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OvmfPkg: PciHostBridgeDxe: shorten search for extra root buses 

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.justen@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Regression-tested-by: Gabriel Somlo <somlo@cmu.edu>
Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>

git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@17963 6f19259b-4bc3-4df7-8a09-765794883524
This commit is contained in:
Laszlo Ersek 2015-07-14 12:02:34 +00:00 committed by lersek
parent bdb1c98f03
commit 68306ac2f2
2 changed files with 23 additions and 1 deletions
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22
OvmfPkg/PciHostBridgeDxe/PciHostBridge.c
View File

@ -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;
@ -236,6 +241,20 @@ InitializePciHostBridge (
goto FreeHostBridge;
}
//
// 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.
//
@ -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;
}
}

2
OvmfPkg/PciHostBridgeDxe/PciHostBridgeDxe.inf
View File

@ -26,6 +26,7 @@
[Packages]
MdePkg/MdePkg.dec
OvmfPkg/OvmfPkg.dec
[LibraryClasses]
UefiDriverEntryPoint
@ -39,6 +40,7 @@
DevicePathLib
IoLib
PciLib
QemuFwCfgLib
[Sources]
PciHostBridge.c