Re: [Qemu-devel] [PATCH 1/2] pcie_root_port: Allow ACS to be disabled

["Dr. David Alan Gilbert" <dgilbert@redhat.com>]

* Igor Mammedov (imammedo@redhat.com) wrote:
> On Tue, 30 Jul 2019 12:13:06 +0100
> "Dr. David Alan Gilbert" <dgilbert@redhat.com> wrote:
> 
> > * Igor Mammedov (imammedo@redhat.com) wrote:
> > > On Tue, 30 Jul 2019 10:37:18 +0100
> > > "Dr. David Alan Gilbert (git)" <dgilbert@redhat.com> wrote:
> > > 
> > > > From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
> > > > 
> > > > ACS was added in 4.0 unconditionally, this breaks migration
> > > > compatibility.
> > > > Allow ACS to be disabled by adding a property that's
> > > > checked by pcie_root_port.
> > > > 
> > > > Unfortunately pcie-root-port doesn't have any instance data,
> > > > so there's no where for that flag to live, so stuff it into
> > > > PCIESlot.
> > > > 
> > > > Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
> > > > ---
> > > >  hw/pci-bridge/pcie_root_port.c | 3 ++-
> > > >  include/hw/pci/pcie_port.h     | 2 ++
> > > >  2 files changed, 4 insertions(+), 1 deletion(-)
> > > > 
> > > > diff --git a/hw/pci-bridge/pcie_root_port.c b/hw/pci-bridge/pcie_root_port.c
> > > > index 09019ca05d..1d8a778709 100644
> > > > --- a/hw/pci-bridge/pcie_root_port.c
> > > > +++ b/hw/pci-bridge/pcie_root_port.c
> > > > @@ -111,7 +111,7 @@ static void rp_realize(PCIDevice *d, Error **errp)
> > > >      pcie_aer_root_init(d);
> > > >      rp_aer_vector_update(d);
> > > >  
> > > > -    if (rpc->acs_offset) {
> > > > +    if (rpc->acs_offset && !s->disable_acs) {
> > > 
> > > it's not like it would be used per instance,
> > > so could we use class property and with rpc->disable_acs instead of PCIESlot?
> > 
> > I'm not clear I understand how class properties help;
> >     object_class_property_add_bool
> > takes a getter/setter that takes an Object *  parameter;
> > my reading of that is that it's the instance data so has the same
> > problem.
> 
> it's possible to reach class data from setter/getter,
> for example s390_cpu_model_class_register_props().

Ah OK.

> But it will be a bit more code than here and considering
> that it's only field in parent type which is reachable through
> root port specific property only it is also ok as is as a
> fix to 4.1, so if you prefer to keep it like now
> 
> Reviewed-by: Igor Mammedov <imammedo@redhat.com>

Thanks!

> 
> 
> > Dave
> > 
> > > >          pcie_acs_init(d, rpc->acs_offset);
> > > >      }
> > > >      return;
> > > > @@ -145,6 +145,7 @@ static void rp_exit(PCIDevice *d)
> > > >  static Property rp_props[] = {
> > > >      DEFINE_PROP_BIT(COMPAT_PROP_PCP, PCIDevice, cap_present,
> > > >                      QEMU_PCIE_SLTCAP_PCP_BITNR, true),
> > > > +    DEFINE_PROP_BOOL("disable-acs", PCIESlot, disable_acs, false),
> > > >      DEFINE_PROP_END_OF_LIST()
> > > >  };
> > > >  
> > > > diff --git a/include/hw/pci/pcie_port.h b/include/hw/pci/pcie_port.h
> > > > index 09586f4641..7515430087 100644
> > > > --- a/include/hw/pci/pcie_port.h
> > > > +++ b/include/hw/pci/pcie_port.h
> > > > @@ -53,6 +53,8 @@ struct PCIESlot {
> > > >      PCIExpLinkSpeed speed;
> > > >      PCIExpLinkWidth width;
> > > >  
> > > > +    /* Disable ACS (really for a pcie_root_port) */
> > > > +    bool        disable_acs;
> > > >      QLIST_ENTRY(PCIESlot) next;
> > > >  };
> > > >  
> > > 
> > --
> > Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK
> 
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK