summaryrefslogtreecommitdiff
path: root/drivers/hv
diff options
context:
space:
mode:
Diffstat (limited to 'drivers/hv')
-rw-r--r--drivers/hv/Kconfig2
-rw-r--r--drivers/hv/channel.c8
-rw-r--r--drivers/hv/channel_mgmt.c189
-rw-r--r--drivers/hv/connection.c24
-rw-r--r--drivers/hv/hv.c2
-rw-r--r--drivers/hv/hv_balloon.c19
-rw-r--r--drivers/hv/hv_kvp.c26
-rw-r--r--drivers/hv/hyperv_vmbus.h75
-rw-r--r--drivers/hv/vmbus_drv.c20
9 files changed, 216 insertions, 149 deletions
diff --git a/drivers/hv/Kconfig b/drivers/hv/Kconfig
index 97954f575c3f..1c1a2514d6f3 100644
--- a/drivers/hv/Kconfig
+++ b/drivers/hv/Kconfig
@@ -4,7 +4,7 @@ menu "Microsoft Hyper-V guest support"
config HYPERV
tristate "Microsoft Hyper-V client drivers"
- depends on X86 && ACPI && PCI && X86_LOCAL_APIC && HYPERVISOR_GUEST
+ depends on X86 && ACPI && X86_LOCAL_APIC && HYPERVISOR_GUEST
select PARAVIRT
help
Select this option to run Linux as a Hyper-V client operating
diff --git a/drivers/hv/channel.c b/drivers/hv/channel.c
index de8193f3b838..fe00b12e4417 100644
--- a/drivers/hv/channel.c
+++ b/drivers/hv/channel.c
@@ -516,6 +516,14 @@ int vmbus_establish_gpadl(struct vmbus_channel *channel, void *kbuffer,
}
wait_for_completion(&msginfo->waitevent);
+ if (msginfo->response.gpadl_created.creation_status != 0) {
+ pr_err("Failed to establish GPADL: err = 0x%x\n",
+ msginfo->response.gpadl_created.creation_status);
+
+ ret = -EDQUOT;
+ goto cleanup;
+ }
+
if (channel->rescind) {
ret = -ENODEV;
goto cleanup;
diff --git a/drivers/hv/channel_mgmt.c b/drivers/hv/channel_mgmt.c
index 6277597d3d58..edd34c167a9b 100644
--- a/drivers/hv/channel_mgmt.c
+++ b/drivers/hv/channel_mgmt.c
@@ -435,61 +435,16 @@ void vmbus_free_channels(void)
}
}
-/*
- * vmbus_process_offer - Process the offer by creating a channel/device
- * associated with this offer
- */
-static void vmbus_process_offer(struct vmbus_channel *newchannel)
+/* Note: the function can run concurrently for primary/sub channels. */
+static void vmbus_add_channel_work(struct work_struct *work)
{
- struct vmbus_channel *channel;
- bool fnew = true;
+ struct vmbus_channel *newchannel =
+ container_of(work, struct vmbus_channel, add_channel_work);
+ struct vmbus_channel *primary_channel = newchannel->primary_channel;
unsigned long flags;
u16 dev_type;
int ret;
- /* Make sure this is a new offer */
- mutex_lock(&vmbus_connection.channel_mutex);
-
- /*
- * Now that we have acquired the channel_mutex,
- * we can release the potentially racing rescind thread.
- */
- atomic_dec(&vmbus_connection.offer_in_progress);
-
- 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);
-
- mutex_unlock(&vmbus_connection.channel_mutex);
-
- 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);
- channel->num_sc++;
- spin_unlock_irqrestore(&channel->lock, flags);
- } else {
- goto err_free_chan;
- }
- }
-
dev_type = hv_get_dev_type(newchannel);
init_vp_index(newchannel, dev_type);
@@ -507,27 +462,26 @@ static void vmbus_process_offer(struct vmbus_channel *newchannel)
/*
* This state is used to indicate a successful open
* so that when we do close the channel normally, we
- * can cleanup properly
+ * can cleanup properly.
