Re: [Qemu-devel] [PATCH RFC 1/1] s390x/ccw: create s390 phb for compat reasons as well

[David Hildenbrand]

On 15.09.2017 12:14, Cornelia Huck wrote:
> d32bd032d8 ("s390x/ccw: create s390 phb conditionally") made
> registering the s390 pci host bridge conditional on presense
> of the zpci facility bit. Sadly, that breaks migration from
> some old machines.
> 
> Create the s390 phb if we need it for compat reasons, even if
> we don't provide the zpci facility.
> 
> Fixes: d32bd032d8 ("s390x/ccw: create s390 phb conditionally")
> Signed-off-by: Cornelia Huck <address@hidden>
> ---
>  hw/s390x/s390-virtio-ccw.c         | 6 +++++-
>  include/hw/s390x/s390-virtio-ccw.h | 1 +
>  2 files changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/hw/s390x/s390-virtio-ccw.c b/hw/s390x/s390-virtio-ccw.c
> index 0471407187..7e3148eb4a 100644
> --- a/hw/s390x/s390-virtio-ccw.c
> +++ b/hw/s390x/s390-virtio-ccw.c
> @@ -269,6 +269,8 @@ 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;
> @@ -288,7 +290,7 @@ 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()->pci_compat) {
>          DeviceState *dev = qdev_create(NULL, TYPE_S390_PCI_HOST_BRIDGE);
>          object_property_add_child(qdev_get_machine(),
>                                    TYPE_S390_PCI_HOST_BRIDGE,
> @@ -429,6 +431,7 @@ 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->pci_compat = false;
>      mc->init = ccw_init;
>      mc->reset = s390_machine_reset;
>      mc->hot_add_cpu = s390_hot_add_cpu;
> @@ -784,6 +787,7 @@ static void ccw_machine_2_7_class_options(MachineClass 
> *mc)
>      S390CcwMachineClass *s390mc = S390_MACHINE_CLASS(mc);
>  
>      s390mc->cpu_model_allowed = false;
> +    s390mc->pci_compat = pci_available;
>      ccw_machine_2_8_class_options(mc);
>      SET_MACHINE_COMPAT(mc, CCW_COMPAT_2_7);
>  }
> diff --git a/include/hw/s390x/s390-virtio-ccw.h 
> b/include/hw/s390x/s390-virtio-ccw.h
> index a9a90c2022..9978c89e90 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 pci_compat;
>  } S390CcwMachineClass;
>  
>  /* runtime-instrumentation allowed by the machine */
> 

As an alternative, simply

diff --git a/target/s390x/cpu_models.c b/target/s390x/cpu_models.c
index 0f28ebd162..0f22efc3b6 100644
--- a/target/s390x/cpu_models.c
+++ b/target/s390x/cpu_models.c
@@ -195,6 +195,8 @@ bool s390_has_feat(S390Feat feat)
                 return true;
             }
         }
+        if (feat == S390_FEAT_ZPCI)
+            return true;
 #endif
         return 0;
     }


(this is also the way we handle other features without cpu model support
-especially if cpu model support is disabled for older machines)

-- 

Thanks,

David