linux-kernel - RE: [PATCH v2 2/4] hv_utils: Support host-initiated restart request

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Date:   Wed, 22 Jan 2020 17:16:20 +0000
From:   Michael Kelley <mikelley@...rosoft.com>
To:     Dexuan Cui <decui@...rosoft.com>,
        KY Srinivasan <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        "sashal@...nel.org" <sashal@...nel.org>,
        Sasha Levin <Alexander.Levin@...rosoft.com>,
        "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
        vkuznets <vkuznets@...hat.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v2 2/4] hv_utils: Support host-initiated restart request

From: Dexuan Cui <decui@...rosoft.com> Sent: Sunday, January 12, 2020 10:31 PM
> 
> 
> To test the code, run this command on the host:
> 
> Restart-VM $vm -Type Reboot
>

Need a better commit message here.  How about:

The hv_util 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@...rosoft.com>
> ---
>  drivers/hv/hv_util.c | 23 ++++++++++++++++++++++-
>  1 file changed, 22 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/hv/hv_util.c b/drivers/hv/hv_util.c
> index 766bd8457346..fe3a316380c2 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
>  };
> @@ -118,11 +121,21 @@ 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;
> @@ -166,6 +179,14 @@ static void shutdown_onchannelcallback(void *context)
>  				pr_info("Shutdown request received -"
>  					    " graceful shutdown initiated\n");
>  				break;
> +			case 2:
> +			case 3:

How are the flags values 0, 1, 2, and 3 interpreted?  Perhaps a short comment
would be helpful.

> +				pr_info("Restart request received -"
> +					    " graceful restart initiated\n");
> +				icmsghdrp->status = HV_S_OK;
> +
> +				schedule_work(&restart_work);
> +				break;

For case 0 and 1 (shutdown), the schedule_work() call is performed only
after the response packet has been sent to the host.  Is there a reason the
new code for case 2 and 3 (restart) is doing it in the opposite order?

>  			default:
>  				icmsghdrp->status = HV_E_FAIL;
>  				execute_shutdown = false;
> --
> 2.19.1