[PATCH 0/5] Drivers: hv: vmbus: Cleanup the vmbus unload path

[PATCH 0/5] Drivers: hv: vmbus: Cleanup the vmbus unload path

[K. Y. Srinivasan]

This patch-set have several fixes to enable the clean unload of the vmbus.
Typically, vmbus will not be unloadable when Linux is hosted on
Hyper-V since the driver managing the root device needs the vmbus driver.

Dexuan Cui (1):
  hv: vmbus_free_channels(): remove the redundant free_channel()

K. Y. Srinivasan (2):
  drivers: hv: vmbus: Get rid of some unused definitions
  Drivers: hv: vmbus: Implement the protocol for tearing down vmbus
    state

Vitaly Kuznetsov (2):
  Drivers: hv: vmbus: introduce vmbus_acpi_remove
  Drivers: hv: vmbus: unregister panic notifier on module unload

 drivers/hv/channel_mgmt.c |   36 +++++++++++++++++++++++++++++++++---
 drivers/hv/connection.c   |    5 +++++
 drivers/hv/hyperv_vmbus.h |    2 ++
 drivers/hv/vmbus_drv.c    |   14 ++++++++++++++
 include/linux/hyperv.h    |   20 +-------------------
 5 files changed, 55 insertions(+), 22 deletions(-)

-- 
1.7.4.1

[PATCH 1/5] Drivers: hv: vmbus: introduce vmbus_acpi_remove

[K. Y. Srinivasan]

From: Vitaly Kuznetsov <vkuznets@redhat.com>

In case we do request_resource() in vmbus_acpi_add() we need to tear it down
to be able to load the driver again. Otherwise the following crash in observed
when hv_vmbus unload/load sequence is performed on a Generation2 instance:

[   38.165701] BUG: unable to handle kernel paging request at ffffffffa00075a0
[   38.166315] IP: [<ffffffff8107dc5f>] __request_resource+0x2f/0x50
[   38.166315] PGD 1f34067 PUD 1f35063 PMD 3f723067 PTE 0
[   38.166315] Oops: 0000 [#1] SMP
[   38.166315] Modules linked in: hv_vmbus(+) [last unloaded: hv_vmbus]
[   38.166315] CPU: 0 PID: 267 Comm: modprobe Not tainted 3.19.0-rc5_bug923184+ #486
[   38.166315] Hardware name: Microsoft Corporation Virtual Machine/Virtual Machine, BIOS Hyper-V UEFI Release v1.0 11/26/2012
[   38.166315] task: ffff88003f401cb0 ti: ffff88003f60c000 task.ti: ffff88003f60c000
[   38.166315] RIP: 0010:[<ffffffff8107dc5f>]  [<ffffffff8107dc5f>] __request_resource+0x2f/0x50
[   38.166315] RSP: 0018:ffff88003f60fb58  EFLAGS: 00010286

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
---
 drivers/hv/vmbus_drv.c |   10 ++++++++++
 1 files changed, 10 insertions(+), 0 deletions(-)

diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c
index c85235e..0d8d1d7 100644
--- a/drivers/hv/vmbus_drv.c
+++ b/drivers/hv/vmbus_drv.c
@@ -1035,6 +1035,15 @@ acpi_walk_err:
 	return ret_val;
 }
 
+static int vmbus_acpi_remove(struct acpi_device *device)
+{
+	int ret = 0;
+
+	if (hyperv_mmio.start && hyperv_mmio.end)
+		ret = release_resource(&hyperv_mmio);
+	return ret;
+}
+
 static const struct acpi_device_id vmbus_acpi_device_ids[] = {
 	{"VMBUS", 0},
 	{"VMBus", 0},
@@ -1047,6 +1056,7 @@ static struct acpi_driver vmbus_acpi_driver = {
 	.ids = vmbus_acpi_device_ids,
 	.ops = {
 		.add = vmbus_acpi_add,
+		.remove = vmbus_acpi_remove,
 	},
 };
 
