[PATCH v2 2/2] ArmVirtPkg/QemuVirtMemInfoLib: remove 1:1 mapping of top of PA range

[Ard Biesheuvel <ard.biesheuvel@linaro.org>]

Currently, we map DRAM as EFI_MEMORY_WB, and the remainder of the
entire virtual address space is mapped with EFI_MEMORY_UC attributes,
regardless of whether any devices actually reside there.

Now that we are relaxing the address space limit to more than 40 bits,
mapping all that address space actually takes up more space in page
tables than we have so far made available as temporary RAM. So let's
get rid of the mapping rather than increasing the available RAM, given
that the mapping is not particularly useful anyway.

Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
---
 ArmVirtPkg/Library/QemuVirtMemInfoLib/QemuVirtMemInfoLib.c | 17 +++++------------
 1 file changed, 5 insertions(+), 12 deletions(-)

diff --git a/ArmVirtPkg/Library/QemuVirtMemInfoLib/QemuVirtMemInfoLib.c b/ArmVirtPkg/Library/QemuVirtMemInfoLib/QemuVirtMemInfoLib.c
index 815ca145b644..70863abb2e7b 100644
--- a/ArmVirtPkg/Library/QemuVirtMemInfoLib/QemuVirtMemInfoLib.c
+++ b/ArmVirtPkg/Library/QemuVirtMemInfoLib/QemuVirtMemInfoLib.c
@@ -73,21 +73,14 @@ ArmVirtGetMemoryMap (
   VirtualMemoryTable[1].Length       = VirtualMemoryTable[0].PhysicalBase;
   VirtualMemoryTable[1].Attributes   = ARM_MEMORY_REGION_ATTRIBUTE_DEVICE;
 
-  // Peripheral space after DRAM
-  VirtualMemoryTable[2].PhysicalBase = VirtualMemoryTable[0].Length + VirtualMemoryTable[1].Length;
-  VirtualMemoryTable[2].VirtualBase  = VirtualMemoryTable[2].PhysicalBase;
-  VirtualMemoryTable[2].Length       = TopOfAddressSpace -
-                                       VirtualMemoryTable[2].PhysicalBase;
-  VirtualMemoryTable[2].Attributes   = ARM_MEMORY_REGION_ATTRIBUTE_DEVICE;
-
   // Remap the FD region as normal executable memory
-  VirtualMemoryTable[3].PhysicalBase = PcdGet64 (PcdFdBaseAddress);
-  VirtualMemoryTable[3].VirtualBase  = VirtualMemoryTable[3].PhysicalBase;
-  VirtualMemoryTable[3].Length       = FixedPcdGet32 (PcdFdSize);
-  VirtualMemoryTable[3].Attributes   = ARM_MEMORY_REGION_ATTRIBUTE_WRITE_BACK;
+  VirtualMemoryTable[2].PhysicalBase = PcdGet64 (PcdFdBaseAddress);
+  VirtualMemoryTable[2].VirtualBase  = VirtualMemoryTable[2].PhysicalBase;
+  VirtualMemoryTable[2].Length       = FixedPcdGet32 (PcdFdSize);
+  VirtualMemoryTable[2].Attributes   = ARM_MEMORY_REGION_ATTRIBUTE_WRITE_BACK;
 
   // End of Table
-  ZeroMem (&VirtualMemoryTable[4], sizeof (ARM_MEMORY_REGION_DESCRIPTOR));
+  ZeroMem (&VirtualMemoryTable[3], sizeof (ARM_MEMORY_REGION_DESCRIPTOR));
 
   *VirtualMemoryMap = VirtualMemoryTable;
 }
-- 
2.19.1