Re: [RFC v1 4/5] tools/arm: add "scmi_smc" option to xl.cfg

[Oleksii Moisieiev <Oleksii_Moisieiev@xxxxxxxx>]

On Mon, Dec 20, 2021 at 04:54:25PM -0800, Stefano Stabellini wrote:
> On Tue, 14 Dec 2021, Oleksii Moisieiev wrote:
> > This enumeration sets SCI type for the domain. Currently there is
> > two possible options: either 'none' or 'scmi_smc'.
> > 
> > 'none' is the default value and it disables SCI support at all.
> > 
> > 'scmi_smc' enables access to the Firmware from the domains using SCMI
> > protocol and SMC as transport.
> > 
> > Signed-off-by: Oleksii Moisieiev <oleksii_moisieiev@xxxxxxxx>
> > ---
> >  docs/man/xl.cfg.5.pod.in         | 22 ++++++++++++++++++++++
> >  tools/include/libxl.h            |  5 +++++
> >  tools/libs/light/libxl_types.idl |  6 ++++++
> >  tools/xl/xl_parse.c              |  9 +++++++++
> >  4 files changed, 42 insertions(+)
> > 
> > diff --git a/docs/man/xl.cfg.5.pod.in b/docs/man/xl.cfg.5.pod.in
> > index b98d161398..92d0593875 100644
> > --- a/docs/man/xl.cfg.5.pod.in
> > +++ b/docs/man/xl.cfg.5.pod.in
> > @@ -1614,6 +1614,28 @@ This feature is a B<technology preview>.
> >  
> >  =back
> >  
> > +=item B<sci="STRING">
> > +
> > +B<Arm only> Set SCI type for the guest. SCI is System Control Protocol -
> > +allows domain to manage various functions that are provided by HW platform.
> > +
> > +=over 4
> > +
> > +=item B<none>
> > +
> > +Don't allow guest to use SCI if present on the platform. This is the 
> > default
> > +value.
> > +
> > +=item B<scmi_smc>
> > +
> > +Enables SCMI-SMC support for the guest. SCMI is System Control Management
> > +Inferface - allows domain to manage various functions that are provided by 
> > HW
> > +platform, such as clocks, resets and power-domains. Xen will mediate 
> > access to
> > +clocks, power-domains and resets between Domains and ATF. Disabled by 
> > default.
> > +SMC is used as transport.
> 
> Would it make sense to actually enable SCMI-SMC support for the guest by
> default if the guest has any devices directly assigned?

Hi Stefano,

Previously we discussed with Oleksandr about introducing new dom.cfg
parameter, such as scidev[] lists all sci related nodes, which will help to
avoid extra domctl calls.

But there is still a question how mediator types should be set for
different domains? I know currently system supports only one mediator
type, but different implementation should be also possible.

For example, if we have to start dom0 and domd using scmi_mailbox
mediator and domU using scmi_smc, because our system supports only 2
mailboxes.

Best regards,
Oleksii.