-- 
1.7.4.1

[PATCH 2/5] Drivers: hv: vmbus: unregister panic notifier on module unload

[K. Y. Srinivasan]

From: Vitaly Kuznetsov <vkuznets@redhat.com>

Commit 96c1d0581d00f7abe033350edb021a9d947d8d81 ("Drivers: hv: vmbus: Add
support for VMBus panic notifier handler") introduced
atomic_notifier_chain_register() call on module load. We also need to call
atomic_notifier_chain_unregister() on module unload as otherwise the following
crash is observed when we bring hv_vmbus back:

[   39.788877] BUG: unable to handle kernel paging request at ffffffffa00078a8
[   39.788877] IP: [<ffffffff8109d63f>] notifier_call_chain+0x3f/0x80
...
[   39.788877] Call Trace:
[   39.788877]  [<ffffffff8109de7d>] __atomic_notifier_call_chain+0x5d/0x90
...
[   39.788877]  [<ffffffff8109d788>] ? atomic_notifier_chain_register+0x38/0x70
[   39.788877]  [<ffffffff8109d767>] ? atomic_notifier_chain_register+0x17/0x70
[   39.788877]  [<ffffffffa002814f>] hv_acpi_init+0x14f/0x1000 [hv_vmbus]
[   39.788877]  [<ffffffff81002144>] do_one_initcall+0xd4/0x210

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
---
 drivers/hv/vmbus_drv.c |    4 ++++
 1 files changed, 4 insertions(+), 0 deletions(-)

diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c
index 0d8d1d7..7870a90 100644
--- a/drivers/hv/vmbus_drv.c
+++ b/drivers/hv/vmbus_drv.c
@@ -1108,6 +1108,10 @@ static void __exit vmbus_exit(void)
 	hv_synic_clockevents_cleanup();
 	hv_remove_vmbus_irq();
 	vmbus_free_channels();
+	if (ms_hyperv.features & HV_FEATURE_GUEST_CRASH_MSR_AVAILABLE) {
+		atomic_notifier_chain_unregister(&panic_notifier_list,
+						 &hyperv_panic_block);
+	}
 	bus_unregister(&hv_bus);
 	hv_cleanup();
 	for_each_online_cpu(cpu)
-- 
1.7.4.1

[PATCH 3/5] hv: vmbus_free_channels(): remove the redundant free_channel()

[K. Y. Srinivasan]

From: Dexuan Cui <decui@microsoft.com>

free_channel() has been invoked in
vmbus_remove() -> hv_process_channel_removal(), or vmbus_remove() ->
... -> vmbus_close_internal() -> hv_process_channel_removal().

We also change to use list_for_each_entry_safe(), because the entry
is removed in hv_process_channel_removal().

This patch fixes a bug in the vmbus unload path.

Thank Dan Carpenter for finding the issue!

Signed-off-by: Dexuan Cui <decui@microsoft.com>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Cc: K. Y. Srinivasan <kys@microsoft.com>
Cc: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
---
 drivers/hv/channel_mgmt.c |   11 ++++++++---
 1 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/drivers/hv/channel_mgmt.c b/drivers/hv/channel_mgmt.c
index 0eeb1b3..865a3af 100644
--- a/drivers/hv/channel_mgmt.c
+++ b/drivers/hv/channel_mgmt.c
@@ -212,11 +212,16 @@ void hv_process_channel_removal(struct vmbus_channel *channel, u32 relid)
 
 void vmbus_free_channels(void)
 {
-	struct vmbus_channel *channel;
+	struct vmbus_channel *channel, *tmp;
+
+	list_for_each_entry_safe(channel, tmp, &vmbus_connection.chn_list,
+		listentry) {
+		/* if we don't set rescind to true, vmbus_close_internal()
+		 * won't invoke hv_process_channel_removal().
+		 */
+		channel->rescind = true;
 
-	list_for_each_entry(channel, &vmbus_connection.chn_list, listentry) {
 		vmbus_device_unregister(channel->device_obj);
-		free_channel(channel);
 	}
 }
 
-- 
1.7.4.1

[PATCH 4/5] drivers: hv: vmbus: Get rid of some unused definitions

[K. Y. Srinivasan]

Get rid of some unused definitions.

Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
---
 include/linux/hyperv.h |   19 -------------------
 1 files changed, 0 insertions(+), 19 deletions(-)

diff --git a/include/linux/hyperv.h b/include/linux/hyperv.h
index 1744148..e29ccdd 100644
--- a/include/linux/hyperv.h
+++ b/include/linux/hyperv.h
@@ -389,10 +389,6 @@ enum vmbus_channel_message_type {
 	CHANNELMSG_INITIATE_CONTACT		= 14,
 	CHANNELMSG_VERSION_RESPONSE		= 15,
 	CHANNELMSG_UNLOAD			= 16,
-#ifdef VMBUS_FEATURE_PARENT_OR_PEER_MEMORY_MAPPED_INTO_A_CHILD
-	CHANNELMSG_VIEWRANGE_ADD		= 17,
-	CHANNELMSG_VIEWRANGE_REMOVE		= 18,
-#endif
 	CHANNELMSG_COUNT
 };
 
@@ -549,21 +545,6 @@ struct vmbus_channel_gpadl_torndown {
 	u32 gpadl;
 } __packed;
 
-#ifdef VMBUS_FEATURE_PARENT_OR_PEER_MEMORY_MAPPED_INTO_A_CHILD
-struct vmbus_channel_view_range_add {
-	struct vmbus_channel_message_header header;
-	PHYSICAL_ADDRESS viewrange_base;
-	u64 viewrange_length;
-	u32 child_relid;
-} __packed;
-
-struct vmbus_channel_view_range_remove {
-	struct vmbus_channel_message_header header;
-	PHYSICAL_ADDRESS viewrange_base;
-	u32 child_relid;
-} __packed;
-#endif
-
 struct vmbus_channel_relid_released {
 	struct vmbus_channel_message_header header;
 	u32 child_relid;
-- 
1.7.4.1

[PATCH 5/5] Drivers: hv: vmbus: Implement the protocol for tearing down vmbus state

[K. Y. Srinivasan]

Implement the protocol for tearing down the monitor state established with
the host.

Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
---
 drivers/hv/channel_mgmt.c |   25 +++++++++++++++++++++++++
 drivers/hv/connection.c   |    5 +++++
 drivers/hv/hyperv_vmbus.h |    2 ++
 include/linux/hyperv.h    |    1 +
 4 files changed, 33 insertions(+), 0 deletions(-)

diff --git a/drivers/hv/channel_mgmt.c b/drivers/hv/channel_mgmt.c
index 865a3af..4b9d89a 100644
--- a/drivers/hv/channel_mgmt.c
+++ b/drivers/hv/channel_mgmt.c
@@ -422,6 +422,30 @@ static void init_vp_index(struct vmbus_channel *channel, const uuid_le *type_gui
 }
 
 /*
+ * 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.
+	 */
+	complete(&vmbus_connection.unload_event);
+}
+
+void vmbus_initiate_unload(void)
+{
+	struct vmbus_channel_message_header hdr;
+
+	init_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));
+
+	wait_for_completion(&vmbus_connection.unload_event);
+}
+
+/*
  * vmbus_onoffer - Handler for channel offers from vmbus in parent partition.
  *
  */
@@ -717,6 +741,7 @@ struct vmbus_channel_message_table_entry
 	{CHANNELMSG_INITIATE_CONTACT,		0, NULL},
 	{CHANNELMSG_VERSION_RESPONSE,		1, vmbus_onversion_response},
 	{CHANNELMSG_UNLOAD,			0, NULL},
+	{CHANNELMSG_UNLOAD_RESPONSE,		1, vmbus_unload_response},
 };
 
