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From: Ruiyu Ni <ruiyu.ni@intel.com>
To: edk2-devel@lists.01.org
Cc: Eric Dong <eric.dong@intel.com>, Ming Shao <ming.shao@intel.com>
Subject: [PATCH] UefiCpuPkg/CpuCommonFeatures: Follow SDM for MAX CPUID feature detect
Date: Fri, 25 May 2018 17:00:57 +0800	[thread overview]
Message-ID: <20180525090057.392796-1-ruiyu.ni@intel.com> (raw)

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



             reply	other threads:[~2018-05-25  9:00 UTC|newest]

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-05-25  9:00 Ruiyu Ni [this message]
2018-05-28  6:29 ` [PATCH] UefiCpuPkg/CpuCommonFeatures: Follow SDM for MAX CPUID feature detect Dong, Eric

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