Re: [Qemu-devel] [PATCH] spapr: make default PHB optionnal

[Greg Kurz <groug@kaod.org>]

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On Tue, 4 Jul 2017 17:29:01 +1000
David Gibson <david@gibson.dropbear.id.au> wrote:

> On Mon, Jul 03, 2017 at 06:48:25PM +0200, Greg Kurz wrote:
> > The sPAPR machine always create a default PHB during initialization, even
> > if -nodefaults was passed on the command line. This forces the user to
> > rely on -global if she wants to set properties of the default PHB, such
> > as numa_node.
> > 
> > This patch introduces a new machine create-default-phb property to control
> > whether the default PHB must be created or not. It defaults to on in order
> > to preserve old setups (which is also the motivation to not alter the
> > current behavior of -nodefaults).
> > 
> > If create-default-phb is set to off, the default PHB isn't created, nor
> > any other device usually created with it. It is mandatory to provide
> > a PHB on the command line to be able to use PCI devices (otherwise QEMU
> > won't start). For example, the following creates a PHB with the same
> > mappings as the default PHB and also sets the NUMA affinity:
> > 
> >     -machine type=pseries,create-default-phb=off \
> >     -numa node,nodeid=0 -device spapr-pci-host-bridge,index=0,numa_node=0
> > 
> > Signed-off-by: Greg Kurz <groug@kaod.org>  
> 
> So, I agree that the distinction between default devices that are
> disabled with -nodefaults and default devices that aren't is a big
> mess in qemu configuration.  But on the other hand this only addresses
> one tiny aspect of that, and in the meantime means we will silently
> ignore some other configuration options in some conditions.
> 
> So, what's the immediate benefit / use case for this?
> 

With the current code base, the only way to set properties of the default
PHB, is to pass -global spapr-pci-host-bridge.prop=value for each property.
The immediate benefit of this patch is to unify the way libvirt passes
PHB description to the command line:

ie, do:

    -machine type=pseries,create-default-phb=off \
    -device spapr-pci-host-bridge,prop1=a,prop2=b,prop3=c \
    -device spapr-pci-host-bridge,prop1=d,prop2=e,prop3=f

instead of:

    -machine type=pseries \
    -global spapr-pci-host-bridge.prop1=a \
    -global spapr-pci-host-bridge.prop2=b \
    -global spapr-pci-host-bridge.prop3=c \
    -device spapr-pci-host-bridge,prop1=d,prop2=e,prop3=f