 /*
diff --git a/drivers/hv/connection.c b/drivers/hv/connection.c
index b27220a..acd50e9 100644
--- a/drivers/hv/connection.c
+++ b/drivers/hv/connection.c
@@ -227,6 +227,11 @@ cleanup:
 
 void vmbus_disconnect(void)
 {
+	/*
+	 * First send the unload request to the host.
+	 */
+	vmbus_initiate_unload();
+
 	if (vmbus_connection.work_queue) {
 		drain_workqueue(vmbus_connection.work_queue);
 		destroy_workqueue(vmbus_connection.work_queue);
diff --git a/drivers/hv/hyperv_vmbus.h b/drivers/hv/hyperv_vmbus.h
index 138d663..cddc0c9 100644
--- a/drivers/hv/hyperv_vmbus.h
+++ b/drivers/hv/hyperv_vmbus.h
@@ -647,6 +647,7 @@ struct vmbus_connection {
 
 	atomic_t next_gpadl_handle;
 
+	struct completion  unload_event;
 	/*
 	 * Represents channel interrupts. Each bit position represents a
 	 * channel.  When a channel sends an interrupt via VMBUS, it finds its
@@ -741,6 +742,7 @@ void hv_vss_onchannelcallback(void *);
 int hv_fcopy_init(struct hv_util_service *);
 void hv_fcopy_deinit(void);
 void hv_fcopy_onchannelcallback(void *);
+void vmbus_initiate_unload(void);
 
 static inline void hv_poll_channel(struct vmbus_channel *channel,
 				   void (*cb)(void *))
diff --git a/include/linux/hyperv.h b/include/linux/hyperv.h
index e29ccdd..ea93486 100644
--- a/include/linux/hyperv.h
+++ b/include/linux/hyperv.h
@@ -389,6 +389,7 @@ enum vmbus_channel_message_type {
 	CHANNELMSG_INITIATE_CONTACT		= 14,
 	CHANNELMSG_VERSION_RESPONSE		= 15,
 	CHANNELMSG_UNLOAD			= 16,
+	CHANNELMSG_UNLOAD_RESPONSE		= 17,
 	CHANNELMSG_COUNT
 };
 
-- 
1.7.4.1

Re: [PATCH 5/5] Drivers: hv: vmbus: Implement the protocol for tearing down vmbus state

[Vitaly Kuznetsov]

"K. Y. Srinivasan" <kys@microsoft.com> writes:

> Implement the protocol for tearing down the monitor state established with
> the host.
>
> Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>

Unfortunatelly this patch leads to the following crash:

