[edk2-devel] [PATCH 1/1] UefiCpuPkg/BaseXApicX2ApicLib: fix CPUID_V2_EXTENDED_TOPOLOGY detection

["Gerd Hoffmann" <kraxel@redhat.com>]

Checking the max cpuid leaf is not enough to figure whenever
CPUID_V2_EXTENDED_TOPOLOGY is supported.  Quoting a comment for
CPUID_EXTENDED_TOPOLOGY in GetProcessorLocationByApicId():

// 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.

Add a similar check for CPUID_V2_EXTENDED_TOPOLOGY to
GetProcessorLocation2ByApicId().  Without this fix OVMF triggers
an ASSERT when running in a kvm guest on latest (12th gen) intel
processors.

Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2241388
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
---
 UefiCpuPkg/Library/BaseXApicX2ApicLib/BaseXApicX2ApicLib.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/UefiCpuPkg/Library/BaseXApicX2ApicLib/BaseXApicX2ApicLib.c b/UefiCpuPkg/Library/BaseXApicX2ApicLib/BaseXApicX2ApicLib.c
index aa4eb11181f6..eff7f1f2043b 100644
--- a/UefiCpuPkg/Library/BaseXApicX2ApicLib/BaseXApicX2ApicLib.c
+++ b/UefiCpuPkg/Library/BaseXApicX2ApicLib/BaseXApicX2ApicLib.c
@@ -1424,6 +1424,7 @@ GetProcessorLocation2ByApicId (
   )
 {
   CPUID_EXTENDED_TOPOLOGY_EAX  ExtendedTopologyEax;
+  CPUID_EXTENDED_TOPOLOGY_EBX  ExtendedTopologyEbx;
   CPUID_EXTENDED_TOPOLOGY_ECX  ExtendedTopologyEcx;
   UINT32                       MaxStandardCpuIdIndex;
   UINT32                       Index;
@@ -1440,6 +1441,12 @@ GetProcessorLocation2ByApicId (
   //
   AsmCpuid (CPUID_SIGNATURE, &MaxStandardCpuIdIndex, NULL, NULL, NULL);
   if (MaxStandardCpuIdIndex < CPUID_V2_EXTENDED_TOPOLOGY) {
+    ExtendedTopologyEbx.Uint32 = 0;
+  } else {
+    AsmCpuidEx (CPUID_V2_EXTENDED_TOPOLOGY, 0, NULL, &ExtendedTopologyEbx.Uint32, NULL, NULL);
+  }
+
+  if (ExtendedTopologyEbx.Uint32 == 0) {
     if (Die != NULL) {
       *Die = 0;
     }
-- 
2.41.0



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