[PATCH] UefiCpuPkg/MtrrLib: Fix MtrrDebugPrintAllMtrrsWorker to avoid hang

[Ruiyu Ni <ruiyu.ni@intel.com>]

ARRAY_SIZE(Mtrrs->Variables.Mtrr) was used in
MtrrDebugPrintAllMtrrsWorker() to parse the MTRR registers.
Instead, the actual variable MTRR count should be used.
Otherwise, the uninitialized random data in MtrrSetting may cause
MtrrLibSetMemoryType() hang.

Steven Shi found this bug in QEMU when using Q35 chip.

Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Ruiyu Ni <ruiyu.ni@intel.com>
Cc: Steven Shi <steven.shi@intel.com>
Cc: Laszlo Ersek <lersek@redhat.com>
---
 UefiCpuPkg/Library/MtrrLib/MtrrLib.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/UefiCpuPkg/Library/MtrrLib/MtrrLib.c b/UefiCpuPkg/Library/MtrrLib/MtrrLib.c
index 2fd1d0153e..cb22558103 100644
--- a/UefiCpuPkg/Library/MtrrLib/MtrrLib.c
+++ b/UefiCpuPkg/Library/MtrrLib/MtrrLib.c
@@ -2776,6 +2776,7 @@ MtrrDebugPrintAllMtrrsWorker (
     UINTN             RangeCount;
     UINT64            MtrrValidBitsMask;
     UINT64            MtrrValidAddressMask;
+    UINT32            VariableMtrrCount;
     MTRR_MEMORY_RANGE Ranges[
       ARRAY_SIZE (mMtrrLibFixedMtrrTable) * sizeof (UINT64) + 2 * ARRAY_SIZE (Mtrrs->Variables.Mtrr) + 1
       ];
@@ -2785,6 +2786,8 @@ MtrrDebugPrintAllMtrrsWorker (
       return;
     }
 
+    VariableMtrrCount = GetVariableMtrrCountWorker ();
+
     if (MtrrSetting != NULL) {
       Mtrrs = MtrrSetting;
     } else {
@@ -2802,7 +2805,7 @@ MtrrDebugPrintAllMtrrsWorker (
       DEBUG((DEBUG_CACHE, "Fixed MTRR[%02d]   : %016lx\n", Index, Mtrrs->Fixed.Mtrr[Index]));
     }
 
-    for (Index = 0; Index < ARRAY_SIZE (Mtrrs->Variables.Mtrr); Index++) {
+    for (Index = 0; Index < VariableMtrrCount; Index++) {
       if (((MSR_IA32_MTRR_PHYSMASK_REGISTER *)&Mtrrs->Variables.Mtrr[Index].Mask)->Bits.V == 0) {
         //
         // If mask is not valid, then do not display range
@@ -2829,11 +2832,11 @@ MtrrDebugPrintAllMtrrsWorker (
     RangeCount = 1;
 
     MtrrLibGetRawVariableRanges (
-      &Mtrrs->Variables, ARRAY_SIZE (Mtrrs->Variables.Mtrr),
+      &Mtrrs->Variables, VariableMtrrCount,
       MtrrValidBitsMask, MtrrValidAddressMask, RawVariableRanges
       );
     MtrrLibApplyVariableMtrrs (
-      RawVariableRanges, ARRAY_SIZE (RawVariableRanges),
+      RawVariableRanges, VariableMtrrCount,
       Ranges, ARRAY_SIZE (Ranges), &RangeCount
       );
 
-- 
2.12.2.windows.2