pre-udev:/# modprobe hv_vmbus
modprobe hv_vmbus
[   14.832334] hv_vmbus: Hyper-V Host Build:9600-6.3-17-0.17039; Vmbus version:3.0
[   14.834179] hv_vmbus: CPU offlining is not supported by hypervisor
pre-udev:/# modprobe -r hv_vmbus
modprobe -r hv_vmbus
[   20.640893] BUG: unable to handle kernel NULL pointer dereference at           (null)
[   20.641104] IP: [<          (null)>]           (null)
[   20.641104] PGD 3037b067 PUD 2f41c067 PMD 0 
[   20.641104] Oops: 0010 [#1] SMP DEBUG_PAGEALLOC KASAN
[   20.641104] Modules linked in: hv_vmbus(-)
[   20.641104] CPU: 4 PID: 296 Comm: modprobe Not tainted 4.0.0-rc5_vmbus_acpi_remove2+ #583
[   20.641104] Hardware name: Microsoft Corporation Virtual Machine/Virtual Machine, BIOS Hyper-V UEFI Release v1.0 11/26/2012
[   20.641104] task: ffff88002f47e360 ti: ffff88002f618000 task.ti: ffff88002f618000
[   20.641104] RIP: 0010:[<0000000000000000>]  [<          (null)>]           (null)
[   20.641104] RSP: 0018:ffff88002f61fe60  EFLAGS: 00010246
[   20.641104] RAX: 0000000030374000 RBX: ffff880030374000 RCX: 000000000000005c
[   20.641104] RDX: 0000000030374000 RSI: ffff88002f61fee0 RDI: ffff880030374000
[   20.641104] RBP: ffff88002f61fe88 R08: 0000000000000000 R09: ffff88002f61fed8
[   20.641104] R10: ffff880034008240 R11: 0000000000000010 R12: 0000000000000014
[   20.641104] R13: 0000000000000008 R14: ffff88002f61fed8 R15: 0000000000000000
[   20.641104] FS:  00007fc1ffdaa700(0000) GS:ffff880034500000(0000) knlGS:0000000000000000
[   20.641104] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   20.641104] CR2: 0000000000000000 CR3: 000000002f4ec000 CR4: 00000000001407e0
[   20.641104] Stack:
[   20.641104]  ffffffffa00016c7 0000000000000000 00000000b7f74867 ffffffffa0005ec9
[   20.641104]  0000000000000001 ffff88002f61fec8 ffffffffa000209c ffff88002f61fec8
[   20.641104]  0000000000000200 ffffffff8210ccc0 0000000000000001 0000000001c7d460
[   20.641104] Call Trace:
[   20.641104]  [<ffffffffa00016c7>] ? hv_post_message+0x87/0xb0 [hv_vmbus]
[   20.641104]  [<ffffffffa000209c>] vmbus_post_msg+0x3c/0xc0 [hv_vmbus]
[   20.641104]  [<ffffffffa00045b5>] vmbus_initiate_unload+0x65/0x90 [hv_vmbus]
[   20.641104]  [<ffffffffa0001d7e>] vmbus_disconnect+0xe/0x80 [hv_vmbus]
[   20.641104]  [<ffffffffa0004dd1>] vmbus_exit+0xe9/0x318 [hv_vmbus]
[   20.641104]  [<ffffffff8110704c>] SyS_delete_module+0x1ac/0x230
[   20.641104]  [<ffffffff81aa83f6>] ? int_with_check+0x27/0x69
[   20.641104]  [<ffffffff81aa8209>] system_call_fastpath+0x12/0x17
[   20.641104] Code:  Bad RIP value.
[   20.641104] RIP  [<          (null)>]           (null)
[   20.641104]  RSP <ffff88002f61fe60>
[   20.641104] CR2: 0000000000000000
[   20.708666] ---[ end trace 76d9daf92f0e3af8 ]---
[   20.709944] Kernel panic - not syncing: Fatal exception
[   20.710933] Kernel Offset: 0x0 from 0xffffffff81000000 (relocation range: 0xffffffff80000000-0xffffffff9fffffff)
[   20.710933] ---[ end Kernel panic - not syncing: Fatal exception

I'll try to investigate.

