[PATCH v2] HV: properly delay KVP packets when negotiation is in progress

[PATCH v2] HV: properly delay KVP packets when negotiation is in progress

[Long Li]

The host may send multiple negotiation packets (due to timeout) before 
the KVP user-mode daemon is connected. We need to defer processing  
those packets until the daemon is negotiated and connected. It's okay
for guest to respond to all negotiation packets.

In addition, the host may send multiple staged KVP requests as soon as
negotiation is done. We need to properly process those packets using 
one tasklet for exclusive access to ring buffer.

This patch is based on the work of Nick Meier 
<Nick.Meier@microsoft.com>

The patch v2 has incorporated suggestion from Vitaly Kuznetsov 
<vkuznets@redhat.com>.

Signed-off-by: Long Li <longli@microsoft.com>
---
 drivers/hv/hv_kvp.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/drivers/hv/hv_kvp.c b/drivers/hv/hv_kvp.c
index de26371..845b70b 100644
--- a/drivers/hv/hv_kvp.c
+++ b/drivers/hv/hv_kvp.c
@@ -113,7 +113,7 @@ static void kvp_poll_wrapper(void *channel)
 {
 	/* Transaction is finished, reset the state here to avoid races. */
 	kvp_transaction.state = HVUTIL_READY;
-	hv_kvp_onchannelcallback(channel);
+	tasklet_schedule(&((struct vmbus_channel*)channel)->callback_event);
 }
 
 static void kvp_register_done(void)
@@ -628,16 +628,17 @@ void hv_kvp_onchannelcallback(void *context)
 		     NEGO_IN_PROGRESS,
 		     NEGO_FINISHED} host_negotiatied = NEGO_NOT_STARTED;
 
-	if (host_negotiatied == NEGO_NOT_STARTED &&
-	    kvp_transaction.state < HVUTIL_READY) {
+	if (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,
+		if (host_negotiatied == NEGO_NOT_STARTED) {
+			host_negotiatied = NEGO_IN_PROGRESS;
+			schedule_delayed_work(&kvp_host_handshake_work,
 				      HV_UTIL_NEGO_TIMEOUT * HZ);
+		}
 		return;
 	}
 	if (kvp_transaction.state > HVUTIL_READY)
@@ -705,6 +706,7 @@ void hv_kvp_onchannelcallback(void *context)
 				       VM_PKT_DATA_INBAND, 0);
 
 		host_negotiatied = NEGO_FINISHED;
+		hv_poll_channel(kvp_transaction.recv_channel, kvp_poll_wrapper);
 	}
 
 }
-- 
2.7.4

Re: [PATCH v2] HV: properly delay KVP packets when negotiation is in progress

[Vitaly Kuznetsov]

Long Li <longli@microsoft.com> writes:

> The host may send multiple negotiation packets (due to timeout) before 
> the KVP user-mode daemon is connected. We need to defer processing  
> those packets until the daemon is negotiated and connected. It's okay
> for guest to respond to all negotiation packets.
>
> In addition, the host may send multiple staged KVP requests as soon as
> negotiation is done. We need to properly process those packets using 
> one tasklet for exclusive access to ring buffer.
>
> This patch is based on the work of Nick Meier 
> <Nick.Meier@microsoft.com>
>
> The patch v2 has incorporated suggestion from Vitaly Kuznetsov 
> <vkuznets@redhat.com>.
>
> Signed-off-by: Long Li <longli@microsoft.com>
> ---
>  drivers/hv/hv_kvp.c | 12 +++++++-----
>  1 file changed, 7 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/hv/hv_kvp.c b/drivers/hv/hv_kvp.c
> index de26371..845b70b 100644
> --- a/drivers/hv/hv_kvp.c
> +++ b/drivers/hv/hv_kvp.c
> @@ -113,7 +113,7 @@ static void kvp_poll_wrapper(void *channel)
>  {
>  	/* Transaction is finished, reset the state here to avoid races. */
>  	kvp_transaction.state = HVUTIL_READY;
> -	hv_kvp_onchannelcallback(channel);
> +	tasklet_schedule(&((struct vmbus_channel*)channel)->callback_event);
>  }

There is one more function in the code which calls
hv_kvp_onchannelcallback():

static void kvp_host_handshake_func(struct work_struct *dummy)
{
	hv_poll_channel(kvp_transaction.recv_channel, hv_kvp_onchannelcallback);
}

we can't replace hv_kvp_onchannelcallback with kvp_poll_wrapper here as
we don't want to reset kvp_transaction.state but it seems this should
also get updated, e.g. hv_poll_channel() here can be replaced with the 
direct 

 tasklet_schedule(&((struct vmbus_channel*)channel)->callback_event);

call. This will ensure hv_kvp_onchannelcallback() calls are always
serialized.

