Re: [RFC v3 1/3] MdeModulePkg/PciHostBridgeDxe: Add support for address translation

[Guo Heyi <heyi.guo@linaro.org>]

On Sat, Feb 24, 2018 at 04:30:42PM +0800, Ni, Ruiyu wrote:
> On 2/24/2018 11:59 AM, Guo Heyi wrote:
> >On Sat, Feb 24, 2018 at 11:11:35AM +0800, Ni, Ruiyu wrote:
> >>On 2/24/2018 9:51 AM, Guo Heyi wrote:
> >>>On Fri, Feb 23, 2018 at 04:05:17PM +0100, Laszlo Ersek wrote:
> >>>>Thanks for writing up the details!
> >>>>
> >>>>Comments:
> >>>>
> >>>>On 02/23/18 09:53, Heyi Guo wrote:
> >>>>>PCI address translation is necessary for some non-x86 platforms. On
> >>>>>such platforms, address value (denoted as "device address" or "address
> >>>>>in PCI view") set to PCI BAR registers in configuration space might be
> >>>>>different from the address which is used by CPU to access the
> >>>>>registers in memory BAR or IO BAR spaces (denoted as "host address" or
> >>>>>"address in CPU view"). The difference between the two addresses is
> >>>>>called "Address Translation Offset" or simply "translation", and can
> >>>>>be represented by "Address Translation Offset" in ACPI QWORD Address
> >>>>>Space Descriptor (Offset 0x1E). However UEFI and ACPI differs on the
> >>>>>definitions of QWORD Address Space Descriptor, and we will follow UEFI
> >>>>>definition on UEFI protocols, such as PCI root bridge IO protocol and
> >>>>>PCI IO protocol. In UEFI 2.7, "Address Translation Offset" is "Offset
> >>>>>to apply to the Starting address to convert it to a PCI address". This
> >>>>>means:
> >>>>>
> >>>>>1. Translation = device address - host address.
> >>>>
> >>>>OK, this looks like a sensible choice to me. It means that the "apply"
> >>>>term used in the UEFI spec means "add", which (I think) is the "natural"
> >>>>interpretation.
> >>>>
> >>>>>2. PciRootBridgeIo->Configuration should return CPU view address, as
> >>>>>well as PciIo->GetBarAttributes.
> >>>>
> >>>>OK.
> >>>>
> >>>>>
> >>>>>Summary of addresses used:
> >>>>>
> >>>>>1. Base and Limit in PCI_ROOT_BRIDGE_APERTURE are device address, for
> >>>>>it is easy to check whether the address is below 4G or above 4G.
> >>>>
> >>>>I agree that PciHostBridgeLib instances that do not set a nonzero
> >>>>Translation need not care about the difference.
> >>>>
> >>>>(1) Still, can you confirm this is a "natural" choice? Were the
> >>>>DmaAbove4G, MemAbove4G and PMemAbove4G fields originally introduced with
> >>>>the device (PCI) view in mind?
> >>>>
> >>>>... I also meant to raise a concern about the InitializePciHostBridge()
> >>>>function where we call AddIoSpace() and AddMemoryMappedIoSpace() --
> >>>>which end up manipulating GCD -- with data from
> >>>>PCI_ROOT_BRIDGE_APERTURE. I can see you modify those call sites in the
> >>>>patch, so that's good. (I do have more comments on the actual
> >>>>implementation.)
> >>DmaAbove4G in PCI_ROOT_BRIDGE_APERTURE indicates the capability of
> >>the root bridge HW, whether it's capable to do DMA on device address
> >>above 4GB.
> >>
> >>>>
> >>>>>
> >>>>>2. Address returned by
> >>>>>EFI_PCI_HOST_BRIDGE_RESOURCE_ALLOCATION_PROTOCOL::GetProposedResources
> >>>>>is device address, or else PCI bus driver cannot set correct address
> >>>>>into PCI BAR registers.
> >>>>>
> >>>>>3. Address returned by PciRootBridgeIo->Configuration is host address
> >>>>>per UEFI 2.7 definition.
> >>>>>
> >>>>>4. Addresses used in GCD manipulation are host address.
> >>>>>
> >>>>>5. Addresses in ResAllocNode of PCI_ROOT_BRIDGE_INSTANCE are host
> >>>>>address, for they are allocated from GCD.
> >>>>>
> >>>>>6. Address passed to PciHostBridgeResourceConflict is host address,
> >>>>>for it comes from ResAllocNode.
