if (channel->offermsg.offer.sub_channel_index >= ncpu ||
i > ncpu || !hv_cpuself_used(target_cpu, channel))
break;
}
channel->target_cpu = target_cpu;
free_cpumask_var(available_mask);
}
#define UNLOAD_DELAY_UNIT_MS 10 /* 10 milliseconds */
#define UNLOAD_WAIT_MS (100*1000) /* 100 seconds */
#define UNLOAD_WAIT_LOOPS (UNLOAD_WAIT_MS/UNLOAD_DELAY_UNIT_MS)
#define UNLOAD_MSG_MS (5*1000) /* Every 5 seconds */
#define UNLOAD_MSG_LOOPS (UNLOAD_MSG_MS/UNLOAD_DELAY_UNIT_MS)
static void vmbus_wait_for_unload(void)
{
int cpu;
void *page_addr;
struct hv_message *msg;
struct vmbus_channel_message_header *hdr;
u32 message_type, i;
/*
* CHANNELMSG_UNLOAD_RESPONSE is always delivered to the CPU which was
* used for initial contact or to CPU0 depending on host version. When
* we're crashing on a different CPU let's hope that IRQ handler on
* the cpu which receives CHANNELMSG_UNLOAD_RESPONSE is still
* functional and vmbus_unload_response() will complete
* vmbus_connection.unload_event. If not, the last thing we can do is
* read message pages for all CPUs directly.
*
* Wait up to 100 seconds since an Azure host must writeback any dirty
* data in its disk cache before the VMbus UNLOAD request will
* complete. This flushing has been empirically observed to take up
* to 50 seconds in cases with a lot of dirty data, so allow additional
* leeway and for inaccuracies in mdelay(). But eventually time out so
* that the panic path can't get hung forever in case the response
* message isn't seen.
*/
for (i = 1; i <= UNLOAD_WAIT_LOOPS; i++) {
if (completion_done(&vmbus_connection.unload_event))
goto completed;
for_each_online_cpu(cpu) {
struct hv_per_cpu_context *hv_cpu
= per_cpu_ptr(hv_context.cpu_context, cpu);
page_addr = hv_cpu->synic_message_page;
msg = (struct hv_message *)page_addr
+ VMBUS_MESSAGE_SINT;
message_type = READ_ONCE(msg->header.message_type);
if (message_type == HVMSG_NONE)
continue;
hdr = (struct vmbus_channel_message_header *)
msg->u.payload;
if (hdr->msgtype == CHANNELMSG_UNLOAD_RESPONSE)
complete(&vmbus_connection.unload_event);
vmbus_signal_eom(msg, message_type);
}
/*
* Give a notice periodically so someone watching the
* serial output won't think it is completely hung.
*/
if (!(i % UNLOAD_MSG_LOOPS))
pr_notice("Waiting for VMBus UNLOAD to complete\n");
mdelay(UNLOAD_DELAY_UNIT_MS);
}
pr_err("Continuing even though VMBus UNLOAD did not complete\n");
completed:
/*
* We're crashing and already got the UNLOAD_RESPONSE, cleanup all
* maybe-pending messages on all CPUs to be able to receive new
* messages after we reconnect.
*/
for_each_online_cpu(cpu) {
struct hv_per_cpu_context *hv_cpu
= per_cpu_ptr(hv_context.cpu_context, cpu);
page_addr = hv_cpu->synic_message_page;
msg = (struct hv_message *)page_addr + VMBUS_MESSAGE_SINT;
msg->header.message_type = HVMSG_NONE;
}
}
/*
* vmbus_unload_response - Handler for the unload response.
*/
static void vmbus_unload_response(struct vmbus_channel_message_header *hdr)
{
/*
* This is a global event; just wakeup the waiting thread.
* Once we successfully unload, we can cleanup the monitor state.
*
* NB. A malicious or compromised Hyper-V could send a spurious
* message of type CHANNELMSG_UNLOAD_RESPONSE, and trigger a call
* of the complete() below. Make sure that unload_event has been
* initialized by the time this complete() is executed.
