[VIDEOPRT] Handle VIDEO_MEMORY_SPACE_P6CACHE flag

JIRA issue: CORE-20298

Author: hpoussin

win32ss/drivers/videoprt/resource.c

@@ -297,11 +297,6 @@ IntVideoPortMapMemory(
    INFO_(VIDEOPRT, "- InIoSpace: %x\n", InIoSpace);
 
    InIoSpace &= ~VIDEO_MEMORY_SPACE_DENSE;
-   if ((InIoSpace & VIDEO_MEMORY_SPACE_P6CACHE) != 0)
-   {
-      INFO_(VIDEOPRT, "VIDEO_MEMORY_SPACE_P6CACHE not supported, turning off\n");
-      InIoSpace &= ~VIDEO_MEMORY_SPACE_P6CACHE;
-   }
 
    if (ProcessHandle != NULL && (InIoSpace & VIDEO_MEMORY_SPACE_USER_MODE) == 0)
    {
@@ -345,7 +340,7 @@ IntVideoPortMapMemory(
    }
 
    AddressSpace = (ULONG)InIoSpace;
-   AddressSpace &= ~VIDEO_MEMORY_SPACE_USER_MODE;
+   AddressSpace &= ~(VIDEO_MEMORY_SPACE_USER_MODE | VIDEO_MEMORY_SPACE_P6CACHE);
    if (HalTranslateBusAddress(
           DeviceExtension->AdapterInterfaceType,
           DeviceExtension->SystemIoBusNumber,
@@ -373,11 +368,16 @@ IntVideoPortMapMemory(
    if ((InIoSpace & VIDEO_MEMORY_SPACE_USER_MODE) != 0)
    {
       NTSTATUS NtStatus;
+      ULONG Protect;
+      if (InIoSpace & VIDEO_MEMORY_SPACE_P6CACHE)
+          Protect = PAGE_READWRITE | PAGE_WRITECOMBINE;
+      else
+          Protect = PAGE_READWRITE | PAGE_NOCACHE;
       MappedAddress = NULL;
       NtStatus = IntVideoPortMapPhysicalMemory(ProcessHandle,
                                                TranslatedAddress,
                                                NumberOfUchars,
-                                               PAGE_READWRITE/* | PAGE_WRITECOMBINE*/,
+                                               Protect,
                                                &MappedAddress);
       if (!NT_SUCCESS(NtStatus))
       {