> >>>>>
> >>>>>Contributed-under: TianoCore Contribution Agreement 1.1
> >>>>>Signed-off-by: Heyi Guo <heyi.guo@linaro.org>
> >>>>>Cc: Ruiyu Ni <ruiyu.ni@intel.com>
> >>>>>Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> >>>>>Cc: Star Zeng <star.zeng@intel.com>
> >>>>>Cc: Eric Dong <eric.dong@intel.com>
> >>>>>Cc: Laszlo Ersek <lersek@redhat.com>
> >>>>>Cc: Michael D Kinney <michael.d.kinney@intel.com>
> >>>>>---
> >>>>>  .../Bus/Pci/PciHostBridgeDxe/PciHostBridge.c       |  74 +++++++++++---
> >>>>>  .../Bus/Pci/PciHostBridgeDxe/PciHostResource.h     |   2 +
> >>>>>  .../Bus/Pci/PciHostBridgeDxe/PciRootBridgeIo.c     | 112 ++++++++++++++++++---
> >>>>>  MdeModulePkg/Include/Library/PciHostBridgeLib.h    |   8 ++
> >>>>>  4 files changed, 167 insertions(+), 29 deletions(-)
> >>>>>
> >>>>>diff --git a/MdeModulePkg/Bus/Pci/PciHostBridgeDxe/PciHostBridge.c b/MdeModulePkg/Bus/Pci/PciHostBridgeDxe/PciHostBridge.c
> >>>>>index 1494848..e8979eb 100644
> >>>>>--- a/MdeModulePkg/Bus/Pci/PciHostBridgeDxe/PciHostBridge.c
> >>>>>+++ b/MdeModulePkg/Bus/Pci/PciHostBridgeDxe/PciHostBridge.c
> >>>>>@@ -32,6 +32,29 @@ EDKII_IOMMU_PROTOCOL        *mIoMmuProtocol;
> >>>>>  EFI_EVENT                   mIoMmuEvent;
> >>>>>  VOID                        *mIoMmuRegistration;
> >>>>>
> >>>>>+STATIC
> >>>>>+UINT64
> >>>>>+GetTranslationByResourceType (
> >>>>>+  IN  PCI_ROOT_BRIDGE_INSTANCE     *RootBridge,
> >>>>>+  IN  PCI_RESOURCE_TYPE            ResourceType
> >>>>>+  )
> >>>>>+{
> >>>>>+  switch (ResourceType) {
> >>>>>+    case TypeIo:
> >>>>>+      return RootBridge->Io.Translation;
> >>>>>+    case TypeMem32:
> >>>>>+      return RootBridge->Mem.Translation;
> >>>>>+    case TypePMem32:
> >>>>>+      return RootBridge->PMem.Translation;
> >>>>>+    case TypeMem64:
> >>>>>+      return RootBridge->MemAbove4G.Translation;
> >>>>>+    case TypePMem64:
> >>>>>+      return RootBridge->PMemAbove4G.Translation;
> >>>>>+    default:
> >>>>
> >>>>(2) How about we return zero for TypeBus, explicitly, and then
> >>>>ASSERT(FALSE) and return zero for "default"?
> >>>>
> >>>>>+      return 0;
> >>>>>+  }
> >>>>>+}
> >>>>>+
> >>>>>  /**
> >>>>>    Ensure the compatibility of an IO space descriptor with the IO aperture.
> >>>>>
> >>>>>@@ -411,8 +434,12 @@ InitializePciHostBridge (
> >>>>>      }
> >>>>>
> >>>>>      if (RootBridges[Index].Io.Base <= RootBridges[Index].Io.Limit) {
> >>>>>+      // Base and Limit in PCI_ROOT_BRIDGE_APERTURE are device address.
> >>>>>+      // According to UEFI 2.7, device address = host address + Translation.
> >>>>>+      // For GCD resource manipulation, we should use host address, so
> >>>>>+      // Translation is subtracted from device address here.
> >>>>
> >>>>(3) In general, the comment style requires comments like this:
> >>>>
> >>>>   //
> >>>>   // Add empty comment lines both before and after.
> >>>>   //
> >>>>
> >>>>>        Status = AddIoSpace (
> >>>>>-                 RootBridges[Index].Io.Base,
> >>>>>+                 RootBridges[Index].Io.Base - RootBridges[Index].Io.Translation,
> >>>>>                   RootBridges[Index].Io.Limit - RootBridges[Index].Io.Base + 1
> >>>>>                   );
> >>>>>        ASSERT_EFI_ERROR (Status);
> >>>>
> >>>>This looks fine.
> >>>>
> >>>>>@@ -422,7 +449,7 @@ InitializePciHostBridge (
> >>>>>                          EfiGcdIoTypeIo,
> >>>>>                          0,
> >>>>>                          RootBridges[Index].Io.Limit - RootBridges[Index].Io.Base + 1,
> >>>>>-                        &RootBridges[Index].Io.Base,
> >>>>>+                        &RootBridges[Index].Io.Base - RootBridges[Index].Io.Translation,
> >>>>>                          gImageHandle,
> >>>>>                          NULL
> >>>>>                          );
> >>>>
> >>>>(4) But this is wrong (operating under the assumption that
> >>>>PCI_ROOT_BRIDGE_APERTURE providing device addresses). Namely, 5th
> >>>>parameter of gDS->AllocateIoSpace() is an in/out parameter:
> >>>>
> >>>>[MdeModulePkg/Core/Dxe/Gcd/Gcd.c]
> >>>>
> >>>>EFI_STATUS
> >>>>EFIAPI
> >>>>CoreAllocateIoSpace (
> >>>>   IN     EFI_GCD_ALLOCATE_TYPE  GcdAllocateType,
> >>>>   IN     EFI_GCD_IO_TYPE        GcdIoType,
> >>>>   IN     UINTN                  Alignment,
> >>>>   IN     UINT64                 Length,
> >>>>   IN OUT EFI_PHYSICAL_ADDRESS   *BaseAddress,
> >>>>   IN     EFI_HANDLE             ImageHandle,
> >>>>   IN     EFI_HANDLE             DeviceHandle OPTIONAL
> >>>>   )
> >>>>
> >>>>The patch, as written, takes the address of the Base field, and then
> >>>>decreases that address by Translation * sizeof Base. The resultant
> >>>>pointer is passed to the function as 5th argument.
> >>>>
> >>>>I don't think that's what you meant :)
> >>>>
> >>>>Instead, you have to translate the device address to host address first
> >>>>(using a temporary variable), and pass that to the function. (Updating
> >>>>the Base field back to the resultant / output value shouldn't be
> >>>>necessary, because GcdAllocateType==EfiGcdAllocateAddress, so the
> >>>>allocation is required to succeed at the exact address requested.)
