[PATCH 0/6] Drivers: hv: vmbus: Fix mmio management

[PATCH 0/6] Drivers: hv: vmbus: Fix mmio management

[K. Y. Srinivasan]

Fix mmio management for vmbus devices. Also included is a patch
to fix an issue in KVP.

Jake Oshins (5):
  hv: Make a function to free mmio regions through vmbus
  hv: Lock access to hyperv_mmio resource tree
  hv: Use new vmbus_mmio_free() from client drivers.
  hv: Reverse order of resources in hyperv_mmio
  hv: Track allocations of children of hv_vmbus in private resource
    tree

Vitaly Kuznetsov (1):
  Drivers: hv: kvp: fix IP Failover

 drivers/hv/hv_kvp.c             |   30 +++++++++++++++++++++
 drivers/hv/hyperv_vmbus.h       |    5 +++
 drivers/hv/vmbus_drv.c          |   56 ++++++++++++++++++++++++++++++++++-----
 drivers/video/fbdev/hyperv_fb.c |    4 +-
 include/linux/hyperv.h          |    2 +-
 5 files changed, 87 insertions(+), 10 deletions(-)

-- 
1.7.4.1

[PATCH 1/6] Drivers: hv: kvp: fix IP Failover

[K. Y. Srinivasan]

From: Vitaly Kuznetsov <vkuznets@redhat.com>

Hyper-V VMs can be replicated to another hosts and there is a feature to
set different IP for replicas, it is called 'Failover TCP/IP'. When
such guest starts Hyper-V host sends it KVP_OP_SET_IP_INFO message as soon
as we finish negotiation procedure. The problem is that it can happen (and
it actually happens) before userspace daemon connects and we reply with
HV_E_FAIL to the message. As there are no repetitions we fail to set the
requested IP.

Solve the issue by postponing our reply to the negotiation message till
userspace daemon is connected. We can't wait too long as there is a
host-side timeout (cca. 75 seconds) and if we fail to reply in this time
frame the whole KVP service will become inactive. The solution is not
ideal - if it takes userspace daemon more than 60 seconds to connect
IP Failover will still fail but I don't see a solution with our current
separation between kernel and userspace parts.

Other two modules (VSS and FCOPY) don't require such delay, leave them
untouched.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
---
 drivers/hv/hv_kvp.c       |   30 ++++++++++++++++++++++++++++++
 drivers/hv/hyperv_vmbus.h |    5 +++++
 2 files changed, 35 insertions(+), 0 deletions(-)

diff --git a/drivers/hv/hv_kvp.c b/drivers/hv/hv_kvp.c
index 9b9b370..0d3fcd6 100644
--- a/drivers/hv/hv_kvp.c
+++ b/drivers/hv/hv_kvp.c
@@ -78,9 +78,11 @@ static void kvp_send_key(struct work_struct *dummy);
 
 static void kvp_respond_to_host(struct hv_kvp_msg *msg, int error);
 static void kvp_timeout_func(struct work_struct *dummy);
+static void kvp_host_handshake_func(struct work_struct *dummy);
 static void kvp_register(int);
 
 static DECLARE_DELAYED_WORK(kvp_timeout_work, kvp_timeout_func);
+static DECLARE_DELAYED_WORK(kvp_host_handshake_work, kvp_host_handshake_func);
 static DECLARE_WORK(kvp_sendkey_work, kvp_send_key);
 
 static const char kvp_devname[] = "vmbus/hv_kvp";
@@ -130,6 +132,11 @@ static void kvp_timeout_func(struct work_struct *dummy)
 	hv_poll_channel(kvp_transaction.recv_channel, kvp_poll_wrapper);
 }
 
