Create a new PCD boolean token in MdeModulePkg for global use.
We use this token to indicate if the configuration, parsed from
fw-cfg, requires pre-populated BARs to be preserved.

During creation of root bridges configurations, the flag is set
according to the "pre-populated-bars" item in fw-cfg. The Pcd token
is created as a dynamic item for consumption in both Pei and Dxe PCI
modules.

The token provides a globally accessible configuration flag to
determine, during PCI BAR allocation, if pre-populated BARs must
be respected. The pre-allocated PCI BARs are used in platforms in
which MMIO resources are configured with host physical addresses so
that DMA transactions can happen between PCI devices without packets
going through the IOMMU. Performance is improved due to PCI packets
travelling shorter distances and avoiding links reaching the Root
Complex, which can get busy during I/O intensive periods.

Signed-off-by: Nicolas Ojeda Leon <ncoleon@amazon.com>
Cc: Alexander Graf <graf@amazon.de>
---
 MdeModulePkg/MdeModulePkg.dec                   |  6 ++++++
 OvmfPkg/OvmfPkgX64.dsc                          |  1 +
 MdeModulePkg/Bus/Pci/PciBusDxe/PciBusDxe.inf    |  1 +
 .../PciHostBridgeUtilityLib.inf                 |  4 ++++
 OvmfPkg/PlatformPei/PlatformPei.inf             |  1 +
 .../PciHostBridgeUtilityLib.c                   | 17 +++++++++++++++++
 6 files changed, 30 insertions(+)

diff --git a/MdeModulePkg/MdeModulePkg.dec b/MdeModulePkg/MdeModulePkg.dec
index 133e04ee86..44a2150628 100644
--- a/MdeModulePkg/MdeModulePkg.dec
+++ b/MdeModulePkg/MdeModulePkg.dec
@@ -1902,6 +1902,12 @@
   # @Prompt Disable full PCI enumeration.
   gEfiMdeModulePkgTokenSpaceGuid.PcdPciDisableBusEnumeration|FALSE|BOOLEAN|0x10000048
 
+  ## The flag to control preservation of pre-populated PCI BARs
+  #   TRUE  - Respect pre-populated PCI BARs
+  #   FALSE - No pre-populated BARs, place all BARs
+  # @Prompt Enable preservsation of pre-populated PCI BARs
+  gEfiMdeModulePkgTokenSpaceGuid.PcdPciPreservePopulatedMappings|FALSE|BOOLEAN|0x10000050
+
   ## Disk I/O - Number of Data Buffer block.
   # Define the size in block of the pre-allocated buffer. It provide better
   # performance for large Disk I/O requests.
diff --git a/OvmfPkg/OvmfPkgX64.dsc b/OvmfPkg/OvmfPkgX64.dsc
index e56b83d95e..fff50355b0 100644
--- a/OvmfPkg/OvmfPkgX64.dsc
+++ b/OvmfPkg/OvmfPkgX64.dsc
@@ -605,6 +605,7 @@
   gEfiMdeModulePkgTokenSpaceGuid.PcdFlashNvStorageFtwWorkingBase|0
   gEfiMdeModulePkgTokenSpaceGuid.PcdFlashNvStorageFtwSpareBase|0
 !endif
+  gEfiMdeModulePkgTokenSpaceGuid.PcdPciPreservePopulatedMappings|FALSE
   gEfiMdeModulePkgTokenSpaceGuid.PcdVideoHorizontalResolution|800
   gEfiMdeModulePkgTokenSpaceGuid.PcdVideoVerticalResolution|600
   gEfiMdeModulePkgTokenSpaceGuid.PcdAcpiS3Enable|FALSE
diff --git a/MdeModulePkg/Bus/Pci/PciBusDxe/PciBusDxe.inf b/MdeModulePkg/Bus/Pci/PciBusDxe/PciBusDxe.inf
index e317169d9c..046876bb3b 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.PcdPciPreservePopulatedMappings## CONSUMES
 
