[edk2-devel] [PATCH 1/2] UefiCpuPkg/MpInitLib: Use AsmCpuidEx() for CPUID_EXTENDED_TOPOLOGY leaf

["Lendacky, Thomas via groups.io" <thomas.lendacky=amd.com@groups.io>]

The CPUID_EXTENDED_TOPOLOGY CPUID leaf takes a subleaf as input when
returning CPUID information. However, the AsmCpuid() function does not
zero out ECX before the CPUID instruction, so the input leaf is used as
the sub-leaf for the CPUID request and returns erroneous/invalid CPUID
data, since the intent of the request was to get data related to sub-leaf
0. Instead, use AsmCpuidEx() for the CPUID_EXTENDED_TOPOLOGY leaf.

Fixes: d4d7c9ad5fe5 ("UefiCpuPkg/MpInitLib: use BSP to do extended ...")
Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
---
 UefiCpuPkg/Library/MpInitLib/AmdSev.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/UefiCpuPkg/Library/MpInitLib/AmdSev.c b/UefiCpuPkg/Library/MpInitLib/AmdSev.c
index bda4960f6fd3..d34f9513e002 100644
--- a/UefiCpuPkg/Library/MpInitLib/AmdSev.c
+++ b/UefiCpuPkg/Library/MpInitLib/AmdSev.c
@@ -256,7 +256,14 @@ FillExchangeInfoDataSevEs (
   if (StdRangeMax >= CPUID_EXTENDED_TOPOLOGY) {
     CPUID_EXTENDED_TOPOLOGY_EBX  ExtTopoEbx;
 
-    AsmCpuid (CPUID_EXTENDED_TOPOLOGY, NULL, &ExtTopoEbx.Uint32, NULL, NULL);
+    AsmCpuidEx (
+      CPUID_EXTENDED_TOPOLOGY,
+      0,
+      NULL,
+      &ExtTopoEbx.Uint32,
+      NULL,
+      NULL
+      );
     ExchangeInfo->ExtTopoAvail = !!ExtTopoEbx.Bits.LogicalProcessors;
   }
 }
-- 
2.42.0



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