+static void kvp_host_handshake_func(struct work_struct *dummy)
+{
+	hv_poll_channel(kvp_transaction.recv_channel, hv_kvp_onchannelcallback);
+}
+
 static int kvp_handle_handshake(struct hv_kvp_msg *msg)
 {
 	switch (msg->kvp_hdr.operation) {
@@ -154,6 +161,12 @@ static int kvp_handle_handshake(struct hv_kvp_msg *msg)
 	pr_debug("KVP: userspace daemon ver. %d registered\n",
 		 KVP_OP_REGISTER);
 	kvp_register(dm_reg_value);
+
+	/*
+	 * If we're still negotiating with the host cancel the timeout
+	 * work to not poll the channel twice.
+	 */
+	cancel_delayed_work_sync(&kvp_host_handshake_work);
 	hv_poll_channel(kvp_transaction.recv_channel, kvp_poll_wrapper);
 
 	return 0;
@@ -594,7 +607,22 @@ void hv_kvp_onchannelcallback(void *context)
 	struct icmsg_negotiate *negop = NULL;
 	int util_fw_version;
 	int kvp_srv_version;
+	static enum {NEGO_NOT_STARTED,
+		     NEGO_IN_PROGRESS,
+		     NEGO_FINISHED} host_negotiatied = NEGO_NOT_STARTED;
 
+	if (host_negotiatied == NEGO_NOT_STARTED &&
+	    kvp_transaction.state < HVUTIL_READY) {
+		/*
+		 * If userspace daemon is not connected and host is asking
+		 * us to negotiate we need to delay to not lose messages.
+		 * This is important for Failover IP setting.
+		 */
+		host_negotiatied = NEGO_IN_PROGRESS;
+		schedule_delayed_work(&kvp_host_handshake_work,
+				      HV_UTIL_NEGO_TIMEOUT * HZ);
+		return;
+	}
 	if (kvp_transaction.state > HVUTIL_READY)
 		return;
 
@@ -672,6 +700,8 @@ void hv_kvp_onchannelcallback(void *context)
 		vmbus_sendpacket(channel, recv_buffer,
 				       recvlen, requestid,
 				       VM_PKT_DATA_INBAND, 0);
+
+		host_negotiatied = NEGO_FINISHED;
 	}
 
 }
diff --git a/drivers/hv/hyperv_vmbus.h b/drivers/hv/hyperv_vmbus.h
index a64b176..28e9df9 100644
--- a/drivers/hv/hyperv_vmbus.h
+++ b/drivers/hv/hyperv_vmbus.h
@@ -36,6 +36,11 @@
 #define HV_UTIL_TIMEOUT 30
 
 /*
+ * Timeout for guest-host handshake for services.
+ */
+#define HV_UTIL_NEGO_TIMEOUT 60
+
+/*
  * The below CPUID leaves are present if VersionAndFeatures.HypervisorPresent
  * is set by CPUID(HVCPUID_VERSION_FEATURES).
  */
-- 
1.7.4.1

[PATCH 2/6] hv: Make a function to free mmio regions through vmbus

[K. Y. Srinivasan]

From: Jake Oshins <jakeo@microsoft.com>

This patch introduces a function that reverses everything
done by vmbus_allocate_mmio().  Existing code just called
release_mem_region().  Future patches in this series
require a more complex sequence of actions, so this function
is introduced to wrap those actions.

Signed-off-by: Jake Oshins <jakeo@microsoft.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
---
 drivers/hv/vmbus_drv.c |   15 +++++++++++++++
 include/linux/hyperv.h |    2 +-
 2 files changed, 16 insertions(+), 1 deletions(-)

diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c
index 64713ff..44e95a4 100644
--- a/drivers/hv/vmbus_drv.c
+++ b/drivers/hv/vmbus_drv.c
@@ -1180,6 +1180,21 @@ int vmbus_allocate_mmio(struct resource **new, struct hv_device *device_obj,
 EXPORT_SYMBOL_GPL(vmbus_allocate_mmio);
 