> >>>>
> >>>>>@@ -443,14 +470,18 @@ InitializePciHostBridge (
> >>>>>
> >>>>>      for (MemApertureIndex = 0; MemApertureIndex < ARRAY_SIZE (MemApertures); MemApertureIndex++) {
> >>>>>        if (MemApertures[MemApertureIndex]->Base <= MemApertures[MemApertureIndex]->Limit) {
> >>>>>+        // Base and Limit in PCI_ROOT_BRIDGE_APERTURE are device address.
> >>>>>+        // According to UEFI 2.7, device address = host address + Translation.
> >>>>>+        // For GCD resource manipulation, we should use host address, so
> >>>>>+        // Translation is subtracted from device address here.
> >>>>>          Status = AddMemoryMappedIoSpace (
> >>>>>-                   MemApertures[MemApertureIndex]->Base,
> >>>>>+                   MemApertures[MemApertureIndex]->Base - MemApertures[MemApertureIndex]->Translation,
> >>>>>                     MemApertures[MemApertureIndex]->Limit - MemApertures[MemApertureIndex]->Base + 1,
> >>>>>                     EFI_MEMORY_UC
> >>>>>                     );
> >>>>>          ASSERT_EFI_ERROR (Status);
> >>>>>          Status = gDS->SetMemorySpaceAttributes (
> >>>>>-                        MemApertures[MemApertureIndex]->Base,
> >>>>>+                        MemApertures[MemApertureIndex]->Base - MemApertures[MemApertureIndex]->Translation,
> >>>>>                          MemApertures[MemApertureIndex]->Limit - MemApertures[MemApertureIndex]->Base + 1,
> >>>>>                          EFI_MEMORY_UC
> >>>>>                          );
> >>>>>@@ -463,7 +494,7 @@ InitializePciHostBridge (
> >>>>>                            EfiGcdMemoryTypeMemoryMappedIo,
> >>>>>                            0,
> >>>>>                            MemApertures[MemApertureIndex]->Limit - MemApertures[MemApertureIndex]->Base + 1,
> >>>>>-                          &MemApertures[MemApertureIndex]->Base,
> >>>>>+                          &MemApertures[MemApertureIndex]->Base - MemApertures[MemApertureIndex]->Translation,
> >>>>>                            gImageHandle,
> >>>>>                            NULL
> >>>>>                            );
> >>>>
> >>>>(5) Same comment as (4) applies, to the 5th argument.
> >>>>
> >>>>>@@ -824,12 +855,17 @@ NotifyPhase (
> >>>>>
> >>>>>            switch (Index) {
> >>>>>            case TypeIo:
> >>>>>+            // Base and Limit in PCI_ROOT_BRIDGE_APERTURE are device address.
> >>>>>+            // According to UEFI 2.7, device address = host address + Translation.
> >>>>>+            // For AllocateResource is manipulating GCD resource, we should use
> >>>>>+            // host address here, so Translation is subtracted from Base and
> >>>>>+            // Limit.
> >>>>>              BaseAddress = AllocateResource (
> >>>>>                              FALSE,
> >>>>>                              RootBridge->ResAllocNode[Index].Length,
> >>>>>                              MIN (15, BitsOfAlignment),
> >>>>>-                            ALIGN_VALUE (RootBridge->Io.Base, Alignment + 1),
> >>>>>-                            RootBridge->Io.Limit
> >>>>>+                            ALIGN_VALUE (RootBridge->Io.Base, Alignment + 1) - RootBridge->Io.Translation,
> >>>>>+                            RootBridge->Io.Limit - RootBridge->Io.Translation
> >>>>>                              );
> >>>>>              break;
> >>>>>
> >>>>>@@ -838,8 +874,8 @@ NotifyPhase (
> >>>>>                              TRUE,
> >>>>>                              RootBridge->ResAllocNode[Index].Length,
> >>>>>                              MIN (63, BitsOfAlignment),
> >>>>>-                            ALIGN_VALUE (RootBridge->MemAbove4G.Base, Alignment + 1),
> >>>>>-                            RootBridge->MemAbove4G.Limit
> >>>>>+                            ALIGN_VALUE (RootBridge->MemAbove4G.Base, Alignment + 1) - RootBridge->MemAbove4G.Translation,
> >>>>>+                            RootBridge->MemAbove4G.Limit - RootBridge->MemAbove4G.Translation
> >>>>>                              );
> >>>>>              if (BaseAddress != MAX_UINT64) {
> >>>>>                break;
> >>>>>@@ -853,8 +889,8 @@ NotifyPhase (
> >>>>>                              TRUE,
> >>>>>                              RootBridge->ResAllocNode[Index].Length,
> >>>>>                              MIN (31, BitsOfAlignment),
> >>>>>-                            ALIGN_VALUE (RootBridge->Mem.Base, Alignment + 1),
> >>>>>-                            RootBridge->Mem.Limit
> >>>>>+                            ALIGN_VALUE (RootBridge->Mem.Base, Alignment + 1) - RootBridge->Mem.Translation,
> >>>>>+                            RootBridge->Mem.Limit - RootBridge->Mem.Translation
> >>>>>                              );
> >>>>>              break;
> >>>>>
> >>>>>@@ -863,8 +899,8 @@ NotifyPhase (
> >>>>>                              TRUE,
> >>>>>                              RootBridge->ResAllocNode[Index].Length,
> >>>>>                              MIN (63, BitsOfAlignment),
> >>>>>-                            ALIGN_VALUE (RootBridge->PMemAbove4G.Base, Alignment + 1),
> >>>>>-                            RootBridge->PMemAbove4G.Limit
> >>>>>+                            ALIGN_VALUE (RootBridge->PMemAbove4G.Base, Alignment + 1) - RootBridge->PMemAbove4G.Translation,
> >>>>>+                            RootBridge->PMemAbove4G.Limit - RootBridge->PMemAbove4G.Translation
> >>>>>                              );
> >>>>>              if (BaseAddress != MAX_UINT64) {
> >>>>>                break;
> >>>>>@@ -877,8 +913,8 @@ NotifyPhase (
> >>>>>                              TRUE,
> >>>>>                              RootBridge->ResAllocNode[Index].Length,
> >>>>>                              MIN (31, BitsOfAlignment),
> >>>>>-                            ALIGN_VALUE (RootBridge->PMem.Base, Alignment + 1),
> >>>>>-                            RootBridge->PMem.Limit
> >>>>>+                            ALIGN_VALUE (RootBridge->PMem.Base, Alignment + 1) - RootBridge->PMem.Translation,
> >>>>>+                            RootBridge->PMem.Limit - RootBridge->PMem.Translation
> >>>>>                              );
> >>>>>              break;
> >>>>
> >>>>(6) For all of these, I believe that we have to think about the corner
> >>>>case when the Translation value is not a multiple of (Alignment + 1).
