RE: [EXTERNAL] [PATCH 2/2] Add AutoReboot capability

[Paul Durrant <xadimgnik@xxxxxxxxx>]

> -----Original Message-----
> From: win-pv-devel <win-pv-devel-bounces@xxxxxxxxxxxxxxxxxxxx> On Behalf Of 
> Owen Smith
> Sent: 09 December 2020 13:29
> To: win-pv-devel@xxxxxxxxxxxxxxxxxxxx
> Cc: Owen Smith <owen.smith@xxxxxxxxxx>
> Subject: [EXTERNAL] [PATCH 2/2] Add AutoReboot capability
> 
> Setting HKLM\System\CCS\Services\xenbus_monitor\AutoReboot to non-zero
> will allow xenbus_monitor to trigger a reboot when another driver
> requests a reboot. AutoReboot is set to the maximum number of reboots
> to perform. Auto reboots display a message with a 60 second timeout.
> 
> This setting can be used to allow headless/unmonitored VMs to complete
> the neccessary number of reboots to return to PV disks/networks. Without
> this capability its possible to update the driver on a parent device,
> which may prompt for a reboot. After this reboot, its likely that
> emulated devices are used whilst drivers are rebound to the device
> nodes. This can leave headless/unmonitored VMs in a state where emulated
> devices are in use with a pending reboot. If network settings have been
> changed for PV devices (e.g. static IP addressing), then the VM may not
> be accessible over RDP or similar connections.
> 
> Signed-off-by: Owen Smith <owen.smith@xxxxxxxxxx>
> ---
>  src/monitor/monitor.c | 133 ++++++++++++++++++++++++++++++++++++++++--
>  1 file changed, 129 insertions(+), 4 deletions(-)
> 
> diff --git a/src/monitor/monitor.c b/src/monitor/monitor.c
> index 07bf8c1..5d58be4 100644
> --- a/src/monitor/monitor.c
> +++ b/src/monitor/monitor.c
> @@ -301,7 +301,8 @@ WTSStateName(
> 
>  static VOID
>  DoReboot(
> -    VOID
> +    IN PTCHAR   Message,
> +    IN DWORD    Timeout
>      )
>  {
>      Log("waiting for pending install events...");
> @@ -312,8 +313,8 @@ DoReboot(
> 
>  #pragma prefast(suppress:28159)
>      (VOID) InitiateSystemShutdownEx(NULL,
> -                                    NULL,
> -                                    0,
> +                                    Message,
> +                                    Timeout,
>                                      TRUE,
>                                      TRUE,
>                                      SHTDN_REASON_MAJOR_OPERATINGSYSTEM |
> @@ -451,6 +452,125 @@ fail1:
>      return NULL;
>  }
> 
> +static BOOL
> +TryAutoReboot(
> +    IN PTCHAR           DriverName
> +    )
> +{
> +    PMONITOR_CONTEXT    Context = &MonitorContext;
> +    HRESULT             Result;
> +    DWORD               Type;
> +    DWORD               AutoReboot;
> +    DWORD               RebootCount;
> +    DWORD               Length;
> +    PTCHAR              DisplayName;
> +    PTCHAR              Description;
> +    PTCHAR              Text;
> +    DWORD               TextLength;
> +    HRESULT             Error;
> +
> +    Length = sizeof (DWORD);
> +
> +    Error = RegQueryValueEx(Context->ParametersKey,
> +                            "AutoReboot",
> +                            NULL,
> +                            &Type,
> +                            (LPBYTE)&AutoReboot,
> +                            &Length);
> +    if (Error != ERROR_SUCCESS ||
> +        Type != REG_DWORD)
> +        AutoReboot = 0;
> +
> +    if (AutoReboot == 0)
> +        goto done;
> +
> +    Length = sizeof (DWORD);
> +
> +    Error = RegQueryValueEx(Context->ParametersKey,
> +                            "RebootCount",
> +                            NULL,
> +                            &Type,
> +                            (LPBYTE)&RebootCount,
> +                            &Length);
> +    if (Error != ERROR_SUCCESS ||
> +        Type != REG_DWORD)
> +        RebootCount = 0;
> +
> +    if (RebootCount >= AutoReboot)
> +        goto done;
> +
> +    Log("AutoRebooting (reboot %u of %u)\n",
> +        RebootCount,
> +        AutoReboot);
> +
> +    ++RebootCount;
> +
> +    (VOID) RegSetValueEx(Context->ParametersKey,
> +                         "RebootCount",
> +                         0,
> +                         REG_DWORD,
> +                         (const BYTE*)&RebootCount,
> +                         (DWORD) sizeof(DWORD));
> +

I can't see anything that zeroes/deletes this once there are no more pending 
reboots. Is there something else that does this, or am
I just missing something?

  Paul