[PATCH] lib: sbi: Try to make each domain have boot hart

[Anup Patel]

On Tue, Jul 4, 2023 at 2:16 PM Xiang W <wxjstz at 126.com> wrote:
>
> 在 2023-07-04星期二的 09:18 +0530，Anup Patel写道：
> > On Tue, Jun 20, 2023 at 6:02 PM Xiang W <wxjstz at 126.com> wrote:
> > >
> > > domain register will move the hart from the old domain to the
> > > new domain, and should not move the boot hart to prevent the
> > > old domain from losing the boot hart.
> > >
> > > Signed-off-by: Xiang W <wxjstz at 126.com>
> > > ---
> > >  lib/sbi/sbi_domain.c | 16 +++++++++++++++-
> > >  1 file changed, 15 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/lib/sbi/sbi_domain.c b/lib/sbi/sbi_domain.c
> > > index 38a5902..46a4aef 100644
> > > --- a/lib/sbi/sbi_domain.c
> > > +++ b/lib/sbi/sbi_domain.c
> > > @@ -543,9 +543,23 @@ int sbi_domain_register(struct sbi_domain *dom,
> > >                         continue;
> > >
> > >                 tdom = sbi_hartid_to_domain(i);
> > > -               if (tdom)
> > > +               if (tdom) {
> > > +                       if (i == tdom->boot_hartid) {
> > > +                               /* Newly registered domain should not
> > > +                                * take up the boot hart of the older domain */
> > > +                               if (i == dom->boot_hartid)
> > > +                                       sbi_printf("%s: failed assign Hart%d to %s, "
> > > +                                               "conflict with %s\n",
> > > +                                               __func__, i, dom->name, tdom->name);
> > > +                               else
> > > +                                       sbi_printf("%s: skip assign Hart%d to %s, "
> > > +                                               "because Hart%d is boot hart of %s\n",
> > > +                                               __func__, i, dom->name, i, tdom->name);
> > > +                               continue;
> > > +                       }
> >
> > This is not needed because sbi_domain_finalize() already checks that
> > dom->boot_hartid is assigned to dom before starting dom->boot_hartid.
> >
> > The cold boot HART is by default boot HART of the root domain and
> > assigned to the root domain. This patch prevents cold boot HART from
> > changing its own domain.
>
> If the cold boot hart changes its own domain, the root domain will not
> lost boot hart and will not be able to start.
>
> Is it not a mistake that root dmain cannot be started?

No it's not a mistake. For instance, look at example in the
docs/domain_support.md where we have two additional
domains "trusted" and "untrusted" apart from the root domain
which cover all HARTs already covered by the root domain. In
this example, the root domain never runs because the boot
HART changes its own domain to "untrusted" domain.

The root domain is a default/fallback domain which exists in the
system even when no domains are defined via FDT. We can have
many domains defined in the system but a HART is running in exactly
one domain context.

Regards,
Anup

>
> Regards,
> Xiang W
> >
> > NACK for this patch.
> >
> > Regards,
> > Anup
> >
> > >                         sbi_hartmask_clear_hart(i,
> > >                                         &tdom->assigned_harts);
> > > +               }
> > >                 update_hartid_to_domain(i, dom);
> > >                 sbi_hartmask_set_hart(i, &dom->assigned_harts);
> > >
> > > --
> > > 2.39.2
> > >
> > >
> > > --
> > > opensbi mailing list
> > > opensbi at lists.infradead.org
> > > http://lists.infradead.org/mailman/listinfo/opensbi
>