MdeModulePkg/NonDiscoverablePciDeviceDxe: expose unique B/D/F identifiers

Currently, the implementation of EFI_PCI_IO_PROTOCOL::GetLocation()
in NonDiscoverablePciDeviceDxe returns the same set of dummy values
for each instance of the NON_DISCOVERABLE_DEVICE protocol that it
attaches itself to. However, this turns out to be causing problems
in cases where software (such as the ARM Compliance Test Suite [ACS])
attempts to use these values to uniquely identify controllers, since
the collisions create ambiguity in this regard.

So let's modify GetLocation() to return an arbitrary bus/device tuple
on segment 0xff instead. This is guaranteed not to clash with other
non-discoverable PCI devices, and highly unlikely to clash with real
PCIe devices.

Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Tested-by: Marcin Wojtas <mw@semihalf.com>
Reviewed-by: Star Zeng <star.zeng@intel.com>

MdeModulePkg/Bus/Pci/NonDiscoverablePciDeviceDxe/NonDiscoverablePciDeviceIo.h

@@ -100,6 +100,12 @@ typedef struct {
   // on behalf of this device
   //
   LIST_ENTRY                UncachedAllocationList;
+  //
+  // Unique ID for this device instance: needed so that we can report unique
+  // segment/bus/device number for each device instance. Note that this number
+  // may change when disconnecting/reconnecting the driver.
+  //
+  UINTN                     UniqueId;
 } NON_DISCOVERABLE_PCI_DEVICE;
 
 /**