*/
complete(&vmbus_connection.unload_event);
}
void vmbus_initiate_unload(bool crash)
{
struct vmbus_channel_message_header hdr;
if (xchg(&vmbus_connection.conn_state, DISCONNECTED) == DISCONNECTED)
return;
/* Pre-Win2012R2 hosts don't support reconnect */
if (vmbus_proto_version < VERSION_WIN8_1)
return;
reinit_completion(&vmbus_connection.unload_event);
memset(&hdr, 0, sizeof(struct vmbus_channel_message_header));
hdr.msgtype = CHANNELMSG_UNLOAD;
vmbus_post_msg(&hdr, sizeof(struct vmbus_channel_message_header),
!crash);
/*
* vmbus_initiate_unload() is also called on crash and the crash can be
* happening in an interrupt context, where scheduling is impossible.
*/
if (!crash)
wait_for_completion(&vmbus_connection.unload_event);
else
vmbus_wait_for_unload();
}
static void check_ready_for_resume_event(void)
{
/*
* If all the old primary channels have been fixed up, then it's safe
* to resume.
*/
if (atomic_dec_and_test(&vmbus_connection.nr_chan_fixup_on_resume))
complete(&vmbus_connection.ready_for_resume_event);
}
static void vmbus_setup_channel_state(struct vmbus_channel *channel,
struct vmbus_channel_offer_channel *offer)
{
/*
* Setup state for signalling the host.
*/
channel->sig_event = VMBUS_EVENT_CONNECTION_ID;
channel->is_dedicated_interrupt =
(offer->is_dedicated_interrupt != 0);
channel->sig_event = offer->connection_id;
memcpy(&channel->offermsg, offer,
sizeof(struct vmbus_channel_offer_channel));
channel->monitor_grp = (u8)offer->monitorid / 32;
channel->monitor_bit = (u8)offer->monitorid % 32;
channel->device_id = hv_get_dev_type(channel);
}
/*
* find_primary_channel_by_offer - Get the channel object given the new offer.
* This is only used in the resume path of hibernation.
*/
static struct vmbus_channel *
find_primary_channel_by_offer(const struct vmbus_channel_offer_channel *offer)
{
struct vmbus_channel *channel = NULL, *iter;
const guid_t *inst1, *inst2;
/* Ignore sub-channel offers. */
if (offer->offer.sub_channel_index != 0)
return NULL;
mutex_lock(&vmbus_connection.channel_mutex);
list_for_each_entry(iter, &vmbus_connection.chn_list, listentry) {
inst1 = &iter->offermsg.offer.if_instance;
inst2 = &offer->offer.if_instance;
if (guid_equal(inst1, inst2)) {
channel = iter;
break;
}
}
mutex_unlock(&vmbus_connection.channel_mutex);
return channel;
}
static bool vmbus_is_valid_offer(const struct vmbus_channel_offer_channel *offer)
{
const guid_t *guid = &offer->offer.if_type;
u16 i;
if (!hv_is_isolation_supported())
return true;
if (is_hvsock_offer(offer))
return true;
for (i = 0; i < ARRAY_SIZE(vmbus_devs); i++) {
if (guid_equal(guid, &vmbus_devs[i].guid))
return vmbus_devs[i].allowed_in_isolated;
}
return false;
}
/*
* 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 *oldchannel, *newchannel;
size_t offer_sz;
offer = (struct vmbus_channel_offer_channel *)hdr;
trace_vmbus_onoffer(offer);
if (!vmbus_is_valid_offer(offer)) {
pr_err_ratelimited("Invalid offer %d from the host supporting isolation\n",
offer->child_relid);
atomic_dec(&vmbus_connection.offer_in_progress);
return;
}
oldchannel = find_primary_channel_by_offer(offer);
if (oldchannel != NULL) {
/*
* We're resuming from hibernation: all the sub-channel and
* hv_sock channels we had before the hibernation should have
* been cleaned up, and now we must be seeing a re-offered
* primary channel that we had before the hibernation.
