Re: [Qemu-devel] [PATCH 1/1] s390x: create a compat s390 phb for <=2.10

[Yi Min Zhao]

在 2017/9/27 下午5:47, Cornelia Huck 写道:
> On Tue, 26 Sep 2017 20:40:25 +0200
> David Hildenbrand <address@hidden> wrote:
>
> > On 26.09.2017 18:20, Cornelia Huck wrote:
> > > d32bd032d8 ("s390x/ccw: create s390 phb conditionally") made
> > > creating the s390 phb dependant on the zpci facility. This broke
> > > migration from pre-cpu model machines which was fixed with
> > > 8ad9087c4a ("s390x/ccw: create s390 phb for compat reasons as well").
> > > However, that is not enough: Migration from 2.10 with -cpu z13
> > > breaks as well.
> > >
> > > Let's create a phb for all pre-2.11 compat machines to fix this.
> > > We leave the zpci facility off to avoid a guest-visible change
> > > with cpu models on.
> > >
> > > Reported-by: Christian Borntraeger <address@hidden>
> > > Fixes: d32bd032d8 ("s390x/ccw: create s390 phb conditionally")
> > > Signed-off-by: Cornelia Huck <address@hidden>
> > > ---
> > >   hw/s390x/s390-virtio-ccw.c         | 8 +++++++-
> > >   include/hw/s390x/s390-virtio-ccw.h | 1 +
> > >   2 files changed, 8 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/hw/s390x/s390-virtio-ccw.c b/hw/s390x/s390-virtio-ccw.c
> > > index 1bcb7000ab..981f1c4336 100644
> > > --- a/hw/s390x/s390-virtio-ccw.c
> > > +++ b/hw/s390x/s390-virtio-ccw.c
> > > @@ -247,6 +247,8 @@ static void s390_create_virtio_net(BusState *bus, const 
> > > char *name)
> > >       }
> > >   }
> > >   
> > > +static S390CcwMachineClass *get_machine_class(void);
> > > +
> > >   static void ccw_init(MachineState *machine)
> > >   {
> > >       int ret;
> > > @@ -266,7 +268,7 @@ static void ccw_init(MachineState *machine)
> > >                         machine->initrd_filename, "s390-ccw.img",
> > >                         "s390-netboot.img", true);
> > >   
> > > -    if (s390_has_feat(S390_FEAT_ZPCI)) {
> > > +    if (s390_has_feat(S390_FEAT_ZPCI) || get_machine_class()->phb_compat) {
> > >           DeviceState *dev = qdev_create(NULL, TYPE_S390_PCI_HOST_BRIDGE);
> > >           object_property_add_child(qdev_get_machine(),
> > >                                     TYPE_S390_PCI_HOST_BRIDGE,
> > > @@ -407,6 +409,7 @@ static void ccw_machine_class_init(ObjectClass *oc, void 
> > > *data)
> > >       s390mc->cpu_model_allowed = true;
> > >       s390mc->css_migration_enabled = true;
> > >       s390mc->gs_allowed = true;
> > > +    s390mc->phb_compat = false;
> > >       mc->init = ccw_init;
> > >       mc->reset = s390_machine_reset;
> > >       mc->hot_add_cpu = s390_hot_add_cpu;
> > > @@ -716,6 +719,9 @@ static void ccw_machine_2_10_instance_options(MachineState 
> > > *machine)
> > >   
> > >   static void ccw_machine_2_10_class_options(MachineClass *mc)
> > >   {
> > > +    S390CcwMachineClass *s390mc = S390_MACHINE_CLASS(mc);
> > > +
> > > +    s390mc->phb_compat = pci_available;
> > >       ccw_machine_2_11_class_options(mc);
> > >       SET_MACHINE_COMPAT(mc, CCW_COMPAT_2_10);
> > >   }
> > > diff --git a/include/hw/s390x/s390-virtio-ccw.h 
> > > b/include/hw/s390x/s390-virtio-ccw.h
> > > index a9a90c2022..fb717afe92 100644
> > > --- a/include/hw/s390x/s390-virtio-ccw.h
> > > +++ b/include/hw/s390x/s390-virtio-ccw.h
> > > @@ -41,6 +41,7 @@ typedef struct S390CcwMachineClass {
> > >       bool cpu_model_allowed;
> > >       bool css_migration_enabled;
> > >       bool gs_allowed;
> > > +    bool phb_compat;
> > >   } S390CcwMachineClass;
> > >   
> > >   /* runtime-instrumentation allowed by the machine */
> > >    
> > I'd really really really (did I mention really?) favor something like a
> > dummy device, because we could easily handle the !CONFIG_PCI case then.
> >
> > All these compat options and conditions will kill us someday... we're
> > already patching around that whole stuff way too much.
> >
> > If we ever unconditionally created a device, we should keep doing so.
> Yes, that whole thing is horrible, especially interaction with compat
> machines.
>
> Do you have an idea on how to create such a dummy device (without
> having to effectively copy a lot of configured-out code)?
How about in s390_pcihost_hot_plug() we check s390_has_feat(zpci)?
If no zpci feature, we avoid plugging any pci device.
Then we could always create phb.
I think pcibus's vmstate is only data to migrate.