> > ---
> >  hw/ppc/spapr.c         |   63 ++++++++++++++++++++++++++++++++++--------------
> >  include/hw/ppc/spapr.h |    2 ++
> >  2 files changed, 47 insertions(+), 18 deletions(-)
> > 
> > diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> > index ba8f57a5a054..3395bb3774b9 100644
> > --- a/hw/ppc/spapr.c
> > +++ b/hw/ppc/spapr.c
> > @@ -2103,7 +2103,7 @@ static void ppc_spapr_init(MachineState *machine)
> >      sPAPRMachineClass *smc = SPAPR_MACHINE_GET_CLASS(machine);
> >      const char *kernel_filename = machine->kernel_filename;
> >      const char *initrd_filename = machine->initrd_filename;
> > -    PCIHostState *phb;
> > +    PCIHostState *phb = NULL;
> >      int i;
> >      MemoryRegion *sysmem = get_system_memory();
> >      MemoryRegion *ram = g_new(MemoryRegion, 1);
> > @@ -2294,7 +2294,9 @@ static void ppc_spapr_init(MachineState *machine)
> >      /* Set up PCI */
> >      spapr_pci_rtas_init();
> >  
> > -    phb = spapr_create_phb(spapr, 0);
> > +    if (spapr->create_default_phb) {
> > +        phb = spapr_create_phb(spapr, 0);
> > +    }
> >  
> >      for (i = 0; i < nb_nics; i++) {
> >          NICInfo *nd = &nd_table[i];
> > @@ -2305,7 +2307,7 @@ static void ppc_spapr_init(MachineState *machine)
> >  
> >          if (strcmp(nd->model, "ibmveth") == 0) {
> >              spapr_vlan_create(spapr->vio_bus, nd);
> > -        } else {
> > +        } else if (phb) {
> >              pci_nic_init_nofail(&nd_table[i], phb->bus, nd->model, NULL);
> >          }
> >      }
> > @@ -2314,24 +2316,26 @@ static void ppc_spapr_init(MachineState *machine)
> >          spapr_vscsi_create(spapr->vio_bus);
> >      }
> >  
> > -    /* Graphics */
> > -    if (spapr_vga_init(phb->bus, &error_fatal)) {
> > -        spapr->has_graphics = true;
> > -        machine->usb |= defaults_enabled() && !machine->usb_disabled;
> > -    }
> > -
> > -    if (machine->usb) {
> > -        if (smc->use_ohci_by_default) {
> > -            pci_create_simple(phb->bus, -1, "pci-ohci");
> > -        } else {
> > -            pci_create_simple(phb->bus, -1, "nec-usb-xhci");
> > +    if (phb) {
> > +        /* Graphics */
> > +        if (spapr_vga_init(phb->bus, &error_fatal)) {
> > +            spapr->has_graphics = true;
> > +            machine->usb |= defaults_enabled() && !machine->usb_disabled;
> >          }
> >  
> > -        if (spapr->has_graphics) {
> > -            USBBus *usb_bus = usb_bus_find(-1);
> > +        if (machine->usb) {
> > +            if (smc->use_ohci_by_default) {
> > +                pci_create_simple(phb->bus, -1, "pci-ohci");
> > +            } else {
> > +                pci_create_simple(phb->bus, -1, "nec-usb-xhci");
> > +            }
> > +
> > +            if (spapr->has_graphics) {
> > +                USBBus *usb_bus = usb_bus_find(-1);
> >  
> > -            usb_create_simple(usb_bus, "usb-kbd");
> > -            usb_create_simple(usb_bus, "usb-mouse");
> > +                usb_create_simple(usb_bus, "usb-kbd");
> > +                usb_create_simple(usb_bus, "usb-mouse");
> > +            }
> >          }
> >      }
> >  
> > @@ -2544,12 +2548,27 @@ static void spapr_set_modern_hotplug_events(Object *obj, bool value,
> >      spapr->use_hotplug_event_source = value;
> >  }
> >  
> > +static bool spapr_get_create_default_phb(Object *obj, Error **errp)
> > +{
> > +    sPAPRMachineState *spapr = SPAPR_MACHINE(obj);
> > +
> > +    return spapr->create_default_phb;
> > +}
> > +
> > +static void spapr_set_create_default_phb(Object *obj, bool value, Error **errp)
> > +{
> > +    sPAPRMachineState *spapr = SPAPR_MACHINE(obj);
> > +
> > +    spapr->create_default_phb = value;
> > +}
> > +
> >  static void spapr_machine_initfn(Object *obj)
> >  {
> >      sPAPRMachineState *spapr = SPAPR_MACHINE(obj);
> >  
> >      spapr->htab_fd = -1;
> >      spapr->use_hotplug_event_source = true;
> > +    spapr->create_default_phb = true;
> >      object_property_add_str(obj, "kvm-type",
> >                              spapr_get_kvm_type, spapr_set_kvm_type, NULL);
> >      object_property_set_description(obj, "kvm-type",
> > @@ -2568,6 +2587,14 @@ static void spapr_machine_initfn(Object *obj)
> >      ppc_compat_add_property(obj, "max-cpu-compat", &spapr->max_compat_pvr,
> >                              "Maximum permitted CPU compatibility mode",
> >                              &error_fatal);
> > +
> > +    object_property_add_bool(obj, "create-default-phb",
> > +                            spapr_get_create_default_phb,
> > +                            spapr_set_create_default_phb,
> > +                            NULL);
> > +    object_property_set_description(obj, "create-default-phb",
> > +                                    "Create a default PCI Host Bridge",
> > +                                    NULL);
> >  }
> >  
> >  static void spapr_machine_finalizefn(Object *obj)
> > diff --git a/include/hw/ppc/spapr.h b/include/hw/ppc/spapr.h
> > index a184ffab0ebc..6ee914764807 100644
> > --- a/include/hw/ppc/spapr.h
> > +++ b/include/hw/ppc/spapr.h
> > @@ -93,6 +93,8 @@ struct sPAPRMachineState {
> >      bool use_hotplug_event_source;
> >      sPAPREventSource *event_sources;
> >  
> > +    bool create_default_phb;
> > +
> >      /* ibm,client-architecture-support option negotiation */
> >      bool cas_reboot;
> >      bool cas_legacy_guest_workaround;
> >   
> 


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