 /**
+ * vmbus_free_mmio() - Free a memory-mapped I/O range.
+ * @start:		Base address of region to release.
+ * @size:		Size of the range to be allocated
+ *
+ * This function releases anything requested by
+ * vmbus_mmio_allocate().
+ */
+void vmbus_free_mmio(resource_size_t start, resource_size_t size)
+{
+	release_mem_region(start, size);
+
+}
+EXPORT_SYMBOL_GPL(vmbus_free_mmio);
+
+/**
  * vmbus_cpu_number_to_vp_number() - Map CPU to VP.
  * @cpu_number: CPU number in Linux terms
  *
diff --git a/include/linux/hyperv.h b/include/linux/hyperv.h
index aa0fadc..ecd81c3 100644
--- a/include/linux/hyperv.h
+++ b/include/linux/hyperv.h
@@ -1091,7 +1091,7 @@ int vmbus_allocate_mmio(struct resource **new, struct hv_device *device_obj,
 			resource_size_t min, resource_size_t max,
 			resource_size_t size, resource_size_t align,
 			bool fb_overlap_ok);
-
+void vmbus_free_mmio(resource_size_t start, resource_size_t size);
 int vmbus_cpu_number_to_vp_number(int cpu_number);
 u64 hv_do_hypercall(u64 control, void *input, void *output);
 
-- 
1.7.4.1

[PATCH 3/6] hv: Lock access to hyperv_mmio resource tree

[K. Y. Srinivasan]

From: Jake Oshins <jakeo@microsoft.com>

In existing code, this tree of resources is created
in single-threaded code and never modified after it is
created, and thus needs no locking.  This patch introduces
a semaphore for tree access, as other patches in this
series introduce run-time modifications of this resource
tree which can happen on multiple threads.

Signed-off-by: Jake Oshins <jakeo@microsoft.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
---
 drivers/hv/vmbus_drv.c |   16 ++++++++++++----
 1 files changed, 12 insertions(+), 4 deletions(-)

diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c
index 44e95a4..60553c1 100644
--- a/drivers/hv/vmbus_drv.c
+++ b/drivers/hv/vmbus_drv.c
@@ -102,6 +102,7 @@ static struct notifier_block hyperv_panic_block = {
 };
 
 struct resource *hyperv_mmio;
+DEFINE_SEMAPHORE(hyperv_mmio_lock);
 
 static int vmbus_exists(void)
 {
@@ -1132,7 +1133,10 @@ int vmbus_allocate_mmio(struct resource **new, struct hv_device *device_obj,
 	resource_size_t range_min, range_max, start, local_min, local_max;
 	const char *dev_n = dev_name(&device_obj->device);
 	u32 fb_end = screen_info.lfb_base + (screen_info.lfb_size << 1);
-	int i;
+	int i, retval;
+
+	retval = -ENXIO;
+	down(&hyperv_mmio_lock);
 
 	for (iter = hyperv_mmio; iter; iter = iter->sibling) {
 		if ((iter->start >= max) || (iter->end <= min))
@@ -1169,13 +1173,17 @@ int vmbus_allocate_mmio(struct resource **new, struct hv_device *device_obj,
 			for (; start + size - 1 <= local_max; start += align) {
 				*new = request_mem_region_exclusive(start, size,
 								    dev_n);
-				if (*new)
-					return 0;
+				if (*new) {
+					retval = 0;
+					goto exit;
+				}
 			}
 		}
 	}
 
-	return -ENXIO;
+exit:
+	up(&hyperv_mmio_lock);
+	return retval;
 }
 EXPORT_SYMBOL_GPL(vmbus_allocate_mmio);
 
-- 
1.7.4.1

[PATCH 4/6] hv: Use new vmbus_mmio_free() from client drivers.

[K. Y. Srinivasan]

From: Jake Oshins <jakeo@microsoft.com>

This patch modifies all the callers of vmbus_mmio_allocate()
to call vmbus_mmio_free() instead of release_mem_region().

