Index: /trunk/src/VBox/Additions/WINNT/Graphics/Video/mp/wddm/VBoxMPWddm.cpp
===================================================================
--- /trunk/src/VBox/Additions/WINNT/Graphics/Video/mp/wddm/VBoxMPWddm.cpp	(revision 55226)
+++ /trunk/src/VBox/Additions/WINNT/Graphics/Video/mp/wddm/VBoxMPWddm.cpp	(revision 55227)
@@ -901,14 +901,10 @@
                             - VBVA_ADAPTER_INFORMATION_SIZE;
 
-    ULONG cbCmdVbva = cbAvailable / 2;
-    ULONG cbCmdVbvaApprox = VBOXCMDVBVA_BUFFERSIZE(4096);
-    if (cbCmdVbvaApprox > cbCmdVbva)
-    {
-        WARN(("too few VRAM memory %d, cmdVbva %d, while approximately needed %d, trying to adjust", cbAvailable, cbCmdVbva, cbCmdVbvaApprox));
-        cbCmdVbva = cbCmdVbvaApprox;
-    }
-
-    cbCmdVbva = VBOXWDDM_ROUNDBOUND(cbCmdVbva, 0x1000);
-    if (cbCmdVbva > cbAvailable - 0x1000)
+    /* Size of the VBVA buffer which is used to pass VBOXCMDVBVA_* commands to the host.
+     * Estimate max 4KB per command.
+     */
+    ULONG cbCmdVbva = VBOXCMDVBVA_BUFFERSIZE(4096);
+
+    if (cbCmdVbva >= cbAvailable)
     {
         WARN(("too few VRAM memory fatal, %d, requested for CmdVbva %d", cbAvailable, cbCmdVbva));