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

[David Hildenbrand]

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.

-- 

Thanks,

David