On 2015-07-07 08:09:23, Laszlo Ersek wrote:
> QEMU provides an fw_cfg file called "etc/extra-pci-roots", containing a
How long were the extra roots in qemu without the fw_cfg entry?
That's a leading question for, what if we only were to only scan for
the roots if the fw_cfg entry is present?
Does seabios scan up to 255 if the fw_cfg entry is not found?
-Jordan
> 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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