> >>>>
> >>>>"Alignment" comes from the PCI BAR in question, whereas Base comes from
> >>>>the platform PciHostBridgeLib. I think these are fairly independent (you
> >>>>can plug a 3rd party, discrete PCI card into a board). I find it
> >>>>plausible that the card has such a huge MMIO BAR (and alignment) that
> >>>>the platform's Translation offset is not a multiple thereof.
> >>>>
> >>>>So, which "view" has to be aligned here? The PCI (device) view, or the
> >>>>host (CPU) view?
> >>>
> >>>I believe the alignment requirement is from PCI view, not the CPU view. This
> >>>also implies alignment in allocating GCD resources becomes meaningless.
> >>I agree. It's an issue we need to think about.
> >>
> >>All address spaces in GCD are added by gDS->AddXXX().
> >>So it means for a given range of address [HostBase, HostLimit) in GCD,
> >>the corresponding device address is
> >>[HostBase + Offset, HostLimit + Offset).
> >>E.g.: GCD entry = [0xFFD, 0x3FFD), Offset = 0x3
> >>The corresponding device address range is [0x1000, 0x4000)
> >>If we want to allocate 3 page-aligned pages of MMIO from GCD,
> >>current AllocateResource() implementation will fail to allocate.
> >>
> >>What will the Offset be in real world?
> >>If it's quite small (smaller than device required alignment),
> >>thing becomes complicated. I even cannot think of any solution.
> >>If it's quite large (larger than device required alignment),
> >>thing becomes easy. Today's implementation can handle it well.
> >
> >I believe the Offset is normally large, so that we may place some assumption or
> >restriction here, to make things easier. You can see the translation on our platform:
> >https://github.com/tianocore/edk2-platforms/blob/master/Silicon/Hisilicon/Hi1616/D05AcpiTables/Dsdt/D05Pci.asl#L204
> >
> >How about we assume ATO alignment >= the whole region length (denoted as
> >L)? Then there are two possibilities:
> This assumption is a bit strict I think.
> Can we assume ATO alignment >= RootBridge->ResAllocNode[i].Alignment?
> RootBridge->ResAllocNode[i].Alignment carries the alignment requirement
> from the specific resource type.
> Supposing there are three 32bit BARs from 2 PCI devices, each requires
> alignment/length 0x100, 0x2000, 0x400,
> RootBridge->ResAllocNode[i].Alignment equals to 0x2000.
> RootBridge->ResAllocNode[i].Length equals to 0x2000 + 0x400 + 0x100.
> We only require ATO alignment >= 0x2000 in this case, but don't require
> ATO alignment >= 0x2500.
> 
> Agree?

So RootBridge->ResAllocNode[i].Alignment contains the maximum alignment for
resource type i? I didn't know that before :)

One concern is that the maximum alignment requirement depends on what device we
insert on the board; for open platforms, user may insert any PCIe card. So this
becomes a dynamic value, while ATO is normally determined by OEM as a static
value. Then to support as many kinds of devices as possible, we may still try to
enlarge the alignment of ATO, maybe almost the same as the length of whole
range.

However, your proposed restriction is still good for me, which places a minimum
requirement for the current code and has no impact to the real platforms.

Thanks,

Gary (Heyi Guo)


> 
> >
> >1. BAR alignment <= L, so BAR alignment <= ATO alignment, so
> >  (each host address % BAR alignment) == (each device address % BAR alignment),
> >and the current code can handle this.
> >
> >This should cover most of cases, since BAR alignment <= BAR length, and the
> >other possibility is actually out of resource.
> >
> >2. BAR alignment > L, e.g.
> >    BAR alignment = 1MB
> >    L = 4KB
> >    ATO = 4KB or -4KB
> >
> >   1) If device address = 0, host address = 4KB, then AllocateResource will
> >return -1 and result to OUT_OF_RESOURCES;
> >   2) If device address = 4KB, host address = 0, then AllocateResource will also
> >return -1
> >Anyway we will get the expected OUT_OF_RESOURCES result by current code.
> >
> >And this assumption is not a very strict one.
> >
> >Any comments?