*/
/*
* { Initially: channel relid = INVALID_RELID,
* channels[valid_relid] = NULL }
*
* CPU1 CPU2
*
* [vmbus_onoffer()] [vmbus_device_release()]
*
* LOCK channel_mutex LOCK channel_mutex
* STORE channel relid = valid_relid LOAD r1 = channel relid
* MAP_RELID channel if (r1 != INVALID_RELID)
* UNLOCK channel_mutex UNMAP_RELID channel
* UNLOCK channel_mutex
*
* Forbids: r1 == valid_relid &&
* channels[valid_relid] == channel
*
* Note. r1 can be INVALID_RELID only for an hv_sock channel.
* None of the hv_sock channels which were present before the
* suspend are re-offered upon the resume. See the WARN_ON()
* in hv_process_channel_removal().
*/
mutex_lock(&vmbus_connection.channel_mutex);
atomic_dec(&vmbus_connection.offer_in_progress);
WARN_ON(oldchannel->offermsg.child_relid != INVALID_RELID);
/* Fix up the relid. */
oldchannel->offermsg.child_relid = offer->child_relid;
offer_sz = sizeof(*offer);
if (memcmp(offer, &oldchannel->offermsg, offer_sz) != 0) {
/*
* This is not an error, since the host can also change
* the other field(s) of the offer, e.g. on WS RS5
* (Build 17763), the offer->connection_id of the
* Mellanox VF vmbus device can change when the host
* reoffers the device upon resume.
*/
pr_debug("vmbus offer changed: relid=%d\n",
offer->child_relid);
print_hex_dump_debug("Old vmbus offer: ",
DUMP_PREFIX_OFFSET, 16, 4,
&oldchannel->offermsg, offer_sz,
false);
print_hex_dump_debug("New vmbus offer: ",
DUMP_PREFIX_OFFSET, 16, 4,
offer, offer_sz, false);
/* Fix up the old channel. */
vmbus_setup_channel_state(oldchannel, offer);
}
/* Add the channel back to the array of channels. */
vmbus_channel_map_relid(oldchannel);
check_ready_for_resume_event();
mutex_unlock(&vmbus_connection.channel_mutex);
return;
}
/* Allocate the channel object and save this offer. */
newchannel = alloc_channel();
if (!newchannel) {
vmbus_release_relid(offer->child_relid);
atomic_dec(&vmbus_connection.offer_in_progress);
pr_err("Unable to allocate channel object\n");
return;
}
vmbus_setup_channel_state(newchannel, offer);
vmbus_process_offer(newchannel);
}
static void check_ready_for_suspend_event(void)
{
/*
* If all the sub-channels or hv_sock channels have been cleaned up,
* then it's safe to suspend.
*/
if (atomic_dec_and_test(&vmbus_connection.nr_chan_close_on_suspend))
complete(&vmbus_connection.ready_for_suspend_event);
}
/*
* 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;
struct device *dev;
bool clean_up_chan_for_suspend;
rescind = (struct vmbus_channel_rescind_offer *)hdr;
trace_vmbus_onoffer_rescind(rescind);
/*
* The offer msg and the corresponding rescind msg
* from the host are guranteed to be ordered -
* offer comes in first and then the rescind.
* Since we process these events in work elements,
* and with preemption, we may end up processing
* the events out of order. We rely on the synchronization
* provided by offer_in_progress and by channel_mutex for
* ordering these events:
*
* { Initially: offer_in_progress = 1 }
*
* CPU1 CPU2
*
* [vmbus_onoffer()] [vmbus_onoffer_rescind()]
*
* LOCK channel_mutex WAIT_ON offer_in_progress == 0
* DECREMENT offer_in_progress LOCK channel_mutex
* STORE channels[] LOAD channels[]
* UNLOCK channel_mutex UNLOCK channel_mutex
*
* Forbids: CPU2's LOAD from *not* seeing CPU1's STORE
*/
while (atomic_read(&vmbus_connection.offer_in_progress) != 0) {
/*
* We wait here until any channel offer is currently
* being processed.
*/
msleep(1);
}
mutex_lock(&vmbus_connection.channel_mutex);
channel = relid2channel(rescind->child_relid);
if (channel != NULL) {
/*
* Guarantee that no other instance of vmbus_onoffer_rescind()
* has got a reference to the channel object. Synchronize on
* &vmbus_connection.channel_mutex.
