Re: [edk2-devel] [PATCH V2 06/28] MdePkg: Update BaseIoLibIntrinsicSev to support Tdx

["Min Xu" <min.m.xu@intel.com>]

On October 12, 2021 6:06 PM, Gerd Hoffmann wrote:
> On Tue, Oct 05, 2021 at 11:39:17AM +0800, Min Xu wrote:
> > RFC： https://bugzilla.tianocore.org/show_bug.cgi?id=3429
> >
> > Intel TDX architecture does not prescribe a specific software
> > convention to perform I/O from the guest TD. Guest TD providers have
> > many choices to provide I/O to the guest. The common I/O models are
> > emulated devices, para-virtualized devices, SRIOV devices and Direct Device
> assignments.
> 
> This monster patch needs splitting up.  At least into io + mmio + fifo.
> Adding the tdx helper functions can be a separate patch too.
Ok, this patch will be split up into io+mmio+fifo in the next version.
> 
> Calling CPUID should not be needed, we have a new fancy
> ConfidentialComputing PCD for that now.
The gUefiCpuPkgTokenSpaceGuid.PcdConfidentialComputingGuestAttr is defined in UefiCpuPkg. While BaseIoLibIntrinsicSev is in MdePkg.
If the ConfidentialComputing PCD is used, then UefiCpuPkg has to be included in BaseIoLibIntrinsicSev.inf. 
I check all the *.inf under MdePkg but no one *.inf include UefiCpuPkg. 
I am not sure if UefiCpuPkg can be included in BaseIoLibIntrinsicSev.inf.
> 
> The new wrappers in IoLibFifo.c should also check for sev, so we have
> something along the lines of ...
> 
>   switch (getpcd(cc)) {
>   case tdx:
>     TdxFifo(...)
>     break;
>   case sev:
>     SevFifo(...)
>     break;
>   default:
>     DefaultFifo(...)
>     break;
>   }
> 
> ... instead of hiding the default case in IoFifoSev.nasm.
> 
> Maybe that's something to cleanup for amd (Brijesh?) beforehand, so the
> structure is there already and the tdx patches just need to add the "case tdx:"
> bits.
Tdx patches can first use above structure. AMD can update it later. Either way is ok.

Thanks!
Min