[PATCH] MdeModulePkg/NonDiscoverablePciDeviceDxe: expose unique B/D/F identifiers

[Ard Biesheuvel <ard.biesheuvel@linaro.org>]

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>
---
 MdeModulePkg/Bus/Pci/NonDiscoverablePciDeviceDxe/NonDiscoverablePciDeviceDxe.c |  4 ++++
 MdeModulePkg/Bus/Pci/NonDiscoverablePciDeviceDxe/NonDiscoverablePciDeviceIo.c  | 10 +++++++---
 MdeModulePkg/Bus/Pci/NonDiscoverablePciDeviceDxe/NonDiscoverablePciDeviceIo.h  |  6 ++++++
 3 files changed, 17 insertions(+), 3 deletions(-)

diff --git a/MdeModulePkg/Bus/Pci/NonDiscoverablePciDeviceDxe/NonDiscoverablePciDeviceDxe.c b/MdeModulePkg/Bus/Pci/NonDiscoverablePciDeviceDxe/NonDiscoverablePciDeviceDxe.c
index 3e9ff6620d8d..ed5256f3c7ea 100644
--- a/MdeModulePkg/Bus/Pci/NonDiscoverablePciDeviceDxe/NonDiscoverablePciDeviceDxe.c
+++ b/MdeModulePkg/Bus/Pci/NonDiscoverablePciDeviceDxe/NonDiscoverablePciDeviceDxe.c
@@ -18,6 +18,8 @@
 
 EFI_CPU_ARCH_PROTOCOL      *mCpu;
 
+STATIC UINTN mUniqueIdCounter;
+
 //
 // We only support the following device types
 //
@@ -167,6 +169,8 @@ NonDiscoverablePciDeviceStart (
     goto CloseProtocol;
   }
 
+  Dev->UniqueId = mUniqueIdCounter++;
+
   return EFI_SUCCESS;
 
 CloseProtocol:
diff --git a/MdeModulePkg/Bus/Pci/NonDiscoverablePciDeviceDxe/NonDiscoverablePciDeviceIo.c b/MdeModulePkg/Bus/Pci/NonDiscoverablePciDeviceDxe/NonDiscoverablePciDeviceIo.c
index 0e42ae4bf6ec..58cb5d8b1fc5 100644
--- a/MdeModulePkg/Bus/Pci/NonDiscoverablePciDeviceDxe/NonDiscoverablePciDeviceIo.c
+++ b/MdeModulePkg/Bus/Pci/NonDiscoverablePciDeviceDxe/NonDiscoverablePciDeviceIo.c
@@ -1181,6 +1181,8 @@ PciIoGetLocation (
   OUT  UINTN                *FunctionNumber
   )
 {
+  NON_DISCOVERABLE_PCI_DEVICE         *Dev;
+
   if (SegmentNumber == NULL ||
       BusNumber == NULL ||
       DeviceNumber == NULL ||
@@ -1188,9 +1190,11 @@ PciIoGetLocation (
     return EFI_INVALID_PARAMETER;
   }
 
-  *SegmentNumber  = 0;
-  *BusNumber      = 0xff;
-  *DeviceNumber   = 0;
+  Dev = NON_DISCOVERABLE_PCI_DEVICE_FROM_PCI_IO(This);
+
+  *SegmentNumber  = 0xff;
+  *BusNumber      = Dev->UniqueId >> 5;
+  *DeviceNumber   = Dev->UniqueId & 0x1f;
   *FunctionNumber = 0;
 
   return EFI_SUCCESS;
diff --git a/MdeModulePkg/Bus/Pci/NonDiscoverablePciDeviceDxe/NonDiscoverablePciDeviceIo.h b/MdeModulePkg/Bus/Pci/NonDiscoverablePciDeviceDxe/NonDiscoverablePciDeviceIo.h
index e641189267ee..5b4c57fa2a8e 100644
--- a/MdeModulePkg/Bus/Pci/NonDiscoverablePciDeviceDxe/NonDiscoverablePciDeviceIo.h
+++ b/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;
 
 /**
-- 
2.17.1