Re: [PATCH v5 12/14] OvmfPkg/QemuFwCfgLib: Implement SEV internal function for Dxe phase

[Laszlo Ersek <lersek@redhat.com>]

comments below:

On 05/22/17 17:23, Brijesh Singh wrote:
> When SEV is enabled, the DMA must be performed on unencrypted pages.
> So when get asked to perfom FWCFG DMA read or write, we allocate a
> intermediate (bounce buffer) unencrypted buffer and use this buffer
> for DMA read or write.
> 
> 
> 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/QemuFwCfgDxeLib.inf |   7 ++
>  OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgDxe.c      | 108 ++++++++++++++++++++
>  2 files changed, 115 insertions(+)
> 
> diff --git a/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgDxeLib.inf b/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgDxeLib.inf
> index d7e368e5435d..ec128f82c702 100644
> --- a/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgDxeLib.inf
> +++ b/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgDxeLib.inf
> @@ -39,6 +39,7 @@ [Sources]
>  
>  [Packages]
>    MdePkg/MdePkg.dec
> +  MdeModulePkg/MdeModulePkg.dec
>    OvmfPkg/OvmfPkg.dec
>  
>  [LibraryClasses]
> @@ -47,4 +48,10 @@ [LibraryClasses]
>    DebugLib
>    IoLib
>    MemoryAllocationLib
> +  MemEncryptSevLib
>  
> +[Protocols]
> +  gEdkiiIoMmuProtocolGuid                         ## SOMETIMES_CONSUMES
> +
> +[Depex]
> +  gEdkiiIoMmuProtocolGuid OR gIoMmuDetectedProtocolGuid

I'll comment on the depex elsewhere (returning to an earlier spot in the
series). Other than that, I have only cosmetic comments:

> diff --git a/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgDxe.c b/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgDxe.c
> index ac05f4c347f3..bda1a80b5eb9 100644
> --- a/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgDxe.c
> +++ b/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgDxe.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
> @@ -14,14 +15,36 @@
>    WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
>  **/
>  
> +#include <Uefi.h>
> +
> +#include <Protocol/IoMmu.h>
> +
> +#include <Library/BaseLib.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 whether SEV is enabled
> +
> + @retval    TRUE    SEV is enabled
> + @retval    FALSE   SEV is disabled
> +**/
> +BOOLEAN
> +InternalQemuFwCfgSevIsEnabled (
> +  VOID
> +  )
> +{
> +  return MemEncryptSevIsEnabled ();
> +}
>  
>  /**
>    Returns a boolean indicating if the firmware configuration interface
> @@ -79,6 +102,22 @@ QemuFwCfgInitialize (
>      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, "QemuwCfgSevDma: failed to locate IOMMU protocol\n"));

(1) The word "QemuwCfgSevDma" has a typo, it should be "QemuFwCfgSevDma".

Also, I recommend printing gEfiCallerBaseName / __FUNCTION__ here as well.

(2) A number of DEBUGs are incorrectly indented below.

I'm not comfortable giving my R-b in advance, with those fixed, because
my comments on the depex (to be made elsewhere in the series) might
induce a change to the depex, and I'd like to review that separately.

If it turns out that the v5 depex will be fine, then the above two
remarks don't necessitate a v6, and I'll be OK to R-b this v5 patch.

Thanks,
Laszlo

> +      ASSERT (FALSE);
> +      CpuDeadLoop ();
> +    }
> +  }
> +
>    return RETURN_SUCCESS;
>  }
>  
> @@ -114,3 +153,72 @@ InternalQemuFwCfgDmaIsAvailable (
>  {
>    return mQemuFwCfgDmaSupported;
>  }
> +
> +/**
> + Allocate a bounce buffer for SEV DMA.
> +
> +  @param[in]     NumPage  Number of pages.
> +  @param[out]    Buffer   Allocated DMA Buffer pointer
> +
> +**/
> +VOID
> +InternalQemuFwCfgSevDmaAllocateBuffer (
> +  OUT    VOID     **Buffer,
> +  IN     UINT32   NumPages
> +  )
> +{
> +  EFI_STATUS    Status;
> +
> +  ASSERT (mIoMmuProtocol != NULL);
> +
> +  Status = mIoMmuProtocol->AllocateBuffer (
> +                            mIoMmuProtocol,
> +                            0,
> +                            EfiBootServicesData,
> +                            NumPages,
> +                            Buffer,
> +                            EDKII_IOMMU_ATTRIBUTE_MEMORY_CACHED
> +                          );
> +  if (EFI_ERROR (Status)) {
> +    DEBUG ((DEBUG_ERROR, "%a:%a failed to allocate %u pages\n", gEfiCallerBaseName,
> +          __FUNCTION__, NumPages));
> +    ASSERT (FALSE);
> +    CpuDeadLoop ();
> +  }
> +
> +  DEBUG ((DEBUG_VERBOSE, "%a:%a buffer 0x%Lx Pages %u\n", gEfiCallerBaseName,
> +        __FUNCTION__, (UINT64)(UINTN)Buffer, NumPages));
> +}
> +
> +/**
> + 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
> +  )
> +{
> +  EFI_STATUS    Status;
> +
> +  ASSERT (mIoMmuProtocol != NULL);
> +
> +  Status = mIoMmuProtocol->FreeBuffer (
> +                            mIoMmuProtocol,
> +                            NumPages,
> +                            Buffer
> +                          );
> +  if (EFI_ERROR (Status)) {
> +    DEBUG ((DEBUG_ERROR, "%a:%a failed to free buffer 0x%Lx pages %u\n",
> +          gEfiCallerBaseName, __FUNCTION__, (UINT64)(UINTN)Buffer, NumPages));
> +    ASSERT (FALSE);
> +    CpuDeadLoop ();
> +  }
> +
> +  DEBUG ((DEBUG_VERBOSE, "%a:%a buffer 0x%Lx Pages %u\n", gEfiCallerBaseName,
> +        __FUNCTION__, (UINT64)(UINTN)Buffer, NumPages));
> +}
>