*/
if (channel->rescind_ref) {
mutex_unlock(&vmbus_connection.channel_mutex);
return;
}
channel->rescind_ref = true;
}
mutex_unlock(&vmbus_connection.channel_mutex);
if (channel == NULL) {
/*
* We failed in processing the offer message;
* we would have cleaned up the relid in that
* failure path.
*/
return;
}
clean_up_chan_for_suspend = is_hvsock_channel(channel) ||
is_sub_channel(channel);
/*
* Before setting channel->rescind in vmbus_rescind_cleanup(), we
* should make sure the channel callback is not running any more.
*/
vmbus_reset_channel_cb(channel);
/*
* Now wait for offer handling to complete.
*/
vmbus_rescind_cleanup(channel);
while (READ_ONCE(channel->probe_done) == false) {
/*
* We wait here until any channel offer is currently
* being processed.
*/
msleep(1);
}
/*
* At this point, the rescind handling can proceed safely.
*/
if (channel->device_obj) {
if (channel->chn_rescind_callback) {
channel->chn_rescind_callback(channel);
if (clean_up_chan_for_suspend)
check_ready_for_suspend_event();
return;
}
/*
* We will have to unregister this device from the
* driver core.
*/
dev = get_device(&channel->device_obj->device);
if (dev) {
vmbus_device_unregister(channel->device_obj);
put_device(dev);
}
} else if (channel->primary_channel != NULL) {
/*
* Sub-channel is being rescinded. Following is the channel
* close sequence when initiated from the driveri (refer to
* vmbus_close() for details):
* 1. Close all sub-channels first
* 2. Then close the primary channel.
*/
mutex_lock(&vmbus_connection.channel_mutex);
if (channel->state == CHANNEL_OPEN_STATE) {
/*
* The channel is currently not open;
* it is safe for us to cleanup the channel.
*/
hv_process_channel_removal(channel);
} else {
complete(&channel->rescind_event);
}
mutex_unlock(&vmbus_connection.channel_mutex);
}
/* The "channel" may have been freed. Do not access it any longer. */
if (clean_up_chan_for_suspend)
check_ready_for_suspend_event();
}
void vmbus_hvsock_device_unregister(struct vmbus_channel *channel)
{
BUG_ON(!is_hvsock_channel(channel));
/* We always get a rescind msg when a connection is closed. */
while (!READ_ONCE(channel->probe_done) || !READ_ONCE(channel->rescind))
msleep(1);
vmbus_device_unregister(channel->device_obj);
}
EXPORT_SYMBOL_GPL(vmbus_hvsock_device_unregister);
/*
* 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;
trace_vmbus_onopen_result(result);
/*
* 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;
trace_vmbus_ongpadl_created(gpadlcreated);
/*
* 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_onmodifychannel_response - Modify Channel response handler.
*
* This is invoked when we received a response to our channel modify request.
* Find the matching request, copy the response and signal the requesting thread.
