1 files changed, 61 insertions, 0 deletions
diff --git a/src/VBox/Runtime/r0drv/nt/RTTimerGetSystemGranularity-r0drv-nt.cpp b/src/VBox/Runtime/r0drv/nt/RTTimerGetSystemGranularity-r0drv-nt.cpp
new file mode 100644
index 00000000..d2c22e5c
--- /dev/null
+++ b/src/VBox/Runtime/r0drv/nt/RTTimerGetSystemGranularity-r0drv-nt.cpp
@@ -0,0 +1,61 @@
+/* $Id: RTTimerGetSystemGranularity-r0drv-nt.cpp $ */
+/** @file
+ * IPRT - RTTimerGetSystemGranularity, Ring-0 Driver, NT.
+ */
+
+/*
+ * Copyright (C) 2006-2020 Oracle Corporation
+ *
+ * This file is part of VirtualBox Open Source Edition (OSE), as
+ * available from http://www.virtualbox.org. This file is free software;
+ * you can redistribute it and/or modify it under the terms of the GNU
+ * General Public License (GPL) as published by the Free Software
+ * Foundation, in version 2 as it comes in the "COPYING" file of the
+ * VirtualBox OSE distribution. VirtualBox OSE is distributed in the
+ * hope that it will be useful, but WITHOUT ANY WARRANTY of any kind.
+ *
+ * The contents of this file may alternatively be used under the terms
+ * of the Common Development and Distribution License Version 1.0
+ * (CDDL) only, as it comes in the "COPYING.CDDL" file of the
+ * VirtualBox OSE distribution, in which case the provisions of the
+ * CDDL are applicable instead of those of the GPL.
+ *
+ * You may elect to license modified versions of this file under the
+ * terms and conditions of either the GPL or the CDDL or both.
+ */
+
+
+/*********************************************************************************************************************************
+*   Header Files                                                                                                                 *
+*********************************************************************************************************************************/
+#include "the-nt-kernel.h"
+
+#include <iprt/timer.h>
+#include <iprt/errcore.h>
+#include <iprt/asm.h>
+#include <iprt/assert.h>
+
+#include "internal-r0drv-nt.h"
+#include "internal/magics.h"
+
+
+RTDECL(uint32_t) RTTimerGetSystemGranularity(void)
+{
+    /*
+     * Get the default/max timer increment value, return it if ExSetTimerResolution
+     * isn't available. According to the sysinternals guys NtQueryTimerResolution
+     * is only available in userland and they find it equally annoying.
+     */
+    ULONG ulTimeInc = KeQueryTimeIncrement();
+    if (!g_pfnrtNtExSetTimerResolution)
+        return ulTimeInc * 100; /* The value is in 100ns, the funny NT unit. */
+
+    /*
+     * Use the value returned by ExSetTimerResolution. Since the kernel is keeping
+     * count of these calls, we have to do two calls that cancel each other out.
+     */
+    g_pfnrtNtExSetTimerResolution(ulTimeInc, TRUE);
+    ULONG ulResolution = g_pfnrtNtExSetTimerResolution(0 /*ignored*/, FALSE);
+    return ulResolution * 100; /* NT -> ns */
+}
+