IntelSiliconPkg IntelVTdDxe: Check HeaderType if func 0 is implemented

REF: https://bugzilla.tianocore.org/show_bug.cgi?id=1169

Current code checks HeaderType of Function 0 even Function 0 is not
implemented. HeaderType value will be 0xFF if Function 0 is not
implemented, then MaxFunction will be set to PCI_MAX_FUNC + 1.

The code can be optimized to only check HeaderType if Function 0 is
implemented.

Test done:
With this patch, the result is same with the result after the patch at
https://lists.01.org/pipermail/edk2-devel/2018-September/029623.html.

Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Rangasai V Chaganty <rangasai.v.chaganty@intel.com>
Cc: Tomson Chang <tomson.chang@intel.com>
Cc: Jenny Huang <jenny.huang@intel.com>
Cc: Amy Chan <amy.chan@intel.com>
Cc: Ruiyu Ni <ruiyu.ni@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Star Zeng <star.zeng@intel.com>
Reviewed-by: Jiewen Yao <jiewen.yao@intel.com>

1 files changed, 12 insertions, 8 deletions

diff --git a/IntelSiliconPkg/Feature/VTd/IntelVTdDxe/PciInfo.c b/IntelSiliconPkg/Feature/VTd/IntelVTdDxe/PciInfo.c
index 305995de03..6ae5df589c 100644
--- a/IntelSiliconPkg/Feature/VTd/IntelVTdDxe/PciInfo.c
+++ b/IntelSiliconPkg/Feature/VTd/IntelVTdDxe/PciInfo.c
@@ -231,19 +231,13 @@ ScanPciBus (
   UINT8                   HeaderType;

   UINT8                   BaseClass;

   UINT8                   SubClass;

-  UINT32                  MaxFunction;

   UINT16                  VendorID;

   UINT16                  DeviceID;

   EFI_STATUS              Status;

 

   // Scan the PCI bus for devices

-  for (Device = 0; Device < PCI_MAX_DEVICE + 1; Device++) {

-    HeaderType = PciSegmentRead8 (PCI_SEGMENT_LIB_ADDRESS(Segment, Bus, Device, 0, PCI_HEADER_TYPE_OFFSET));

-    MaxFunction = PCI_MAX_FUNC + 1;

-    if ((HeaderType & HEADER_TYPE_MULTI_FUNCTION) == 0x00) {

-      MaxFunction = 1;

-    }

-    for (Function = 0; Function < MaxFunction; Function++) {

+  for (Device = 0; Device <= PCI_MAX_DEVICE; Device++) {

+    for (Function = 0; Function <= PCI_MAX_FUNC; Function++) {

       VendorID  = PciSegmentRead16 (PCI_SEGMENT_LIB_ADDRESS(Segment, Bus, Device, Function, PCI_VENDOR_ID_OFFSET));

       DeviceID  = PciSegmentRead16 (PCI_SEGMENT_LIB_ADDRESS(Segment, Bus, Device, Function, PCI_DEVICE_ID_OFFSET));

       if (VendorID == 0xFFFF && DeviceID == 0xFFFF) {

@@ -275,6 +269,16 @@ ScanPciBus (
           }

         }

       }

+

+      if (Function == 0) {

+        HeaderType = PciSegmentRead8 (PCI_SEGMENT_LIB_ADDRESS(Segment, Bus, Device, 0, PCI_HEADER_TYPE_OFFSET));

+        if ((HeaderType & HEADER_TYPE_MULTI_FUNCTION) == 0x00) {

+          //

+          // It is not a multi-function device, do not scan other functions.

+          //

+          break;

+        }

+      }

     }

   }