RE: [PATCH v3 2/4] hv_utils: Support host-initiated restart request

[Michael Kelley <mikelley@microsoft.com>]

From: Dexuan Cui <decui@microsoft.com> Sent: Saturday, January 25, 2020 11:54 AM
>
> The hv_utils driver currently supports a "shutdown" operation initiated
> from the Hyper-V host. Newer versions of Hyper-V also support a "restart"
> operation. So add support for the updated protocol version that has
> "restart" support, and perform a clean reboot when such a message is
> received from Hyper-V.
> 
> To test the restart functionality, run this PowerShell command on the
> Hyper-V host:
> 
> Restart-VM  <vmname>  -Type Reboot
> 
> Signed-off-by: Dexuan Cui <decui@microsoft.com>
> 
> ---
> Changes in v2:
>    It's the same as v1.
> 
> Changes in v3 (I addressed Michael's comments):
>     Used a better version of changelog from  Michael.
>     Added a comment about the meaning of shutdown_msg->flags.
>     Call schedule_work() at the end of the function for consistency.
> 
>  drivers/hv/hv_util.c | 32 +++++++++++++++++++++++++++++++-
>  1 file changed, 31 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/hv/hv_util.c b/drivers/hv/hv_util.c
> index 766bd8457346..d815bea0fda3 100644
> --- a/drivers/hv/hv_util.c
> +++ b/drivers/hv/hv_util.c
> @@ -24,6 +24,8 @@
> 
>  #define SD_MAJOR	3
>  #define SD_MINOR	0
> +#define SD_MINOR_1	1
> +#define SD_VERSION_3_1	(SD_MAJOR << 16 | SD_MINOR_1)
>  #define SD_VERSION	(SD_MAJOR << 16 | SD_MINOR)
> 
>  #define SD_MAJOR_1	1
> @@ -50,8 +52,9 @@ static int sd_srv_version;
>  static int ts_srv_version;
>  static int hb_srv_version;
> 
> -#define SD_VER_COUNT 2
> +#define SD_VER_COUNT 3
>  static const int sd_versions[] = {
> +	SD_VERSION_3_1,
>  	SD_VERSION,
>  	SD_VERSION_1
>  };
> @@ -118,17 +121,28 @@ static void perform_shutdown(struct work_struct *dummy)
>  	orderly_poweroff(true);
>  }
> 
> +static void perform_restart(struct work_struct *dummy)
> +{
> +	orderly_reboot();
> +}
> +
>  /*
>   * Perform the shutdown operation in a thread context.
>   */
>  static DECLARE_WORK(shutdown_work, perform_shutdown);
> 
> +/*
> + * Perform the restart operation in a thread context.
> + */
> +static DECLARE_WORK(restart_work, perform_restart);
> +
>  static void shutdown_onchannelcallback(void *context)
>  {
>  	struct vmbus_channel *channel = context;
>  	u32 recvlen;
>  	u64 requestid;
>  	bool execute_shutdown = false;
> +	bool execute_reboot = false;
>  	u8  *shut_txf_buf = util_shutdown.recv_buffer;
> 
>  	struct shutdown_msg_data *shutdown_msg;
> @@ -157,6 +171,12 @@ static void shutdown_onchannelcallback(void *context)
>  					sizeof(struct vmbuspipe_hdr) +
>  					sizeof(struct icmsg_hdr)];
> 
> +			/*
> +			 * shutdown_msg->flags can be 0 (shut down), 2(reboot),
> +			 * or 4(hibernate). It may bitwise-OR 1, which means
> +			 * performing the request by force. Linux always tries
> +			 * to perform the request by force.
> +			 */
>  			switch (shutdown_msg->flags) {
>  			case 0:
>  			case 1:
> @@ -166,6 +186,14 @@ static void shutdown_onchannelcallback(void *context)
>  				pr_info("Shutdown request received -"
>  					    " graceful shutdown initiated\n");
>  				break;
> +			case 2:
> +			case 3:
> +				icmsghdrp->status = HV_S_OK;
> +				execute_reboot = true;
> +
> +				pr_info("Restart request received -"
> +					    " graceful restart initiated\n");
> +				break;
>  			default:
>  				icmsghdrp->status = HV_E_FAIL;
>  				execute_shutdown = false;
> @@ -186,6 +214,8 @@ static void shutdown_onchannelcallback(void *context)
> 
>  	if (execute_shutdown == true)
>  		schedule_work(&shutdown_work);
> +	if (execute_reboot == true)
> +		schedule_work(&restart_work);

This works, and responds to my comment.  But FWIW, a more compact
approach would be to drop the boolean execute_shutdown, execute_restart,
etc. local variables and have just this local variable:

	struct work_struct *work_to_do = NULL;

In the "case" branches do:

	work_to_do = &shutdown_work;

or
	work_to_do = &restart_work;

Then at the bottom of the function, just do:

	if (work_to_do)
		schedule_work(work_to_do);

Patch 3 of this series would then be a little simpler as well.

>  }
> 
>  /*
> --
> 2.19.1