system76-edk2/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgDxe.c

/** @file

  Stateful and implicitly initialized fw_cfg library implementation.

  Copyright (C) 2013, Red Hat, Inc.
  Copyright (c) 2011 - 2013, Intel Corporation. All rights reserved.<BR>
  Copyright (c) 2017, Advanced Micro Devices. All rights reserved.<BR>

  This program and the accompanying materials are licensed and made available
  under the terms and conditions of the BSD License which accompanies this
  distribution.  The full text of the license may be found at
  http://opensource.org/licenses/bsd-license.php

  THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS, WITHOUT
  WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
**/

#include <Uefi.h>

#include <Protocol/IoMmu.h>

#include <Library/BaseLib.h>
#include <Library/BaseMemoryLib.h>
#include <Library/IoLib.h>
#include <Library/DebugLib.h>
#include <Library/QemuFwCfgLib.h>
#include <Library/UefiBootServicesTableLib.h>
#include <Library/MemEncryptSevLib.h>

#include "QemuFwCfgLibInternal.h"

STATIC BOOLEAN mQemuFwCfgSupported = FALSE;
STATIC BOOLEAN mQemuFwCfgDmaSupported;

STATIC EDKII_IOMMU_PROTOCOL        *mIoMmuProtocol;

/**
  Returns a boolean indicating if the firmware configuration interface
  is available or not.

  This function may change fw_cfg state.

  @retval    TRUE   The interface is available
  @retval    FALSE  The interface is not available

**/
BOOLEAN
EFIAPI
QemuFwCfgIsAvailable (
  VOID
  )
{
  return InternalQemuFwCfgIsAvailable ();
}


RETURN_STATUS
EFIAPI
QemuFwCfgInitialize (
  VOID
  )
{
  UINT32 Signature;
  UINT32 Revision;

  //
  // Enable the access routines while probing to see if it is supported.
  // For probing we always use the IO Port (IoReadFifo8()) access method.
  //
  mQemuFwCfgSupported = TRUE;
  mQemuFwCfgDmaSupported = FALSE;

  QemuFwCfgSelectItem (QemuFwCfgItemSignature);
  Signature = QemuFwCfgRead32 ();
  DEBUG ((EFI_D_INFO, "FW CFG Signature: 0x%x\n", Signature));
  QemuFwCfgSelectItem (QemuFwCfgItemInterfaceVersion);
  Revision = QemuFwCfgRead32 ();
  DEBUG ((EFI_D_INFO, "FW CFG Revision: 0x%x\n", Revision));
  if ((Signature != SIGNATURE_32 ('Q', 'E', 'M', 'U')) ||
      (Revision < 1)
     ) {
    DEBUG ((EFI_D_INFO, "QemuFwCfg interface not supported.\n"));
    mQemuFwCfgSupported = FALSE;
    return RETURN_SUCCESS;
  }

  if ((Revision & FW_CFG_F_DMA) == 0) {
    DEBUG ((DEBUG_INFO, "QemuFwCfg interface (IO Port) is supported.\n"));
  } else {
    mQemuFwCfgDmaSupported = TRUE;
    DEBUG ((DEBUG_INFO, "QemuFwCfg interface (DMA) is supported.\n"));
  }

  if (mQemuFwCfgDmaSupported && MemEncryptSevIsEnabled ()) {
    EFI_STATUS   Status;

    //
    // IoMmuDxe driver must have installed the IOMMU protocol. If we are not
    // able to locate the protocol then something must have gone wrong.
    //
    Status = gBS->LocateProtocol (&gEdkiiIoMmuProtocolGuid, NULL,
                    (VOID **)&mIoMmuProtocol);
    if (EFI_ERROR (Status)) {
      DEBUG ((DEBUG_ERROR,
        "QemuFwCfgSevDma %a:%a Failed to locate IOMMU protocol.\n",
        gEfiCallerBaseName, __FUNCTION__));
      ASSERT (FALSE);
      CpuDeadLoop ();
    }
  }

  return RETURN_SUCCESS;
}


/**
  Returns a boolean indicating if the firmware configuration interface is
  available for library-internal purposes.

