Re: [RFC PATCH v2 20/44] i386/tdx: Parse tdx metadata and store the result into TdxGuestState

[Gerd Hoffmann]

> > If you go without pflash, then you likely will not have a
> > standards-conformant UEFI variable store. (Unless you reimplement the
> > variable arch protocols in edk2 on top of something else than the Fault
> > Tolerant Write and Firmware Volume Block protocols.) Whether a
> > conformant UEFI varstore matters to you (or to TDX in general) is
> > something I can't comment on.
> 
> Thanks for your reply! Laszlo
> 
> regarding "standards-conformant UEFI variable store", I guess you mean the
> change to UEFI non-volatile variables needs to be synced back to the
> OVMF_VARS.fd file. right?

Yes.  UEFI variables are expected to be persistent, and syncing to
OVMF_VARS.fd handles that.

Not fully sure whenever that expectation holds up in the CC world.  At
least the AmdSev variant has just OVMF.fd, i.e. no CODE/VARS split.

> > Regarding pflash itself, the read-only KVM memslot is required for it.
> > Otherwise pflash cannot work as a "ROMD device" (= you can't flip it
> > back and forth between ROM mode and programming (MMIO) mode).
> 
> We don't need Read-only mode for TDVF so far. If for this purpose, is it
> acceptable that allowing a pflash without KVM readonly memslot support if
> read-only is not required for the specific pflash device?

In case you don't want/need persistent VARS (which strictly speaking is
a UEFI spec violation) you should be able to go for a simple "-bios
OVMF.fd".

take care,
  Gerd