[edk2-devel] [PATCH v2] ArmPkg/ArmMmuLib AARCH64: invalidate page tables before populating them

[Ard Biesheuvel]

As it turns out, ARMv8 also permits accesses made with the MMU and
caches off to hit in the caches, so to ensure that any modifications
we make before enabling the MMU are visible afterwards as well, we
should invalidate page tables right after allocation like we do now on
ARM, if the MMU is still disabled at that point.

Also, make sure that we don't only invalidate block and page entries
when updating the individual entries, but give table entries the same
treatment.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel at linaro.org>
---
v2:
- drop redundant MMU enabled check when allocating the root table
- add dmb+ivac for individual table entries (the change that was merged
  already only does this on block/page entries)

 ArmPkg/Library/ArmMmuLib/AArch64/ArmMmuLibCore.c | 30 ++++++++++++++++++++
 1 file changed, 30 insertions(+)

diff --git a/ArmPkg/Library/ArmMmuLib/AArch64/ArmMmuLibCore.c b/ArmPkg/Library/ArmMmuLib/AArch64/ArmMmuLibCore.c
index 204e33c75f95..d4d823780a6a 100644
--- a/ArmPkg/Library/ArmMmuLib/AArch64/ArmMmuLibCore.c
+++ b/ArmPkg/Library/ArmMmuLib/AArch64/ArmMmuLibCore.c
@@ -129,6 +129,8 @@ ReplaceLiveEntry (
 {
   if (!ArmMmuEnabled ()) {
     *Entry = Value;
+    ArmDataMemoryBarrier ();
+    ArmInvalidateDataCacheEntryByMVA ((UINTN)Entry);
   } else {
     ArmReplaceLiveTranslationEntry (Entry, Value, RegionStart);
   }
@@ -282,6 +284,15 @@ GetBlockEntryListFromAddress (
           return NULL;
         }
 
+        if (!ArmMmuEnabled ()) {
+          //
+          // Make sure we are not inadvertently hitting in the caches
+          // when populating the page tables.
+          //
+          InvalidateDataCacheRange (TranslationTable,
+            TT_ENTRY_COUNT * sizeof(UINT64));
+        }
+
         // Populate the newly created lower level table
         SubTableBlockEntry = TranslationTable;
         for (Index = 0; Index < TT_ENTRY_COUNT; Index++) {
@@ -306,10 +317,23 @@ GetBlockEntryListFromAddress (
           return NULL;
         }
 
+        if (!ArmMmuEnabled ()) {
+          //
+          // Make sure we are not inadvertently hitting in the caches
+          // when populating the page tables.
+          //
+          InvalidateDataCacheRange (TranslationTable,
+            TT_ENTRY_COUNT * sizeof(UINT64));
+        }
         ZeroMem (TranslationTable, TT_ENTRY_COUNT * sizeof(UINT64));
 
         // Fill the new BlockEntry with the TranslationTable
         *BlockEntry = ((UINTN)TranslationTable & TT_ADDRESS_MASK_DESCRIPTION_TABLE) | TT_TYPE_TABLE_ENTRY;
+
+        if (!ArmMmuEnabled ()) {
+          ArmDataMemoryBarrier ();
+          ArmInvalidateDataCacheEntryByMVA ((UINTN)BlockEntry);
+        }
       }
     }
   }
@@ -697,6 +721,12 @@ ArmConfigureMmu (
     *TranslationTableSize = RootTableEntryCount * sizeof(UINT64);
   }
 
+  //
+  // Make sure we are not inadvertently hitting in the caches
+  // when populating the page tables.
+  //
+  InvalidateDataCacheRange (TranslationTable,
+    RootTableEntryCount * sizeof(UINT64));
   ZeroMem (TranslationTable, RootTableEntryCount * sizeof(UINT64));
 
   TranslationTableAttribute = TT_ATTR_INDX_INVALID;
-- 
2.17.1


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