Signed-off-by: Jake Oshins <jakeo@microsoft.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
---
 drivers/video/fbdev/hyperv_fb.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/video/fbdev/hyperv_fb.c b/drivers/video/fbdev/hyperv_fb.c
index e2451bd..2fd49b2 100644
--- a/drivers/video/fbdev/hyperv_fb.c
+++ b/drivers/video/fbdev/hyperv_fb.c
@@ -743,7 +743,7 @@ static int hvfb_getmem(struct hv_device *hdev, struct fb_info *info)
 err3:
 	iounmap(fb_virt);
 err2:
-	release_mem_region(par->mem->start, screen_fb_size);
+	vmbus_free_mmio(par->mem->start, screen_fb_size);
 	par->mem = NULL;
 err1:
 	if (!gen2vm)
@@ -758,7 +758,7 @@ static void hvfb_putmem(struct fb_info *info)
 	struct hvfb_par *par = info->par;
 
 	iounmap(info->screen_base);
-	release_mem_region(par->mem->start, screen_fb_size);
+	vmbus_free_mmio(par->mem->start, screen_fb_size);
 	par->mem = NULL;
 }
 
-- 
1.7.4.1

[PATCH 5/6] hv: Reverse order of resources in hyperv_mmio

[K. Y. Srinivasan]

From: Jake Oshins <jakeo@microsoft.com>

A patch later in this series allocates child nodes
in this resource tree.  For that to work, this tree
needs to be sorted in ascending order.

Signed-off-by: Jake Oshins <jakeo@microsoft.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
---
 drivers/hv/vmbus_drv.c |    3 +--
 1 files changed, 1 insertions(+), 2 deletions(-)

diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c
index 60553c1..1ce47d0 100644
--- a/drivers/hv/vmbus_drv.c
+++ b/drivers/hv/vmbus_drv.c
@@ -1049,7 +1049,6 @@ static acpi_status vmbus_walk_resources(struct acpi_resource *res, void *ctx)
 	new_res->end = end;
 
 	/*
-	 * Stick ranges from higher in address space at the front of the list.
 	 * If two ranges are adjacent, merge them.
 	 */
 	do {
@@ -1070,7 +1069,7 @@ static acpi_status vmbus_walk_resources(struct acpi_resource *res, void *ctx)
 			break;
 		}
 
-		if ((*old_res)->end < new_res->start) {
+		if ((*old_res)->start > new_res->end) {
 			new_res->sibling = *old_res;
 			if (prev_res)
 				(*prev_res)->sibling = new_res;
-- 
1.7.4.1

[PATCH 6/6] hv: Track allocations of children of hv_vmbus in private resource tree

[K. Y. Srinivasan]

From: Jake Oshins <jakeo@microsoft.com>

This patch changes vmbus_allocate_mmio() and vmbus_free_mmio() so
that when child paravirtual devices allocate memory-mapped I/O
space, they allocate it privately from a resource tree pointed
at by hyperv_mmio and also by the public resource tree
iomem_resource.  This allows the region to be marked as "busy"
in the private tree, but a "bridge window" in the public tree,
guaranteeing that no two bridge windows will overlap each other
but while also allowing the PCI device children of the bridge
windows to overlap that window.

One might conclude that this belongs in the pnp layer, rather
than in this driver.  Rafael Wysocki, the maintainter of the
pnp layer, has previously asked that we not modify the pnp layer
as it is considered deprecated.  This patch is thus essentially
a workaround.

Signed-off-by: Jake Oshins <jakeo@microsoft.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
---
 drivers/hv/vmbus_drv.c |   22 +++++++++++++++++++++-
 1 files changed, 21 insertions(+), 1 deletions(-)

diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c
index 1ce47d0..dfc6149 100644
--- a/drivers/hv/vmbus_drv.c
+++ b/drivers/hv/vmbus_drv.c
@@ -1128,7 +1128,7 @@ int vmbus_allocate_mmio(struct resource **new, struct hv_device *device_obj,
 			resource_size_t size, resource_size_t align,
 			bool fb_overlap_ok)
 {
-	struct resource *iter;
+	struct resource *iter, *shadow;
 	resource_size_t range_min, range_max, start, local_min, local_max;
 	const char *dev_n = dev_name(&device_obj->device);
 	u32 fb_end = screen_info.lfb_base + (screen_info.lfb_size << 1);
@@ -1170,12 +1170,22 @@ int vmbus_allocate_mmio(struct resource **new, struct hv_device *device_obj,
 
