Re: [Xen-devel] [PATCH RFC 00/19] arm64 EFI stub

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Wed, 2014-07-09 at 11:24 -0700, Roy Franz wrote:
> >> +    if ( fdtfile->ptr )
> >> +        fdt_size = fdt_totalsize(fdtfile->ptr);
> >> +    else
> >> +    {
> >> +        /* RFRANZ_TODO - missing fdt_create_empty_tree() in libfdt. */
> >> +        return NULL;
> >> +    }
> >
> >
> > I don't think we currently support booting with no FDT at all, and even
> > in the ACPI world we would get one. So I think this would be an error.
> > IOW no need to worry about it.
> >
> 
> I think that for the ACPI-only case, the EFI stub will be the one
> responsible for creating the FDT for passing the UEFI/ACPI to the XEN
> kernel.  (I had overlooked the ACPI-only
> case when considering the no-FDT case - for Linux we support this
> since a kernel could be configured such that it needs nothing from the
> FDT other than UEFI stuff, so we need to support it.)
> So I think we will need this, but only for the ACPI-only case.

I think you probably know better than I but I thought that the way the
presence of ACPI was communicated to the kernel (whether via zImage or
UEFI stub) was via entries in the FDT's /chosen/ node containing the
address of the RSDP. Am I wrong about that?

Or maybe I'm thinking about the UEFI services tables being referenced
via /chosen/?

Ian.


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