Use a better algorithm to calculate MTRR

[edk2] [PATCH 04/10] UefiCpuPkg/MtrrLib: GetVariableMtrrCountWorker uses definitions in Msr.h

Posted by Ruiyu Ni 7 years, 7 months ago

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Ruiyu Ni <ruiyu.ni@intel.com>
Cc: Jeff Fan <jeff.fan@intel.com>
---
 UefiCpuPkg/Library/MtrrLib/MtrrLib.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/UefiCpuPkg/Library/MtrrLib/MtrrLib.c b/UefiCpuPkg/Library/MtrrLib/MtrrLib.c
index 38083d4..7e8a19a 100644
--- a/UefiCpuPkg/Library/MtrrLib/MtrrLib.c
+++ b/UefiCpuPkg/Library/MtrrLib/MtrrLib.c
@@ -124,11 +124,11 @@ GetVariableMtrrCountWorker (
   VOID
   )
 {
-  UINT32  VariableMtrrCount;
+  MSR_IA32_MTRRCAP_REGISTER MtrrCap;
 
-  VariableMtrrCount = (UINT32)(AsmReadMsr64 (MTRR_LIB_IA32_MTRR_CAP) & MTRR_LIB_IA32_MTRR_CAP_VCNT_MASK);
-  ASSERT (VariableMtrrCount <= MTRR_NUMBER_OF_VARIABLE_MTRR);
-  return VariableMtrrCount;
+  MtrrCap.Uint64 = AsmReadMsr64 (MSR_IA32_MTRRCAP);
+  ASSERT (MtrrCap.Bits.VCNT <= MTRR_NUMBER_OF_VARIABLE_MTRR);
+  return MtrrCap.Bits.VCNT;
 }
 
 /**
-- 
2.9.0.windows.1

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