 			start = (local_min + align - 1) & ~(align - 1);
 			for (; start + size - 1 <= local_max; start += align) {
+				shadow = __request_region(iter, start,
+							  size,
+							  NULL,
+							  IORESOURCE_BUSY);
+				if (!shadow)
+					continue;
+
 				*new = request_mem_region_exclusive(start, size,
 								    dev_n);
 				if (*new) {
+					shadow->name = (char *)*new;
 					retval = 0;
 					goto exit;
 				}
+
+				__release_region(iter, start, size);
 			}
 		}
 	}
@@ -1196,7 +1206,17 @@ EXPORT_SYMBOL_GPL(vmbus_allocate_mmio);
  */
 void vmbus_free_mmio(resource_size_t start, resource_size_t size)
 {
+	struct resource *iter;
+
+	down(&hyperv_mmio_lock);
+	for (iter = hyperv_mmio; iter; iter = iter->sibling) {
+		if ((iter->start >= start + size) || (iter->end <= start))
+			continue;
+
+		__release_region(iter, start, size);
+	}
 	release_mem_region(start, size);
+	up(&hyperv_mmio_lock);
 
 }
 EXPORT_SYMBOL_GPL(vmbus_free_mmio);
-- 
1.7.4.1

Re: [PATCH 1/6] Drivers: hv: kvp: fix IP Failover

[Vitaly Kuznetsov]

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

> From: Vitaly Kuznetsov <vkuznets@redhat.com>
>
> Hyper-V VMs can be replicated to another hosts and there is a feature to
> set different IP for replicas, it is called 'Failover TCP/IP'. When
> such guest starts Hyper-V host sends it KVP_OP_SET_IP_INFO message as soon
> as we finish negotiation procedure. The problem is that it can happen (and
> it actually happens) before userspace daemon connects and we reply with
> HV_E_FAIL to the message. As there are no repetitions we fail to set the
> requested IP.
>
> Solve the issue by postponing our reply to the negotiation message till
> userspace daemon is connected. We can't wait too long as there is a
> host-side timeout (cca. 75 seconds) and if we fail to reply in this time
> frame the whole KVP service will become inactive. The solution is not
> ideal - if it takes userspace daemon more than 60 seconds to connect
> IP Failover will still fail but I don't see a solution with our current
> separation between kernel and userspace parts.
>
> Other two modules (VSS and FCOPY) don't require such delay, leave them
> untouched.
>
> Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
> Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>

An issue was found with this patch: we don't cancel
kvp_host_handshake_work on module unload and if the work is still
pending we end up crashing. As far as I can see this series didn't make
it to char-misc tree so instead of sending a patch to this patch I'll
send v2 for the original issue.

Sorry for the inconvenience.

