[PATCH] lib: utils: fdt_domain: add support for root domain region inheritance

[Anup Patel]

On Tue, May 12, 2026 at 9:20 PM Anup Patel <anup at brainfault.org> wrote:
>
> On Tue, May 12, 2026 at 1:53 PM Yu-Chien Peter Lin <peter.lin at sifive.com> wrote:
> >
> > Hi Anup,
> >
> > Thanks for suggetion, I'd like to double-check before
> > sending v2 patch.
> >
> > On Sun, May 10, 2026 at 11:34:49AM +0530, Anup Patel wrote:
> > > On Fri, Mar 27, 2026 at 10:04 AM Yu-Chien Peter Lin
> > > <peter.lin at sifive.com> wrote:
> > > >
> > > > Add the "root-regions" property in domain device-tree nodes to
> > > > allow domains to inherit all regions from the root domain. This
> > > > simplifies configuration for domains that need access to most
> > > > root domain regions with only minor exclusions or additions.
> > >
> > > Overall, this is a good approach but I suggest renaming this property
> > > to "root-regions-inheritance" which takes the following possible values:
> > >
> > > 1) "all" : Inherit all regions from the root domain
> > > 2) "su-only": Inherit regions accessible to S-mode or U-mode from the
> > > root domain
> >
> > 1. Do you mean:
> >    a) any root regions that have any SU permission bits set regardless of the
> >       M‑mode permission bits, or
> >    b) only regions that satisfy SBI_DOMAIN_MEMREGION_SU_ONLY_ACCESS(flags)?
>
> Actually, none of these. Apologies for the confusion.
>
> I meant the current policy of copying select regions from
> root domain to non-root domain which is only copy regions
> which have no SU permissions set.
>
> This means the following possible values:
>
> 1) "all" : Inherit all regions from the root domain
> 2) "m-only": Inherit regions of root domain not having
> any SU permissions set (current policy) which also
> covers firmware regions.
> 3) "none": Inherit no regions from the root domain
>
> > 2. For firmware regions marked with SBI_DOMAIN_MEMREGION_FW, should those always
> >    be inherited, even when "root-regions-inheritance" is "none" or "su-only"?
>
> Yes, FW regions should always be inherited because these are for
> OpenSBI itself and OpenSBI is always resident in background.
>

Thinking about this more, the "none" option should not be
there because m-only regions (including fw regions) are
always required for proper functioning of OpenSBI.

Regards,
Anup