> >
> >Thanks,
> >
> >Gary (Heyi Guo)
> >
> >
> >>
> >>
> >>
> >>>
> >>>Thanks,
> >>>
> >>>Gary (Heyi Guo)
> >>>
> >>>
> >>>>
> >>>>... Hmmm wait, the AllocateResource() function aligns BaseAddress
> >>>>internally anyway. So, first, I don't understand why the pre-patch code
> >>>>uses ALIGN_VALUE at the call site as well; second, due to the alignment
> >>>>internal to AllocateResource(), we couldn't align *just* the PCI view
> >>>>even if we wanted to.
> >>>>
> >>>>So I guess this code is correct (due to the alignment internal to
> >>>>AllocateResource()), but could we perhaps simplify it by passing
> >>>>
> >>>>   RootBridge->Xxx.Base - RootBridge->Xxx.Translation
> >>>>
> >>>>i.e., by dropping the outer alignment?
> >>>>
> >>>>(To be clear, dropping the "outer" alignment, if it's a valid change,
> >>>>should be done as a separate patch, before the translation is
> >>>>introduced. I hope Ray can comment on this.)
> >>>>
> >>>>>
> >>>>>@@ -1152,6 +1188,7 @@ StartBusEnumeration (
> >>>>>        Descriptor->AddrSpaceGranularity  = 0;
> >>>>>        Descriptor->AddrRangeMin          = RootBridge->Bus.Base;
> >>>>>        Descriptor->AddrRangeMax          = 0;
> >>>>>+      // Ignore translation offset for bus
> >>>>>        Descriptor->AddrTranslationOffset = 0;
> >>>>>        Descriptor->AddrLen               = RootBridge->Bus.Limit - RootBridge->Bus.Base + 1;
> >>>>>
> >>>>
> >>>>(7) Ah, in this case, adding TypeBus under (2) is not necessary, just
> >>>>ASSERT(FALSE) under the currently proposed "default" label.
> >>>>
> >>>>
> >>>>>@@ -1421,7 +1458,12 @@ GetProposedResources (
> >>>>>            Descriptor->Desc                  = ACPI_ADDRESS_SPACE_DESCRIPTOR;
> >>>>>            Descriptor->Len                   = sizeof (EFI_ACPI_ADDRESS_SPACE_DESCRIPTOR) - 3;;
> >>>>>            Descriptor->GenFlag               = 0;
> >>>>>-          Descriptor->AddrRangeMin          = RootBridge->ResAllocNode[Index].Base;
> >>>>>+          // AddrRangeMin in Resource Descriptor here should be device address
> >>>>>+          // instead of host address, or else PCI bus driver cannot set correct
> >>>>>+          // address into PCI BAR registers.
> >>>>>+          // Base in ResAllocNode is a host address, so Translation is added.
> >>>>>+          Descriptor->AddrRangeMin          = RootBridge->ResAllocNode[Index].Base +
> >>>>>+              GetTranslationByResourceType (RootBridge, Index);
> >>>>>            Descriptor->AddrRangeMax          = 0;
> >>>>>            Descriptor->AddrTranslationOffset = (ResStatus == ResAllocated) ? EFI_RESOURCE_SATISFIED : PCI_RESOURCE_LESS;
> >>>>>            Descriptor->AddrLen               = RootBridge->ResAllocNode[Index].Length;
> >>>>>diff --git a/MdeModulePkg/Bus/Pci/PciHostBridgeDxe/PciHostResource.h b/MdeModulePkg/Bus/Pci/PciHostBridgeDxe/PciHostResource.h
> >>>>>index 8612c0c..662c2dd 100644
> >>>>>--- a/MdeModulePkg/Bus/Pci/PciHostBridgeDxe/PciHostResource.h
> >>>>>+++ b/MdeModulePkg/Bus/Pci/PciHostBridgeDxe/PciHostResource.h
> >>>>>@@ -38,6 +38,8 @@ typedef enum {
> >>>>>
> >>>>>  typedef struct {
> >>>>>    PCI_RESOURCE_TYPE Type;
> >>>>>+  // Base is a host address instead of a device address when address translation
> >>>>>+  // exists and host address != device address
> >>>>>    UINT64            Base;
> >>>>>    UINT64            Length;
> >>>>>    UINT64            Alignment;
> >>>>>diff --git a/MdeModulePkg/Bus/Pci/PciHostBridgeDxe/PciRootBridgeIo.c b/MdeModulePkg/Bus/Pci/PciHostBridgeDxe/PciRootBridgeIo.c
> >>>>>index dc06c16..04ed411 100644
> >>>>>--- a/MdeModulePkg/Bus/Pci/PciHostBridgeDxe/PciRootBridgeIo.c
> >>>>>+++ b/MdeModulePkg/Bus/Pci/PciHostBridgeDxe/PciRootBridgeIo.c
> >>>>>@@ -86,12 +86,23 @@ CreateRootBridge (
> >>>>>            (Bridge->AllocationAttributes & EFI_PCI_HOST_BRIDGE_COMBINE_MEM_PMEM) != 0 ? L"CombineMemPMem " : L"",
> >>>>>            (Bridge->AllocationAttributes & EFI_PCI_HOST_BRIDGE_MEM64_DECODE) != 0 ? L"Mem64Decode" : L""
> >>>>>            ));
> >>>>>+  // We don't see any scenario for bus translation, so translation for bus is just ignored.
