system76-edk2/OvmfPkg/AmdSevDxe/AmdSevDxe.c

/** @file

  AMD Sev Dxe driver. This driver is dispatched early in DXE, due to being list
  in APRIORI. It clears C-bit from MMIO and NonExistent Memory space when SEV
  is enabled.

  Copyright (c) 2017 - 2020, AMD Inc. All rights reserved.<BR>

  SPDX-License-Identifier: BSD-2-Clause-Patent

**/

#include <IndustryStandard/Q35MchIch9.h>
#include <Library/BaseLib.h>
#include <Library/BaseMemoryLib.h>
#include <Library/DebugLib.h>
#include <Library/DxeServicesTableLib.h>
#include <Library/MemEncryptSevLib.h>
#include <Library/MemoryAllocationLib.h>
#include <Library/UefiBootServicesTableLib.h>
#include <Guid/ConfidentialComputingSevSnpBlob.h>
#include <Library/PcdLib.h>
#include <Pi/PrePiDxeCis.h>
#include <Protocol/SevMemoryAcceptance.h>
#include <Protocol/MemoryAccept.h>
#include <Uefi/UefiSpec.h>

// Present, initialized, tested bits defined in MdeModulePkg/Core/Dxe/DxeMain.h
#define EFI_MEMORY_INTERNAL_MASK  0x0700000000000000ULL

STATIC
EFI_STATUS
AllocateConfidentialComputingBlob (
  OUT CONFIDENTIAL_COMPUTING_SNP_BLOB_LOCATION  **CcBlobPtr
  )
{
  EFI_STATUS                                Status;
  CONFIDENTIAL_COMPUTING_SNP_BLOB_LOCATION  *CcBlob;

  Status = gBS->AllocatePool (
                  EfiACPIReclaimMemory,
                  sizeof (CONFIDENTIAL_COMPUTING_SNP_BLOB_LOCATION),
                  (VOID **)&CcBlob
                  );
  if (EFI_ERROR (Status)) {
    return Status;
  }

  CcBlob->Header                 = SIGNATURE_32 ('A', 'M', 'D', 'E');
  CcBlob->Version                = 1;
  CcBlob->Reserved               = 0;
  CcBlob->SecretsPhysicalAddress = (UINT64)(UINTN)FixedPcdGet32 (PcdOvmfSnpSecretsBase);
  CcBlob->SecretsSize            = FixedPcdGet32 (PcdOvmfSnpSecretsSize);
  CcBlob->Reserved1              = 0;
  CcBlob->CpuidPhysicalAddress   = (UINT64)(UINTN)FixedPcdGet32 (PcdOvmfCpuidBase);
  CcBlob->CpuidLSize             = FixedPcdGet32 (PcdOvmfCpuidSize);
  CcBlob->Reserved2              = 0;

  *CcBlobPtr = CcBlob;

  return EFI_SUCCESS;
}

STATIC EFI_HANDLE  mAmdSevDxeHandle = NULL;

STATIC BOOLEAN  mAcceptAllMemoryAtEBS = TRUE;

STATIC EFI_EVENT  mAcceptAllMemoryEvent = NULL;

STATIC
EFI_STATUS
EFIAPI
AmdSevMemoryAccept (
  IN EDKII_MEMORY_ACCEPT_PROTOCOL  *This,
  IN EFI_PHYSICAL_ADDRESS          StartAddress,
  IN UINTN                         Size
  )
{
  //
  // The StartAddress must be page-aligned, and the Size must be a positive
  // multiple of SIZE_4KB. Use an assert instead of returning an erros since
  // this is an EDK2-internal protocol.
  //
  ASSERT (IS_ALIGNED (StartAddress, SIZE_4KB));
  ASSERT (IS_ALIGNED (Size, SIZE_4KB));
  ASSERT (Size != 0);

  MemEncryptSevSnpPreValidateSystemRam (
    StartAddress,
    EFI_SIZE_TO_PAGES (Size)
    );

  return EFI_SUCCESS;
}

STATIC
EFI_STATUS
AcceptAllMemory (
  VOID
  )
{
  EFI_GCD_MEMORY_SPACE_DESCRIPTOR  *AllDescMap;
  UINTN                            NumEntries;
  UINTN                            Index;
  EFI_STATUS                       Status;

  DEBUG ((DEBUG_INFO, "Accepting all memory\n"));

