ACK: [Vivid][PATCH] UBUNTU: SAUCE: Drivers: hv: vmbus: Fix a Host signaling bug

[Brad Figg]

On Thu, Nov 19, 2015 at 03:46:47PM -0800, Jay Vosburgh wrote:
> 
> From: K. Y. Srinivasan <kys at microsoft.com>
> 
> BugLink: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1508706
> 
> Currently we have two policies for deciding when to signal the host:
> One based on the ring buffer state and the other based on what the
> VMBUS client driver wants to do. Consider the case when the client
> wants to explicitly control when to signal the host. In this case,
> if the client were to defer signaling, we will not be able to signal
> the host subsequently when the client does want to signal since the
> ring buffer state will prevent the signaling. Implement logic to
> have only one signaling policy in force for a given channel.
> 
> Signed-off-by: K. Y. Srinivasan <kys at microsoft.com>
> Reviewed-by: Haiyang Zhang <haiyangz at microsoft.com>
> Tested-by: Haiyang Zhang <haiyangz at microsoft.com>
> Cc: <stable at vger.kernel.org> # v4.2+
> Signed-off-by: Jay Vosburgh <jay.vosburgh at canonical.com>
> ---
>  drivers/hv/channel.c   | 16 ++++++++++++++++
>  include/linux/hyperv.h | 12 ++++++++++++
>  2 files changed, 28 insertions(+)
> 
> diff --git a/drivers/hv/channel.c b/drivers/hv/channel.c
> index 053dd4cae445..e983d0c92c6c 100644
> --- a/drivers/hv/channel.c
> +++ b/drivers/hv/channel.c
> @@ -602,6 +602,14 @@ int vmbus_sendpacket_ctl(struct vmbus_channel *channel, void *buffer,
>  
>  	ret = hv_ringbuffer_write(&channel->outbound, bufferlist, 3, &signal);
>  
> +	/* Based on the channel signal state, we will decide
> +	 * which signaling policy will be applied.
> +	 */
> +	if (channel->signal_state)
> +		signal = true;
> +	else
> +		kick_q = true;
> +
>  	if ((ret == 0) && kick_q && signal)
>  		vmbus_setevent(channel);
>  
> @@ -693,6 +701,14 @@ int vmbus_sendpacket_pagebuffer_ctl(struct vmbus_channel *channel,
>  
>  	ret = hv_ringbuffer_write(&channel->outbound, bufferlist, 3, &signal);
>  
> +	/* Based on the channel signal state, we will decide
> +	 * which signaling policy will be applied.
> +	 */
> +	if (channel->signal_state)
> +		signal = true;
> +	else
> +		kick_q = true;
> +
>  	if ((ret == 0) && kick_q && signal)
>  		vmbus_setevent(channel);
>  
> diff --git a/include/linux/hyperv.h b/include/linux/hyperv.h
> index 504b9ec36fe6..0f194ac40326 100644
> --- a/include/linux/hyperv.h
> +++ b/include/linux/hyperv.h
> @@ -758,8 +758,20 @@ struct vmbus_channel {
>  	 * link up channels based on their CPU affinity.
>  	 */
>  	struct list_head percpu_list;
> +	/*
> +	 * Host signaling policy: The default policy will be
> +	 * based on the ring buffer state. We will also support
> +	 * a policy where the client driver can have explicit
> +	 * signaling control.
> +	 */
> +	bool signal_state;
>  };
>  
> +static inline void set_channel_signal_state(struct vmbus_channel *c, bool state)
> +{
> +	c->signal_state = state;
> +}
> +
>  static inline void set_channel_read_state(struct vmbus_channel *c, bool state)
>  {
>  	c->batched_reading = state;
> -- 
> 1.9.1
> 
> 
> -- 
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Positive testing.

-- 
Brad Figg brad.figg at canonical.com http://www.canonical.com