Re: [RFC v4 10/13] OvmfPkg/QemuFwCfgLib: Implement SEV internal functions for PEI phase

[Laszlo Ersek <lersek@redhat.com>]

On 05/11/17 00:09, Brijesh Singh wrote:
> Cc: Jordan Justen <jordan.l.justen@intel.com>
> Cc: Laszlo Ersek <lersek@redhat.com>
> Contributed-under: TianoCore Contribution Agreement 1.0
> Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
> ---
>  OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgPeiLib.inf |  1 +
>  OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgPei.c      | 72 +++++++++++++++++++-
>  2 files changed, 71 insertions(+), 2 deletions(-)

Reviewed-by: Laszlo Ersek <lersek@redhat.com>

Thanks,
Laszlo

> diff --git a/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgPeiLib.inf b/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgPeiLib.inf
> index 4f966a85088a..b97b475c7cad 100644
> --- a/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgPeiLib.inf
> +++ b/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgPeiLib.inf
> @@ -47,4 +47,5 @@ [LibraryClasses]
>    DebugLib
>    IoLib
>    MemoryAllocationLib
> +  MemEncryptSevLib
>  
> diff --git a/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgPei.c b/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgPei.c
> index ac05f4c347f3..1696512bccaf 100644
> --- a/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgPei.c
> +++ b/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgPei.c
> @@ -4,6 +4,7 @@
>  
>    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
> @@ -14,8 +15,10 @@
>    WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
>  **/
>  
> +#include <Library/BaseLib.h>
>  #include <Library/DebugLib.h>
>  #include <Library/QemuFwCfgLib.h>
> +#include <Library/MemEncryptSevLib.h>
>  
>  #include "QemuFwCfgLibInternal.h"
>  
> @@ -76,8 +79,18 @@ QemuFwCfgInitialize (
>    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 SEV is enabled then we do not support DMA operations in PEI phase.
> +    // This is mainly because DMA in SEV guest requires using bounce buffer
> +    // (which need to allocate dynamic memory and allocating a PAGE size'd
> +    // buffer can be challenge in PEI phase)
> +    //
> +    if (InternalQemuFwCfgSevIsEnabled ()) {
> +      DEBUG ((DEBUG_INFO, "SEV: QemuFwCfg fallback to IO Port interface.\n"));
> +    } else {
> +      mQemuFwCfgDmaSupported = TRUE;
> +      DEBUG ((DEBUG_INFO, "QemuFwCfg interface (DMA) is supported.\n"));
> +    }
>    }
>    return RETURN_SUCCESS;
>  }
> @@ -114,3 +127,58 @@ InternalQemuFwCfgDmaIsAvailable (
>  {
>    return mQemuFwCfgDmaSupported;
>  }
> +
> +/**
> +
> + Returns a boolean indicating whether SEV is enabled
> +
> + @retval    TRUE    SEV is enabled
> + @retval    FALSE   SEV is disabled
> +**/
> +BOOLEAN
> +InternalQemuFwCfgSevIsEnabled (
> +  VOID
> +  )
> +{
> +  return MemEncryptSevIsEnabled ();
> +}
> +
> +/**
> + Allocate a bounce buffer for SEV DMA.
> +
> +  @param[in]     NumPage  Number of pages.
> +  @param[out]    Buffer   Allocated DMA Buffer pointer
> +
> +**/
> +VOID
> +InternalQemuFwCfgSevDmaAllocateBuffer (
> +  IN     UINT32   NumPages,
> +  OUT    VOID     **Buffer
> +  )
> +{
> +  //
> +  // We should never reach here
> +  //
> +  ASSERT (FALSE);
> +  CpuDeadLoop ();
> +}
> +
> +/**
> + Free the DMA buffer allocated using InternalQemuFwCfgSevDmaAllocateBuffer
> +
> +  @param[in]     NumPage  Number of pages.
> +  @param[in]     Buffer   DMA Buffer pointer
> +
> +**/
> +VOID
> +InternalQemuFwCfgSevDmaFreeBuffer (
> +  IN     VOID     *Buffer,
> +  IN     UINT32   NumPages
> +  )
> +{
> +  //
> +  // We should never reach here
> +  //
> +  ASSERT (FALSE);
> +  CpuDeadLoop ();
> +}
>