OvmfPkg: PlatformPei: determine the 64-bit PCI host aperture for X64 DXE

The main observation about the 64-bit PCI host aperture is that it is the
highest part of the useful address space. It impacts the top of the GCD
memory space map, and, consequently, our maximum address width calculation
for the CPU HOB too.

Thus, modify the GetFirstNonAddress() function to consider the following
areas above the high RAM, while calculating the first non-address (i.e.,
the highest inclusive address, plus one):

- the memory hotplug area (optional, the size comes from QEMU),

- the 64-bit PCI host aperture (we set a default size).

While computing the first non-address, capture the base and the size of
the 64-bit PCI host aperture at once in PCDs, since they are natural parts
of the calculation.

(Similarly to how PcdPciMmio32* are not rewritten on the S3 resume path
(see the InitializePlatform() -> MemMapInitialization() condition), nor
are PcdPciMmio64*. Only the core PciHostBridgeDxe driver consumes them,
through our PciHostBridgeLib instance.)

Set 32GB as the default size for the aperture. Issue#59 mentions the
NVIDIA Tesla K80 as an assignable device. According to nvidia.com, these
cards may have 24GB of memory (probably 16GB + 8GB BARs).

As a strictly experimental feature, the user can specify the size of the
aperture (in MB) as well, with the QEMU option

  -fw_cfg name=opt/ovmf/X-PciMmio64Mb,string=65536

The "X-" prefix follows the QEMU tradition (spelled "x-" there), meaning
that the property is experimental, unstable, and might go away any time.
Gerd has proposed heuristics for sizing the aperture automatically (based
on 1GB page support and PCPU address width), but such should be delayed to
a later patch (which may very well back out "X-PciMmio64Mb" then).

For "everyday" guests, the 32GB default for the aperture size shouldn't
impact the PEI memory demand (the size of the page tables that the DXE IPL
PEIM builds). Namely, we've never reported narrower than 36-bit addresses;
the DXE IPL PEIM has always built page tables for 64GB at least.

For the aperture to bump the address width above 36 bits, either the guest
must have quite a bit of memory itself (in which case the additional PEI
memory demand shouldn't matter), or the user must specify a large aperture
manually with "X-PciMmio64Mb" (and then he or she is also responsible for
giving enough RAM to the VM, to satisfy the PEI memory demand).

Cc: Gerd Hoffmann <kraxel@redhat.com>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Marcel Apfelbaum <marcel@redhat.com>
Cc: Thomas Lamprecht <t.lamprecht@proxmox.com>
Ref: https://github.com/tianocore/edk2/issues/59
Ref: http://www.nvidia.com/object/tesla-servers.html
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>

2 files changed, 112 insertions, 0 deletions

diff --git a/OvmfPkg/PlatformPei/MemDetect.c b/OvmfPkg/PlatformPei/MemDetect.c
index 286f6914a7..ed13c57beb 100644
--- a/OvmfPkg/PlatformPei/MemDetect.c
+++ b/OvmfPkg/PlatformPei/MemDetect.c
@@ -32,6 +32,7 @@ Module Name:
 #include <Library/PeimEntryPoint.h>

 #include <Library/ResourcePublicationLib.h>

 #include <Library/MtrrLib.h>

+#include <Library/QemuFwCfgLib.h>

 

 #include "Platform.h"

 #include "Cmos.h"

@@ -97,8 +98,117 @@ GetFirstNonAddress (
   )

 {

   UINT64               FirstNonAddress;

+  UINT64               Pci64Base, Pci64Size;

+  CHAR8                MbString[7 + 1];

+  EFI_STATUS           Status;

+  FIRMWARE_CONFIG_ITEM FwCfgItem;

+  UINTN                FwCfgSize;

+  UINT64               HotPlugMemoryEnd;

 

   FirstNonAddress = BASE_4GB + GetSystemMemorySizeAbove4gb ();

+

+  //

+  // If DXE is 32-bit, then we're done; PciBusDxe will degrade 64-bit MMIO

+  // resources to 32-bit anyway. See DegradeResource() in

+  // "PciResourceSupport.c".

+  //

+#ifdef MDE_CPU_IA32

+  if (!FeaturePcdGet (PcdDxeIplSwitchToLongMode)) {

+    return FirstNonAddress;

+  }

+#endif

+

+  //

+  // Otherwise, in order to calculate the highest address plus one, we must

+  // consider the 64-bit PCI host aperture too. Fetch the default size.

+  //

+  Pci64Size = PcdGet64 (PcdPciMmio64Size);

+

+  //

+  // See if the user specified the number of megabytes for the 64-bit PCI host

+  // aperture. The number of non-NUL characters in MbString allows for

+  // 9,999,999 MB, which is approximately 10 TB.

+  //

+  // As signaled by the "X-" prefix, this knob is experimental, and might go

+  // away at any time.

