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Re: [Xen-devel] [edk2] [PATCH] MdeModulePkg: mark completion of PCI enumeration in PciEnumeratorLight

No you cannot install gEfiPciEnumerationCompleteProtocolGuid in 
For a real platform, PCI BUS is fully enumerated in PciEnumerator() and later 
if reconnect happens, it's light enumerated in PciEnumeratorLight(). The 
protocol should only be installed once in PeiEnumerator(). Your fix will cause 
this protocol installed every time a reconnect happens.
The protocol 's meaning is that the PCI BUS is fully enumerated. If the PCI BUS 
is fully enumerated before starting PciBus driver, light PCI enumeration is 
For your OVMF/QEMU case, an alternative fix is to install this protocol in a 
platform driver when it detects that the PCI BUS is fully enumerated.


-----Original Message-----
From: Wei Liu [mailto:wei.liu2@xxxxxxxxxx] 
Sent: Thursday, February 12, 2015 4:24 AM
To: edk2-devel@xxxxxxxxxxxxxxxxxxxxx
Cc: xen-devel@xxxxxxxxxxxxx; Laszlo
Subject: [edk2] [PATCH] MdeModulePkg: mark completion of PCI enumeration in 

I had an issue when trying to boot Xen HVM guest with latest OVMF
master. Guest crashed with memory violation, and the bisection pointed
to 66b280df2 ("OvmfPkg: AcpiPlatformDxe: make dependency on PCI
enumeration explicit"). That commit made AcpiPlatformDxe depend on PCI
enumeration using gEfiPciEnumerationCompleteProtocolGuid, which is a
very reasonable change.

The real culprit is that Xen HVM is using PciEnumeratorLight which
doesn't install gEfiPciEnumerationCompleteProtocolGuid. This, in
combination with 66b280df2, makes AcpiPlatformDxe not able to be loaded,
resulting in guest crash.

The fix is to install gEfiPciEnumerationCompleteProtocolGuid in

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Wei Liu <wei.liu2@xxxxxxxxxx>
Cc: Feng Tian <feng.tian@xxxxxxxxx>
Cc: Anthony Perard <anthony.perard@xxxxxxxxxx>
Cc: Laszlo Ersek <lersek@xxxxxxxxxx>
Cc: Jordan Justen <jordan.l.justen@xxxxxxxxx>
 MdeModulePkg/Bus/Pci/PciBusDxe/PciEnumeratorSupport.c | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/MdeModulePkg/Bus/Pci/PciBusDxe/PciEnumeratorSupport.c 
index 9e7ac74..7659585 100644
--- a/MdeModulePkg/Bus/Pci/PciBusDxe/PciEnumeratorSupport.c
+++ b/MdeModulePkg/Bus/Pci/PciBusDxe/PciEnumeratorSupport.c
@@ -2256,6 +2256,7 @@ PciEnumeratorLight (
   EFI_STATUS                        Status;
+  EFI_HANDLE                        HostBridgeHandle;
   PCI_IO_DEVICE                     *RootBridgeDev;
   UINT16                            MinBus;
@@ -2288,6 +2289,11 @@ PciEnumeratorLight (
     return Status;
+  //
+  // Get the host bridge handle
+  //
+  HostBridgeHandle = PciRootBridgeIo->ParentHandle;
   Status = PciRootBridgeIo->Configuration (PciRootBridgeIo, (VOID **) 
   if (EFI_ERROR (Status)) {
@@ -2348,7 +2354,14 @@ PciEnumeratorLight (
-  return EFI_SUCCESS;
+  Status = gBS->InstallProtocolInterface (
+                  &HostBridgeHandle,
+                  &gEfiPciEnumerationCompleteProtocolGuid,
+                  EFI_NATIVE_INTERFACE,
+                  NULL
+                  );
+  return Status;

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