> ---
>  drivers/hv/hv_kvp.c       |   30 ++++++++++++++++++++++++++++++
>  drivers/hv/hyperv_vmbus.h |    5 +++++
>  2 files changed, 35 insertions(+), 0 deletions(-)
>
> diff --git a/drivers/hv/hv_kvp.c b/drivers/hv/hv_kvp.c
> index 9b9b370..0d3fcd6 100644
> --- a/drivers/hv/hv_kvp.c
> +++ b/drivers/hv/hv_kvp.c
> @@ -78,9 +78,11 @@ static void kvp_send_key(struct work_struct *dummy);
>
>  static void kvp_respond_to_host(struct hv_kvp_msg *msg, int error);
>  static void kvp_timeout_func(struct work_struct *dummy);
> +static void kvp_host_handshake_func(struct work_struct *dummy);
>  static void kvp_register(int);
>
>  static DECLARE_DELAYED_WORK(kvp_timeout_work, kvp_timeout_func);
> +static DECLARE_DELAYED_WORK(kvp_host_handshake_work, kvp_host_handshake_func);
>  static DECLARE_WORK(kvp_sendkey_work, kvp_send_key);
>
>  static const char kvp_devname[] = "vmbus/hv_kvp";
> @@ -130,6 +132,11 @@ static void kvp_timeout_func(struct work_struct *dummy)
>  	hv_poll_channel(kvp_transaction.recv_channel, kvp_poll_wrapper);
>  }
>
> +static void kvp_host_handshake_func(struct work_struct *dummy)
> +{
> +	hv_poll_channel(kvp_transaction.recv_channel, hv_kvp_onchannelcallback);
> +}
> +
>  static int kvp_handle_handshake(struct hv_kvp_msg *msg)
>  {
>  	switch (msg->kvp_hdr.operation) {
> @@ -154,6 +161,12 @@ static int kvp_handle_handshake(struct hv_kvp_msg *msg)
>  	pr_debug("KVP: userspace daemon ver. %d registered\n",
>  		 KVP_OP_REGISTER);
>  	kvp_register(dm_reg_value);
> +
> +	/*
> +	 * If we're still negotiating with the host cancel the timeout
> +	 * work to not poll the channel twice.
> +	 */
> +	cancel_delayed_work_sync(&kvp_host_handshake_work);
>  	hv_poll_channel(kvp_transaction.recv_channel, kvp_poll_wrapper);
>
>  	return 0;
> @@ -594,7 +607,22 @@ void hv_kvp_onchannelcallback(void *context)
>  	struct icmsg_negotiate *negop = NULL;
>  	int util_fw_version;
>  	int kvp_srv_version;
> +	static enum {NEGO_NOT_STARTED,
> +		     NEGO_IN_PROGRESS,
> +		     NEGO_FINISHED} host_negotiatied = NEGO_NOT_STARTED;
>
> +	if (host_negotiatied == NEGO_NOT_STARTED &&
> +	    kvp_transaction.state < HVUTIL_READY) {
> +		/*
> +		 * If userspace daemon is not connected and host is asking
> +		 * us to negotiate we need to delay to not lose messages.
> +		 * This is important for Failover IP setting.
> +		 */
> +		host_negotiatied = NEGO_IN_PROGRESS;
> +		schedule_delayed_work(&kvp_host_handshake_work,
> +				      HV_UTIL_NEGO_TIMEOUT * HZ);
> +		return;
> +	}
>  	if (kvp_transaction.state > HVUTIL_READY)
>  		return;
>
> @@ -672,6 +700,8 @@ void hv_kvp_onchannelcallback(void *context)
>  		vmbus_sendpacket(channel, recv_buffer,
>  				       recvlen, requestid,
>  				       VM_PKT_DATA_INBAND, 0);
> +
> +		host_negotiatied = NEGO_FINISHED;
>  	}
>
>  }
> diff --git a/drivers/hv/hyperv_vmbus.h b/drivers/hv/hyperv_vmbus.h
> index a64b176..28e9df9 100644
> --- a/drivers/hv/hyperv_vmbus.h
> +++ b/drivers/hv/hyperv_vmbus.h
> @@ -36,6 +36,11 @@
>  #define HV_UTIL_TIMEOUT 30
>
>  /*
> + * Timeout for guest-host handshake for services.
> + */
> +#define HV_UTIL_NEGO_TIMEOUT 60
> +
> +/*
>   * The below CPUID leaves are present if VersionAndFeatures.HypervisorPresent
>   * is set by CPUID(HVCPUID_VERSION_FEATURES).
>   */

-- 
  Vitaly

Re: [PATCH 1/6] Drivers: hv: kvp: fix IP Failover

[Greg KH]

