Adding EFI runtime support to the Arm's FF-A bus

[Shantur Rathore]

Hi Illias,

On Wed, Dec 20, 2023 at 3:43 PM Peter Robinson <pbrobinson at gmail.com> wrote:
>
> On Wed, Dec 20, 2023 at 6:37 AM Ilias Apalodimas
> <ilias.apalodimas at linaro.org> wrote:
> >
> > Hi Michael
> >
> > On Tue, 19 Dec 2023 at 14:47, Michael Walle <mwalle at kernel.org> wrote:
> > >
> > > Hi Mark,
> > >
> > > >> > Any runtime device drivers for variable storage should not be in the
> > > >> > U-Boot runtime but live in the secure world (e.g. OP-TEE) FF-A is the
> > > >> > new ARM protocol for talking to the secure world and hence fits into
> > > >> > the picture.
> > > >>
> > > >> What if I just want a simple embedded boot stack where I don't
> > > >> want any secure world and just want to be able to boot a COTS linux
> > > >> distribution via EFI?
> > > >
> > > > That already works for many Linux distros.  As long as the distro
> > > > installs the appropriate BOOTxxx.EFI file you don't actually need to
> > > > set any EFI variables for the OS to boot.  It can't get any simpler
> > > > than that.  Of the main Linux distros it seems that only Debian
> > > > doesn't do this.  Someone should probably lobby Debian to do this as
> > > > well as it would mean that Debian would just work on an EBBR compliant
> > > > system.
> > >
> > > I know. Last time I checked CentOS (or was it Ubuntu?) tried to
> > > set EFI variables and the installer just failed. Might be fixed now,
> > > though.
> >
> > It's not. The error message is less scary in distros nowadays, but
> > setting the variable for Boot0000 is still not working. That being
> > said I have a plan to fix it for variables stored in a file, that's
> > why we standardized the efi variable format in EBBR.

Does this mean supporting SetVariableRT for files ?
If yes, would it work without the driver model in runtime?

Kind regards,
Shantur