Re: Remaining EFI Xen on ARM issues (on Juno at least)

[Ian Campbell <Ian.Campbell@citrix.com>]

On Wed, 2014-10-22 at 15:14 +0100, Jan Beulich wrote:

> >> Did you verify that your EFI binary got control passed at all (i.e.
> >> whether it really is an issue with reading the config file)?
> > 
> > It prints:
> >         Xen 4.5-unstable (c/s Mon Oct 20 20:55:25 2014 -0700 git:91086d0) 
> > EFI loader
> >         No configuration file found.
> > So I'm pretty sure xen.efi has been called.
> 
> Definitely. Did I overlook that being mentioned before?

I think it had been trimmed by the time you were CCd.

> >> > work, since they specify the disk directly, but maybe I just don't
> >> > understand this aspect of EFI and the application/stub needs to parse
> >> > that if it wants to support loading things from other volumes (and
> >> > doesn't, which is fine).
> >> > 
> >> > It's interesting that Linux on juno is correctly able to load the
> >> > dtb=juno from its command line. Is there some difference here between
> >> > the interfaces used by the Linux stub vs the Xen one?
> >> 
> >> Quite possible - ours is derived from code we had been using for an
> >> abandoned OS project over ten years ago.
> > 
> > OK, so it probably is worth investigating what Xen does differently a
> > little then.
> 
> Or at least adding verbosity to the operations it does, to see when
> which error code(s) get(s) returned. Since failure is being accounted
> for (and recovered from), those error codes wouldn't normally make
> sense to print out.

Yes.

>  But first of all - I suppose this NOR thing has a
> proper file system (and hence a respective EFI protocol) on it? I ask
> because iirc we can't currently handle being remote booted because
> we expect a file system protocol, yet in that case it's a different one
> that would need to be used. There simply was no-one to ask for
> that functionality yet...

A proper filesystem is perhaps a bit of a stretch, you feed the lower
level firmware an index file mapping filenames to regions of flash and
it fakes up a filesystem, so it looks like a file system protocol to the
UEFI app I think.

It doesn't do subdirs (AFAIK) or any modern newfangled concepts like
that ;-)

Ian.