  This function never changes fw_cfg state.

  @retval    TRUE   The interface is available internally.
  @retval    FALSE  The interface is not available internally.
**/
BOOLEAN
InternalQemuFwCfgIsAvailable (
  VOID
  )
{
  return mQemuFwCfgSupported;
}

/**
  Returns a boolean indicating whether QEMU provides the DMA-like access method
  for fw_cfg.

  @retval    TRUE   The DMA-like access method is available.
  @retval    FALSE  The DMA-like access method is unavailable.
**/
BOOLEAN
InternalQemuFwCfgDmaIsAvailable (
  VOID
  )
{
  return mQemuFwCfgDmaSupported;
}

/**
  Function is used for allocating a bi-directional FW_CFG_DMA_ACCESS used
  between Host and device to exchange the information. The buffer must be free'd
  using FreeFwCfgDmaAccessBuffer ().

**/
STATIC
VOID
AllocFwCfgDmaAccessBuffer (
  OUT   VOID     **Access,
  OUT   VOID     **MapInfo
  )
{
  UINTN                 Size;
  UINTN                 NumPages;
  EFI_STATUS            Status;
  VOID                  *HostAddress;
  EFI_PHYSICAL_ADDRESS  DmaAddress;
  VOID                  *Mapping;

  Size = sizeof (FW_CFG_DMA_ACCESS);
  NumPages = EFI_SIZE_TO_PAGES (Size);

  //
  // As per UEFI spec, in order to map a host address with
  // BusMasterCommomBuffer64, the buffer must be allocated using the IOMMU
  // AllocateBuffer()
  //
  Status = mIoMmuProtocol->AllocateBuffer (
                             mIoMmuProtocol,
                             AllocateAnyPages,
                             EfiBootServicesData,
                             NumPages,
                             &HostAddress,
                             EDKII_IOMMU_ATTRIBUTE_DUAL_ADDRESS_CYCLE
                             );
  if (EFI_ERROR (Status)) {
    DEBUG ((DEBUG_ERROR,
      "%a:%a failed to allocate FW_CFG_DMA_ACCESS\n", gEfiCallerBaseName,
      __FUNCTION__));
    ASSERT (FALSE);
    CpuDeadLoop ();
  }

  //
  // Avoid exposing stale data even temporarily: zero the area before mapping
  // it.
  //
  ZeroMem (HostAddress, Size);

  //
  // Map the host buffer with BusMasterCommonBuffer64
  //
  Status = mIoMmuProtocol->Map (
                             mIoMmuProtocol,
                             EdkiiIoMmuOperationBusMasterCommonBuffer64,
                             HostAddress,
                             &Size,
                             &DmaAddress,
                             &Mapping
                             );
  if (EFI_ERROR (Status)) {
    mIoMmuProtocol->FreeBuffer (mIoMmuProtocol, NumPages, HostAddress);
    DEBUG ((DEBUG_ERROR,
      "%a:%a failed to Map() FW_CFG_DMA_ACCESS\n", gEfiCallerBaseName,
      __FUNCTION__));
    ASSERT (FALSE);
    CpuDeadLoop ();
  }

  if (Size < sizeof (FW_CFG_DMA_ACCESS)) {
    mIoMmuProtocol->Unmap (mIoMmuProtocol, Mapping);
    mIoMmuProtocol->FreeBuffer (mIoMmuProtocol, NumPages, HostAddress);
    DEBUG ((DEBUG_ERROR,
      "%a:%a failed to Map() - requested 0x%Lx got 0x%Lx\n", gEfiCallerBaseName,
      __FUNCTION__, (UINT64)sizeof (FW_CFG_DMA_ACCESS), (UINT64)Size));
    ASSERT (FALSE);
    CpuDeadLoop ();
  }