  /*
   * Get a copy of the memory space map to iterate over while
   * changing the map.
   */
  Status = gDS->GetMemorySpaceMap (&NumEntries, &AllDescMap);
  if (EFI_ERROR (Status)) {
    return Status;
  }

  for (Index = 0; Index < NumEntries; Index++) {
    CONST EFI_GCD_MEMORY_SPACE_DESCRIPTOR  *Desc;

    Desc = &AllDescMap[Index];
    if (Desc->GcdMemoryType != EFI_GCD_MEMORY_TYPE_UNACCEPTED) {
      continue;
    }

    Status = AmdSevMemoryAccept (
               NULL,
               Desc->BaseAddress,
               Desc->Length
               );
    if (EFI_ERROR (Status)) {
      break;
    }

    Status = gDS->RemoveMemorySpace (Desc->BaseAddress, Desc->Length);
    if (EFI_ERROR (Status)) {
      break;
    }

    Status = gDS->AddMemorySpace (
                    EfiGcdMemoryTypeSystemMemory,
                    Desc->BaseAddress,
                    Desc->Length,
                    // Allocable system memory resource capabilities as masked
                    // in MdeModulePkg/Core/Dxe/Mem/Page.c:PromoteMemoryResource
                    Desc->Capabilities & ~(EFI_MEMORY_INTERNAL_MASK | EFI_MEMORY_RUNTIME)
                    );
    if (EFI_ERROR (Status)) {
      break;
    }
  }

  gBS->FreePool (AllDescMap);
  gBS->CloseEvent (mAcceptAllMemoryEvent);
  return Status;
}

VOID
EFIAPI
ResolveUnacceptedMemory (
  IN EFI_EVENT  Event,
  IN VOID       *Context
  )
{
  EFI_STATUS  Status;

  if (!mAcceptAllMemoryAtEBS) {
    return;
  }

  Status = AcceptAllMemory ();
  ASSERT_EFI_ERROR (Status);
}

STATIC
EFI_STATUS
EFIAPI
AllowUnacceptedMemory (
  IN  OVMF_SEV_MEMORY_ACCEPTANCE_PROTOCOL  *This
  )
{
  mAcceptAllMemoryAtEBS = FALSE;
  return EFI_SUCCESS;
}

STATIC
OVMF_SEV_MEMORY_ACCEPTANCE_PROTOCOL
  mMemoryAcceptanceProtocol = { AllowUnacceptedMemory };

STATIC EDKII_MEMORY_ACCEPT_PROTOCOL  mMemoryAcceptProtocol = {
  AmdSevMemoryAccept
};

EFI_STATUS
EFIAPI
AmdSevDxeEntryPoint (
  IN EFI_HANDLE        ImageHandle,
  IN EFI_SYSTEM_TABLE  *SystemTable
  )
{
  EFI_STATUS                                Status;
  EFI_GCD_MEMORY_SPACE_DESCRIPTOR           *AllDescMap;
  UINTN                                     NumEntries;
  UINTN                                     Index;
  CONFIDENTIAL_COMPUTING_SNP_BLOB_LOCATION  *SnpBootDxeTable;

  //
  // Do nothing when SEV is not enabled
  //
  if (!MemEncryptSevIsEnabled ()) {
    return EFI_UNSUPPORTED;
  }

  //
  // Iterate through the GCD map and clear the C-bit from MMIO and NonExistent
  // memory space. The NonExistent memory space will be used for mapping the
  // MMIO space added later (eg PciRootBridge). By clearing both known MMIO and
  // NonExistent memory space can gurantee that current and furture MMIO adds
  // will have C-bit cleared.
  //
  Status = gDS->GetMemorySpaceMap (&NumEntries, &AllDescMap);
  if (!EFI_ERROR (Status)) {
    for (Index = 0; Index < NumEntries; Index++) {
      CONST EFI_GCD_MEMORY_SPACE_DESCRIPTOR  *Desc;

      Desc = &AllDescMap[Index];
      if ((Desc->GcdMemoryType == EfiGcdMemoryTypeMemoryMappedIo) ||
          (Desc->GcdMemoryType == EfiGcdMemoryTypeNonExistent))
      {
        Status = MemEncryptSevClearMmioPageEncMask (
                   0,
                   Desc->BaseAddress,
                   EFI_SIZE_TO_PAGES (Desc->Length)
                   );
        ASSERT_EFI_ERROR (Status);
      }
    }