+  //

+  Status = QemuFwCfgFindFile ("opt/ovmf/X-PciMmio64Mb", &FwCfgItem,

+             &FwCfgSize);

+  if (!EFI_ERROR (Status)) {

+    if (FwCfgSize >= sizeof MbString) {

+      DEBUG ((EFI_D_WARN,

+        "%a: ignoring malformed 64-bit PCI host aperture size from fw_cfg\n",

+        __FUNCTION__));

+    } else {

+      QemuFwCfgSelectItem (FwCfgItem);

+      QemuFwCfgReadBytes (FwCfgSize, MbString);

+      MbString[FwCfgSize] = '\0';

+      Pci64Size = LShiftU64 (AsciiStrDecimalToUint64 (MbString), 20);

+    }

+  }

+

+  if (Pci64Size == 0) {

+    if (mBootMode != BOOT_ON_S3_RESUME) {

+      DEBUG ((EFI_D_INFO, "%a: disabling 64-bit PCI host aperture\n",

+        __FUNCTION__));

+      PcdSet64 (PcdPciMmio64Size, 0);

+    }

+

+    //

+    // There's nothing more to do; the amount of memory above 4GB fully

+    // determines the highest address plus one. The memory hotplug area (see

+    // below) plays no role for the firmware in this case.

+    //

+    return FirstNonAddress;

+  }

+

+  //

+  // The "etc/reserved-memory-end" fw_cfg file, when present, contains an

+  // absolute, exclusive end address for the memory hotplug area. This area

+  // starts right at the end of the memory above 4GB. The 64-bit PCI host

+  // aperture must be placed above it.

+  //

+  Status = QemuFwCfgFindFile ("etc/reserved-memory-end", &FwCfgItem,

+             &FwCfgSize);

+  if (!EFI_ERROR (Status) && FwCfgSize == sizeof HotPlugMemoryEnd) {

+    QemuFwCfgSelectItem (FwCfgItem);

+    QemuFwCfgReadBytes (FwCfgSize, &HotPlugMemoryEnd);

+

+    ASSERT (HotPlugMemoryEnd >= FirstNonAddress);

+    FirstNonAddress = HotPlugMemoryEnd;

+  }

+

+  //

+  // SeaBIOS aligns both boundaries of the 64-bit PCI host aperture to 1GB, so

+  // that the host can map it with 1GB hugepages. Follow suit.

+  //

+  Pci64Base = ALIGN_VALUE (FirstNonAddress, (UINT64)SIZE_1GB);

+  Pci64Size = ALIGN_VALUE (Pci64Size, (UINT64)SIZE_1GB);

+

+  //

+  // The 64-bit PCI host aperture should also be "naturally" aligned. The

+  // alignment is determined by rounding the size of the aperture down to the

+  // next smaller or equal power of two. That is, align the aperture by the

+  // largest BAR size that can fit into it.

+  //

+  Pci64Base = ALIGN_VALUE (Pci64Base, GetPowerOfTwo64 (Pci64Size));

+

+  if (mBootMode != BOOT_ON_S3_RESUME) {

+    //

+    // The core PciHostBridgeDxe driver will automatically add this range to

+    // the GCD memory space map through our PciHostBridgeLib instance; here we

+    // only need to set the PCDs.

+    //

+    PcdSet64 (PcdPciMmio64Base, Pci64Base);

+    PcdSet64 (PcdPciMmio64Size, Pci64Size);

+    DEBUG ((EFI_D_INFO, "%a: Pci64Base=0x%Lx Pci64Size=0x%Lx\n",

+      __FUNCTION__, Pci64Base, Pci64Size));

+  }

+

+  //

+  // The useful address space ends with the 64-bit PCI host aperture.

+  //

+  FirstNonAddress = Pci64Base + Pci64Size;

   return FirstNonAddress;

 }

 

diff --git a/OvmfPkg/PlatformPei/PlatformPei.inf b/OvmfPkg/PlatformPei/PlatformPei.inf
index 6dc5ff079f..5b643a358f 100644
--- a/OvmfPkg/PlatformPei/PlatformPei.inf
+++ b/OvmfPkg/PlatformPei/PlatformPei.inf
@@ -79,6 +79,8 @@
   gUefiOvmfPkgTokenSpaceGuid.PcdPciIoSize

   gUefiOvmfPkgTokenSpaceGuid.PcdPciMmio32Base

   gUefiOvmfPkgTokenSpaceGuid.PcdPciMmio32Size

+  gUefiOvmfPkgTokenSpaceGuid.PcdPciMmio64Base

+  gUefiOvmfPkgTokenSpaceGuid.PcdPciMmio64Size

   gUefiOvmfPkgTokenSpaceGuid.PcdOvmfDecompressionScratchEnd

   gUefiOvmfPkgTokenSpaceGuid.PcdQ35TsegMbytes

   gEfiIntelFrameworkModulePkgTokenSpaceGuid.PcdS3AcpiReservedMemorySize