*/
newchannel->state = CHANNEL_OPEN_STATE;
- if (!fnew) {
- struct hv_device *dev
- = newchannel->primary_channel->device_obj;
+ 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_free_chan;
+ goto err_deq_chan;
+
+ if (primary_channel->sc_creation_callback != NULL)
+ primary_channel->sc_creation_callback(newchannel);
- if (channel->sc_creation_callback != NULL)
- channel->sc_creation_callback(newchannel);
newchannel->probe_done = true;
return;
}
/*
- * Start the process of binding this offer to the driver
- * We need to set the DeviceObject field before calling
- * vmbus_child_dev_add()
+ * Start the process of binding the primary channel to the driver
*/
newchannel->device_obj = vmbus_device_create(
&newchannel->offermsg.offer.if_type,
@@ -556,13 +510,28 @@ static void vmbus_process_offer(struct vmbus_channel *newchannel)
err_deq_chan:
mutex_lock(&vmbus_connection.channel_mutex);
- list_del(&newchannel->listentry);
+
+ /*
+ * 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 {
+ spin_lock_irqsave(&primary_channel->lock, flags);
+ list_del(&newchannel->sc_list);
+ spin_unlock_irqrestore(&primary_channel->lock, flags);
+ }
+
mutex_unlock(&vmbus_connection.channel_mutex);
if (newchannel->target_cpu != get_cpu()) {
put_cpu();
smp_call_function_single(newchannel->target_cpu,
- percpu_channel_deq, newchannel, true);
+ percpu_channel_deq,
+ newchannel, true);
} else {
percpu_channel_deq(newchannel);
put_cpu();
@@ -570,14 +539,104 @@ err_deq_chan:
vmbus_release_relid(newchannel->offermsg.child_relid);
-err_free_chan:
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;
+ unsigned long flags;
+ bool fnew = true;
+
+ mutex_lock(&vmbus_connection.channel_mutex);
+
+ /*
+ * Now that we have acquired the channel_mutex,
+ * we can release the potentially racing rescind thread.
+ */
+ atomic_dec(&vmbus_connection.offer_in_progress);
+
+ 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);
+ 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);
+ /*
+ * Don't call free_channel(), because newchannel->kobj
+ * is not initialized yet.
+ */
+ kfree(newchannel);
+ WARN_ON_ONCE(1);
+ return;
+ }
+ /*
+ * 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);
+ }
+
+ mutex_unlock(&vmbus_connection.channel_mutex);
+
+ /*
+ * 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);
+}
+
+/*
* We use this state to statically distribute the channel interrupt load.
*/
static int next_numa_node_id;
+/*
+ * init_vp_index() accesses global variables like next_numa_node_id, and
+ * it can run concurrently for primary channels and sub-channels: see
+ * vmbus_process_offer(), so we need the lock to protect the global
+ * variables.
+ */
+static DEFINE_SPINLOCK(bind_channel_to_cpu_lock);
/*
* Starting with Win8, we can statically distribute the incoming
@@ -613,6 +672,8 @@ static void init_vp_index(struct vmbus_channel *channel, u16 dev_type)
return;
}
+ spin_lock(&bind_channel_to_cpu_lock);
+
/*
* Based on the channel affinity policy, we will assign the NUMA
* nodes.
@@ -695,6 +756,8 @@ static void init_vp_index(struct vmbus_channel *channel, u16 dev_type)
channel->target_cpu = cur_cpu;
channel->target_vp = hv_cpu_number_to_vp_number(cur_cpu);
+ spin_unlock(&bind_channel_to_cpu_lock);
+
free_cpumask_var(available_mask);
}
diff --git a/drivers/hv/connection.c b/drivers/hv/connection.c
index f4d08c8ac7f8..4fe117b761ce 100644
--- a/drivers/hv/connection.c
+++ b/drivers/hv/connection.c
@@ -190,6 +190,20 @@ int vmbus_connect(void)
goto cleanup;
}
+ vmbus_connection.handle_primary_chan_wq =
+ create_workqueue("hv_pri_chan");