> ---
>  drivers/hv/channel_mgmt.c |   25 +++++++++++++++++++++++++
>  drivers/hv/connection.c   |    5 +++++
>  drivers/hv/hyperv_vmbus.h |    2 ++
>  include/linux/hyperv.h    |    1 +
>  4 files changed, 33 insertions(+), 0 deletions(-)
>
> diff --git a/drivers/hv/channel_mgmt.c b/drivers/hv/channel_mgmt.c
> index 865a3af..4b9d89a 100644
> --- a/drivers/hv/channel_mgmt.c
> +++ b/drivers/hv/channel_mgmt.c
> @@ -422,6 +422,30 @@ static void init_vp_index(struct vmbus_channel *channel, const uuid_le *type_gui
>  }
>
>  /*
> + * 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.
> +	 */
> +	complete(&vmbus_connection.unload_event);
> +}
> +
> +void vmbus_initiate_unload(void)
> +{
> +	struct vmbus_channel_message_header hdr;
> +
> +	init_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));
> +
> +	wait_for_completion(&vmbus_connection.unload_event);
> +}
> +
> +/*
>   * vmbus_onoffer - Handler for channel offers from vmbus in parent partition.
>   *
>   */
> @@ -717,6 +741,7 @@ struct vmbus_channel_message_table_entry
>  	{CHANNELMSG_INITIATE_CONTACT,		0, NULL},
>  	{CHANNELMSG_VERSION_RESPONSE,		1, vmbus_onversion_response},
>  	{CHANNELMSG_UNLOAD,			0, NULL},
> +	{CHANNELMSG_UNLOAD_RESPONSE,		1, vmbus_unload_response},
>  };
>
>  /*
> diff --git a/drivers/hv/connection.c b/drivers/hv/connection.c
> index b27220a..acd50e9 100644
> --- a/drivers/hv/connection.c
> +++ b/drivers/hv/connection.c
> @@ -227,6 +227,11 @@ cleanup:
>
>  void vmbus_disconnect(void)
>  {
> +	/*
> +	 * First send the unload request to the host.
> +	 */
> +	vmbus_initiate_unload();
> +
>  	if (vmbus_connection.work_queue) {
>  		drain_workqueue(vmbus_connection.work_queue);
>  		destroy_workqueue(vmbus_connection.work_queue);
> diff --git a/drivers/hv/hyperv_vmbus.h b/drivers/hv/hyperv_vmbus.h
> index 138d663..cddc0c9 100644
> --- a/drivers/hv/hyperv_vmbus.h
> +++ b/drivers/hv/hyperv_vmbus.h
> @@ -647,6 +647,7 @@ struct vmbus_connection {
>
>  	atomic_t next_gpadl_handle;
>
> +	struct completion  unload_event;
>  	/*
>  	 * Represents channel interrupts. Each bit position represents a
>  	 * channel.  When a channel sends an interrupt via VMBUS, it finds its
> @@ -741,6 +742,7 @@ void hv_vss_onchannelcallback(void *);
>  int hv_fcopy_init(struct hv_util_service *);
>  void hv_fcopy_deinit(void);
>  void hv_fcopy_onchannelcallback(void *);
> +void vmbus_initiate_unload(void);
>
>  static inline void hv_poll_channel(struct vmbus_channel *channel,
>  				   void (*cb)(void *))
> diff --git a/include/linux/hyperv.h b/include/linux/hyperv.h
> index e29ccdd..ea93486 100644
> --- a/include/linux/hyperv.h
> +++ b/include/linux/hyperv.h
> @@ -389,6 +389,7 @@ enum vmbus_channel_message_type {
>  	CHANNELMSG_INITIATE_CONTACT		= 14,
>  	CHANNELMSG_VERSION_RESPONSE		= 15,
>  	CHANNELMSG_UNLOAD			= 16,
> +	CHANNELMSG_UNLOAD_RESPONSE		= 17,
>  	CHANNELMSG_COUNT
>  };

-- 
  Vitaly

Re: [PATCH 5/5] Drivers: hv: vmbus: Implement the protocol for tearing down vmbus state

[Vitaly Kuznetsov]

Vitaly Kuznetsov <vkuznets@redhat.com> writes:

> "K. Y. Srinivasan" <kys@microsoft.com> writes:
>
>> Implement the protocol for tearing down the monitor state established with
>> the host.
>>
>> Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
>
> Unfortunatelly this patch leads to the following crash:
>
> pre-udev:/# modprobe hv_vmbus
> modprobe hv_vmbus
> [   14.832334] hv_vmbus: Hyper-V Host Build:9600-6.3-17-0.17039; Vmbus version:3.0
> [   14.834179] hv_vmbus: CPU offlining is not supported by hypervisor
> pre-udev:/# modprobe -r hv_vmbus
> modprobe -r hv_vmbus
> [   20.640893] BUG: unable to handle kernel NULL pointer dereference at           (null)
> [   20.641104] IP: [<          (null)>]           (null)
>
> I'll try to investigate.
>

The problem is that we call vmbus_disconnect() too late in
vmbus_exit(). We need to call it:
1) Before hv_cleanup() call as we free hypercall page there (that's what
you see in my crash)
2) Before hv_remove_vmbus_irq() as we're waiting for the hypervisor to
reply.

