Re: [PATCH v3 3/5] OvmfPkg: Define a new PPI GUID to signal TPM MMIO accessability

["Lendacky, Thomas" <thomas.lendacky@amd.com>]

On 4/29/21 12:12 PM, Tom Lendacky wrote:
> Define a new PPI GUID that is to be used as a signal of when it is safe
> to access the TPM MMIO range. This is needed so that, when SEV is active,
> the MMIO range can be mapped unencrypted before it is accessed.
> 
> 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: Erdem Aktas <erdemaktas@google.com>
> Cc: James Bottomley <jejb@linux.ibm.com>
> Cc: Jiewen Yao <jiewen.yao@intel.com>
> Cc: Min Xu <min.m.xu@intel.com>
> Cc: Marc-André Lureau <marcandre.lureau@redhat.com>
> Cc: Stefan Berger <stefanb@linux.ibm.com>
> Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>

Sorry, Laszlo, I forgot to include your Reviewed-by: on this patch.

Tom

> ---
>  OvmfPkg/OvmfPkg.dec | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/OvmfPkg/OvmfPkg.dec b/OvmfPkg/OvmfPkg.dec
> index 9629707020ba..6ae733f6e39f 100644
> --- a/OvmfPkg/OvmfPkg.dec
> +++ b/OvmfPkg/OvmfPkg.dec
> @@ -128,6 +128,10 @@ [Ppis]
>    # has been discovered and recorded
>    gOvmfTpmDiscoveredPpiGuid             = {0xb9a61ad0, 0x2802, 0x41f3, {0xb5, 0x13, 0x96, 0x51, 0xce, 0x6b, 0xd5, 0x75}}
>  
> +  # This PPI signals that accessing the MMIO range of the TPM is possible in
> +  # the PEI phase, regardless of memory encryption
> +  gOvmfTpmMmioAccessiblePpiGuid         = {0x35c84ff2, 0x7bfe, 0x453d, {0x84, 0x5f, 0x68, 0x3a, 0x49, 0x2c, 0xf7, 0xb7}}
> +
>  [Protocols]
>    gVirtioDeviceProtocolGuid             = {0xfa920010, 0x6785, 0x4941, {0xb6, 0xec, 0x49, 0x8c, 0x57, 0x9f, 0x16, 0x0a}}
>    gXenBusProtocolGuid                   = {0x3d3ca290, 0xb9a5, 0x11e3, {0xb7, 0x5d, 0xb8, 0xac, 0x6f, 0x7d, 0x65, 0xe6}}
>