+ if (!vmbus_connection.handle_primary_chan_wq) {
+ ret = -ENOMEM;
+ goto cleanup;
+ }
+
+ vmbus_connection.handle_sub_chan_wq =
+ create_workqueue("hv_sub_chan");
+ if (!vmbus_connection.handle_sub_chan_wq) {
+ ret = -ENOMEM;
+ goto cleanup;
+ }
+
INIT_LIST_HEAD(&vmbus_connection.chn_msg_list);
spin_lock_init(&vmbus_connection.channelmsg_lock);
@@ -280,10 +294,14 @@ void vmbus_disconnect(void)
*/
vmbus_initiate_unload(false);
- if (vmbus_connection.work_queue) {
- drain_workqueue(vmbus_connection.work_queue);
+ if (vmbus_connection.handle_sub_chan_wq)
+ destroy_workqueue(vmbus_connection.handle_sub_chan_wq);
+
+ if (vmbus_connection.handle_primary_chan_wq)
+ destroy_workqueue(vmbus_connection.handle_primary_chan_wq);
+
+ if (vmbus_connection.work_queue)
destroy_workqueue(vmbus_connection.work_queue);
- }
if (vmbus_connection.int_page) {
free_pages((unsigned long)vmbus_connection.int_page, 0);
diff --git a/drivers/hv/hv.c b/drivers/hv/hv.c
index 332d7c34be5c..11273cd384d6 100644
--- a/drivers/hv/hv.c
+++ b/drivers/hv/hv.c
@@ -143,7 +143,7 @@ static int hv_ce_shutdown(struct clock_event_device *evt)
static int hv_ce_set_oneshot(struct clock_event_device *evt)
{
- union hv_timer_config timer_cfg;
+ union hv_stimer_config timer_cfg;
timer_cfg.as_uint64 = 0;
timer_cfg.enable = 1;
diff --git a/drivers/hv/hv_balloon.c b/drivers/hv/hv_balloon.c
index 41631512ae97..5301fef16c31 100644
--- a/drivers/hv/hv_balloon.c
+++ b/drivers/hv/hv_balloon.c
@@ -1090,6 +1090,7 @@ static void process_info(struct hv_dynmem_device *dm, struct dm_info_msg *msg)
static unsigned long compute_balloon_floor(void)
{
unsigned long min_pages;
+ unsigned long nr_pages = totalram_pages();
#define MB2PAGES(mb) ((mb) << (20 - PAGE_SHIFT))
/* Simple continuous piecewiese linear function:
* max MiB -> min MiB gradient
@@ -1102,16 +1103,16 @@ static unsigned long compute_balloon_floor(void)
* 8192 744 (1/16)
* 32768 1512 (1/32)
*/
- if (totalram_pages < MB2PAGES(128))
- min_pages = MB2PAGES(8) + (totalram_pages >> 1);
- else if (totalram_pages < MB2PAGES(512))
- min_pages = MB2PAGES(40) + (totalram_pages >> 2);
- else if (totalram_pages < MB2PAGES(2048))
- min_pages = MB2PAGES(104) + (totalram_pages >> 3);
- else if (totalram_pages < MB2PAGES(8192))
- min_pages = MB2PAGES(232) + (totalram_pages >> 4);
+ if (nr_pages < MB2PAGES(128))
+ min_pages = MB2PAGES(8) + (nr_pages >> 1);
+ else if (nr_pages < MB2PAGES(512))
+ min_pages = MB2PAGES(40) + (nr_pages >> 2);
+ else if (nr_pages < MB2PAGES(2048))
+ min_pages = MB2PAGES(104) + (nr_pages >> 3);
+ else if (nr_pages < MB2PAGES(8192))
+ min_pages = MB2PAGES(232) + (nr_pages >> 4);
else
- min_pages = MB2PAGES(488) + (totalram_pages >> 5);
+ min_pages = MB2PAGES(488) + (nr_pages >> 5);
#undef MB2PAGES
return min_pages;
}
diff --git a/drivers/hv/hv_kvp.c b/drivers/hv/hv_kvp.c
index a7513a8a8e37..d6106e1a0d4a 100644
--- a/drivers/hv/hv_kvp.c
+++ b/drivers/hv/hv_kvp.c
@@ -353,6 +353,9 @@ static void process_ib_ipinfo(void *in_msg, void *out_msg, int op)
out->body.kvp_ip_val.dhcp_enabled = in->kvp_ip_val.dhcp_enabled;
+ /* fallthrough */
+
+ case KVP_OP_GET_IP_INFO:
utf16s_to_utf8s((wchar_t *)in->kvp_ip_val.adapter_id,
MAX_ADAPTER_ID_SIZE,
UTF16_LITTLE_ENDIAN,
@@ -405,7 +408,11 @@ kvp_send_key(struct work_struct *dummy)
process_ib_ipinfo(in_msg, message, KVP_OP_SET_IP_INFO);
break;
case KVP_OP_GET_IP_INFO:
- /* We only need to pass on message->kvp_hdr.operation. */
+ /*
+ * We only need to pass on the info of operation, adapter_id
+ * and addr_family to the userland kvp daemon.
