Re: [PATCH v2 00/21] hw/uefi: add uefi variable service

[Gerd Hoffmann]

  Hi,

> > The design idea is to reuse the request serialization protocol edk2 uses
> > for communication between SMM and non-SMM code, so large chunks of the
> > edk2 variable driver stack can be used unmodified.  Only the driver
> > which traps into SMM mode must be replaced by a driver which talks to
> > qemu instead.
> 
> In the coconut-svsm project there's a likely need for coconut to
> provide a UEFI variable store, since we can't store plain text
> variables in host context for confidential VMs.
> 
> Am I right in thinking that this design approach could be reused
> in coconut context with coconut providing the equivalent backend
> service, and EDK2 using the same driver to talk to either QEMU
> or Coconut's service  ?

Yes, that is the idea.  Right now the edk2 driver has two modes, one
talking to the isa device and one talking to the sysbus device.  Adding
a third mode which uses a svsm protocol should be easy.

Writing the efi variable service for coconut is the more challenging
item here.  /me plans to look into that later this year.

take care,
  Gerd