Re: [XENBUS PATCH v2 2/2] Be more tolerant of RealTimeIsUniversal values

[Owen Smith <owen.smith@xxxxxxxxx>]

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

On Mon, Aug 18, 2025 at 6:55 AM Tu Dinh <ngoc-tu.dinh@xxxxxxxxxx> wrote:

Tolerate RealTimeIsUniversal having the REG_QWORD value type.

In addition, don't fail SystemInitialize when SystemGetTimeInformation
fails to read RealTimeIsUniversal as critical boot drivers (e.g. xenvbd)
may fail to load otherwise.

Signed-off-by: Tu Dinh <ngoc-tu.dinh@xxxxxxxxxx>
---
v2: Log error code from SystemGetTimeInformation
---
 src/xen/system.c | 41 +++++++++++++++++++++--------------------
 1 file changed, 21 insertions(+), 20 deletions(-)

diff --git a/src/xen/system.c b/src/xen/system.c
index 48f9af0..991ce4b 100644
--- a/src/xen/system.c
+++ b/src/xen/system.c
@@ -1183,7 +1183,8 @@ SystemGetTimeInformation(
     PSYSTEM_CONTEXT Context = &SystemContext;
     UNICODE_STRING  Unicode;
     HANDLE          Key;
-    ULONG           RealTimeIsUniversal;
+    ULONG           ValueDword;
+    ULONGLONG       ValueQword;
     NTSTATUS        status;

     RtlInitUnicodeString(&Unicode, L"\\Registry\\Machine\\SYSTEM\\CurrentControlSet\\Control\\TimeZoneInformation");
@@ -1192,27 +1193,30 @@ SystemGetTimeInformation(
     if (!NT_SUCCESS(status))
         goto fail1;

-    status = RegistryQueryDwordValue(Key, "RealTimeIsUniversal",
-                                     &RealTimeIsUniversal);
-    if (!NT_SUCCESS(status)) {
-        if (status != STATUS_OBJECT_NAME_NOT_FOUND)
-            goto fail2;
+    status = RegistryQueryDwordValue(Key, "RealTimeIsUniversal", &ValueDword);
+    if (status == STATUS_OBJECT_NAME_NOT_FOUND) {
+        Context->RealTimeIsUniversal = FALSE;
+        goto done;
+    } else if (NT_SUCCESS(status)) {
+        Context->RealTimeIsUniversal = !!ValueDword;
+        goto done;
+    }

-        RealTimeIsUniversal = 0;
+    status = RegistryQueryQwordValue(Key, "RealTimeIsUniversal", &ValueQword);
+    if (NT_SUCCESS(status)) {
+        Context->RealTimeIsUniversal = !!ValueQword;
+        goto done;
     }

-    Context->RealTimeIsUniversal = RealTimeIsUniversal ? TRUE : FALSE;
+    status = STATUS_UNSUCCESSFUL;
+    Context->RealTimeIsUniversal = FALSE;

+done:
     Info("%s\n", Context->RealTimeIsUniversal ? "TRUE" : "FALSE");

     RegistryCloseKey(Key);

-    return STATUS_SUCCESS;
-
-fail2:
-    Error("fail2\n");
-
-    RegistryCloseKey(Key);
+    return status;

 fail1:
     Error("fail1 (%08x)\n", status);
@@ -1318,19 +1322,16 @@ SystemInitialize(
     if (!NT_SUCCESS(status))
         goto fail8;

-    status = SystemGetTimeInformation();
+    status = SystemCheckProcessors();
     if (!NT_SUCCESS(status))
         goto fail9;

-    status = SystemCheckProcessors();
+    status = SystemGetTimeInformation();
     if (!NT_SUCCESS(status))
-        goto fail10;
+        Error("Cannot read RealTimeIsUniversal (%08x)\n", status);

     return STATUS_SUCCESS;

-fail10:
-    Error("fail10\n");
-
 fail9:
     Error("fail9\n");

--
2.50.1.windows.1



Ngoc Tu Dinh | Vates XCP-ng Developer

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