> >>>>>    DEBUG ((EFI_D_INFO, "           Bus: %lx - %lx\n", Bridge->Bus.Base, Bridge->Bus.Limit));
> >>>>>-  DEBUG ((EFI_D_INFO, "            Io: %lx - %lx\n", Bridge->Io.Base, Bridge->Io.Limit));
> >>>>>-  DEBUG ((EFI_D_INFO, "           Mem: %lx - %lx\n", Bridge->Mem.Base, Bridge->Mem.Limit));
> >>>>>-  DEBUG ((EFI_D_INFO, "    MemAbove4G: %lx - %lx\n", Bridge->MemAbove4G.Base, Bridge->MemAbove4G.Limit));
> >>>>>-  DEBUG ((EFI_D_INFO, "          PMem: %lx - %lx\n", Bridge->PMem.Base, Bridge->PMem.Limit));
> >>>>>-  DEBUG ((EFI_D_INFO, "   PMemAbove4G: %lx - %lx\n", Bridge->PMemAbove4G.Base, Bridge->PMemAbove4G.Limit));
> >>>>>+  DEBUG ((DEBUG_INFO, "            Io: %lx - %lx translation=%lx\n",
> >>>>>+          Bridge->Io.Base, Bridge->Io.Limit, Bridge->Io.Translation
> >>>>>+          ));
> >>>>>+  DEBUG ((DEBUG_INFO, "           Mem: %lx - %lx translation=%lx\n",
> >>>>>+          Bridge->Mem.Base, Bridge->Mem.Limit, Bridge->Mem.Translation
> >>>>>+          ));
> >>>>>+  DEBUG ((DEBUG_INFO, "    MemAbove4G: %lx - %lx translation=%lx\n",
> >>>>>+          Bridge->MemAbove4G.Base, Bridge->MemAbove4G.Limit, Bridge->MemAbove4G.Translation
> >>>>>+          ));
> >>>>>+  DEBUG ((DEBUG_INFO, "          PMem: %lx - %lx translation=%lx\n",
> >>>>>+          Bridge->PMem.Base, Bridge->PMem.Limit, Bridge->PMem.Translation
> >>>>>+          ));
> >>>>>+  DEBUG ((DEBUG_INFO, "   PMemAbove4G: %lx - %lx translation=%lx\n",
> >>>>>+          Bridge->PMemAbove4G.Base, Bridge->PMemAbove4G.Limit, Bridge->PMemAbove4G.Translation
> >>>>>+          ));
> >>>>
> >>>>(8) I suggest capitalizing "Translation" in the debug output.
> >>>>
> >>>>(9) The indentation is not idiomatic, it should be
> >>>>
> >>>>   DEBUG ((
> >>>>     ...
> >>>>     ...
> >>>>     ));
> >>>>
> >>>>>
> >>>>>    //
> >>>>>    // Make sure Mem and MemAbove4G apertures are valid
> >>>>>@@ -206,7 +217,10 @@ CreateRootBridge (
> >>>>>      }
> >>>>>      RootBridge->ResAllocNode[Index].Type     = Index;
> >>>>>      if (Bridge->ResourceAssigned && (Aperture->Limit >= Aperture->Base)) {
> >>>>>-      RootBridge->ResAllocNode[Index].Base   = Aperture->Base;
> >>>>>+      // Base in ResAllocNode is a host address, while Base in Aperture is a
> >>>>>+      // device address, so translation needs to be subtracted.
> >>>>>+      RootBridge->ResAllocNode[Index].Base   = Aperture->Base -
> >>>>>+        Aperture->Translation;
> >>>>>        RootBridge->ResAllocNode[Index].Length = Aperture->Limit - Aperture->Base + 1;
> >>>>>        RootBridge->ResAllocNode[Index].Status = ResAllocated;
> >>>>>      } else {
> >>>>>@@ -403,6 +417,28 @@ RootBridgeIoCheckParameter (
> >>>>>    return EFI_SUCCESS;
> >>>>>  }
> >>>>>
> >>>>>+EFI_STATUS
> >>>>>+RootBridgeIoGetMemTranslationByAddress (
> >>>>>+  IN PCI_ROOT_BRIDGE_INSTANCE               *RootBridge,
> >>>>>+  IN UINT64                                 Address,
> >>>>>+  IN OUT UINT64                             *Translation
> >>>>>+  )
> >>>>>+{
> >>>>>+  if (Address >= RootBridge->Mem.Base && Address <= RootBridge->Mem.Limit) {
> >>>>>+    *Translation = RootBridge->Mem.Translation;
> >>>>>+  } else if (Address >= RootBridge->PMem.Base && Address <= RootBridge->PMem.Limit) {
> >>>>>+    *Translation = RootBridge->PMem.Translation;
> >>>>>+  } else if (Address >= RootBridge->MemAbove4G.Base && Address <= RootBridge->MemAbove4G.Limit) {
> >>>>>+    *Translation = RootBridge->MemAbove4G.Translation;
> >>>>>+  } else if (Address >= RootBridge->PMemAbove4G.Base && Address <= RootBridge->PMemAbove4G.Limit) {
> >>>>>+    *Translation = RootBridge->PMemAbove4G.Translation;
> >>>>>+  } else {
> >>>>>+    return EFI_INVALID_PARAMETER;
> >>>>>+  }
> >>>>>+
> >>>>>+  return EFI_SUCCESS;
> >>>>>+}
> >>>>>+
> >>>>>  /**
> >>>>>    Polls an address in memory mapped I/O space until an exit condition is met,
> >>>>>    or a timeout occurs.
