Re: [edk2-devel] [PATCH 1/2] UefiCpuPkg: Retrive EXTENDED_PROCESSOR_INFORMATION

["Laszlo Ersek" <lersek@redhat.com>]

On 1/4/24 08:32, duntan wrote:
> Retrive EXTENDED_PROCESSOR_INFORMATION in the API
> MpInitLibGetProcessorInfo() of MpInitLibUp instance
> when the BIT24 of input ProcessorNumber is set.
> It's to align with the behavior in PEI/DXE MpInitLib
> 
> Signed-off-by: Dun Tan <dun.tan@intel.com>
> Cc: Ray Ni <ray.ni@intel.com>
> Cc: Laszlo Ersek <lersek@redhat.com>
> Cc: Rahul Kumar <rahul1.kumar@intel.com>
> Cc: Gerd Hoffmann <kraxel@redhat.com>
> Cc: Min Xu <min.m.xu@intel.com>
> ---
>  UefiCpuPkg/Include/Library/MpInitLib.h       |  2 ++
>  UefiCpuPkg/Library/MpInitLib/MpLib.c         |  2 ++
>  UefiCpuPkg/Library/MpInitLibUp/MpInitLibUp.c | 12 ++++++++++++
>  3 files changed, 16 insertions(+)
> 
> diff --git a/UefiCpuPkg/Include/Library/MpInitLib.h b/UefiCpuPkg/Include/Library/MpInitLib.h
> index 1853c46415..842c6f7ff9 100644
> --- a/UefiCpuPkg/Include/Library/MpInitLib.h
> +++ b/UefiCpuPkg/Include/Library/MpInitLib.h
> @@ -63,6 +63,8 @@ MpInitLibGetNumberOfProcessors (
>    instant this call is made. This service may only be called from the BSP.
>  
>    @param[in]  ProcessorNumber       The handle number of processor.
> +                                    Lower 24 bits contains the actual processor number.
> +                                    BIT24 indicates if the EXTENDED_PROCESSOR_INFORMATION will be retrived.
>    @param[out] ProcessorInfoBuffer   A pointer to the buffer where information for
>                                      the requested processor is deposited.
>    @param[out] HealthData            Return processor health data.
> diff --git a/UefiCpuPkg/Library/MpInitLib/MpLib.c b/UefiCpuPkg/Library/MpInitLib/MpLib.c
> index a359906923..cdfb570e61 100644
> --- a/UefiCpuPkg/Library/MpInitLib/MpLib.c
> +++ b/UefiCpuPkg/Library/MpInitLib/MpLib.c
> @@ -2333,6 +2333,8 @@ MpInitLibInitialize (
>    instant this call is made. This service may only be called from the BSP.
>  
>    @param[in]  ProcessorNumber       The handle number of processor.
> +                                    Lower 24 bits contains the actual processor number.
> +                                    BIT24 indicates if the EXTENDED_PROCESSOR_INFORMATION will be retrived.
>    @param[out] ProcessorInfoBuffer   A pointer to the buffer where information for
>                                      the requested processor is deposited.
>    @param[out]  HealthData            Return processor health data.
> diff --git a/UefiCpuPkg/Library/MpInitLibUp/MpInitLibUp.c b/UefiCpuPkg/Library/MpInitLibUp/MpInitLibUp.c
> index 86f9fbf903..3af4911d4b 100644
> --- a/UefiCpuPkg/Library/MpInitLibUp/MpInitLibUp.c
> +++ b/UefiCpuPkg/Library/MpInitLibUp/MpInitLibUp.c
> @@ -77,6 +77,8 @@ MpInitLibGetNumberOfProcessors (
>    instant this call is made. This service may only be called from the BSP.
>  
>    @param[in]  ProcessorNumber       The handle number of processor.
> +                                    Lower 24 bits contains the actual processor number.
> +                                    BIT24 indicates if the EXTENDED_PROCESSOR_INFORMATION will be retrived.
>    @param[out] ProcessorInfoBuffer   A pointer to the buffer where information for
>                                      the requested processor is deposited.
>    @param[out] HealthData            Return processor health data.
> @@ -115,6 +117,16 @@ MpInitLibGetProcessorInfo (
>    ProcessorInfoBuffer->Location.Package = 0;
>    ProcessorInfoBuffer->Location.Core    = 0;
>    ProcessorInfoBuffer->Location.Thread  = 0;
> +
> +  if ((ProcessorNumber & CPU_V2_EXTENDED_TOPOLOGY) != 0) {
> +    ProcessorInfoBuffer->ExtendedInformation.Location2.Package = 0;
> +    ProcessorInfoBuffer->ExtendedInformation.Location2.Die     = 0;
> +    ProcessorInfoBuffer->ExtendedInformation.Location2.Tile    = 0;
> +    ProcessorInfoBuffer->ExtendedInformation.Location2.Module  = 0;
> +    ProcessorInfoBuffer->ExtendedInformation.Location2.Core    = 0;
> +    ProcessorInfoBuffer->ExtendedInformation.Location2.Thread  = 0;
> +  }
> +
>    if (HealthData != NULL) {
>      GuidHob = GetFirstGuidHob (&gEfiSecPlatformInformationPpiGuid);
>      if (GuidHob != NULL) {

(1) For the UP implementation of MpInitLibGetProcessorInfo():

How about, for a *complete* solution (covering both pre-patch and
post-patch functionality):

  ZeroMem (ProcessorInfoBuffer, sizeof *ProcessorInfoBuffer);
  ProcessorInfoBuffer->StatusFlag  = PROCESSOR_AS_BSP_BIT  |
                                     PROCESSOR_ENABLED_BIT |
                                     PROCESSOR_HEALTH_STATUS_BIT;

This approach is not slow (most of the time I expect the platform will
have an optimized ZeroMem() implementation), it is frugal with code
(replaces a bunch of manual zeroing of fields), and it is relatively
future-proof (the next time EFI_PROCESSOR_INFORMATION is extended, you
likely won't have to touch up the code again, because the ZeroMem() will
cover the new fields automatically).

Also, this approach will zero out
ProcessorInfoBuffer->ExtendedInformation *regardless* of BIT24 in the
input, which I kind of consider an advantage! (No garbage in the output
structure.) Again, I don't think the zeroing is wasteful, regarding CPU
cycles.

I do agree that the leading function comments should mention BIT24

Thanks
Laszlo



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