This simple patch fixes the issue:
diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c
index 7870a90..2b56260 100644
--- a/drivers/hv/vmbus_drv.c
+++ b/drivers/hv/vmbus_drv.c
@@ -1106,6 +1106,7 @@ static void __exit vmbus_exit(void)
 
        vmbus_connection.conn_state = DISCONNECTED;
        hv_synic_clockevents_cleanup();
+       vmbus_disconnect();
        hv_remove_vmbus_irq();
        vmbus_free_channels();
        if (ms_hyperv.features & HV_FEATURE_GUEST_CRASH_MSR_AVAILABLE) {
@@ -1118,7 +1119,6 @@ static void __exit vmbus_exit(void)
                smp_call_function_single(cpu, hv_synic_cleanup, NULL,
        1);
        acpi_bus_unregister_driver(&vmbus_acpi_driver);
        hv_cpu_hotplug_quirk(false);
-       vmbus_disconnect();
 }

I suggest we incorporate it into your PATCH 5/5.

-- 
  Vitaly

RE: [PATCH 5/5] Drivers: hv: vmbus: Implement the protocol for tearing down vmbus state

[KY Srinivasan]

> -----Original Message-----
> From: Vitaly Kuznetsov [mailto:vkuznets@redhat.com]
> Sent: Monday, April 20, 2015 2:40 AM
> To: KY Srinivasan
> Cc: gregkh@linuxfoundation.org; linux-kernel@vger.kernel.org;
> devel@linuxdriverproject.org; olaf@aepfle.de; apw@canonical.com;
> jasowang@redhat.com
> Subject: Re: [PATCH 5/5] Drivers: hv: vmbus: Implement the protocol for
> tearing down vmbus state
> 
> "K. Y. Srinivasan" <kys@microsoft.com> writes:
> 
> > Implement the protocol for tearing down the monitor state established
> with
> > the host.
> >
> > Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
> 
> Unfortunatelly this patch leads to the following crash:

Thanks for testing Vitaly. The unload handling is what we want, maybe I need to
Invoke unload a little earlier.

Regards,

K. Y

Re: [PATCH 5/5] Drivers: hv: vmbus: Implement the protocol for tearing down vmbus state

[Vitaly Kuznetsov]

KY Srinivasan <kys@microsoft.com> writes:

>> -----Original Message-----
>> From: Vitaly Kuznetsov [mailto:vkuznets@redhat.com]
>> Sent: Monday, April 20, 2015 2:40 AM
>> To: KY Srinivasan
>> Cc: gregkh@linuxfoundation.org; linux-kernel@vger.kernel.org;
>> devel@linuxdriverproject.org; olaf@aepfle.de; apw@canonical.com;
>> jasowang@redhat.com
>> Subject: Re: [PATCH 5/5] Drivers: hv: vmbus: Implement the protocol for
>> tearing down vmbus state
>> 
>> "K. Y. Srinivasan" <kys@microsoft.com> writes:
>> 
>> > Implement the protocol for tearing down the monitor state established
>> with
>> > the host.
>> >
>> > Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
>> 
>> Unfortunatelly this patch leads to the following crash:
>
> Thanks for testing Vitaly. The unload handling is what we want, maybe I need to
> Invoke unload a little earlier.

I actually sent two letters this morning :-) The other was:

The problem is that we call vmbus_disconnect() too late in
vmbus_exit(). We need to call it:
1) Before hv_cleanup() call as we free hypercall page there (that's what
you see in my crash)
2) Before hv_remove_vmbus_irq() as we're waiting for the hypervisor to
reply.