On Tue, Mar 29, 2016 at 02:27:16PM +0200, Vitaly Kuznetsov wrote:
> "K. Y. Srinivasan" <kys@microsoft.com> writes:
> 
> > From: Vitaly Kuznetsov <vkuznets@redhat.com>
> >
> > Hyper-V VMs can be replicated to another hosts and there is a feature to
> > set different IP for replicas, it is called 'Failover TCP/IP'. When
> > such guest starts Hyper-V host sends it KVP_OP_SET_IP_INFO message as soon
> > as we finish negotiation procedure. The problem is that it can happen (and
> > it actually happens) before userspace daemon connects and we reply with
> > HV_E_FAIL to the message. As there are no repetitions we fail to set the
> > requested IP.
> >
> > Solve the issue by postponing our reply to the negotiation message till
> > userspace daemon is connected. We can't wait too long as there is a
> > host-side timeout (cca. 75 seconds) and if we fail to reply in this time
> > frame the whole KVP service will become inactive. The solution is not
> > ideal - if it takes userspace daemon more than 60 seconds to connect
> > IP Failover will still fail but I don't see a solution with our current
> > separation between kernel and userspace parts.
> >
> > Other two modules (VSS and FCOPY) don't require such delay, leave them
> > untouched.
> >
> > Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
> > Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
> 
> An issue was found with this patch: we don't cancel
> kvp_host_handshake_work on module unload and if the work is still
> pending we end up crashing. As far as I can see this series didn't make
> it to char-misc tree so instead of sending a patch to this patch I'll
> send v2 for the original issue.
> 
> Sorry for the inconvenience.

Ok, I'll drop this whole series.  K.Y., can you resend this series after
fixing this up?

thanks,

greg k-h

RE: [PATCH 1/6] Drivers: hv: kvp: fix IP Failover

[KY Srinivasan]

> -----Original Message-----
> From: Greg KH [mailto:gregkh@linuxfoundation.org]
> Sent: Thursday, March 31, 2016 1:19 PM
> To: Vitaly Kuznetsov <vkuznets@redhat.com>
> Cc: KY Srinivasan <kys@microsoft.com>; olaf@aepfle.de;
> jasowang@redhat.com; linux-kernel@vger.kernel.org; apw@canonical.com;
> devel@linuxdriverproject.org
> Subject: Re: [PATCH 1/6] Drivers: hv: kvp: fix IP Failover
> 
> On Tue, Mar 29, 2016 at 02:27:16PM +0200, Vitaly Kuznetsov wrote:
> > "K. Y. Srinivasan" <kys@microsoft.com> writes:
> >
> > > From: Vitaly Kuznetsov <vkuznets@redhat.com>
> > >
> > > Hyper-V VMs can be replicated to another hosts and there is a feature to
> > > set different IP for replicas, it is called 'Failover TCP/IP'. When
> > > such guest starts Hyper-V host sends it KVP_OP_SET_IP_INFO message
> as soon
> > > as we finish negotiation procedure. The problem is that it can happen
> (and
> > > it actually happens) before userspace daemon connects and we reply
> with
> > > HV_E_FAIL to the message. As there are no repetitions we fail to set the
> > > requested IP.
> > >
> > > Solve the issue by postponing our reply to the negotiation message till
> > > userspace daemon is connected. We can't wait too long as there is a
> > > host-side timeout (cca. 75 seconds) and if we fail to reply in this time
> > > frame the whole KVP service will become inactive. The solution is not
> > > ideal - if it takes userspace daemon more than 60 seconds to connect
> > > IP Failover will still fail but I don't see a solution with our current
> > > separation between kernel and userspace parts.
> > >
> > > Other two modules (VSS and FCOPY) don't require such delay, leave
> them
> > > untouched.
> > >
> > > Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
> > > Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
> >
> > An issue was found with this patch: we don't cancel
> > kvp_host_handshake_work on module unload and if the work is still
> > pending we end up crashing. As far as I can see this series didn't make
> > it to char-misc tree so instead of sending a patch to this patch I'll
> > send v2 for the original issue.
> >
> > Sorry for the inconvenience.
> 
> Ok, I'll drop this whole series.  K.Y., can you resend this series after
> fixing this up?

Will do.

Thanks,

K. Y
> 
> thanks,
> 
> greg k-h