[Spice-devel] [PATCH 1/4] qxl-wddm-dod: Startup case when OS does not supply frame buffer address

[Yuri Benditovich]

https://bugzilla.redhat.com/show_bug.cgi?id=1417448
When the OS does not provide physical address of the frame buffer,
the driver retrieves it from allocated PCI resource for BAR0.
https://msdn.microsoft.com/en-us/library/hh451339(v=vs.85).aspx
In DxgkCbAcquirePostDisplayOwnership OS not always fills
the DXGK_DISPLAY_INFORMATION structure with valid data.

Signed-off-by: Yuri Benditovich <yuri.benditovich at daynix.com>
---
 qxldod/QxlDod.cpp | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)

diff --git a/qxldod/QxlDod.cpp b/qxldod/QxlDod.cpp
index 001cd67..46176f0 100755
--- a/qxldod/QxlDod.cpp
+++ b/qxldod/QxlDod.cpp
@@ -2534,6 +2534,24 @@ NTSTATUS VgaDevice::GetCurrentMode(ULONG* pMode)
     return Status;
 }
 
+static void GetVgaFrameBuffer(PCM_RESOURCE_LIST pResList, PPHYSICAL_ADDRESS pPhys)
+{
+    for (ULONG i = 0; i < pResList->Count; ++i)
+    {
+        CM_PARTIAL_RESOURCE_DESCRIPTOR *prd = pResList->List[i].PartialResourceList.PartialDescriptors;
+        for (ULONG j = 0; j < pResList->List[i].PartialResourceList.Count; ++j)
+        {
+            if (prd[j].Type == CmResourceTypeMemory)
+            {
+                // bar 0 is VGA area
+                *pPhys = prd[j].u.Memory.Start;
+                break;
+            }
+        }
+    }
+    DbgPrint(TRACE_LEVEL_INFORMATION, ("%s: found %I64x\n", __FUNCTION__, pPhys->QuadPart));
+}
+
 NTSTATUS VgaDevice::HWInit(PCM_RESOURCE_LIST pResList, DXGK_DISPLAY_INFORMATION* pDispInfo)
 {
     PAGED_CODE();
@@ -2541,6 +2559,13 @@ NTSTATUS VgaDevice::HWInit(PCM_RESOURCE_LIST pResList, DXGK_DISPLAY_INFORMATION*
     DbgPrint(TRACE_LEVEL_VERBOSE, ("---> %s\n", __FUNCTION__));
     UNREFERENCED_PARAMETER(pResList);
     AcquireDisplayInfo(*(pDispInfo));
+    // it is possible that the OS does not have current display information
+    // in this case the driver uses defaults, but physical address
+    // is still not initialized
+    if (!pDispInfo->PhysicAddress.QuadPart)
+    {
+        GetVgaFrameBuffer(pResList, &pDispInfo->PhysicAddress);
+    }
     DbgPrint(TRACE_LEVEL_VERBOSE, ("<--- %s\n", __FUNCTION__));
     return GetModeList(pDispInfo);
 }
-- 
2.7.0.windows.1