[PATCH 1/1] PciBusDxe: Add PcdPciProbePcieConfig

["Pedro Falcato" <pedro.falcato@gmail.com>]

Virtualization software like QEMU can introduce interesting impossible
topologies like PCIe devices on legacy PCI buses.

Add a new PCD PcdPciProbePcieConfig to control PCIe extended configuration space
probing, given that currently PCIe config space probing can trigger
asserts in BasePciCf8Lib, making it hard to use on virtual
platforms.

Signed-off-by: Pedro Falcato <pedro.falcato@gmail.com>
Cc: Jian J Wang <jian.j.wang@intel.com>
Cc: Liming Gao <gaoliming@byosoft.com.cn>
Cc: Hao A Wu <hao.a.wu@intel.com>
Cc: Ray Ni <ray.ni@intel.com>
---
 MdeModulePkg/Bus/Pci/PciBusDxe/PciBusDxe.inf | 1 +
 MdeModulePkg/Bus/Pci/PciBusDxe/PciCommand.c  | 4 ++++
 MdeModulePkg/MdeModulePkg.dec                | 6 ++++++
 3 files changed, 11 insertions(+)

diff --git a/MdeModulePkg/Bus/Pci/PciBusDxe/PciBusDxe.inf b/MdeModulePkg/Bus/Pci/PciBusDxe/PciBusDxe.inf
index e317169d9c57..c3e52ccd3e2e 100644
--- a/MdeModulePkg/Bus/Pci/PciBusDxe/PciBusDxe.inf
+++ b/MdeModulePkg/Bus/Pci/PciBusDxe/PciBusDxe.inf
@@ -107,6 +107,7 @@
   gEfiMdeModulePkgTokenSpaceGuid.PcdMrIovSupport                ## CONSUMES
   gEfiMdeModulePkgTokenSpaceGuid.PcdPciDisableBusEnumeration    ## SOMETIMES_CONSUMES
   gEfiMdeModulePkgTokenSpaceGuid.PcdPcieResizableBarSupport     ## CONSUMES
+  gEfiMdeModulePkgTokenSpaceGuid.PcdPciProbePcieConfig          ## CONSUMES
 
 [UserExtensions.TianoCore."ExtraFiles"]
   PciBusDxeExtra.uni
diff --git a/MdeModulePkg/Bus/Pci/PciBusDxe/PciCommand.c b/MdeModulePkg/Bus/Pci/PciBusDxe/PciCommand.c
index ba4b099bc5c1..1c4e7fa23cb5 100644
--- a/MdeModulePkg/Bus/Pci/PciBusDxe/PciCommand.c
+++ b/MdeModulePkg/Bus/Pci/PciBusDxe/PciCommand.c
@@ -211,6 +211,10 @@ LocatePciExpressCapabilityRegBlock (
     return EFI_UNSUPPORTED;
   }
 
+  if (PcdGetBool (PcdPciProbePcieConfig) == FALSE) {
+    return EFI_UNSUPPORTED;
+  }
+
   if (*Offset != 0) {
     CapabilityPtr = *Offset;
   } else {
diff --git a/MdeModulePkg/MdeModulePkg.dec b/MdeModulePkg/MdeModulePkg.dec
index be5e829ca9c5..d5005535e8fb 100644
--- a/MdeModulePkg/MdeModulePkg.dec
+++ b/MdeModulePkg/MdeModulePkg.dec
@@ -2098,6 +2098,12 @@
   # @Prompt Enable PCIe Resizable BAR Capability support.
   gEfiMdeModulePkgTokenSpaceGuid.PcdPcieResizableBarSupport|FALSE|BOOLEAN|0x10000024
 
+  ## Indicates if the PCIe configuration space should be probed.
+  #    TRUE  - Probe PCIe space for PCIe devices.
+  #    FALSE - Do not touch PCIe configuration space.
+  # @Prompt Enable PCIe configuration space probing
+  gEfiMdeModulePkgTokenSpaceGuid.PcdPciProbePcieConfig|FALSE|BOOLEAN|0x10000026
+
   ## This PCD holds the shared bit mask for page table entries when Tdx is enabled.
   # @Prompt The shared bit mask when Intel Tdx is enabled.
   gEfiMdeModulePkgTokenSpaceGuid.PcdTdxSharedBitMask|0x0|UINT64|0x10000025
-- 
2.39.0