[RFC PATCH 1/2] ArmVirtPkg/NorFlashQemuLib: disregard our primary FV

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

The primary FV contains the firmware boot image, which is not
runtime updatable in our case. So exposing it to the NOR flash
driver is undesirable, since it may attempt to modify the NOR
flash contents. It is also rather pointless, since we don't
keep anything there that we don't already expose via the FVB
protocol instances that DXE core creates for us based on the
FV HOBs (and so there is nothing the partition or file system
drivers could potentially attach to via the block I/O and disk
I/O protocol instances that the NOR flash driver creates)

So let's disregard the NOR flash block that covers the primary
FV.

Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
---
 ArmVirtPkg/Library/NorFlashQemuLib/NorFlashQemuLib.inf |  5 +++++
 ArmVirtPkg/Library/NorFlashQemuLib/NorFlashQemuLib.c   | 13 +++++++++++--
 2 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/ArmVirtPkg/Library/NorFlashQemuLib/NorFlashQemuLib.inf b/ArmVirtPkg/Library/NorFlashQemuLib/NorFlashQemuLib.inf
index d86ff36dbd58..c5752a243e6b 100644
--- a/ArmVirtPkg/Library/NorFlashQemuLib/NorFlashQemuLib.inf
+++ b/ArmVirtPkg/Library/NorFlashQemuLib/NorFlashQemuLib.inf
@@ -28,6 +28,7 @@ [Sources.common]
 [Packages]
   MdePkg/MdePkg.dec
   ArmPlatformPkg/ArmPlatformPkg.dec
+  ArmPkg/ArmPkg.dec
   ArmVirtPkg/ArmVirtPkg.dec
 
 [LibraryClasses]
@@ -40,3 +41,7 @@ [Protocols]
 
 [Depex]
   gFdtClientProtocolGuid
+
+[Pcd]
+  gArmTokenSpaceGuid.PcdFvBaseAddress
+  gArmTokenSpaceGuid.PcdFvSize
diff --git a/ArmVirtPkg/Library/NorFlashQemuLib/NorFlashQemuLib.c b/ArmVirtPkg/Library/NorFlashQemuLib/NorFlashQemuLib.c
index 2678f57eaaad..72b47bdb5a78 100644
--- a/ArmVirtPkg/Library/NorFlashQemuLib/NorFlashQemuLib.c
+++ b/ArmVirtPkg/Library/NorFlashQemuLib/NorFlashQemuLib.c
@@ -75,13 +75,22 @@ NorFlashPlatformGetDevices (
       Size = SwapBytes64 (ReadUnaligned64 ((VOID *)&Reg[2]));
       Reg += 4;
 
+      PropSize -= 4 * sizeof (UINT32);
+
+      //
+      // Disregard any flash devices that overlap with the primary FV.
+      // The firmware is not updatable from inside the guest anyway.
+      //
+      if ((PcdGet64 (PcdFvBaseAddress) + PcdGet32 (PcdFvSize) >= Base) &&
+          (Base + Size) >= PcdGet64 (PcdFvBaseAddress)) {
+        continue;
+      }
+
       mNorFlashDevices[Num].DeviceBaseAddress = (UINTN)Base;
       mNorFlashDevices[Num].RegionBaseAddress = (UINTN)Base;
       mNorFlashDevices[Num].Size              = (UINTN)Size;
       mNorFlashDevices[Num].BlockSize         = QEMU_NOR_BLOCK_SIZE;
       Num++;
-
-      PropSize -= 4 * sizeof (UINT32);
     }
   }
 
-- 
2.19.1