> >>>>>@@ -658,13 +694,24 @@ RootBridgeIoMemRead (
> >>>>>    )
> >>>>>  {
> >>>>>    EFI_STATUS                             Status;
> >>>>>+  PCI_ROOT_BRIDGE_INSTANCE               *RootBridge;
> >>>>>+  UINT64                                 Translation;
> >>>>>
> >>>>>    Status = RootBridgeIoCheckParameter (This, MemOperation, Width, Address,
> >>>>>                                         Count, Buffer);
> >>>>>    if (EFI_ERROR (Status)) {
> >>>>>      return Status;
> >>>>>    }
> >>>>>-  return mCpuIo->Mem.Read (mCpuIo, (EFI_CPU_IO_PROTOCOL_WIDTH) Width, Address, Count, Buffer);
> >>>>>+
> >>>>>+  RootBridge = ROOT_BRIDGE_FROM_THIS (This);
> >>>>>+  Status = RootBridgeIoGetMemTranslationByAddress (RootBridge, Address, &Translation);
> >>>>>+  if (EFI_ERROR (Status)) {
> >>>>>+    return Status;
> >>>>>+  }
> >>>>>+
> >>>>>+  // Address passed to CpuIo->Mem.Read should be a host address instead of
> >>>>>+  // device address, so Translation should be subtracted.
> >>>>>+  return mCpuIo->Mem.Read (mCpuIo, (EFI_CPU_IO_PROTOCOL_WIDTH) Width, Address - Translation, Count, Buffer);
> >>>>>  }
> >>>>>
> >>>>>  /**
> >>>>>@@ -705,13 +752,24 @@ RootBridgeIoMemWrite (
> >>>>>    )
> >>>>>  {
> >>>>>    EFI_STATUS                             Status;
> >>>>>+  PCI_ROOT_BRIDGE_INSTANCE               *RootBridge;
> >>>>>+  UINT64                                 Translation;
> >>>>>
> >>>>>    Status = RootBridgeIoCheckParameter (This, MemOperation, Width, Address,
> >>>>>                                         Count, Buffer);
> >>>>>    if (EFI_ERROR (Status)) {
> >>>>>      return Status;
> >>>>>    }
> >>>>>-  return mCpuIo->Mem.Write (mCpuIo, (EFI_CPU_IO_PROTOCOL_WIDTH) Width, Address, Count, Buffer);
> >>>>>+
> >>>>>+  RootBridge = ROOT_BRIDGE_FROM_THIS (This);
> >>>>>+  Status = RootBridgeIoGetMemTranslationByAddress (RootBridge, Address, &Translation);
> >>>>>+  if (EFI_ERROR (Status)) {
> >>>>>+    return Status;
> >>>>>+  }
> >>>>>+
> >>>>>+  // Address passed to CpuIo->Mem.Write should be a host address instead of
> >>>>>+  // device address, so Translation should be subtracted.
> >>>>>+  return mCpuIo->Mem.Write (mCpuIo, (EFI_CPU_IO_PROTOCOL_WIDTH) Width, Address - Translation, Count, Buffer);
> >>>>>  }
> >>>>>
> >>>>>  /**
> >>>>>@@ -746,6 +804,8 @@ RootBridgeIoIoRead (
> >>>>>    )
> >>>>>  {
> >>>>>    EFI_STATUS                                    Status;
> >>>>>+  PCI_ROOT_BRIDGE_INSTANCE                      *RootBridge;
> >>>>>+
> >>>>>    Status = RootBridgeIoCheckParameter (
> >>>>>               This, IoOperation, Width,
> >>>>>               Address, Count, Buffer
> >>>>>@@ -753,7 +813,12 @@ RootBridgeIoIoRead (
> >>>>>    if (EFI_ERROR (Status)) {
> >>>>>      return Status;
> >>>>>    }
> >>>>>-  return mCpuIo->Io.Read (mCpuIo, (EFI_CPU_IO_PROTOCOL_WIDTH) Width, Address, Count, Buffer);
> >>>>>+
> >>>>>+  RootBridge = ROOT_BRIDGE_FROM_THIS (This);
> >>>>>+
> >>>>>+  // Address passed to CpuIo->Io.Read should be a host address instead of
> >>>>>+  // device address, so Translation should be subtracted.
> >>>>>+  return mCpuIo->Io.Read (mCpuIo, (EFI_CPU_IO_PROTOCOL_WIDTH) Width, Address - RootBridge->Io.Translation, Count, Buffer);
> >>>>>  }
> >>>>>
> >>>>>  /**
> >>>>>@@ -788,6 +853,8 @@ RootBridgeIoIoWrite (
> >>>>>    )
> >>>>>  {
> >>>>>    EFI_STATUS                                    Status;
> >>>>>+  PCI_ROOT_BRIDGE_INSTANCE                      *RootBridge;
> >>>>>+
> >>>>>    Status = RootBridgeIoCheckParameter (
> >>>>>               This, IoOperation, Width,
> >>>>>               Address, Count, Buffer
> >>>>>@@ -795,7 +862,12 @@ RootBridgeIoIoWrite (
> >>>>>    if (EFI_ERROR (Status)) {
> >>>>>      return Status;
> >>>>>    }
> >>>>>-  return mCpuIo->Io.Write (mCpuIo, (EFI_CPU_IO_PROTOCOL_WIDTH) Width, Address, Count, Buffer);
> >>>>>+
> >>>>>+  RootBridge = ROOT_BRIDGE_FROM_THIS (This);
> >>>>>+
> >>>>>+  // Address passed to CpuIo->Io.Write should be a host address instead of
> >>>>>+  // device address, so Translation should be subtracted.
