Re: [PATCH] UefiCpuPkg/CpuDxe: Fix assert issue on IA32 platform

["Zeng, Star" <star.zeng@intel.com>]

Reviewed-by: Star Zeng <star.zeng@intel.com>

Thanks,
Star
-----Original Message-----
From: edk2-devel [mailto:edk2-devel-bounces@lists.01.org] On Behalf Of Jian J Wang
Sent: Friday, September 29, 2017 1:40 PM
To: edk2-devel@lists.01.org
Cc: Kinney, Michael D <michael.d.kinney@intel.com>; Yao, Jiewen <jiewen.yao@intel.com>
Subject: [edk2] [PATCH] UefiCpuPkg/CpuDxe: Fix assert issue on IA32 platform

This patch is to fix an assert issue during booting IA32 platforms such as OvmfIa32 or Quark. This issue is caused by trying to access page table on a platform without page table. A check is added to avoid the assert.

Bug tracker: https://bugzilla.tianocore.org/show_bug.cgi?id=724

c: Star Zeng <star.zeng@intel.com>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Michael Kinney <michael.d.kinney@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Jian J Wang <jian.j.wang@intel.com>
---
 UefiCpuPkg/CpuDxe/CpuDxe.c | 48 ++++++++++++++++++++++++++++++++++++----------
 1 file changed, 38 insertions(+), 10 deletions(-)

diff --git a/UefiCpuPkg/CpuDxe/CpuDxe.c b/UefiCpuPkg/CpuDxe/CpuDxe.c index 4e8fa100e0..85a520079f 100644
--- a/UefiCpuPkg/CpuDxe/CpuDxe.c
+++ b/UefiCpuPkg/CpuDxe/CpuDxe.c
@@ -683,7 +683,7 @@ SetGcdMemorySpaceAttributes (
 
 **/
 VOID
-RefreshGcdMemoryAttributes (
+RefreshMemoryAttributesFromMtrr (
   VOID
   )
 {
@@ -704,14 +704,9 @@ RefreshGcdMemoryAttributes (
   UINT32                              FirmwareVariableMtrrCount;
   UINT8                               DefaultMemoryType;
 
-  if (!IsMtrrSupported ()) {
-    return;
-  }
-
   FirmwareVariableMtrrCount = GetFirmwareVariableMtrrCount ();
   ASSERT (FirmwareVariableMtrrCount <= MTRR_NUMBER_OF_VARIABLE_MTRR);
 
-  mIsFlushingGCD = TRUE;
   MemorySpaceMap = NULL;
 
   //
@@ -862,11 +857,44 @@ RefreshGcdMemoryAttributes (
   if (MemorySpaceMap != NULL) {
     FreePool (MemorySpaceMap);
   }
+}
 
-  //
-  // Update page attributes
-  //
-  RefreshGcdMemoryAttributesFromPaging();
+/**
+ Check if paging is enabled or not.
+**/
+BOOLEAN
+IsPagingSupported (
+  VOID
+  )
+{
+  return (
+          (AsmReadCr0 () & BIT31) != 0
+          &&
+          (AsmReadCr4 () & BIT5) != 0
+         );
+}
+
+/**
+  Refreshes the GCD Memory Space attributes according to MTRRs and Paging.
+
+  This function refreshes the GCD Memory Space attributes according to 
+ MTRRs  and page tables.
+
+**/
+VOID
+RefreshGcdMemoryAttributes (
+  VOID
+  )
+{
+  mIsFlushingGCD = TRUE;
+
+  if (IsMtrrSupported ()) {
+    RefreshMemoryAttributesFromMtrr ();  }
+
+  if (IsPagingSupported ()) {
+    RefreshGcdMemoryAttributesFromPaging ();  }
 
   mIsFlushingGCD = FALSE;
 }
--
2.14.1.windows.1

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