  *Access = HostAddress;
  *MapInfo = Mapping;
}

/**
  Function is to used for freeing the Access buffer allocated using
  AllocFwCfgDmaAccessBuffer()

**/
STATIC
VOID
FreeFwCfgDmaAccessBuffer (
  IN  VOID    *Access,
  IN  VOID    *Mapping
  )
{
  UINTN       NumPages;
  EFI_STATUS  Status;

  NumPages = EFI_SIZE_TO_PAGES (sizeof (FW_CFG_DMA_ACCESS));

  Status = mIoMmuProtocol->Unmap (mIoMmuProtocol, Mapping);
  if (EFI_ERROR (Status)) {
    DEBUG ((DEBUG_ERROR,
      "%a:%a failed to UnMap() Mapping 0x%Lx\n", gEfiCallerBaseName,
      __FUNCTION__, (UINT64)(UINTN)Mapping));
    ASSERT (FALSE);
    CpuDeadLoop ();
  }

  Status = mIoMmuProtocol->FreeBuffer (mIoMmuProtocol, NumPages, Access);
  if (EFI_ERROR (Status)) {
    DEBUG ((DEBUG_ERROR,
      "%a:%a failed to Free() 0x%Lx\n", gEfiCallerBaseName, __FUNCTION__,
      (UINT64)(UINTN)Access));
    ASSERT (FALSE);
    CpuDeadLoop ();
  }
}

/**
  Function is used for mapping host address to device address. The buffer must
  be unmapped with UnmapDmaDataBuffer ().

**/
STATIC
VOID
MapFwCfgDmaDataBuffer (
  IN  BOOLEAN               IsWrite,
  IN  VOID                  *HostAddress,
  IN  UINT32                Size,
  OUT EFI_PHYSICAL_ADDRESS  *DeviceAddress,
  OUT VOID                  **MapInfo
  )
{
  EFI_STATUS              Status;
  UINTN                   NumberOfBytes;
  VOID                    *Mapping;
  EFI_PHYSICAL_ADDRESS    PhysicalAddress;

  NumberOfBytes = Size;
  Status = mIoMmuProtocol->Map (
                             mIoMmuProtocol,
                             (IsWrite ?
                              EdkiiIoMmuOperationBusMasterRead64 :
                              EdkiiIoMmuOperationBusMasterWrite64),
                             HostAddress,
                             &NumberOfBytes,
                             &PhysicalAddress,
                             &Mapping
                             );
  if (EFI_ERROR (Status)) {
    DEBUG ((DEBUG_ERROR,
      "%a:%a failed to Map() Address 0x%Lx Size 0x%Lx\n", gEfiCallerBaseName,
      __FUNCTION__, (UINT64)(UINTN)HostAddress, (UINT64)Size));
    ASSERT (FALSE);
    CpuDeadLoop ();
  }

  if (NumberOfBytes < Size) {
    mIoMmuProtocol->Unmap (mIoMmuProtocol, Mapping);
    DEBUG ((DEBUG_ERROR,
      "%a:%a failed to Map() - requested 0x%x got 0x%Lx\n", gEfiCallerBaseName,
      __FUNCTION__, Size, (UINT64)NumberOfBytes));
    ASSERT (FALSE);
    CpuDeadLoop ();
  }

  *DeviceAddress = PhysicalAddress;
  *MapInfo = Mapping;
}

STATIC
VOID
UnmapFwCfgDmaDataBuffer (
  IN  VOID  *Mapping
  )
{
  EFI_STATUS  Status;

  Status = mIoMmuProtocol->Unmap (mIoMmuProtocol, Mapping);
  if (EFI_ERROR (Status)) {
    DEBUG ((DEBUG_ERROR,
      "%a:%a failed to UnMap() Mapping 0x%Lx\n", gEfiCallerBaseName,
      __FUNCTION__, (UINT64)(UINTN)Mapping));
    ASSERT (FALSE);
    CpuDeadLoop ();
  }
}

/**
  Transfer an array of bytes, or skip a number of bytes, using the DMA
  interface.