+ */
+ process_ib_ipinfo(in_msg, message, KVP_OP_GET_IP_INFO);
break;
case KVP_OP_SET:
switch (in_msg->body.kvp_set.data.value_type) {
@@ -446,9 +453,9 @@ kvp_send_key(struct work_struct *dummy)
}
- break;
-
- case KVP_OP_GET:
+ /*
+ * The key is always a string - utf16 encoding.
+ */
message->body.kvp_set.data.key_size =
utf16s_to_utf8s(
(wchar_t *)in_msg->body.kvp_set.data.key,
@@ -456,6 +463,17 @@ kvp_send_key(struct work_struct *dummy)
UTF16_LITTLE_ENDIAN,
message->body.kvp_set.data.key,
HV_KVP_EXCHANGE_MAX_KEY_SIZE - 1) + 1;
+
+ break;
+
+ case KVP_OP_GET:
+ message->body.kvp_get.data.key_size =
+ utf16s_to_utf8s(
+ (wchar_t *)in_msg->body.kvp_get.data.key,
+ in_msg->body.kvp_get.data.key_size,
+ UTF16_LITTLE_ENDIAN,
+ message->body.kvp_get.data.key,
+ HV_KVP_EXCHANGE_MAX_KEY_SIZE - 1) + 1;
break;
case KVP_OP_DELETE:
diff --git a/drivers/hv/hyperv_vmbus.h b/drivers/hv/hyperv_vmbus.h
index 72eaba3d50fc..ea201034b248 100644
--- a/drivers/hv/hyperv_vmbus.h
+++ b/drivers/hv/hyperv_vmbus.h
@@ -44,74 +44,6 @@
*/
#define HV_UTIL_NEGO_TIMEOUT 55
-/* Define synthetic interrupt controller flag constants. */
-#define HV_EVENT_FLAGS_COUNT (256 * 8)
-#define HV_EVENT_FLAGS_LONG_COUNT (256 / sizeof(unsigned long))
-
-/*
- * Timer configuration register.
- */
-union hv_timer_config {
- u64 as_uint64;
- struct {
- u64 enable:1;
- u64 periodic:1;
- u64 lazy:1;
- u64 auto_enable:1;
- u64 apic_vector:8;
- u64 direct_mode:1;
- u64 reserved_z0:3;
- u64 sintx:4;
- u64 reserved_z1:44;
- };
-};
-
-
-/* Define the synthetic interrupt controller event flags format. */
-union hv_synic_event_flags {
- unsigned long flags[HV_EVENT_FLAGS_LONG_COUNT];
-};
-
-/* Define SynIC control register. */
-union hv_synic_scontrol {
- u64 as_uint64;
- struct {
- u64 enable:1;
- u64 reserved:63;
- };
-};
-
-/* Define synthetic interrupt source. */
-union hv_synic_sint {
- u64 as_uint64;
- struct {
- u64 vector:8;
- u64 reserved1:8;
- u64 masked:1;
- u64 auto_eoi:1;
- u64 reserved2:46;
- };
-};
-
-/* Define the format of the SIMP register */
-union hv_synic_simp {
- u64 as_uint64;
- struct {
- u64 simp_enabled:1;
- u64 preserved:11;
- u64 base_simp_gpa:52;
- };
-};
-
-/* Define the format of the SIEFP register */
-union hv_synic_siefp {
- u64 as_uint64;
- struct {
- u64 siefp_enabled:1;
- u64 preserved:11;
- u64 base_siefp_gpa:52;
- };
-};
/* Definitions for the monitored notification facility */
union hv_monitor_trigger_group {
@@ -335,7 +267,14 @@ struct vmbus_connection {
struct list_head chn_list;
struct mutex channel_mutex;
+ /*
+ * An offer message is handled first on the work_queue, and then
+ * is further handled on handle_primary_chan_wq or
+ * handle_sub_chan_wq.
