Re: [XENIFACE PATCH v2] xenagent: Add TimeSyncMode option

[Owen Smith <owen.smith@xxxxxxxxx>]

Reviewed-by: Owen Smith <owen.smith@xxxxxxxxx>

On Wed, Jul 9, 2025 at 9:24 AM Tu Dinh <ngoc-tu.dinh@xxxxxxxxxx> wrote:

xenagent's time sync mechanism interferes with w32time's own time sync,
especially in a domain environment where domain members are expected to
follow the PDCe.

Add a REG_DWORD value TimeSyncMode in xenagent. Setting this value to 0
will disable the XenTime sync.
Note that this setting is not honored during time sync attempts after
resume.

Signed-off-by: Tu Dinh <ngoc-tu.dinh@xxxxxxxxxx>
---
 src/xenagent/service.cpp        |  4 ++--
 src/xenagent/xenifacedevice.cpp | 31 +++++++++++++++++++++++++++----
 src/xenagent/xenifacedevice.h   |  4 ++--
 3 files changed, 31 insertions(+), 8 deletions(-)

diff --git a/src/xenagent/service.cpp b/src/xenagent/service.cpp
index 535d761..6ef7b1a 100644
--- a/src/xenagent/service.cpp
+++ b/src/xenagent/service.cpp
@@ -216,7 +216,7 @@ bool CXenAgent::ServiceMainLoop()

     case WAIT_OBJECT_0+2:
         ResetEvent(m_xeniface.m_evt_suspend);
-        m_xeniface.CheckXenTime();
+        m_xeniface.CheckXenTime(true);
         m_xeniface.CheckSuspend();
         return true; // continue loop

@@ -230,7 +230,7 @@ bool CXenAgent::ServiceMainLoop()
         return true; // continue loop
     }
     case WAIT_TIMEOUT:
-        m_xeniface.CheckXenTime();
+        m_xeniface.CheckXenTime(false);
         __fallthrough;
     case WAIT_IO_COMPLETION:
         m_xeniface.CheckSuspend();
diff --git a/src/xenagent/xenifacedevice.cpp b/src/xenagent/xenifacedevice.cpp
index 69a584b..7b45c8c 100644
--- a/src/xenagent/xenifacedevice.cpp
+++ b/src/xenagent/xenifacedevice.cpp
@@ -40,6 +40,13 @@
 #include "xeniface_ioctls.h"
 #include "messages.h"

+#define SERVICES_KEY "SYSTEM\\CurrentControlSet\\Services"
+
+#define SERVICE_KEY(_Service) \
+        SERVICES_KEY ## "\\" ## _Service
+
+#define TIME_SYNC_MODE_DISABLED 0
+
 CXenIfaceDevice::CXenIfaceDevice(const wchar_t* path) : CDevice(path)
 {}

@@ -213,7 +220,7 @@ CXenIfaceDeviceList::CXenIfaceDeviceList(CXenAgent* agent) : CDeviceList(GUID_IN
     if (m_agent->ConvDevicePresent())
         StartSlateModeWatch(device);

-    SetXenTime(device);
+    SetXenTime(device, false);
 }

 /*virtual*/ void CXenIfaceDeviceList::OnDeviceRemoved(CDevice* dev)
@@ -339,7 +346,7 @@ bool CXenIfaceDeviceList::CheckShutdown()
     return false;
 }

-void CXenIfaceDeviceList::CheckXenTime()
+void CXenIfaceDeviceList::CheckXenTime(bool forced)
 {
     CCritSec crit(&m_crit);
     CXenIfaceDevice* device = (CXenIfaceDevice*)GetFirstDevice();
@@ -347,7 +354,7 @@ void CXenIfaceDeviceList::CheckXenTime()
     if (device == NULL)
         return;

-    SetXenTime(device);
+    SetXenTime(device, forced);
 }

 void CXenIfaceDeviceList::CheckSuspend()
@@ -485,10 +492,26 @@ void CXenIfaceDeviceList::AcquireShutdownPrivilege()
     CloseHandle(token);
 }

-void CXenIfaceDeviceList::SetXenTime(CXenIfaceDevice* device)
+void CXenIfaceDeviceList::SetXenTime(CXenIfaceDevice* device, bool forced)
 {
     bool local;

+    if (!forced) {
+        DWORD   mode = 0;
+        DWORD   size = sizeof(mode);
+        LSTATUS lstatus;
+
+        lstatus = RegGetValue(HKEY_LOCAL_MACHINE,
+                              TEXT(SERVICE_KEY(__MODULE__)),
+                              TEXT("TimeSyncMode"),
+                              RRF_RT_DWORD,
+                              NULL,
+                              &mode,
+                              &size);
+        if (lstatus == ERROR_SUCCESS && mode == TIME_SYNC_MODE_DISABLED)
+            return;
+    }
+
     FILETIME now = { 0 };
     if (!device->SharedInfoGetTime(&now, &local))
         return;
diff --git a/src/xenagent/xenifacedevice.h b/src/xenagent/xenifacedevice.h
index d85e469..8a89036 100644
--- a/src/xenagent/xenifacedevice.h
+++ b/src/xenagent/xenifacedevice.h
@@ -84,7 +84,7 @@ public:

     void Log(const char* message);
     bool CheckShutdown();
-    void CheckXenTime();
+    void CheckXenTime(bool forced);
     void CheckSuspend();
     bool CheckSlateMode(std::string& mode);
     void LogIfRebootPending();
@@ -95,7 +95,7 @@ private:
     void StartSlateModeWatch(CXenIfaceDevice* device);
     void StopSlateModeWatch(CXenIfaceDevice* device);
     void AcquireShutdownPrivilege();
-    void SetXenTime(CXenIfaceDevice* device);
+    void SetXenTime(CXenIfaceDevice* device, bool forced);

 private:
     CXenAgent*  m_agent;
--
2.50.1.windows.1



Ngoc Tu Dinh | Vates XCP-ng Developer

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