X-Git-Url: https://git.proxmox.com/?p=mirror_edk2.git;a=blobdiff_plain;f=UefiCpuPkg%2FLibrary%2FBaseXApicX2ApicLib%2FBaseXApicX2ApicLib.c;h=e690d2aa144524e703a4002c1145703f1918b87b;hp=9720d26e60e2044951c01bcb5cfe8e2ca2118a94;hb=4af3ae1463796ef7b2ecf2bfe8b390e72817212c;hpb=7b9b576c71c71ed134f50497fd58f862109dd80b

diff --git a/UefiCpuPkg/Library/BaseXApicX2ApicLib/BaseXApicX2ApicLib.c b/UefiCpuPkg/Library/BaseXApicX2ApicLib/BaseXApicX2ApicLib.c
index 9720d26e60..e690d2aa14 100644
--- a/UefiCpuPkg/Library/BaseXApicX2ApicLib/BaseXApicX2ApicLib.c
+++ b/UefiCpuPkg/Library/BaseXApicX2ApicLib/BaseXApicX2ApicLib.c
@@ -411,12 +411,15 @@ GetInitialApicId (
     AsmCpuid (CPUID_SIGNATURE, &MaxCpuIdIndex, NULL, NULL, NULL);
     //
     // If CPUID Leaf B is supported, 
+    // And CPUID.0BH:EBX[15:0] reports a non-zero value,
     // Then the initial 32-bit APIC ID = CPUID.0BH:EDX
     // Else the initial 8-bit APIC ID = CPUID.1:EBX[31:24]
     //
     if (MaxCpuIdIndex >= CPUID_EXTENDED_TOPOLOGY) {
-      AsmCpuidEx (CPUID_EXTENDED_TOPOLOGY, 0, NULL, NULL, NULL, &ApicId);
-      return ApicId;
+      AsmCpuidEx (CPUID_EXTENDED_TOPOLOGY, 0, NULL, &RegEbx, NULL, &ApicId);
+      if ((RegEbx & (BIT16 - 1)) != 0) {
+        return ApicId;
+      }
     }
     AsmCpuid (CPUID_VERSION_INFO, NULL, &RegEbx, NULL, NULL);
     return RegEbx >> 24;