>
>  static void kvp_register_done(void)
> @@ -628,16 +628,17 @@ void hv_kvp_onchannelcallback(void *context)
>  		     NEGO_IN_PROGRESS,
>  		     NEGO_FINISHED} host_negotiatied = NEGO_NOT_STARTED;
>
> -	if (host_negotiatied == NEGO_NOT_STARTED &&
> -	    kvp_transaction.state < HVUTIL_READY) {
> +	if (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,
> +		if (host_negotiatied == NEGO_NOT_STARTED) {
> +			host_negotiatied = NEGO_IN_PROGRESS;
> +			schedule_delayed_work(&kvp_host_handshake_work,
>  				      HV_UTIL_NEGO_TIMEOUT * HZ);
> +		}
>  		return;
>  	}
>  	if (kvp_transaction.state > HVUTIL_READY)
> @@ -705,6 +706,7 @@ void hv_kvp_onchannelcallback(void *context)
>  				       VM_PKT_DATA_INBAND, 0);
>
>  		host_negotiatied = NEGO_FINISHED;
> +		hv_poll_channel(kvp_transaction.recv_channel, kvp_poll_wrapper);
>  	}
>
>  }

-- 
  Vitaly

RE: [PATCH v2] HV: properly delay KVP packets when negotiation is in progress

[Long Li]

> -----Original Message-----
> From: Vitaly Kuznetsov [mailto:vkuznets@redhat.com]
> Sent: Thursday, March 23, 2017 9:04 AM
> To: Long Li <longli@microsoft.com>
> Cc: KY Srinivasan <kys@microsoft.com>; Haiyang Zhang
> <haiyangz@microsoft.com>; Stephen Hemminger
> <sthemmin@microsoft.com>; devel@linuxdriverproject.org; linux-
> kernel@vger.kernel.org; stable@vger.kernel.org
> Subject: Re: [PATCH v2] HV: properly delay KVP packets when negotiation is
> in progress
> 
> Long Li <longli@microsoft.com> writes:
> 
> > The host may send multiple negotiation packets (due to timeout) before
> > the KVP user-mode daemon is connected. We need to defer processing
> > those packets until the daemon is negotiated and connected. It's okay
> > for guest to respond to all negotiation packets.
> >
> > In addition, the host may send multiple staged KVP requests as soon as
> > negotiation is done. We need to properly process those packets using
> > one tasklet for exclusive access to ring buffer.
> >
> > This patch is based on the work of Nick Meier
> > <Nick.Meier@microsoft.com>
> >
> > The patch v2 has incorporated suggestion from Vitaly Kuznetsov
> > <vkuznets@redhat.com>.
> >
> > Signed-off-by: Long Li <longli@microsoft.com>
> > ---
> >  drivers/hv/hv_kvp.c | 12 +++++++-----
> >  1 file changed, 7 insertions(+), 5 deletions(-)
> >
> > diff --git a/drivers/hv/hv_kvp.c b/drivers/hv/hv_kvp.c index
> > de26371..845b70b 100644
> > --- a/drivers/hv/hv_kvp.c
> > +++ b/drivers/hv/hv_kvp.c
> > @@ -113,7 +113,7 @@ static void kvp_poll_wrapper(void *channel)  {
> >  	/* Transaction is finished, reset the state here to avoid races. */
> >  	kvp_transaction.state = HVUTIL_READY;
> > -	hv_kvp_onchannelcallback(channel);
> > +	tasklet_schedule(&((struct vmbus_channel*)channel)-
> >callback_event);
> >  }
> 
> There is one more function in the code which calls
> hv_kvp_onchannelcallback():
> 
> static void kvp_host_handshake_func(struct work_struct *dummy) {
> 	hv_poll_channel(kvp_transaction.recv_channel,
> hv_kvp_onchannelcallback); }
> 
> we can't replace hv_kvp_onchannelcallback with kvp_poll_wrapper here as
> we don't want to reset kvp_transaction.state but it seems this should also
> get updated, e.g. hv_poll_channel() here can be replaced with the direct
> 
>  tasklet_schedule(&((struct vmbus_channel*)channel)->callback_event);
> 
> call. This will ensure hv_kvp_onchannelcallback() calls are always serialized.

Thank you. I will send v3.

> 
> >
> >  static void kvp_register_done(void)
> > @@ -628,16 +628,17 @@ void hv_kvp_onchannelcallback(void *context)
> >  		     NEGO_IN_PROGRESS,
> >  		     NEGO_FINISHED} host_negotiatied =
> NEGO_NOT_STARTED;
> >
> > -	if (host_negotiatied == NEGO_NOT_STARTED &&
> > -	    kvp_transaction.state < HVUTIL_READY) {
> > +	if (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,
> > +		if (host_negotiatied == NEGO_NOT_STARTED) {
> > +			host_negotiatied = NEGO_IN_PROGRESS;
> > +
> 	schedule_delayed_work(&kvp_host_handshake_work,
> >  				      HV_UTIL_NEGO_TIMEOUT * HZ);
> > +		}
> >  		return;
> >  	}
> >  	if (kvp_transaction.state > HVUTIL_READY) @@ -705,6 +706,7 @@
> void
> > hv_kvp_onchannelcallback(void *context)
> >  				       VM_PKT_DATA_INBAND, 0);
> >
> >  		host_negotiatied = NEGO_FINISHED;
> > +		hv_poll_channel(kvp_transaction.recv_channel,
> kvp_poll_wrapper);
> >  	}
> >
> >  }
> 
> --
>   Vitaly