Re: [PATCH] IntelSiliconPkg IntelVTdDxe: Optimize when func 0 is not implemented

["Ni, Ruiyu" <ruiyu.ni@Intel.com>]

On 9/13/2018 10:10 AM, Star Zeng wrote:
> REF: https://bugzilla.tianocore.org/show_bug.cgi?id=1169
> 
> PCI spec:
> They are also required to always implement function 0 in the device.
> Implementing other functions is optional and may be assigned in any
> order (i.e., a two-function device must respond to function 0 but
> can choose any of the other possible function numbers (1-7) for the
> second function).
> 
> This patch updates ScanPciBus() to not scan other functions if
> function 0 is not implemented.
> 
> Test done:
> Added debug code below in the second loop of ScanPciBus(),
> compared the debug logs with and without this patch, many
> non-0 unimplemented functions are skipped correctly.
> 
>    DEBUG ((
>      DEBUG_INFO,
>      "%a() B%02xD%02xF%02x VendorId: %04x DeviceId: %04x\n",
>      __FUNCTION__,
>      Bus,
>      Device,
>      Function,
>      VendorID,
>      DeviceID
>      ));
> 
> 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>
> Contributed-under: TianoCore Contribution Agreement 1.1
> Signed-off-by: Star Zeng <star.zeng@intel.com>
> ---
>   IntelSiliconPkg/Feature/VTd/IntelVTdDxe/PciInfo.c | 8 +++++++-
>   1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/IntelSiliconPkg/Feature/VTd/IntelVTdDxe/PciInfo.c b/IntelSiliconPkg/Feature/VTd/IntelVTdDxe/PciInfo.c
> index 36750b3f1d9c..305995de032c 100644
> --- a/IntelSiliconPkg/Feature/VTd/IntelVTdDxe/PciInfo.c
> +++ b/IntelSiliconPkg/Feature/VTd/IntelVTdDxe/PciInfo.c
> @@ -1,6 +1,6 @@
>   /** @file
>   
> -  Copyright (c) 2017, Intel Corporation. All rights reserved.<BR>
> +  Copyright (c) 2017 - 2018, Intel Corporation. All rights reserved.<BR>
>     This program and the accompanying materials
>     are licensed and made available under the terms and conditions of the BSD License
>     which accompanies this distribution.  The full text of the license may be found at
> @@ -247,6 +247,12 @@ ScanPciBus (
>         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) {
> +        if (Function == 0) {
> +          //
> +          // If function 0 is not implemented, do not scan other functions.
> +          //
> +          break;
> +        }
>           continue;
>         }
>   
> 
Reviewed-by: Ruiyu Ni <ruiyu.ni@intel.com>

-- 
Thanks,
Ray