    FreePool (AllDescMap);
  }

  //
  // If PCI Express is enabled, the MMCONFIG area has been reserved, rather
  // than marked as MMIO, and so the C-bit won't be cleared by the above walk
  // through the GCD map. Check for the MMCONFIG area and clear the C-bit for
  // the range.
  //
  if (PcdGet16 (PcdOvmfHostBridgePciDevId) == INTEL_Q35_MCH_DEVICE_ID) {
    Status = MemEncryptSevClearMmioPageEncMask (
               0,
               FixedPcdGet64 (PcdPciExpressBaseAddress),
               EFI_SIZE_TO_PAGES (SIZE_256MB)
               );

    ASSERT_EFI_ERROR (Status);
  }

  //
  // When SMM is enabled, clear the C-bit from SMM Saved State Area
  //
  // NOTES: The SavedStateArea address cleared here is before SMBASE
  // relocation. Currently, we do not clear the SavedStateArea address after
  // SMBASE is relocated due to the following reasons:
  //
  // 1) Guest BIOS never access the relocated SavedStateArea.
  //
  // 2) The C-bit works on page-aligned address, but the SavedStateArea
  // address is not a page-aligned. Theoretically, we could roundup the address
  // and clear the C-bit of aligned address but looking carefully we found
  // that some portion of the page contains code -- which will causes a bigger
  // issues for SEV guest. When SEV is enabled, all the code must be encrypted
  // otherwise hardware will cause trap.
  //
  // We restore the C-bit for this SMM Saved State Area after SMBASE relocation
  // is completed (See OvmfPkg/Library/SmmCpuFeaturesLib/SmmCpuFeaturesLib.c).
  //
  if (FeaturePcdGet (PcdSmmSmramRequire)) {
    UINTN  MapPagesBase;
    UINTN  MapPagesCount;

    Status = MemEncryptSevLocateInitialSmramSaveStateMapPages (
               &MapPagesBase,
               &MapPagesCount
               );
    ASSERT_EFI_ERROR (Status);

    //
    // Although these pages were set aside (i.e., allocated) by PlatformPei, we
    // could be after a warm reboot from the OS. Don't leak any stale OS data
    // to the hypervisor.
    //
    ZeroMem ((VOID *)MapPagesBase, EFI_PAGES_TO_SIZE (MapPagesCount));

    Status = MemEncryptSevClearPageEncMask (
               0,             // Cr3BaseAddress -- use current CR3
               MapPagesBase,  // BaseAddress
               MapPagesCount  // NumPages
               );
    if (EFI_ERROR (Status)) {
      DEBUG ((
        DEBUG_ERROR,
        "%a: MemEncryptSevClearPageEncMask(): %r\n",
        __func__,
        Status
        ));
      ASSERT (FALSE);
      CpuDeadLoop ();
    }
  }

  Status = AllocateConfidentialComputingBlob (&SnpBootDxeTable);
  if (EFI_ERROR (Status)) {
    DEBUG ((
      DEBUG_ERROR,
      "%a: AllocateConfidentialComputingBlob(): %r\n",
      __func__,
      Status
      ));
    ASSERT (FALSE);
    CpuDeadLoop ();
  }

  if (MemEncryptSevSnpIsEnabled ()) {
    //
    // Memory acceptance began being required in SEV-SNP, so install the
    // memory accept protocol implementation for a SEV-SNP active guest.
    //
    Status = gBS->InstallMultipleProtocolInterfaces (
                    &mAmdSevDxeHandle,
                    &gEdkiiMemoryAcceptProtocolGuid,
                    &mMemoryAcceptProtocol,
                    &gOvmfSevMemoryAcceptanceProtocolGuid,
                    &mMemoryAcceptanceProtocol,
                    NULL
                    );
    ASSERT_EFI_ERROR (Status);

    // SEV-SNP support does not automatically imply unaccepted memory support,
    // so make ExitBootServices accept all unaccepted memory if support is
    // not communicated.
    Status = gBS->CreateEventEx (
                    EVT_NOTIFY_SIGNAL,
                    TPL_CALLBACK,
                    ResolveUnacceptedMemory,
                    NULL,
                    &gEfiEventBeforeExitBootServicesGuid,
                    &mAcceptAllMemoryEvent
                    );

    if (EFI_ERROR (Status)) {
      DEBUG ((DEBUG_ERROR, "AllowUnacceptedMemory event creation for EventBeforeExitBootServices failed.\n"));
    }

    //
    // If its SEV-SNP active guest then install the CONFIDENTIAL_COMPUTING_SEV_SNP_BLOB.
    // It contains the location for both the Secrets and CPUID page.
    //
    return gBS->InstallConfigurationTable (
                  &gConfidentialComputingSevSnpBlobGuid,
                  SnpBootDxeTable
                  );
  }

  return EFI_SUCCESS;
}