This simple patch fixes the issue:
diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c
index 7870a90..2b56260 100644
--- a/drivers/hv/vmbus_drv.c
+++ b/drivers/hv/vmbus_drv.c
@@ -1106,6 +1106,7 @@ static void __exit vmbus_exit(void)

        vmbus_connection.conn_state = DISCONNECTED;
        hv_synic_clockevents_cleanup();
+       vmbus_disconnect();
        hv_remove_vmbus_irq();
        vmbus_free_channels();
        if (ms_hyperv.features & HV_FEATURE_GUEST_CRASH_MSR_AVAILABLE) {
@@ -1118,7 +1119,6 @@ static void __exit vmbus_exit(void)
                smp_call_function_single(cpu, hv_synic_cleanup, NULL,
        1);
        acpi_bus_unregister_driver(&vmbus_acpi_driver);
        hv_cpu_hotplug_quirk(false);
-       vmbus_disconnect();
 }

I suggest we incorporate it into your PATCH 5/5.

-- 
  Vitaly

RE: [PATCH 5/5] Drivers: hv: vmbus: Implement the protocol for tearing down vmbus state

[KY Srinivasan]

> -----Original Message-----
> From: Vitaly Kuznetsov [mailto:vkuznets@redhat.com]
> Sent: Monday, April 20, 2015 7:17 AM
> To: KY Srinivasan
> Cc: gregkh@linuxfoundation.org; linux-kernel@vger.kernel.org;
> devel@linuxdriverproject.org; olaf@aepfle.de; apw@canonical.com;
> jasowang@redhat.com
> Subject: Re: [PATCH 5/5] Drivers: hv: vmbus: Implement the protocol for
> tearing down vmbus state
> 
> KY Srinivasan <kys@microsoft.com> writes:
> 
> >> -----Original Message-----
> >> From: Vitaly Kuznetsov [mailto:vkuznets@redhat.com]
> >> Sent: Monday, April 20, 2015 2:40 AM
> >> To: KY Srinivasan
> >> Cc: gregkh@linuxfoundation.org; linux-kernel@vger.kernel.org;
> >> devel@linuxdriverproject.org; olaf@aepfle.de; apw@canonical.com;
> >> jasowang@redhat.com
> >> Subject: Re: [PATCH 5/5] Drivers: hv: vmbus: Implement the protocol for
> >> tearing down vmbus state
> >>
> >> "K. Y. Srinivasan" <kys@microsoft.com> writes:
> >>
> >> > Implement the protocol for tearing down the monitor state established
> >> with
> >> > the host.
> >> >
> >> > Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
> >>
> >> Unfortunatelly this patch leads to the following crash:
> >
> > Thanks for testing Vitaly. The unload handling is what we want, maybe I
> need to
> > Invoke unload a little earlier.
> 
> I actually sent two letters this morning :-) The other was:
> 
> The problem is that we call vmbus_disconnect() too late in
> vmbus_exit(). We need to call it:
> 1) Before hv_cleanup() call as we free hypercall page there (that's what
> you see in my crash)
> 2) Before hv_remove_vmbus_irq() as we're waiting for the hypervisor to
> reply.
> 
> This simple patch fixes the issue:
> diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c
> index 7870a90..2b56260 100644
> --- a/drivers/hv/vmbus_drv.c
> +++ b/drivers/hv/vmbus_drv.c
> @@ -1106,6 +1106,7 @@ static void __exit vmbus_exit(void)
> 
>         vmbus_connection.conn_state = DISCONNECTED;
>         hv_synic_clockevents_cleanup();
> +       vmbus_disconnect();
>         hv_remove_vmbus_irq();
>         vmbus_free_channels();
>         if (ms_hyperv.features &
> HV_FEATURE_GUEST_CRASH_MSR_AVAILABLE) {
> @@ -1118,7 +1119,6 @@ static void __exit vmbus_exit(void)
>                 smp_call_function_single(cpu, hv_synic_cleanup, NULL,
>         1);
>         acpi_bus_unregister_driver(&vmbus_acpi_driver);
>         hv_cpu_hotplug_quirk(false);
> -       vmbus_disconnect();
>  }
> 
> I suggest we incorporate it into your PATCH 5/5.

Thank you; I will resend the patch with your fix.

Regards,

K. Y
> 
> --
>   Vitaly