Re: [PATCH] UefiCpuPkg/MtrrLib: Add comments to recommend to use batch-set API

["Shao, Ming" <ming.shao@intel.com>]

Reviewed-by Shao Ming <ming.shao@intel.com>

-Ming

-----Original Message-----
From: Ni, Ruiyu 
Sent: Thursday, January 18, 2018 2:14 PM
To: edk2-devel@lists.01.org
Cc: Shao, Ming <ming.shao@intel.com>
Subject: [PATCH] UefiCpuPkg/MtrrLib: Add comments to recommend to use batch-set API

MtrrSetMemoryAttributesInMtrrSettings() is a batch-set API.
When setting multiple ranges of memory attributes, the single-set API (MtrrSetMemoryAttributeInMtrrSettings and MtrrSetMemoryAttribute) may fail, but batch-set API may succeed.
Add comments to recommend caller to use batch-set API when setting multiple ranges.

Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Ruiyu Ni <ruiyu.ni@intel.com>
Cc: Ming Shao <ming.shao@intel.com>
---
 UefiCpuPkg/Include/Library/MtrrLib.h | 10 ++++++++++  UefiCpuPkg/Library/MtrrLib/MtrrLib.c | 10 ++++++++++
 2 files changed, 20 insertions(+)

diff --git a/UefiCpuPkg/Include/Library/MtrrLib.h b/UefiCpuPkg/Include/Library/MtrrLib.h
index d56f1057e1..f82c27ea0c 100644
--- a/UefiCpuPkg/Include/Library/MtrrLib.h
+++ b/UefiCpuPkg/Include/Library/MtrrLib.h
@@ -157,6 +157,11 @@ GetFirmwareVariableMtrrCount (
   @retval RETURN_OUT_OF_RESOURCES   There are not enough system resources to
                                     modify the attributes of the memory
                                     resource range.
+                                    Multiple memory range attributes setting by calling this API multiple
+                                    times may fail with status RETURN_OUT_OF_RESOURCES. It may not mean
+                                    the number of CPU MTRRs are too small to set such memory attributes.
+                                    Pass the multiple memory range attributes to one call of
+                                    MtrrSetMemoryAttributesInMtrrSettings() may succeed.
   @retval RETURN_BUFFER_TOO_SMALL   The fixed internal scratch buffer is too small for MTRR calculation.
                                     Caller should use MtrrSetMemoryAttributesInMtrrSettings() to specify
                                     external scratch buffer.
@@ -354,6 +359,11 @@ MtrrGetDefaultMemoryType (
                                     BaseAddress and Length cannot be modified.
   @retval RETURN_OUT_OF_RESOURCES   There are not enough system resources to modify the attributes of
                                     the memory resource range.
+                                    Multiple memory range attributes setting by calling this API multiple
+                                    times may fail with status RETURN_OUT_OF_RESOURCES. It may not mean
+                                    the number of CPU MTRRs are too small to set such memory attributes.
+                                    Pass the multiple memory range attributes to one call of
+                                    MtrrSetMemoryAttributesInMtrrSettings() may succeed.
   @retval RETURN_BUFFER_TOO_SMALL   The fixed internal scratch buffer is too small for MTRR calculation.
                                     Caller should use MtrrSetMemoryAttributesInMtrrSettings() to specify
                                     external scratch buffer.
diff --git a/UefiCpuPkg/Library/MtrrLib/MtrrLib.c b/UefiCpuPkg/Library/MtrrLib/MtrrLib.c
index 2496d08ad4..dfce9a996b 100644
--- a/UefiCpuPkg/Library/MtrrLib/MtrrLib.c
+++ b/UefiCpuPkg/Library/MtrrLib/MtrrLib.c
@@ -2513,6 +2513,11 @@ Exit:
                                     BaseAddress and Length cannot be modified.
   @retval RETURN_OUT_OF_RESOURCES   There are not enough system resources to modify the attributes of
                                     the memory resource range.
+                                    Multiple memory range attributes setting by calling this API multiple
+                                    times may fail with status RETURN_OUT_OF_RESOURCES. It may not mean
+                                    the number of CPU MTRRs are too small to set such memory attributes.
+                                    Pass the multiple memory range attributes to one call of
+                                    MtrrSetMemoryAttributesInMtrrSettings() may succeed.
   @retval RETURN_BUFFER_TOO_SMALL   The fixed internal scratch buffer is too small for MTRR calculation.
                                     Caller should use MtrrSetMemoryAttributesInMtrrSettings() to specify
                                     external scratch buffer.
@@ -2561,6 +2566,11 @@ MtrrSetMemoryAttributeInMtrrSettings (
   @retval RETURN_OUT_OF_RESOURCES   There are not enough system resources to
                                     modify the attributes of the memory
                                     resource range.
+                                    Multiple memory range attributes setting by calling this API multiple
+                                    times may fail with status RETURN_OUT_OF_RESOURCES. It may not mean
+                                    the number of CPU MTRRs are too small to set such memory attributes.
+                                    Pass the multiple memory range attributes to one call of
+                                    MtrrSetMemoryAttributesInMtrrSettings() may succeed.
   @retval RETURN_BUFFER_TOO_SMALL   The fixed internal scratch buffer is too small for MTRR calculation.
                                     Caller should use MtrrSetMemoryAttributesInMtrrSettings() to specify
                                     external scratch buffer.
--
2.15.1.windows.2