ArmVirtPkg: remove PcdKludgeMapPciMmioAsCached

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>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>

5 files changed, 1 insertions, 33 deletions

diff --git a/ArmVirtPkg/ArmVirtPkg.dec b/ArmVirtPkg/ArmVirtPkg.dec
index 9f98f28f01..a5ec421664 100644
--- a/ArmVirtPkg/ArmVirtPkg.dec
+++ b/ArmVirtPkg/ArmVirtPkg.dec
@@ -61,30 +61,6 @@
 

 [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

diff --git a/ArmVirtPkg/ArmVirtQemu.dsc b/ArmVirtPkg/ArmVirtQemu.dsc
index 2d2c653c9e..f8b6140262 100644
--- a/ArmVirtPkg/ArmVirtQemu.dsc
+++ b/ArmVirtPkg/ArmVirtQemu.dsc
@@ -100,9 +100,6 @@
   gEfiMdeModulePkgTokenSpaceGuid.PcdConOutGopSupport|TRUE

   gEfiMdeModulePkgTokenSpaceGuid.PcdConOutUgaSupport|FALSE

 

-  # Activate KVM workaround for now.

-  gArmVirtTokenSpaceGuid.PcdKludgeMapPciMmioAsCached|TRUE

-

 !if $(PURE_ACPI_BOOT_ENABLE) == TRUE

   gArmVirtTokenSpaceGuid.PcdPureAcpiBoot|TRUE

 !endif

diff --git a/ArmVirtPkg/ArmVirtQemuKernel.dsc b/ArmVirtPkg/ArmVirtQemuKernel.dsc
index ba262ac919..ea722ddf8e 100644
--- a/ArmVirtPkg/ArmVirtQemuKernel.dsc
+++ b/ArmVirtPkg/ArmVirtQemuKernel.dsc
@@ -101,9 +101,6 @@
   gEfiMdeModulePkgTokenSpaceGuid.PcdConOutGopSupport|TRUE

   gEfiMdeModulePkgTokenSpaceGuid.PcdConOutUgaSupport|FALSE

 

-  # Activate KVM workaround for now.

-  gArmVirtTokenSpaceGuid.PcdKludgeMapPciMmioAsCached|TRUE

-

 [PcdsFixedAtBuild.common]

   gArmPlatformTokenSpaceGuid.PcdCoreCount|1

 !if $(ARCH) == AARCH64

diff --git a/ArmVirtPkg/PciHostBridgeDxe/PciHostBridge.c b/ArmVirtPkg/PciHostBridgeDxe/PciHostBridge.c
index 4b2b6a562a..5063782bb3 100644
--- a/ArmVirtPkg/PciHostBridgeDxe/PciHostBridge.c
+++ b/ArmVirtPkg/PciHostBridgeDxe/PciHostBridge.c
@@ -365,8 +365,7 @@ InitializePciHostBridge (
                   );

   ASSERT_EFI_ERROR (Status);

 

-  MmioAttributes = FeaturePcdGet (PcdKludgeMapPciMmioAsCached) ?

-                   EFI_MEMORY_WB : EFI_MEMORY_UC;

+  MmioAttributes = EFI_MEMORY_UC;

 

   Status = gDS->AddMemorySpace (

                   EfiGcdMemoryTypeMemoryMappedIo,

diff --git a/ArmVirtPkg/PciHostBridgeDxe/PciHostBridgeDxe.inf b/ArmVirtPkg/PciHostBridgeDxe/PciHostBridgeDxe.inf
index 41e134b24b..8c75eda3de 100644
--- a/ArmVirtPkg/PciHostBridgeDxe/PciHostBridgeDxe.inf
+++ b/ArmVirtPkg/PciHostBridgeDxe/PciHostBridgeDxe.inf
@@ -56,7 +56,6 @@
   gEfiMdePkgTokenSpaceGuid.PcdPciExpressBaseAddress

 

 [FeaturePcd]

-  gArmVirtTokenSpaceGuid.PcdKludgeMapPciMmioAsCached

   gArmVirtTokenSpaceGuid.PcdPureAcpiBoot

 

 [depex]