diff --git a/ArmPlatformPkg/ArmVirtualizationPkg/ArmVirtualizationPkg.dec b/ArmPlatformPkg/ArmVirtualizationPkg/ArmVirtualizationPkg.dec
index 99411548af..d53dab9f65 100644
--- a/ArmPlatformPkg/ArmVirtualizationPkg/ArmVirtualizationPkg.dec
+++ b/ArmPlatformPkg/ArmVirtualizationPkg/ArmVirtualizationPkg.dec
@@ -56,3 +56,28 @@
 
   gArmVirtualizationTokenSpaceGuid.PcdFwCfgSelectorAddress|0x0|UINT64|0x00000004
   gArmVirtualizationTokenSpaceGuid.PcdFwCfgDataAddress|0x0|UINT64|0x00000005
+
+[PcdsFeatureFlag]
+  #
+  # "Map PCI MMIO as Cached"
+  #
+  # Due to the way Stage1 and Stage2 mappings are combined on Aarch64, and
+  # because KVM -- for the time being -- does not try to interfere with the
+  # Stage1 mappings, we must not set EFI_MEMORY_UC for emulated PCI MMIO
+  # regions.
+  #
+  # EFI_MEMORY_UC is mapped to Device-nGnRnE, and that Stage1 attribute would
+  # direct guest writes to host DRAM immediately, bypassing the cache
+  # regardless of Stage2 attributes. However, QEMU's reads of the same range
+  # can easily be served from the (stale) CPU cache.
+  #
+  # Setting this PCD to TRUE will use EFI_MEMORY_WB for mapping PCI MMIO
+  # regions, which ensures that guest writes to such regions go through the CPU
+  # cache. Strictly speaking this is wrong, but it is needed as a temporary
+  # workaround for emulated PCI devices. Setting the PCD to FALSE results in
+  # the theoretically correct EFI_MEMORY_UC mapping, and should be the long
+  # term choice, especially with assigned devices.
+  #
+  # The default is to turn off the kludge; DSC's can selectively enable it.
+  #
+  gArmVirtualizationTokenSpaceGuid.PcdKludgeMapPciMmioAsCached|FALSE|BOOLEAN|0x00000006
diff --git a/ArmPlatformPkg/ArmVirtualizationPkg/ArmVirtualizationQemu.dsc b/ArmPlatformPkg/ArmVirtualizationPkg/ArmVirtualizationQemu.dsc
index 19776100a5..66fe9798c6 100644
--- a/ArmPlatformPkg/ArmVirtualizationPkg/ArmVirtualizationQemu.dsc
+++ b/ArmPlatformPkg/ArmVirtualizationPkg/ArmVirtualizationQemu.dsc
@@ -86,6 +86,9 @@
   #  It could be set FALSE to save size.
   gEfiMdeModulePkgTokenSpaceGuid.PcdConOutGopSupport|FALSE
 
+  # Activate KVM workaround for now.
+  gArmVirtualizationTokenSpaceGuid.PcdKludgeMapPciMmioAsCached|TRUE
+
 [PcdsFixedAtBuild.common]
   gEfiMdePkgTokenSpaceGuid.PcdDebugPrintErrorLevel|0x8000004F
 
diff --git a/ArmPlatformPkg/ArmVirtualizationPkg/PciHostBridgeDxe/PciHostBridge.c b/ArmPlatformPkg/ArmVirtualizationPkg/PciHostBridgeDxe/PciHostBridge.c
index 452465afa8..17d4db85be 100644
--- a/ArmPlatformPkg/ArmVirtualizationPkg/PciHostBridgeDxe/PciHostBridge.c
+++ b/ArmPlatformPkg/ArmVirtualizationPkg/PciHostBridgeDxe/PciHostBridge.c
@@ -97,6 +97,7 @@ InitializePciHostBridge (
   IN EFI_SYSTEM_TABLE  *SystemTable
   )
 {
+  UINT64                      MmioAttributes;
   EFI_STATUS                  Status;
   UINTN                       Loop1;
   UINTN                       Loop2;
@@ -133,17 +134,31 @@ InitializePciHostBridge (
                   );
   ASSERT_EFI_ERROR (Status);
 
+  MmioAttributes = FeaturePcdGet (PcdKludgeMapPciMmioAsCached) ?
+                   EFI_MEMORY_WB : EFI_MEMORY_UC;
+
   Status = gDS->AddMemorySpace (
                   EfiGcdMemoryTypeMemoryMappedIo,
                   PcdGet32 (PcdPciMmio32Base),
                   PcdGet32 (PcdPciMmio32Size),
-                  EFI_MEMORY_UC
+                  MmioAttributes
                   );
   if (EFI_ERROR (Status)) {
     DEBUG ((EFI_D_ERROR, "%a: AddMemorySpace: %r\n", __FUNCTION__, Status));
     return Status;
   }
 
+  Status = gDS->SetMemorySpaceAttributes (
+                  PcdGet32 (PcdPciMmio32Base),
+                  PcdGet32 (PcdPciMmio32Size),
+                  MmioAttributes
+                  );
+  if (EFI_ERROR (Status)) {
+    DEBUG ((EFI_D_ERROR, "%a: SetMemorySpaceAttributes: %r\n", __FUNCTION__,
+      Status));
+    return Status;
+  }
+
   //
   // Create Host Bridge Device Handle
   //
diff --git a/ArmPlatformPkg/ArmVirtualizationPkg/PciHostBridgeDxe/PciHostBridgeDxe.inf b/ArmPlatformPkg/ArmVirtualizationPkg/PciHostBridgeDxe/PciHostBridgeDxe.inf
index 5497fa61d2..ecea088272 100644
--- a/ArmPlatformPkg/ArmVirtualizationPkg/PciHostBridgeDxe/PciHostBridgeDxe.inf
+++ b/ArmPlatformPkg/ArmVirtualizationPkg/PciHostBridgeDxe/PciHostBridgeDxe.inf
@@ -24,6 +24,7 @@
 [Packages]
   MdePkg/MdePkg.dec
   ArmPlatformPkg/ArmPlatformPkg.dec
+  ArmPlatformPkg/ArmVirtualizationPkg/ArmVirtualizationPkg.dec
 
 [LibraryClasses]
   UefiDriverEntryPoint
@@ -60,5 +61,9 @@
   gArmPlatformTokenSpaceGuid.PcdPciMmio32Size
   gEfiMdePkgTokenSpaceGuid.PcdPciExpressBaseAddress
 
+[FeaturePcd]
+  gArmVirtualizationTokenSpaceGuid.PcdKludgeMapPciMmioAsCached
+
 [depex]
-  gEfiMetronomeArchProtocolGuid
+  gEfiMetronomeArchProtocolGuid AND
+  gEfiCpuArchProtocolGuid