[edk2-devel] [PATCH] UefiCpuPkg: add volatile qualifier to page table related variable

[Zhou Jianfeng <jianfeng.zhou@intel.com>]

Add volatile qualifier to page table related variable to prevent
compiler from optimizing away the variables which may lead to
unexpected result.

Signed-off-by: Zhou Jianfeng <jianfeng.zhou@intel.com>
Cc: Ray Ni <ray.ni@intel.com>
Cc: Laszlo Ersek <lersek@redhat.com>
Cc: Rahul Kumar <rahul1.kumar@intel.com>
Cc: Gerd Hoffmann <kraxel@redhat.com>
---
 UefiCpuPkg/Library/CpuPageTableLib/CpuPageTableMap.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/UefiCpuPkg/Library/CpuPageTableLib/CpuPageTableMap.c b/UefiCpuPkg/Library/CpuPageTableLib/CpuPageTableMap.c
index 2ea40666cc..5cf6e8fea0 100644
--- a/UefiCpuPkg/Library/CpuPageTableLib/CpuPageTableMap.c
+++ b/UefiCpuPkg/Library/CpuPageTableLib/CpuPageTableMap.c
@@ -26,7 +26,7 @@ PageTableLibSetPte4K (
   IN IA32_MAP_ATTRIBUTE      *Mask
   )
 {
-  IA32_PTE_4K  LocalPte4K;
+  volatile IA32_PTE_4K  LocalPte4K;

   LocalPte4K.Uint64 = Pte4K->Uint64;
   if (Mask->Bits.PageTableBaseAddressLow || Mask->Bits.PageTableBaseAddressHigh) {
@@ -78,7 +78,7 @@ PageTableLibSetPte4K (
   }

   if (Pte4K->Uint64 != LocalPte4K.Uint64) {
-    Pte4K->Uint64 = LocalPte4K.Uint64;
+    *(volatile UINT64 *)&(Pte4K->Uint64) = LocalPte4K.Uint64;
   }
 }

@@ -100,7 +100,7 @@ PageTableLibSetPleB (
   IN IA32_MAP_ATTRIBUTE                     *Mask
   )
 {
-  IA32_PAGE_LEAF_ENTRY_BIG_PAGESIZE  LocalPleB;
+  volatile IA32_PAGE_LEAF_ENTRY_BIG_PAGESIZE  LocalPleB;

   LocalPleB.Uint64 = PleB->Uint64;
   if (Mask->Bits.PageTableBaseAddressLow || Mask->Bits.PageTableBaseAddressHigh) {
@@ -154,7 +154,7 @@ PageTableLibSetPleB (
   }

   if (PleB->Uint64 != LocalPleB.Uint64) {
-    PleB->Uint64 = LocalPleB.Uint64;
+    *(volatile UINT64 *)&(PleB->Uint64) = LocalPleB.Uint64;
   }
 }

@@ -200,7 +200,7 @@ PageTableLibSetPnle (
   IN IA32_MAP_ATTRIBUTE            *Mask
   )
 {
-  IA32_PAGE_NON_LEAF_ENTRY  LocalPnle;
+  volatile IA32_PAGE_NON_LEAF_ENTRY  LocalPnle;

   LocalPnle.Uint64 = Pnle->Uint64;
   if (Mask->Bits.Present) {
@@ -231,7 +231,7 @@ PageTableLibSetPnle (
   LocalPnle.Bits.WriteThrough  = 0;
   LocalPnle.Bits.CacheDisabled = 0;
   if (Pnle->Uint64 != LocalPnle.Uint64) {
-    Pnle->Uint64 = LocalPnle.Uint64;
+    *(volatile UINT64 *)&(Pnle->Uint64) = LocalPnle.Uint64;
   }
 }

--
2.31.1.windows.1



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