  @param[in]     Size     Size in bytes to transfer or skip.

  @param[in,out] Buffer   Buffer to read data into or write data from. Ignored,
                          and may be NULL, if Size is zero, or Control is
                          FW_CFG_DMA_CTL_SKIP.

  @param[in]     Control  One of the following:
                          FW_CFG_DMA_CTL_WRITE - write to fw_cfg from Buffer.
                          FW_CFG_DMA_CTL_READ  - read from fw_cfg into Buffer.
                          FW_CFG_DMA_CTL_SKIP  - skip bytes in fw_cfg.
**/
VOID
InternalQemuFwCfgDmaBytes (
  IN     UINT32   Size,
  IN OUT VOID     *Buffer OPTIONAL,
  IN     UINT32   Control
  )
{
  volatile FW_CFG_DMA_ACCESS LocalAccess;
  volatile FW_CFG_DMA_ACCESS *Access;
  UINT32                     AccessHigh, AccessLow;
  UINT32                     Status;
  VOID                       *AccessMapping, *DataMapping;
  VOID                       *DataBuffer;

  ASSERT (Control == FW_CFG_DMA_CTL_WRITE || Control == FW_CFG_DMA_CTL_READ ||
    Control == FW_CFG_DMA_CTL_SKIP);

  if (Size == 0) {
    return;
  }

  Access = &LocalAccess;
  AccessMapping = NULL;
  DataMapping = NULL;
  DataBuffer = Buffer;

  //
  // When SEV is enabled, map Buffer to DMA address before issuing the DMA
  // request
  //
  if (MemEncryptSevIsEnabled ()) {
    VOID                  *AccessBuffer;
    EFI_PHYSICAL_ADDRESS  DataBufferAddress;

    //
    // Allocate DMA Access buffer
    //
    AllocFwCfgDmaAccessBuffer (&AccessBuffer, &AccessMapping);

    Access = AccessBuffer;

    //
    // Map actual data buffer
    //
    if (Control != FW_CFG_DMA_CTL_SKIP) {
      MapFwCfgDmaDataBuffer (
        Control == FW_CFG_DMA_CTL_WRITE,
        Buffer,
        Size,
        &DataBufferAddress,
        &DataMapping
        );

      DataBuffer = (VOID *) (UINTN) DataBufferAddress;
    }
  }

  Access->Control = SwapBytes32 (Control);
  Access->Length  = SwapBytes32 (Size);
  Access->Address = SwapBytes64 ((UINTN)DataBuffer);

  //
  // Delimit the transfer from (a) modifications to Access, (b) in case of a
  // write, from writes to Buffer by the caller.
  //
  MemoryFence ();

  //
  // Start the transfer.
  //
  AccessHigh = (UINT32)RShiftU64 ((UINTN)Access, 32);
  AccessLow  = (UINT32)(UINTN)Access;
  IoWrite32 (FW_CFG_IO_DMA_ADDRESS,     SwapBytes32 (AccessHigh));
  IoWrite32 (FW_CFG_IO_DMA_ADDRESS + 4, SwapBytes32 (AccessLow));

  //
  // Don't look at Access.Control before starting the transfer.
  //
  MemoryFence ();

  //
  // Wait for the transfer to complete.
  //
  do {
    Status = SwapBytes32 (Access->Control);
    ASSERT ((Status & FW_CFG_DMA_CTL_ERROR) == 0);
  } while (Status != 0);

  //
  // After a read, the caller will want to use Buffer.
  //
  MemoryFence ();

  //
  // If Access buffer was dynamically allocated then free it.
  //
  if (AccessMapping != NULL) {
    FreeFwCfgDmaAccessBuffer ((VOID *)Access, AccessMapping);
  }

  //
  // If DataBuffer was mapped then unmap it.
  //
  if (DataMapping != NULL) {
    UnmapFwCfgDmaDataBuffer (DataMapping);
  }
}