Re: [PATCH 1/2] x86/sev/vc: fix efi runtime instruction emulation

[Gerd Hoffmann]

On Fri, May 30, 2025 at 01:02:33AM +0200, Borislav Petkov wrote:
> On Wed, May 28, 2025 at 09:38:24AM +0200, Gerd Hoffmann wrote:
> > Use case is coconut-svsm providing an uefi variable store and edk2
> > runtime code doing svsm protocol calls to send requests to the svsm
> > variable store.  edk2 needs a caa page mapping and a working rdmsr
> > instruction for that.
> > 
> > Another less critical but useful case is edk2 debug logging to qemu
> > debugcon port.  That needs a working cpuid instruction because edk2
> > uses that to figure whenever sev is active and adapt ioport access
> > accordingly.
> 
> Yeah, I'd like for those justifications be in the commit messages please.

Ok

> > > We'd like to add them to our test pile.
> > 
> > That is a bit difficult right now because there are a number of pieces
> > which need to fall into place before this is easily testable.  You need:
> > 
> >  * host kernel with vmplanes patch series (for snp vmpl support).
> >  * coconut svsm with uefi variable store patches.
> >  * edk2 patches so it talks to svsm for variable access.
> >  * igvm support patches for qemu.
> > 
> > Hope I didn't forgot something ...
> 
> So why are you sending those for the kernel now is so many other things are
> still moving?
> 
> What if something in those things change? Then you need to touch those
> again...

Well, the need for instruction emulation to work for uefi runtime code
and the need to have access to the caa page is not going to change even
if details of edk2 <=> svsm protocol communication will be updated.

take care,
  Gerd