diff --git a/UefiCpuPkg/Library/BaseXApicX2ApicLib/BaseXApicX2ApicLib.c b/UefiCpuPkg/Library/BaseXApicX2ApicLib/BaseXApicX2ApicLib.c index aa4eb11181..c0a8475833 100644 --- a/UefiCpuPkg/Library/BaseXApicX2ApicLib/BaseXApicX2ApicLib.c +++ b/UefiCpuPkg/Library/BaseXApicX2ApicLib/BaseXApicX2ApicLib.c @@ -1294,11 +1294,12 @@ GetProcessorLocationByApicId ( 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; // @@ -1424,6 +1425,7 @@ GetProcessorLocation2ByApicId ( ) { CPUID_EXTENDED_TOPOLOGY_EAX ExtendedTopologyEax; + CPUID_EXTENDED_TOPOLOGY_EBX ExtendedTopologyEbx; CPUID_EXTENDED_TOPOLOGY_ECX ExtendedTopologyEcx; UINT32 MaxStandardCpuIdIndex; UINT32 Index; @@ -1436,10 +1438,19 @@ GetProcessorLocation2ByApicId ( } // - // 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; }