Re: [qemu-s390x] [PATCH v8 4/6] s390x/ap: base Adjunct Processor (AP) object model

[Thomas Huth]

On 2018-09-12 22:08, Tony Krowiak wrote:
> From: Tony Krowiak <address@hidden>
> 
> Introduces the base object model for virtualizing AP devices.
> 
> Signed-off-by: Tony Krowiak <address@hidden>
> ---
[...]
> diff --git a/hw/s390x/ap-bridge.c b/hw/s390x/ap-bridge.c
> new file mode 100644
> index 0000000..4f10425
> --- /dev/null
> +++ b/hw/s390x/ap-bridge.c
[...]
> +void s390_init_ap(void)
> +{
> +    DeviceState *dev;
> +
> +    /* Create bridge device */
> +    dev = qdev_create(NULL, TYPE_AP_BRIDGE);
> +    object_property_add_child(qdev_get_machine(), TYPE_AP_BRIDGE,
> +                              OBJECT(dev), NULL);
> +    qdev_init_nofail(dev);
> +
> +    /* Create bus on bridge device */
> +    qbus_create(TYPE_VFIO_AP_BUS, dev, TYPE_VFIO_AP_BUS);
> + }
[...]
> +type_init(ap_device_register)
> diff --git a/hw/s390x/s390-virtio-ccw.c b/hw/s390x/s390-virtio-ccw.c
> index f0f7fdc..3c100c2 100644
> --- a/hw/s390x/s390-virtio-ccw.c
> +++ b/hw/s390x/s390-virtio-ccw.c
> @@ -32,6 +32,7 @@
>  #include "ipl.h"
>  #include "hw/s390x/s390-virtio-ccw.h"
>  #include "hw/s390x/css-bridge.h"
> +#include "hw/s390x/ap-bridge.h"
>  #include "migration/register.h"
>  #include "cpu_models.h"
>  #include "hw/nmi.h"
> @@ -263,6 +264,9 @@ static void ccw_init(MachineState *machine)
>      /* init the SIGP facility */
>      s390_init_sigp();
>  
> +    /* create AP bridge and bus(es) */
> +    s390_init_ap();
> +

Not sure since there is no explicit migration state involved here, but I
think you cannot simply create the ap-bridge device always
unconditionally, can you? Did you check whether you can ping-pong
migrate an guest that runs on an older version of QEMU to a QEMU that
contains this patch and back? If it does not work, it might be necessary
to restrict this ap-bridge device for new machine types only, I think.

 Thomas