Re: [PATCH] IntelSiliconPkg IntelVTdDxe: Check HeaderType if func 0 is implemented

["Yao, Jiewen" <jiewen.yao@intel.com>]

Reviewed-by: jiewen.yao@intel.com

> -----Original Message-----
> From: Zeng, Star
> Sent: Thursday, September 13, 2018 2:29 PM
> To: edk2-devel@lists.01.org
> Cc: Zeng, Star <star.zeng@intel.com>; Yao, Jiewen <jiewen.yao@intel.com>;
> Chaganty, Rangasai V <rangasai.v.chaganty@intel.com>; Chang, Tomson
> <tomson.chang@intel.com>; Huang, Jenny <jenny.huang@intel.com>; Chan,
> Amy <amy.chan@intel.com>; Ni, Ruiyu <ruiyu.ni@intel.com>
> Subject: [PATCH] IntelSiliconPkg IntelVTdDxe: Check HeaderType if func 0 is
> implemented
> 
> REF: https://bugzilla.tianocore.org/show_bug.cgi?id=1169
> 
> Current code checks HeaderType of Function 0 even Function 0 is not
> implemented. HeaderType value will be 0xFF if Function 0 is not
> implemented, then MaxFunction will be set to PCI_MAX_FUNC + 1.
> 
> The code can be optimized to only check HeaderType if Function 0 is
> implemented.
> 
> Test done:
> With this patch, the result is same with the result after the patch at
> https://lists.01.org/pipermail/edk2-devel/2018-September/029623.html.
> 
> Cc: Jiewen Yao <jiewen.yao@intel.com>
> Cc: Rangasai V Chaganty <rangasai.v.chaganty@intel.com>
> Cc: Tomson Chang <tomson.chang@intel.com>
> Cc: Jenny Huang <jenny.huang@intel.com>
> Cc: Amy Chan <amy.chan@intel.com>
> Cc: Ruiyu Ni <ruiyu.ni@intel.com>
> Contributed-under: TianoCore Contribution Agreement 1.1
> Signed-off-by: Star Zeng <star.zeng@intel.com>
> ---
>  IntelSiliconPkg/Feature/VTd/IntelVTdDxe/PciInfo.c | 20
> ++++++++++++--------
>  1 file changed, 12 insertions(+), 8 deletions(-)
> 
> diff --git a/IntelSiliconPkg/Feature/VTd/IntelVTdDxe/PciInfo.c
> b/IntelSiliconPkg/Feature/VTd/IntelVTdDxe/PciInfo.c
> index 305995de032c..6ae5df589c1e 100644
> --- a/IntelSiliconPkg/Feature/VTd/IntelVTdDxe/PciInfo.c
> +++ b/IntelSiliconPkg/Feature/VTd/IntelVTdDxe/PciInfo.c
> @@ -231,19 +231,13 @@ ScanPciBus (
>    UINT8                   HeaderType;
>    UINT8                   BaseClass;
>    UINT8                   SubClass;
> -  UINT32                  MaxFunction;
>    UINT16                  VendorID;
>    UINT16                  DeviceID;
>    EFI_STATUS              Status;
> 
>    // Scan the PCI bus for devices
> -  for (Device = 0; Device < PCI_MAX_DEVICE + 1; Device++) {
> -    HeaderType = PciSegmentRead8
> (PCI_SEGMENT_LIB_ADDRESS(Segment, Bus, Device, 0,
> PCI_HEADER_TYPE_OFFSET));
> -    MaxFunction = PCI_MAX_FUNC + 1;
> -    if ((HeaderType & HEADER_TYPE_MULTI_FUNCTION) == 0x00) {
> -      MaxFunction = 1;
> -    }
> -    for (Function = 0; Function < MaxFunction; Function++) {
> +  for (Device = 0; Device <= PCI_MAX_DEVICE; Device++) {
> +    for (Function = 0; Function <= PCI_MAX_FUNC; Function++) {
>        VendorID  = PciSegmentRead16
> (PCI_SEGMENT_LIB_ADDRESS(Segment, Bus, Device, Function,
> PCI_VENDOR_ID_OFFSET));
>        DeviceID  = PciSegmentRead16
> (PCI_SEGMENT_LIB_ADDRESS(Segment, Bus, Device, Function,
> PCI_DEVICE_ID_OFFSET));
>        if (VendorID == 0xFFFF && DeviceID == 0xFFFF) {
> @@ -275,6 +269,16 @@ ScanPciBus (
>            }
>          }
>        }
> +
> +      if (Function == 0) {
> +        HeaderType = PciSegmentRead8
> (PCI_SEGMENT_LIB_ADDRESS(Segment, Bus, Device, 0,
> PCI_HEADER_TYPE_OFFSET));
> +        if ((HeaderType & HEADER_TYPE_MULTI_FUNCTION) == 0x00) {
> +          //
> +          // It is not a multi-function device, do not scan other functions.
> +          //
> +          break;
> +        }
> +      }
>      }
>    }
> 
> --
> 2.7.0.windows.1