Re: [Xen-devel] [PATCH 1/4] xen: use domid check in is_hardware_domain

[Daniel De Graaf <dgdegra@xxxxxxxxxxxxx>]

On 07/08/2013 10:58 AM, Jan Beulich wrote:
> > > > On 08.07.13 at 16:46, Daniel De Graaf <dgdegra@xxxxxxxxxxxxx> wrote:
> > --- a/xen/common/domain.c
> > +++ b/xen/common/domain.c
> > @@ -238,7 +238,7 @@ struct domain *domain_create(
> >       if ( domcr_flags & DOMCRF_hvm )
> >           d->is_hvm = 1;
> >
> > -    if ( domid == 0 )
> > +    if ( is_hardware_domain(d) )
> >       {
> >           d->is_pinned = opt_dom0_vcpus_pin;
> >           d->disable_migrate = 1;
> > @@ -263,10 +263,10 @@ struct domain *domain_create(
> >           d->is_paused_by_controller = 1;
> >           atomic_inc(&d->pause_count);
> >
> > -        if ( domid )
> > -            d->nr_pirqs = nr_static_irqs + extra_domU_irqs;
> > -        else
> > +        if ( is_hardware_domain(d) )
> >               d->nr_pirqs = nr_static_irqs + extra_dom0_irqs;
> > +        else
> > +            d->nr_pirqs = nr_static_irqs + extra_domU_irqs;
> >           if ( d->nr_pirqs > nr_irqs )
> >               d->nr_pirqs = nr_irqs;
> >
> > @@ -600,7 +600,7 @@ void domain_shutdown(struct domain *d, u8 reason)
> >           d->shutdown_code = reason;
> >       reason = d->shutdown_code;
> >
> > -    if ( d->domain_id == 0 )
> > +    if ( is_hardware_domain(d) )
> >           dom0_shutdown(reason);
> All earlier changes can be explained in one way or another to also
> apply to other than Dom0. This one, however, can't: There can
> only ever be one domain controling when to shut down the system,
> and hence I think it is misleading to use is_hardware_domain()
> here. Or is your targeted abstract model aiming at a single such
> domain, just perhaps with a domain ID other than zero?
>
> Jan
Yes, that is the model I am using. It splits dom0 into three domains:

0. Domain builder: bootstraps the system. May remain to perform requested
   builds of domains that need a minimal trust chain (i.e. vTPM domains).
   Other than being built by the hypervisor, nothing is special about this
   domain - although it may be useful to have is_control_domain be true.
1. Hardware domain: manages devices for PCI pass-through to driver domains
   or can act as a driver domain itself, depending on the desired degree
   of disaggregation. This is the only domain where is_hardware_domain()
   is true. The return of is_control_domain() is false for this domain.
2. Control domain: manages other domains, controls guest launch/shutdown,
   manages resource constraints, etc; is_control_domain() returns true.

This model has a working implementation derived from the work in the XOAR
paper. It requires a patch on top of these to change the IOMMU setup to
happen after dom0 starts, and a dedicated domain builder domain.

--
Daniel De Graaf
National Security Agency

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