UefiCpuPkg/MtrrLib: Don't report OutOfResource when MTRR is enough

The MTRR calculation algorithm contains a bug that when left
subtraction cannot produce better MTRR solution, it forgets
to restore the BaseAddress/Length so that MtrrLibGetMtrrNumber()
returns bigger value of actual required MTRR numbers.
As a result, the MtrrLib reports OutOfResource but actually the
MTRR is enough.

MEMORY_RANGE mC[] = {
  0, 0x100000, CacheUncacheable,
  0x100000, 0x89F00000, CacheWriteBack,
  0x8A000000, 0x75000000, CacheUncacheable,
  0xFF000000, 0x01000000, CacheWriteProtected,
  0x100000000, 0x7F00000000, CacheUncacheable,
  0xFC240000, 0x2000, CacheWriteCombining // <-- trigger the error
};

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Ruiyu Ni <ruiyu.ni@intel.com>
Reviewed-by: Jeff Fan <jeff.fan@intel.com>
(cherry picked from commit 3654c4623c9b37ddc64426995fa399d8626b7ced)

1 files changed, 9 insertions, 1 deletions

diff --git a/Core/UefiCpuPkg/Library/MtrrLib/MtrrLib.c b/Core/UefiCpuPkg/Library/MtrrLib/MtrrLib.c
index 9d1927262a..cf1af29936 100644
--- a/Core/UefiCpuPkg/Library/MtrrLib/MtrrLib.c
+++ b/Core/UefiCpuPkg/Library/MtrrLib/MtrrLib.c
@@ -851,6 +851,8 @@ MtrrLibGetMtrrNumber (
   UINT64  SubtractiveLength;

   UINT64  BaseAlignment;

   UINT32  Index;

+  UINT64  OriginalBaseAddress;

+  UINT64  OriginalLength;

 

   *SubLeft = 0;

   *SubRight = 0;

@@ -861,6 +863,9 @@ MtrrLibGetMtrrNumber (
   // Get the optimal left subtraction solution.

   //

   if (BaseAddress != 0) {

+

+    OriginalBaseAddress    = BaseAddress;

+    OriginalLength         = Length;

     SubtractiveBaseAddress = 0;

     SubtractiveLength      = 0;

     //

@@ -915,7 +920,10 @@ MtrrLibGetMtrrNumber (
     //

     if (*SubLeft != 0) {

       BaseAddress = SubtractiveBaseAddress;

-      Length = SubtractiveLength;

+      Length      = SubtractiveLength;

+    } else {

+      BaseAddress = OriginalBaseAddress;

+      Length      = OriginalLength;

     }

   }