QEMU provides an fw_cfg file called "etc/extra-pci-roots", containing a
little-endian UINT64 value that exposes the number of extra root buses. We
can use this value to terminate the scan as soon as we find the last extra
root bus.
Cc: Jordan Justen <jordan.l.jus...@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Laszlo Ersek <ler...@redhat.com>
Regression-tested-by: Gabriel Somlo <so...@cmu.edu>
---
Notes:
v2:
- %Lu is available now in format strings, for printing UINT64 values in
decimal
OvmfPkg/PciHostBridgeDxe/PciHostBridgeDxe.inf | 2 ++
OvmfPkg/PciHostBridgeDxe/PciHostBridge.c | 22 +++++++++++++++++++-
2 files changed, 23 insertions(+), 1 deletion(-)
diff --git a/OvmfPkg/PciHostBridgeDxe/PciHostBridgeDxe.inf
b/OvmfPkg/PciHostBridgeDxe/PciHostBridgeDxe.inf
index 40f4c3c..ca760b5 100644
--- a/OvmfPkg/PciHostBridgeDxe/PciHostBridgeDxe.inf
+++ b/OvmfPkg/PciHostBridgeDxe/PciHostBridgeDxe.inf
@@ -26,6 +26,7 @@ [Defines]
[Packages]
MdePkg/MdePkg.dec
+ OvmfPkg/OvmfPkg.dec
[LibraryClasses]
UefiDriverEntryPoint
@@ -39,6 +40,7 @@ [LibraryClasses]
DevicePathLib
IoLib
PciLib
+ QemuFwCfgLib
[Sources]
PciHostBridge.c
diff --git a/OvmfPkg/PciHostBridgeDxe/PciHostBridge.c
b/OvmfPkg/PciHostBridgeDxe/PciHostBridge.c
index 3486644..efef2ed 100644
--- a/OvmfPkg/PciHostBridgeDxe/PciHostBridge.c
+++ b/OvmfPkg/PciHostBridgeDxe/PciHostBridge.c
@@ -15,6 +15,8 @@
**/
+#include <Library/QemuFwCfgLib.h>
+
#include "PciHostBridge.h"
STATIC
@@ -207,6 +209,9 @@ InitializePciHostBridge (
)
{
EFI_STATUS Status;
+ FIRMWARE_CONFIG_ITEM FwCfgItem;
+ UINTN FwCfgSize;
+ UINT64 ExtraRootBridgesLeft;
UINTN LastRootBridgeNumber;
UINTN RootBridgeNumber;
PCI_HOST_BRIDGE_INSTANCE *HostBridge;
@@ -237,6 +242,20 @@ InitializePciHostBridge (
}
//
+ // QEMU provides the number of extra root buses, shortening the exhaustive
+ // search below. If there is no hint, the feature is missing.
+ //
+ Status = QemuFwCfgFindFile ("etc/extra-pci-roots", &FwCfgItem, &FwCfgSize);
+ if (EFI_ERROR (Status) || FwCfgSize != sizeof ExtraRootBridgesLeft) {
+ ExtraRootBridgesLeft = 0;
+ } else {
+ QemuFwCfgSelectItem (FwCfgItem);
+ QemuFwCfgReadBytes (FwCfgSize, &ExtraRootBridgesLeft);
+ DEBUG ((EFI_D_INFO, "%a: %Lu extra root buses reported by QEMU\n",
+ __FUNCTION__, ExtraRootBridgesLeft));
+ }
+
+ //
// The "main" root bus is always there.
//
LastRootBridgeNumber = 0;
@@ -247,7 +266,7 @@ InitializePciHostBridge (
// alive.
//
for (RootBridgeNumber = 1;
- RootBridgeNumber < 256;
+ RootBridgeNumber < 256 && ExtraRootBridgesLeft > 0;
++RootBridgeNumber) {
UINTN Device;
@@ -271,6 +290,7 @@ InitializePciHostBridge (
}
InsertTailList (&HostBridge->Head, &RootBus->Link);
LastRootBridgeNumber = RootBridgeNumber;
+ --ExtraRootBridgesLeft;
}
}
--
1.8.3.1
------------------------------------------------------------------------------
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