Re: [PATCH 3/3] OvmfPkg/PlatformPei: Mark TPM MMIO range as unencrypted for SEV

[Eric van Tassell <evantass@amd.com>]

On 4/20/21 5:54 PM, Tom Lendacky wrote:
> From: Tom Lendacky <thomas.lendacky@amd.com>
> 
> BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=3345
> 
> The TPM support in OVMF performs MMIO accesses during the PEI phase. At

where are the phases defined and how many other are there?

> this point, MMIO ranges have not been marked un-encyrpted, so an SEV-ES
> guest will fail attempting to perform MMIO to an encrypted address.
> 
> Read the PcdTpmBaseAddress and mark the specification defined range
> (0x5000 in length) as un-encrypted, to allow an SEV-ES guest to process
> the MMIO requests.
> 
> Cc: Laszlo Ersek <lersek@redhat.com>
> Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
> Cc: Jordan Justen <jordan.l.justen@intel.com>
> Cc: Brijesh Singh <brijesh.singh@amd.com>
> Cc: James Bottomley <jejb@linux.ibm.com>
> Cc: Jiewen Yao <jiewen.yao@intel.com>
> Cc: Min Xu <min.m.xu@intel.com>
> Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
> ---
>   OvmfPkg/PlatformPei/PlatformPei.inf |  1 +
>   OvmfPkg/PlatformPei/AmdSev.c        | 19 +++++++++++++++++++
>   2 files changed, 20 insertions(+)
> 
> diff --git a/OvmfPkg/PlatformPei/PlatformPei.inf b/OvmfPkg/PlatformPei/PlatformPei.inf
> index 6ef77ba7bb21..de60332e9390 100644
> --- a/OvmfPkg/PlatformPei/PlatformPei.inf
> +++ b/OvmfPkg/PlatformPei/PlatformPei.inf
> @@ -113,6 +113,7 @@ [Pcd]
>   
>   [FixedPcd]
>     gEfiMdePkgTokenSpaceGuid.PcdPciExpressBaseAddress
> +  gEfiSecurityPkgTokenSpaceGuid.PcdTpmBaseAddress
>     gEmbeddedTokenSpaceGuid.PcdMemoryTypeEfiACPIMemoryNVS
>     gEmbeddedTokenSpaceGuid.PcdMemoryTypeEfiACPIReclaimMemory
>     gEmbeddedTokenSpaceGuid.PcdMemoryTypeEfiReservedMemoryType
> diff --git a/OvmfPkg/PlatformPei/AmdSev.c b/OvmfPkg/PlatformPei/AmdSev.c
> index dddffdebda4b..d524929f9e10 100644
> --- a/OvmfPkg/PlatformPei/AmdSev.c
> +++ b/OvmfPkg/PlatformPei/AmdSev.c
> @@ -141,6 +141,7 @@ AmdSevInitialize (
>     )
>   {
>     UINT64                            EncryptionMask;
> +  UINT64                            TpmBaseAddress;
>     RETURN_STATUS                     PcdStatus;
>   
>     //
> @@ -206,6 +207,24 @@ AmdSevInitialize (
>       }
>     }
>   
> +  //
> +  // PEI TPM support will perform MMIO accesses, be sure this range is not
> +  // marked encrypted.
> +  //
> +  TpmBaseAddress = PcdGet64 (PcdTpmBaseAddress);
> +  if (TpmBaseAddress != 0) {
> +    RETURN_STATUS  DecryptStatus;
> +
> +    DecryptStatus = MemEncryptSevClearPageEncMask (
> +                      0,
> +                      TpmBaseAddress,
> +                      EFI_SIZE_TO_PAGES (0x5000),
> +                      FALSE
> +                      );
> +
> +    ASSERT_RETURN_ERROR (DecryptStatus);
> +  }
> +
>     //
>     // Check and perform SEV-ES initialization if required.
>     //
>