Re: [RFC PATCH v3 17/36] pflash_cfi01/tdx: Introduce ram_mode of pflash for TDVF

[Gerd Hoffmann]

  Hi,

> > Just using -bios OVMF.fd might work too.  Daniel tried that recently for
> > sev, but ran into problems with wiring up ovmf metadata parsing for
> > -bios.  Don't remember the details though.
> 
> It was related to the BIOS shadowing, whereby QEMU loads it at one
> address, and then when CPUs start it is copied to another address.

Is this the top 128k of the firmware being copied below 1M so the
firmware reset vector is available in real mode address space?

> This was not compatible with the way AMD SEV wants to do measurement
> of the firmware. May or may not be relevant for TDX, I don't know
> enough about TDX to say.

TDX boots in 32bit mode, so simply skipping any real mode compatibility
stuff shouldn't cause any problems here.

Not sure about SEV.  There is this SevProcessorReset entry in the ovmf
metadata block.  Is that the SEV reset vector?  If SEV cpu bringup
doesn't go through real mode either we maybe can just skip the BIOS
shadowing setup for confidential computing guests ...

take care,
  Gerd