From: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Date: Thu, 21 Jun 2018 07:17:52 +0000 (+0200)
Subject: ArmPkg/ArmMmuLib ARM: assume page tables are in writeback cacheable memory
X-Git-Tag: edk2-stable201903~1558
X-Git-Url: https://git.proxmox.com/?p=mirror_edk2.git;a=commitdiff_plain;h=6e275c613e15ffc6dc79901fb244e8cb20af9948;hp=713aea34864ce5fc0a248b85bf3caa64fcf22467

ArmPkg/ArmMmuLib ARM: assume page tables are in writeback cacheable memory

Given that these days, our ARM port only supports ARMv7 and later, we
can assume that the page table walker's memory accesses are cache
coherent, and so there is no need to perform cache maintenance. It
does require the page tables themselves to reside in memory mapped as
writeback cacheable so ASSERT() that this is the case.

Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Leif Lindholm <leif.lindholm@linaro.org>
---

diff --git a/ArmPkg/Library/ArmLib/Arm/ArmLibSupport.S b/ArmPkg/Library/ArmLib/Arm/ArmLibSupport.S
index 149b57e059..f2a517671f 100644
--- a/ArmPkg/Library/ArmLib/Arm/ArmLibSupport.S
+++ b/ArmPkg/Library/ArmLib/Arm/ArmLibSupport.S
@@ -100,8 +100,6 @@ ASM_FUNC(ArmGetTTBR0BaseAddress)
 //  IN VOID  *MVA                    // R1
 //  );
 ASM_FUNC(ArmUpdateTranslationTableEntry)
-  mcr     p15,0,R0,c7,c14,1     @ DCCIMVAC Clean data cache by MVA
-  dsb
   mcr     p15,0,R1,c8,c7,1      @ TLBIMVA TLB Invalidate MVA
   mcr     p15,0,R9,c7,c5,6      @ BPIALL Invalidate Branch predictor array. R9 == NoOp
   dsb
diff --git a/ArmPkg/Library/ArmMmuLib/Arm/ArmMmuLibCore.c b/ArmPkg/Library/ArmMmuLib/Arm/ArmMmuLibCore.c
index 9eb6dd8d25..33dd2b173e 100644
--- a/ArmPkg/Library/ArmMmuLib/Arm/ArmMmuLibCore.c
+++ b/ArmPkg/Library/ArmMmuLib/Arm/ArmMmuLibCore.c
@@ -343,17 +343,12 @@ ArmConfigureMmu (
   }
 
   // Translate the Memory Attributes into Translation Table Register Attributes
-  if ((TranslationTableAttribute == ARM_MEMORY_REGION_ATTRIBUTE_UNCACHED_UNBUFFERED) ||
-      (TranslationTableAttribute == ARM_MEMORY_REGION_ATTRIBUTE_NONSECURE_UNCACHED_UNBUFFERED)) {
-    TTBRAttributes = ArmHasMpExtensions () ? TTBR_MP_NON_CACHEABLE : TTBR_NON_CACHEABLE;
-  } else if ((TranslationTableAttribute == ARM_MEMORY_REGION_ATTRIBUTE_WRITE_BACK) ||
+  if ((TranslationTableAttribute == ARM_MEMORY_REGION_ATTRIBUTE_WRITE_BACK) ||
       (TranslationTableAttribute == ARM_MEMORY_REGION_ATTRIBUTE_NONSECURE_WRITE_BACK)) {
     TTBRAttributes = ArmHasMpExtensions () ? TTBR_MP_WRITE_BACK_ALLOC : TTBR_WRITE_BACK_ALLOC;
-  } else if ((TranslationTableAttribute == ARM_MEMORY_REGION_ATTRIBUTE_WRITE_THROUGH) ||
-      (TranslationTableAttribute == ARM_MEMORY_REGION_ATTRIBUTE_NONSECURE_WRITE_THROUGH)) {
-    TTBRAttributes = ArmHasMpExtensions () ? TTBR_MP_WRITE_THROUGH : TTBR_WRITE_THROUGH;
   } else {
-    ASSERT (0); // No support has been found for the attributes of the memory region that the translation table belongs to.
+    // Page tables must reside in memory mapped as write-back cacheable
+    ASSERT (0);
     return RETURN_UNSUPPORTED;
   }
 
@@ -461,9 +456,6 @@ ConvertSectionToPages (
     PageTable[Index] = TT_DESCRIPTOR_PAGE_BASE_ADDRESS(BaseAddress + (Index << 12)) | PageDescriptor;
   }
 
-  // Flush d-cache so descriptors make it back to uncached memory for subsequent table walks
-  WriteBackInvalidateDataCacheRange ((VOID *)PageTable, TT_DESCRIPTOR_PAGE_SIZE);
-
   // Formulate page table entry, Domain=0, NS=0
   PageTableDescriptor = (((UINTN)PageTable) & TT_DESCRIPTOR_SECTION_PAGETABLE_ADDRESS_MASK) | TT_DESCRIPTOR_SECTION_TYPE_PAGE_TABLE;