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

[Gerd Hoffmann]

> Regarding what interface should be used to load TDVF, there are three
> options:
> 
>   1) pflash: the same as how we load OVMF.
> 
>   Suppose TDVF support will finally get into OVMF, using this
>   interface, it's full compatible with normal VMs. No change required
>   to QEMU command line and TDVF binary is mapped to the GPA address
>   right below 4G, but they are actually mapped as RAM.
> 
>   Of course, we need several hacks (special handling) in QEMU.

What kind if "hack"?

>   Of course, they don't work as flash, the change made to it doesn't
>   persist.
> 
>   2) -bios
> 
>   exploit "-bios" parameter to load TDVF. But again, read-only is not
>   supported. TDVF is mapped as RAM.
> 
>   3) generic loader
> 
>   Just like what this series does. Implement specific parser in generic
>   loader to load and parse TDVF as private RAM.
> 
> I'm nor sure if 1) is acceptable from your side. If not, we will go with
> option 3, since 2) doesn't make too much sense.

Yep, Daniel (Cc'ed) tried (2) recently for SEV.  Didn't work due to
differences in -bios and -pflash reset handling.  So that option is
out I guess.

SEV uses (1), and there is some support code which you should be able to
reuse (walker for the list of guid-sections with meta-data in the ovmf
reset vector for example).

So TDX going for (1) too is probably the best option.

take care,
  Gerd