[PATCH] UefiCpuPkg/CpuCommonFeatures: Follow SDM for MAX CPUID feature detect

[PATCH] UefiCpuPkg/CpuCommonFeatures: Follow SDM for MAX CPUID feature detect

[Ruiyu Ni]

According to IA manual:
"Before setting this bit (MSR_IA32_MISC_ENABLE[22]) , BIOS must
execute the CPUID.0H and examine the maximum value returned in
EAX[7:0]. If the maximum value is greater than 2, this bit is
supported."

We need to fix our current detection logic to compare against 2.

Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Ruiyu Ni <ruiyu.ni@intel.com>
Cc: Eric Dong <eric.dong@intel.com>
Cc: Ming Shao <ming.shao@intel.com>
---
 UefiCpuPkg/Library/CpuCommonFeaturesLib/LimitCpuIdMaxval.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/UefiCpuPkg/Library/CpuCommonFeaturesLib/LimitCpuIdMaxval.c b/UefiCpuPkg/Library/CpuCommonFeaturesLib/LimitCpuIdMaxval.c
index 40cc9d5fe0..3d41efe9e9 100644
--- a/UefiCpuPkg/Library/CpuCommonFeaturesLib/LimitCpuIdMaxval.c
+++ b/UefiCpuPkg/Library/CpuCommonFeaturesLib/LimitCpuIdMaxval.c
@@ -1,7 +1,7 @@
 /** @file
   LimitCpuidMaxval Feature.
 
-  Copyright (c) 2017, Intel Corporation. All rights reserved.<BR>
+  Copyright (c) 2017 - 2018, Intel Corporation. All rights reserved.<BR>
   This program and the accompanying materials
   are licensed and made available under the terms and conditions of the BSD License
   which accompanies this distribution.  The full text of the license may be found at
@@ -41,7 +41,7 @@ LimitCpuidMaxvalSupport (
   UINT32  Eax;
 
   AsmCpuid (CPUID_SIGNATURE, &Eax, NULL, NULL, NULL);
-  return (Eax > 3);
+  return (Eax > 2);
 }
 
 /**
-- 
2.16.1.windows.1

Re: [PATCH] UefiCpuPkg/CpuCommonFeatures: Follow SDM for MAX CPUID feature detect

[Dong, Eric]

Reviewed-by: Eric Dong <eric.dong@intel.com>

-----Original Message-----
From: Ni, Ruiyu 
Sent: Friday, May 25, 2018 5:01 PM
To: edk2-devel@lists.01.org
Cc: Dong, Eric <eric.dong@intel.com>; Shao, Ming <ming.shao@intel.com>
Subject: [PATCH] UefiCpuPkg/CpuCommonFeatures: Follow SDM for MAX CPUID feature detect

According to IA manual:
"Before setting this bit (MSR_IA32_MISC_ENABLE[22]) , BIOS must execute the CPUID.0H and examine the maximum value returned in EAX[7:0]. If the maximum value is greater than 2, this bit is supported."

We need to fix our current detection logic to compare against 2.

Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Ruiyu Ni <ruiyu.ni@intel.com>
Cc: Eric Dong <eric.dong@intel.com>
Cc: Ming Shao <ming.shao@intel.com>
---
 UefiCpuPkg/Library/CpuCommonFeaturesLib/LimitCpuIdMaxval.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/UefiCpuPkg/Library/CpuCommonFeaturesLib/LimitCpuIdMaxval.c b/UefiCpuPkg/Library/CpuCommonFeaturesLib/LimitCpuIdMaxval.c
index 40cc9d5fe0..3d41efe9e9 100644
--- a/UefiCpuPkg/Library/CpuCommonFeaturesLib/LimitCpuIdMaxval.c
+++ b/UefiCpuPkg/Library/CpuCommonFeaturesLib/LimitCpuIdMaxval.c
@@ -1,7 +1,7 @@
 /** @file
   LimitCpuidMaxval Feature.
 
-  Copyright (c) 2017, Intel Corporation. All rights reserved.<BR>
+  Copyright (c) 2017 - 2018, Intel Corporation. All rights 
+ reserved.<BR>
   This program and the accompanying materials
   are licensed and made available under the terms and conditions of the BSD License
   which accompanies this distribution.  The full text of the license may be found at @@ -41,7 +41,7 @@ LimitCpuidMaxvalSupport (
   UINT32  Eax;
 
   AsmCpuid (CPUID_SIGNATURE, &Eax, NULL, NULL, NULL);
-  return (Eax > 3);
+  return (Eax > 2);
 }
 
 /**
--
2.16.1.windows.1