Re: [edk2-devel] [PATCH v2 1/3] UefiCpuPkg/BaseXApicLib: Fix CPUID_V2_EXTENDED_TOPOLOGY detection

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

On 11/15/23 12:15, Jiaxin Wu wrote:
> This patch is to complete 170d4ce8, sync the change to BaseXApicLib.
> 
> Checking the max cpuid leaf is not enough to figure whenever
> CPUID_V2_EXTENDED_TOPOLOGY is supported.  Intel SDM says:
> 
> Software must detect the presence of CPUID leaf 1FH by verifying
> (a) the highest leaf index supported by CPUID is >= 1FH, and
> (b) CPUID.1FH:EBX[15:0] reports a non-zero value.
> 
> The same is true for CPUID leaf 0BH.
> 
> This patch adds the EBX check to GetProcessorLocation2ByApicId().  The
> patch also fixes the existing check in GetProcessorLocationByApicId() to
> be in line with the spec by looking at bits 15:0.  The comments are
> updated with a quote from the Intel SDM.
> 
> Cc: Laszlo Ersek <lersek@redhat.com>
> Cc: Eric Dong <eric.dong@intel.com>
> Cc: Ray Ni <ray.ni@intel.com>
> Cc: Rahul Kumar <rahul1.kumar@intel.com>
> Cc: Gerd Hoffmann <kraxel@redhat.com>
> Cc: Star Zeng <star.zeng@intel.com>
> Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
> Signed-off-by: Jiaxin Wu <jiaxin.wu@intel.com>
> ---
>  UefiCpuPkg/Library/BaseXApicLib/BaseXApicLib.c | 21 ++++++++++++++++-----
>  1 file changed, 16 insertions(+), 5 deletions(-)
> 
> diff --git a/UefiCpuPkg/Library/BaseXApicLib/BaseXApicLib.c b/UefiCpuPkg/Library/BaseXApicLib/BaseXApicLib.c
> index d56c6275cc..efb9d71ca1 100644
> --- a/UefiCpuPkg/Library/BaseXApicLib/BaseXApicLib.c
> +++ b/UefiCpuPkg/Library/BaseXApicLib/BaseXApicLib.c
> @@ -1053,15 +1053,16 @@ GetProcessorLocationByApicId (
>        &ExtendedTopologyEbx.Uint32,
>        &ExtendedTopologyEcx.Uint32,
>        NULL
>        );
>      //
> -    // If CPUID.(EAX=0BH, ECX=0H):EBX returns zero and maximum input value for
> -    // basic CPUID information is greater than 0BH, then CPUID.0BH leaf is not
> -    // supported on that processor.
> +    // Quoting Intel SDM:
> +    // Software must detect the presence of CPUID leaf 0BH by
> +    // verifying (a) the highest leaf index supported by CPUID is >=
> +    // 0BH, and (b) CPUID.0BH:EBX[15:0] reports a non-zero value.
>      //
> -    if (ExtendedTopologyEbx.Uint32 != 0) {
> +    if (ExtendedTopologyEbx.Bits.LogicalProcessors != 0) {
>        TopologyLeafSupported = TRUE;
>  
>        //
>        // Sub-leaf index 0 (ECX= 0 as input) provides enumeration parameters to extract
>        // the SMT sub-field of x2APIC ID.
> @@ -1183,10 +1184,11 @@ GetProcessorLocation2ByApicId (
>    OUT UINT32  *Core     OPTIONAL,
>    OUT UINT32  *Thread   OPTIONAL
>    )
>  {
>    CPUID_EXTENDED_TOPOLOGY_EAX  ExtendedTopologyEax;
> +  CPUID_EXTENDED_TOPOLOGY_EBX  ExtendedTopologyEbx;
>    CPUID_EXTENDED_TOPOLOGY_ECX  ExtendedTopologyEcx;
>    UINT32                       MaxStandardCpuIdIndex;
>    UINT32                       Index;
>    UINTN                        LevelType;
>    UINT32                       Bits[CPUID_V2_EXTENDED_TOPOLOGY_LEVEL_TYPE_DIE + 2];
> @@ -1195,14 +1197,23 @@ GetProcessorLocation2ByApicId (
>    for (LevelType = 0; LevelType < ARRAY_SIZE (Bits); LevelType++) {
>      Bits[LevelType] = 0;
>    }
>  
>    //
> -  // Get max index of CPUID
> +  // Quoting Intel SDM:
> +  // Software must detect the presence of CPUID leaf 1FH by verifying
> +  // (a) the highest leaf index supported by CPUID is >= 1FH, and (b)
> +  // CPUID.1FH:EBX[15:0] reports a non-zero value.
>    //
>    AsmCpuid (CPUID_SIGNATURE, &MaxStandardCpuIdIndex, NULL, NULL, NULL);
>    if (MaxStandardCpuIdIndex < CPUID_V2_EXTENDED_TOPOLOGY) {
> +    ExtendedTopologyEbx.Bits.LogicalProcessors = 0;
> +  } else {
> +    AsmCpuidEx (CPUID_V2_EXTENDED_TOPOLOGY, 0, NULL, &ExtendedTopologyEbx.Uint32, NULL, NULL);
> +  }
> +
> +  if (ExtendedTopologyEbx.Bits.LogicalProcessors == 0) {
>      if (Die != NULL) {
>        *Die = 0;
>      }
>  
>      if (Tile != NULL) {

This synchronizes the GetProcessorLocationByApicId() and
GetProcessorLocation2ByApicId() functions in BaseXApicLib with those in
BaseXApicX2ApicLib.

Reviewed-by: Laszlo Ersek <lersek@redhat.com>



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