> >>>>>+  return mCpuIo->Io.Write (mCpuIo, (EFI_CPU_IO_PROTOCOL_WIDTH) Width, Address - RootBridge->Io.Translation, Count, Buffer);
> >>>>>  }
> >>>>>
> >>>>>  /**
> >>>>>@@ -1615,25 +1687,39 @@ RootBridgeIoConfiguration (
> >>>>>
> >>>>>      Descriptor->Desc = ACPI_ADDRESS_SPACE_DESCRIPTOR;
> >>>>>      Descriptor->Len  = sizeof (EFI_ACPI_ADDRESS_SPACE_DESCRIPTOR) - 3;
> >>>>>+    // According to UEFI 2.7, RootBridgeIo->Configuration should return address
> >>>>>+    // range in CPU view (host address), and ResAllocNode->Base is already a CPU
> >>>>>+    // view address (host address).
> >>>>>      Descriptor->AddrRangeMin  = ResAllocNode->Base;
> >>>>>      Descriptor->AddrRangeMax  = ResAllocNode->Base + ResAllocNode->Length - 1;
> >>>>>      Descriptor->AddrLen       = ResAllocNode->Length;
> >>>>>      switch (ResAllocNode->Type) {
> >>>>>
> >>>>>      case TypeIo:
> >>>>>-      Descriptor->ResType       = ACPI_ADDRESS_SPACE_TYPE_IO;
> >>>>>+      Descriptor->ResType               = ACPI_ADDRESS_SPACE_TYPE_IO;
> >>>>>+      Descriptor->AddrTranslationOffset = RootBridge->Io.Translation;
> >>>>>        break;
> >>>>>
> >>>>>      case TypePMem32:
> >>>>>-      Descriptor->SpecificFlag = EFI_ACPI_MEMORY_RESOURCE_SPECIFIC_FLAG_CACHEABLE_PREFETCHABLE;
> >>>>>+      Descriptor->SpecificFlag          = EFI_ACPI_MEMORY_RESOURCE_SPECIFIC_FLAG_CACHEABLE_PREFETCHABLE;
> >>>>>+      Descriptor->AddrTranslationOffset = RootBridge->PMem.Translation;
> >>>>>+      Descriptor->ResType               = ACPI_ADDRESS_SPACE_TYPE_MEM;
> >>>>>+      Descriptor->AddrSpaceGranularity  = 32;
> >>>>>+      break;
> >>>>>+
> >>>>>      case TypeMem32:
> >>>>>+      Descriptor->AddrTranslationOffset = RootBridge->Mem.Translation;
> >>>>>        Descriptor->ResType               = ACPI_ADDRESS_SPACE_TYPE_MEM;
> >>>>>        Descriptor->AddrSpaceGranularity  = 32;
> >>>>>        break;
> >>>>>
> >>>>>      case TypePMem64:
> >>>>>-      Descriptor->SpecificFlag = EFI_ACPI_MEMORY_RESOURCE_SPECIFIC_FLAG_CACHEABLE_PREFETCHABLE;
> >>>>>+      Descriptor->SpecificFlag          = EFI_ACPI_MEMORY_RESOURCE_SPECIFIC_FLAG_CACHEABLE_PREFETCHABLE;
> >>>>>+      Descriptor->AddrTranslationOffset = RootBridge->PMemAbove4G.Translation;
> >>>>>+      Descriptor->ResType               = ACPI_ADDRESS_SPACE_TYPE_MEM;
> >>>>>+      Descriptor->AddrSpaceGranularity  = 64;
> >>>>>      case TypeMem64:
> >>>>>+      Descriptor->AddrTranslationOffset = RootBridge->MemAbove4G.Translation;
> >>>>>        Descriptor->ResType               = ACPI_ADDRESS_SPACE_TYPE_MEM;
> >>>>>        Descriptor->AddrSpaceGranularity  = 64;
> >>>>>        break;
> >>>>>diff --git a/MdeModulePkg/Include/Library/PciHostBridgeLib.h b/MdeModulePkg/Include/Library/PciHostBridgeLib.h
> >>>>>index d42e9ec..21ee8cd 100644
> >>>>>--- a/MdeModulePkg/Include/Library/PciHostBridgeLib.h
> >>>>>+++ b/MdeModulePkg/Include/Library/PciHostBridgeLib.h
> >>>>>@@ -20,8 +20,16 @@
> >>>>>  // (Base > Limit) indicates an aperture is not available.
> >>>>>  //
> >>>>>  typedef struct {
> >>>>>+  // Base and Limit are the device address instead of host address when
> >>>>>+  // Translation is not zero
> >>>>>    UINT64 Base;
> >>>>>    UINT64 Limit;
> >>>>>+  // According to UEFI 2.7, Device Address = Host Address + Translation,
> >>>>>+  // so Translation = Device Address - Host Address.
> >>>>>+  // On platforms where Translation is not zero, Translation is probably
> >>>>>+  // negative for we may translate an above-4G host address into a below-4G
> >>>>>+  // device address for legacy PCIe device compatibility.
> >>>>>+  UINT64 Translation;
> >>>>>  } PCI_ROOT_BRIDGE_APERTURE;
> >>>>>
> >>>>>  typedef struct {
> >>>>>
> >>>>
> >>>>(10) I suggest replacing the "negative" language with "the subtraction
> >>>>is to be performed with UINT64 wrap-around semantics".
> >>>>
> >>>>
> >>>>I've made some comments, but I admit my understanding is quite limited;
> >>>>sorry about that.
> >>>>
> >>>>Thanks
> >>>>Laszlo
> >>
> >>
> >>-- 
> >>Thanks,
> >>Ray
> 
> 
> -- 
> Thanks,
> Ray