X-Git-Url: https://git.proxmox.com/?p=mirror_edk2.git;a=blobdiff_plain;f=UefiCpuPkg%2FLibrary%2FBaseXApicLib%2FBaseXApicLib.c;fp=UefiCpuPkg%2FLibrary%2FBaseXApicLib%2FBaseXApicLib.c;h=f81bbb2252d9e82df9eab00d56b65f8bf9b7e4bb;hp=4064049807b72fcc334520339695fdcffd74fe93;hb=4af3ae1463796ef7b2ecf2bfe8b390e72817212c;hpb=7b9b576c71c71ed134f50497fd58f862109dd80b

diff --git a/UefiCpuPkg/Library/BaseXApicLib/BaseXApicLib.c b/UefiCpuPkg/Library/BaseXApicLib/BaseXApicLib.c
index 4064049807..f81bbb2252 100644
--- a/UefiCpuPkg/Library/BaseXApicLib/BaseXApicLib.c
+++ b/UefiCpuPkg/Library/BaseXApicLib/BaseXApicLib.c
@@ -314,12 +314,15 @@ GetInitialApicId (
 
   //
   // 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);