*/
static void vmbus_onmodifychannel_response(struct vmbus_channel_message_header *hdr)
{
struct vmbus_channel_modifychannel_response *response;
struct vmbus_channel_msginfo *msginfo;
unsigned long flags;
response = (struct vmbus_channel_modifychannel_response *)hdr;
trace_vmbus_onmodifychannel_response(response);
/*
* Find the modify msg, copy the response 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) {
struct vmbus_channel_message_header *responseheader =
(struct vmbus_channel_message_header *)msginfo->msg;
if (responseheader->msgtype == CHANNELMSG_MODIFYCHANNEL) {
struct vmbus_channel_modifychannel *modifymsg;
modifymsg = (struct vmbus_channel_modifychannel *)msginfo->msg;
if (modifymsg->child_relid == response->child_relid) {
memcpy(&msginfo->response.modify_response, response,
sizeof(*response));
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;
trace_vmbus_ongpadl_torndown(gpadl_torndown);
/*
* 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;
trace_vmbus_onversion_response(version_response);
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 */
const struct vmbus_channel_message_table_entry
channel_message_table[CHANNELMSG_COUNT] = {
{ CHANNELMSG_INVALID, 0, NULL, 0},
{ CHANNELMSG_OFFERCHANNEL, 0, vmbus_onoffer,
sizeof(struct vmbus_channel_offer_channel)},
{ CHANNELMSG_RESCIND_CHANNELOFFER, 0, vmbus_onoffer_rescind,
sizeof(struct vmbus_channel_rescind_offer) },
{ CHANNELMSG_REQUESTOFFERS, 0, NULL, 0},
{ CHANNELMSG_ALLOFFERS_DELIVERED, 1, vmbus_onoffers_delivered, 0},
{ CHANNELMSG_OPENCHANNEL, 0, NULL, 0},
{ CHANNELMSG_OPENCHANNEL_RESULT, 1, vmbus_onopen_result,
sizeof(struct vmbus_channel_open_result)},
{ CHANNELMSG_CLOSECHANNEL, 0, NULL, 0},
{ CHANNELMSG_GPADL_HEADER, 0, NULL, 0},
{ CHANNELMSG_GPADL_BODY, 0, NULL, 0},
{ CHANNELMSG_GPADL_CREATED, 1, vmbus_ongpadl_created,
sizeof(struct vmbus_channel_gpadl_created)},
{ CHANNELMSG_GPADL_TEARDOWN, 0, NULL, 0},
{ CHANNELMSG_GPADL_TORNDOWN, 1, vmbus_ongpadl_torndown,
sizeof(struct vmbus_channel_gpadl_torndown) },
{ CHANNELMSG_RELID_RELEASED, 0, NULL, 0},
{ CHANNELMSG_INITIATE_CONTACT, 0, NULL, 0},
{ CHANNELMSG_VERSION_RESPONSE, 1, vmbus_onversion_response,
sizeof(struct vmbus_channel_version_response)},
{ CHANNELMSG_UNLOAD, 0, NULL, 0},
{ CHANNELMSG_UNLOAD_RESPONSE, 1, vmbus_unload_response, 0},
{ CHANNELMSG_18, 0, NULL, 0},
{ CHANNELMSG_19, 0, NULL, 0},
{ CHANNELMSG_20, 0, NULL, 0},
{ CHANNELMSG_TL_CONNECT_REQUEST, 0, NULL, 0},
{ CHANNELMSG_MODIFYCHANNEL, 0, NULL, 0},
{ CHANNELMSG_TL_CONNECT_RESULT, 0, NULL, 0},
{ CHANNELMSG_MODIFYCHANNEL_RESPONSE, 1, vmbus_onmodifychannel_response,
sizeof(struct vmbus_channel_modifychannel_response)},
};
/*
* vmbus_onmessage - Handler for channel protocol messages.
*
* This is invoked in the vmbus worker thread context.
*/
void vmbus_onmessage(struct vmbus_channel_message_header *hdr)
{
trace_vmbus_on_message(hdr);
/*
* vmbus_on_msg_dpc() makes sure the hdr->msgtype here can not go
* out of bound and the message_handler pointer can not be NULL.
*/
channel_message_table[hdr->msgtype].message_handler(hdr);
}
/*
* 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;
msginfo = kzalloc(sizeof(*msginfo) +
sizeof(struct vmbus_channel_message_header),
GFP_KERNEL);
if (!msginfo)
return -ENOMEM;
msg = (struct vmbus_channel_message_header *)msginfo->msg;
msg->msgtype = CHANNELMSG_REQUESTOFFERS;
ret = vmbus_post_msg(msg, sizeof(struct vmbus_channel_message_header),
true);
trace_vmbus_request_offers(ret);
if (ret != 0) {
pr_err("Unable to request offers - %d\n", ret);
goto cleanup;
}
cleanup:
kfree(msginfo);
return ret;
}
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);
void vmbus_set_chn_rescind_callback(struct vmbus_channel *channel,
void (*chn_rescind_cb)(struct vmbus_channel *))
{
channel->chn_rescind_callback = chn_rescind_cb;
}
EXPORT_SYMBOL_GPL(vmbus_set_chn_rescind_callback);
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