[PATCH 11/11] ArmVirtPkg: remove PcdKludgeMapPciMmioAsCached

[Laszlo Ersek <lersek@redhat.com>]

In ARM/AARCH64 guests that run on KVM, we can now use virtio-gpu-pci, so
PcdKludgeMapPciMmioAsCached is no longer necessary. Standard VGA continues
to work on TCG without the kludge.

Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Ref: https://tianocore.acgmultimedia.com/show_bug.cgi?id=66
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
---
 ArmVirtPkg/ArmVirtPkg.dec                        | 24 --------------------
 ArmVirtPkg/ArmVirtQemu.dsc                       |  3 ---
 ArmVirtPkg/ArmVirtQemuKernel.dsc                 |  3 ---
 ArmVirtPkg/PciHostBridgeDxe/PciHostBridgeDxe.inf |  1 -
 ArmVirtPkg/PciHostBridgeDxe/PciHostBridge.c      |  3 +--
 5 files changed, 1 insertion(+), 33 deletions(-)

diff --git a/ArmVirtPkg/ArmVirtPkg.dec b/ArmVirtPkg/ArmVirtPkg.dec
index 9f98f28f01e1..a5ec42166445 100644
--- a/ArmVirtPkg/ArmVirtPkg.dec
+++ b/ArmVirtPkg/ArmVirtPkg.dec
@@ -58,36 +58,12 @@ [PcdsFixedAtBuild, PcdsPatchableInModule]
   # EFI_VT_100_GUID.
   #
   gArmVirtTokenSpaceGuid.PcdTerminalTypeGuidBuffer|{0x65, 0x60, 0xA6, 0xDF, 0x19, 0xB4, 0xD3, 0x11, 0x9A, 0x2D, 0x00, 0x90, 0x27, 0x3F, 0xC1, 0x4D}|VOID*|0x00000007
 
 [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.
-  #
-  gArmVirtTokenSpaceGuid.PcdKludgeMapPciMmioAsCached|FALSE|BOOLEAN|0x00000006
-
-  #
   # Pure ACPI boot
   #
   # Inhibit installation of the FDT as a configuration table if this feature
   # PCD is TRUE. Otherwise, the OS is presented with both a DT and an ACPI
   # description of the platform, and it is up to the OS to choose.
   #
diff --git a/ArmVirtPkg/ArmVirtQemu.dsc b/ArmVirtPkg/ArmVirtQemu.dsc
index 2eb2780a1fca..1d459756f61b 100644
--- a/ArmVirtPkg/ArmVirtQemu.dsc
+++ b/ArmVirtPkg/ArmVirtQemu.dsc
@@ -97,15 +97,12 @@ [PcdsFeatureFlag.common]
 
   ## If TRUE, Graphics Output Protocol will be installed on virtual handle created by ConsplitterDxe.
   #  It could be set FALSE to save size.
   gEfiMdeModulePkgTokenSpaceGuid.PcdConOutGopSupport|TRUE
   gEfiMdeModulePkgTokenSpaceGuid.PcdConOutUgaSupport|FALSE
 
-  # Activate KVM workaround for now.
-  gArmVirtTokenSpaceGuid.PcdKludgeMapPciMmioAsCached|TRUE
-
 !if $(PURE_ACPI_BOOT_ENABLE) == TRUE
   gArmVirtTokenSpaceGuid.PcdPureAcpiBoot|TRUE
 !endif
 
 [PcdsFixedAtBuild.common]
   gArmPlatformTokenSpaceGuid.PcdCoreCount|1
diff --git a/ArmVirtPkg/ArmVirtQemuKernel.dsc b/ArmVirtPkg/ArmVirtQemuKernel.dsc
index d9e62c78d28e..99d2feba202b 100644
--- a/ArmVirtPkg/ArmVirtQemuKernel.dsc
+++ b/ArmVirtPkg/ArmVirtQemuKernel.dsc
@@ -98,15 +98,12 @@ [PcdsFeatureFlag.common]
 
   ## If TRUE, Graphics Output Protocol will be installed on virtual handle created by ConsplitterDxe.
   #  It could be set FALSE to save size.
   gEfiMdeModulePkgTokenSpaceGuid.PcdConOutGopSupport|TRUE
   gEfiMdeModulePkgTokenSpaceGuid.PcdConOutUgaSupport|FALSE
 
-  # Activate KVM workaround for now.
-  gArmVirtTokenSpaceGuid.PcdKludgeMapPciMmioAsCached|TRUE
-
 [PcdsFixedAtBuild.common]
   gArmPlatformTokenSpaceGuid.PcdCoreCount|1
 !if $(ARCH) == AARCH64
   gArmTokenSpaceGuid.PcdVFPEnabled|1
 !endif
 
diff --git a/ArmVirtPkg/PciHostBridgeDxe/PciHostBridgeDxe.inf b/ArmVirtPkg/PciHostBridgeDxe/PciHostBridgeDxe.inf
index 41e134b24b0e..8c75eda3deb5 100644
--- a/ArmVirtPkg/PciHostBridgeDxe/PciHostBridgeDxe.inf
+++ b/ArmVirtPkg/PciHostBridgeDxe/PciHostBridgeDxe.inf
@@ -53,13 +53,12 @@ [Protocols]
   gFdtClientProtocolGuid                                ## CONSUMES
 
 [Pcd]
   gEfiMdePkgTokenSpaceGuid.PcdPciExpressBaseAddress
 
 [FeaturePcd]
-  gArmVirtTokenSpaceGuid.PcdKludgeMapPciMmioAsCached
   gArmVirtTokenSpaceGuid.PcdPureAcpiBoot
 
 [depex]
   gEfiMetronomeArchProtocolGuid AND
   gEfiCpuArchProtocolGuid AND
   gFdtClientProtocolGuid
diff --git a/ArmVirtPkg/PciHostBridgeDxe/PciHostBridge.c b/ArmVirtPkg/PciHostBridgeDxe/PciHostBridge.c
index 4b2b6a562a3f..5063782bb392 100644
--- a/ArmVirtPkg/PciHostBridgeDxe/PciHostBridge.c
+++ b/ArmVirtPkg/PciHostBridgeDxe/PciHostBridge.c
@@ -362,14 +362,13 @@ InitializePciHostBridge (
                   EfiGcdIoTypeIo,
                   IoBase,
                   IoSize
                   );
   ASSERT_EFI_ERROR (Status);
 
-  MmioAttributes = FeaturePcdGet (PcdKludgeMapPciMmioAsCached) ?
-                   EFI_MEMORY_WB : EFI_MEMORY_UC;
+  MmioAttributes = EFI_MEMORY_UC;
 
   Status = gDS->AddMemorySpace (
                   EfiGcdMemoryTypeMemoryMappedIo,
                   MmioBase,
                   MmioSize,
                   MmioAttributes
-- 
2.9.2