 [UserExtensions.TianoCore."ExtraFiles"]
   PciBusDxeExtra.uni
diff --git a/OvmfPkg/Library/PciHostBridgeUtilityLib/PciHostBridgeUtilityLib.inf b/OvmfPkg/Library/PciHostBridgeUtilityLib/PciHostBridgeUtilityLib.inf
index 83a734c172..3643ffd79e 100644
--- a/OvmfPkg/Library/PciHostBridgeUtilityLib/PciHostBridgeUtilityLib.inf
+++ b/OvmfPkg/Library/PciHostBridgeUtilityLib/PciHostBridgeUtilityLib.inf
@@ -39,5 +39,9 @@
   DebugLib
   DevicePathLib
   MemoryAllocationLib
+  PcdLib
   PciLib
   QemuFwCfgLib
+
+[Pcd]
+  gEfiMdeModulePkgTokenSpaceGuid.PcdPciPreservePopulatedMappings
diff --git a/OvmfPkg/PlatformPei/PlatformPei.inf b/OvmfPkg/PlatformPei/PlatformPei.inf
index 67eb7aa716..61bcf25999 100644
--- a/OvmfPkg/PlatformPei/PlatformPei.inf
+++ b/OvmfPkg/PlatformPei/PlatformPei.inf
@@ -93,6 +93,7 @@
   gEfiMdeModulePkgTokenSpaceGuid.PcdFlashNvStorageFtwSpareSize
   gEfiMdeModulePkgTokenSpaceGuid.PcdFlashNvStorageVariableSize
   gEfiMdeModulePkgTokenSpaceGuid.PcdEmuVariableNvStoreReserved
+  gEfiMdeModulePkgTokenSpaceGuid.PcdPciPreservePopulatedMappings
   gEfiMdeModulePkgTokenSpaceGuid.PcdDxeIplSwitchToLongMode
   gEfiMdeModulePkgTokenSpaceGuid.PcdUse1GPageTable
   gEfiMdeModulePkgTokenSpaceGuid.PcdSetNxForStack
diff --git a/OvmfPkg/Library/PciHostBridgeUtilityLib/PciHostBridgeUtilityLib.c b/OvmfPkg/Library/PciHostBridgeUtilityLib/PciHostBridgeUtilityLib.c
index 7567da8423..0a9aac5359 100644
--- a/OvmfPkg/Library/PciHostBridgeUtilityLib/PciHostBridgeUtilityLib.c
+++ b/OvmfPkg/Library/PciHostBridgeUtilityLib/PciHostBridgeUtilityLib.c
@@ -16,6 +16,7 @@
 #include <Library/DebugLib.h>
 #include <Library/DevicePathLib.h>
 #include <Library/MemoryAllocationLib.h>
+#include <Library/PcdLib.h>
 #include <Library/PciHostBridgeUtilityLib.h>
 #include <Library/PciLib.h>
 #include <Library/PciHostBridgeInfoLib.h>
@@ -298,6 +299,7 @@ PciHostBridgeUtilityGetRootBridges (
   FIRMWARE_CONFIG_ITEM FwCfgItem;
   UINTN                FwCfgSize;
   UINT64               ExtraRootBridges;
+  UINT64               PrePopulatedBars;
   PCI_ROOT_BRIDGE      *Bridges;
   UINTN                Initialized;
   UINTN                LastRootBridgeNumber;
@@ -339,6 +341,21 @@ PciHostBridgeUtilityGetRootBridges (
       __FUNCTION__, ExtraRootBridges));
   }
 
+  //
+  // Find file for pre-populated bars and set Pcd token if enabled
+  //
+  Status = QemuFwCfgFindFile ("etc/pre-populated-bars", &FwCfgItem, &FwCfgSize);
+  PrePopulatedBars = 0;
+  if (!EFI_ERROR (Status) && FwCfgSize == sizeof (PrePopulatedBars)) {
+    QemuFwCfgSelectItem (FwCfgItem);
+    QemuFwCfgReadBytes (FwCfgSize, &PrePopulatedBars);
+
+    if (PrePopulatedBars) {
+      PcdSetBoolS (PcdPciPreservePopulatedMappings, TRUE);
+      DEBUG ((DEBUG_INFO, "%a: Pre-populated BARs present\n", __FUNCTION__));
+    }
+  }
+
   //
   // Initialize RootBridgeInfo pointer, so in case no fw-cfg item is found
   // the default configuration is used.
-- 
2.17.1




Amazon Development Center Germany GmbH
Krausenstr. 38
10117 Berlin
Geschaeftsfuehrung: Christian Schlaeger, Jonathan Weiss
Eingetragen am Amtsgericht Charlottenburg unter HRB 149173 B
Sitz: Berlin
Ust-ID: DE 289 237 879





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