[PATCH 6/7] MdeModulePkg/PciHostBridgeDxe: restrict 64-bit DMA to devices that support it

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

Currently, the EFI_PCI_ATTRIBUTE_DUAL_ADDRESS_CYCLE attribute is completely
ignored by the PCI host bridge driver, which means that, on an implementation
that supports DMA above 4 GB, allocations above 4 GB may be provided to
devices that have not expressed support for it.

So in addition to checking 'RootBridge->DmaAbove4G' to establish whether the
root bridge itself supports DMA above 4 GB, we must also take into account
the operation type (EfiPciOperationBusMaster{Read|Write|CommBuffer}64),
and the EFI_PCI_ATTRIBUTE_DUAL_ADDRESS_CYCLE attribute, when mapping and
allocating DMA memory, respectively.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
---
 MdeModulePkg/Bus/Pci/PciHostBridgeDxe/PciRootBridgeIo.c | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/MdeModulePkg/Bus/Pci/PciHostBridgeDxe/PciRootBridgeIo.c b/MdeModulePkg/Bus/Pci/PciHostBridgeDxe/PciRootBridgeIo.c
index b2d76d67afa2..8af131b0af37 100644
--- a/MdeModulePkg/Bus/Pci/PciHostBridgeDxe/PciRootBridgeIo.c
+++ b/MdeModulePkg/Bus/Pci/PciHostBridgeDxe/PciRootBridgeIo.c
@@ -1073,10 +1073,15 @@ RootBridgeIoMap (
   RootBridge = ROOT_BRIDGE_FROM_THIS (This);
 
   PhysicalAddress = (EFI_PHYSICAL_ADDRESS) (UINTN) HostAddress;
-  if (!RootBridge->DmaAbove4G && ((PhysicalAddress + *NumberOfBytes) > SIZE_4GB)) {
+  if ((!RootBridge->DmaAbove4G ||
+       (Operation != EfiPciOperationBusMasterRead64 &&
+        Operation != EfiPciOperationBusMasterWrite64 &&
+        Operation != EfiPciOperationBusMasterCommonBuffer64)) &&
+      ((PhysicalAddress + *NumberOfBytes) > SIZE_4GB)) {
+
     //
-    // If the root bridge can not handle performing DMA above 4GB but
-    // any part of the DMA transfer being mapped is above 4GB, then
+    // If the root bridge or the device cannot handle performing DMA above
+    // 4GB but any part of the DMA transfer being mapped is above 4GB, then
     // map the DMA transfer to a buffer below 4GB.
     //
 
@@ -1308,7 +1313,8 @@ RootBridgeIoAllocateBuffer (
   RootBridge = ROOT_BRIDGE_FROM_THIS (This);
 
   AllocateType = AllocateAnyPages;
-  if (!RootBridge->DmaAbove4G) {
+  if (!RootBridge->DmaAbove4G ||
+      (Attributes & EFI_PCI_ATTRIBUTE_DUAL_ADDRESS_CYCLE) == 0) {
     //
     // Limit allocations to memory below 4GB
     //
-- 
2.7.4