+ */
struct workqueue_struct *work_queue;
+ struct workqueue_struct *handle_primary_chan_wq;
+ struct workqueue_struct *handle_sub_chan_wq;
};
diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c
index 283d184280af..d0ff65675292 100644
--- a/drivers/hv/vmbus_drv.c
+++ b/drivers/hv/vmbus_drv.c
@@ -316,6 +316,8 @@ static ssize_t out_intr_mask_show(struct device *dev,
if (!hv_dev->channel)
return -ENODEV;
+ if (hv_dev->channel->state != CHANNEL_OPENED_STATE)
+ return -EINVAL;
hv_ringbuffer_get_debuginfo(&hv_dev->channel->outbound, &outbound);
return sprintf(buf, "%d\n", outbound.current_interrupt_mask);
}
@@ -329,6 +331,8 @@ static ssize_t out_read_index_show(struct device *dev,
if (!hv_dev->channel)
return -ENODEV;
+ if (hv_dev->channel->state != CHANNEL_OPENED_STATE)
+ return -EINVAL;
hv_ringbuffer_get_debuginfo(&hv_dev->channel->outbound, &outbound);
return sprintf(buf, "%d\n", outbound.current_read_index);
}
@@ -343,6 +347,8 @@ static ssize_t out_write_index_show(struct device *dev,
if (!hv_dev->channel)
return -ENODEV;
+ if (hv_dev->channel->state != CHANNEL_OPENED_STATE)
+ return -EINVAL;
hv_ringbuffer_get_debuginfo(&hv_dev->channel->outbound, &outbound);
return sprintf(buf, "%d\n", outbound.current_write_index);
}
@@ -357,6 +363,8 @@ static ssize_t out_read_bytes_avail_show(struct device *dev,
if (!hv_dev->channel)
return -ENODEV;
+ if (hv_dev->channel->state != CHANNEL_OPENED_STATE)
+ return -EINVAL;
hv_ringbuffer_get_debuginfo(&hv_dev->channel->outbound, &outbound);
return sprintf(buf, "%d\n", outbound.bytes_avail_toread);
}
@@ -371,6 +379,8 @@ static ssize_t out_write_bytes_avail_show(struct device *dev,
if (!hv_dev->channel)
return -ENODEV;
+ if (hv_dev->channel->state != CHANNEL_OPENED_STATE)
+ return -EINVAL;
hv_ringbuffer_get_debuginfo(&hv_dev->channel->outbound, &outbound);
return sprintf(buf, "%d\n", outbound.bytes_avail_towrite);
}
@@ -384,6 +394,8 @@ static ssize_t in_intr_mask_show(struct device *dev,
if (!hv_dev->channel)
return -ENODEV;
+ if (hv_dev->channel->state != CHANNEL_OPENED_STATE)
+ return -EINVAL;
hv_ringbuffer_get_debuginfo(&hv_dev->channel->inbound, &inbound);
return sprintf(buf, "%d\n", inbound.current_interrupt_mask);
}
@@ -397,6 +409,8 @@ static ssize_t in_read_index_show(struct device *dev,
if (!hv_dev->channel)
return -ENODEV;
+ if (hv_dev->channel->state != CHANNEL_OPENED_STATE)
+ return -EINVAL;
hv_ringbuffer_get_debuginfo(&hv_dev->channel->inbound, &inbound);
return sprintf(buf, "%d\n", inbound.current_read_index);
}
@@ -410,6 +424,8 @@ static ssize_t in_write_index_show(struct device *dev,
if (!hv_dev->channel)
return -ENODEV;
+ if (hv_dev->channel->state != CHANNEL_OPENED_STATE)
+ return -EINVAL;
hv_ringbuffer_get_debuginfo(&hv_dev->channel->inbound, &inbound);
return sprintf(buf, "%d\n", inbound.current_write_index);
}
@@ -424,6 +440,8 @@ static ssize_t in_read_bytes_avail_show(struct device *dev,
if (!hv_dev->channel)
return -ENODEV;
+ if (hv_dev->channel->state != CHANNEL_OPENED_STATE)
+ return -EINVAL;
hv_ringbuffer_get_debuginfo(&hv_dev->channel->inbound, &inbound);
return sprintf(buf, "%d\n", inbound.bytes_avail_toread);
}
@@ -438,6 +456,8 @@ static ssize_t in_write_bytes_avail_show(struct device *dev,
if (!hv_dev->channel)
return -ENODEV;
+ if (hv_dev->channel->state != CHANNEL_OPENED_STATE)
+ return -EINVAL;
hv_ringbuffer_get_debuginfo(&hv_dev->channel->inbound, &inbound);
return sprintf(buf, "%d\n", inbound.bytes_avail_towrite);
}