RE: [PATCH v3] Drivers: hv: vm_bus: Handle vmbus rescind calls after vmbus is suspended

[Michael Kelley (LINUX)]

From: Shradha Gupta <shradhagupta@xxxxxxxxxxxxxxxxxxx> Sent: Sunday, July 10, 2022 9:12 PM
> 
> Add a flag to indicate that the vmbus is suspended so we should ignore
> any offer message. Add a new work_queue for rescind msg, so we could drain
> it along with other offer work_queues upon suspension.
> It was observed that in some hibernation related scenario testing, after
> vmbus_bus_suspend() we get rescind offer message for the vmbus. This would
> lead to processing of a rescind message for a channel that has already been
> suspended.
> 
> Signed-off-by: Shradha Gupta <shradhagupta@xxxxxxxxxxxxxxxxxxx>
> ---
> 
> Changes in v3:
> * Remove unused variable hv_cpu from vmbus_bus_resume() call
> 
> ---
>  drivers/hv/connection.c   | 11 +++++++++++
>  drivers/hv/hyperv_vmbus.h |  7 +++++++
>  drivers/hv/vmbus_drv.c    | 27 +++++++++++++++++++--------
>  3 files changed, 37 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/hv/connection.c b/drivers/hv/connection.c
> index 6218bbf6863a..eca7afd366d6 100644
> --- a/drivers/hv/connection.c
> +++ b/drivers/hv/connection.c
> @@ -171,6 +171,14 @@ int vmbus_connect(void)
>  		goto cleanup;
>  	}
> 
> +	vmbus_connection.rescind_work_queue =
> +		create_workqueue("hv_vmbus_rescind");
> +	if (!vmbus_connection.rescind_work_queue) {
> +		ret = -ENOMEM;
> +		goto cleanup;
> +	}
> +	vmbus_connection.ignore_any_offer_msg = false;
> +
>  	vmbus_connection.handle_primary_chan_wq =
>  		create_workqueue("hv_pri_chan");
>  	if (!vmbus_connection.handle_primary_chan_wq) {
> @@ -357,6 +365,9 @@ void vmbus_disconnect(void)
>  	if (vmbus_connection.handle_primary_chan_wq)
>  		destroy_workqueue(vmbus_connection.handle_primary_chan_wq);
> 
> +	if (vmbus_connection.rescind_work_queue)
> +		destroy_workqueue(vmbus_connection.rescind_work_queue);
> +
>  	if (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 4f5b824b16cf..dc673edf053c 100644
> --- a/drivers/hv/hyperv_vmbus.h
> +++ b/drivers/hv/hyperv_vmbus.h
> @@ -261,6 +261,13 @@ struct vmbus_connection {
>  	struct workqueue_struct *work_queue;
>  	struct workqueue_struct *handle_primary_chan_wq;
>  	struct workqueue_struct *handle_sub_chan_wq;
> +	struct workqueue_struct *rescind_work_queue;
> +
> +	/*
> +	 * On suspension of the vmbus, the accumulated offer messages
> +	 * must be dropped.
> +	 */
> +	bool ignore_any_offer_msg;
> 
>  	/*
>  	 * The number of sub-channels and hv_sock channels that should be
> diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c
> index 547ae334e5cd..23c680d1a0f5 100644
> --- a/drivers/hv/vmbus_drv.c
> +++ b/drivers/hv/vmbus_drv.c
> @@ -1160,7 +1160,9 @@ void vmbus_on_msg_dpc(unsigned long data)
>  			 * work queue: the RESCIND handler can not start to
>  			 * run before the OFFER handler finishes.
>  			 */
> -			schedule_work(&ctx->work);
> +			if (vmbus_connection.ignore_any_offer_msg)
> +				break;
> +			queue_work(vmbus_connection.rescind_work_queue, &ctx->work);
>  			break;
> 
>  		case CHANNELMSG_OFFERCHANNEL:
> @@ -1186,6 +1188,8 @@ void vmbus_on_msg_dpc(unsigned long data)
>  			 * to the CPUs which will execute the offer & rescind
>  			 * works by the time these works will start execution.
>  			 */
> +			if (vmbus_connection.ignore_any_offer_msg)
> +				break;
>  			atomic_inc(&vmbus_connection.offer_in_progress);
>  			fallthrough;
> 
> @@ -2446,15 +2450,20 @@ static int vmbus_acpi_add(struct acpi_device *device)
>  #ifdef CONFIG_PM_SLEEP
>  static int vmbus_bus_suspend(struct device *dev)
>  {
> +	struct hv_per_cpu_context *hv_cpu = per_cpu_ptr(
> +			hv_context.cpu_context, VMBUS_CONNECT_CPU);
>  	struct vmbus_channel *channel, *sc;
> 
> -	while (atomic_read(&vmbus_connection.offer_in_progress) != 0) {
> -		/*
> -		 * We wait here until the completion of any channel
> -		 * offers that are currently in progress.
> -		 */
> -		usleep_range(1000, 2000);
> -	}
> +	tasklet_disable(&hv_cpu->msg_dpc);
> +	vmbus_connection.ignore_any_offer_msg = true;
> +	/* The tasklet_enable() takes care of providing a memory barrier */
> +	tasklet_enable(&hv_cpu->msg_dpc);
> +
> +	/* Drain all the workqueues as we are in suspend */
> +	drain_workqueue(vmbus_connection.rescind_work_queue);
> +	drain_workqueue(vmbus_connection.work_queue);
> +	drain_workqueue(vmbus_connection.handle_primary_chan_wq);
> +	drain_workqueue(vmbus_connection.handle_sub_chan_wq);
> 
>  	mutex_lock(&vmbus_connection.channel_mutex);
>  	list_for_each_entry(channel, &vmbus_connection.chn_list, listentry) {
> @@ -2531,6 +2540,8 @@ static int vmbus_bus_resume(struct device *dev)
>  	size_t msgsize;
>  	int ret;
> 
> +	vmbus_connection.ignore_any_offer_msg = false;
> +
>  	/*
>  	 * We only use the 'vmbus_proto_version', which was in use before
>  	 * hibernation, to re-negotiate with the host.
> --
> 2.17.1

Reviewed-by: Michael Kelley <mikelley@xxxxxxxxxxxxx>