Re: [PATCH v7 8/8] s390x/s390-virtio-ccw: add zpcii-disable machine property

[Pierre Morel <pmorel@linux.ibm.com>]

On 6/6/22 22:36, Matthew Rosato wrote:
> The zpcii-disable machine property can be used to force-disable the use
> of zPCI interpretation facilities for a VM.  By default, this setting
> will be off for machine 7.1 and newer.
> 
> Signed-off-by: Matthew Rosato <mjrosato@linux.ibm.com>
> ---
>   hw/s390x/s390-pci-kvm.c            |  4 +++-
>   hw/s390x/s390-virtio-ccw.c         | 24 ++++++++++++++++++++++++
>   include/hw/s390x/s390-virtio-ccw.h |  1 +
>   qemu-options.hx                    |  8 +++++++-
>   util/qemu-config.c                 |  4 ++++
>   5 files changed, 39 insertions(+), 2 deletions(-)
> 
> diff --git a/hw/s390x/s390-pci-kvm.c b/hw/s390x/s390-pci-kvm.c
> index 9134fe185f..5eb7fd12e2 100644
> --- a/hw/s390x/s390-pci-kvm.c
> +++ b/hw/s390x/s390-pci-kvm.c
> @@ -22,7 +22,9 @@
>   
>   bool s390_pci_kvm_interp_allowed(void)
>   {
> -    return kvm_s390_get_zpci_op() && !s390_is_pv();
> +    return (kvm_s390_get_zpci_op() && !s390_is_pv() &&
> +            !object_property_get_bool(OBJECT(qdev_get_machine()),
> +                                      "zpcii-disable", NULL));
>   }

Isn't it a duplication of machine_get_zpcii_disable?

Wouldn't it better go to hw/s390x/kvm/ ?

There get the MachineState *ms = MACHINE(qdev_get_machine()) and return 
the ms->zpcii_disable

?

>   
>   int s390_pci_kvm_aif_enable(S390PCIBusDevice *pbdev, ZpciFib *fib, bool assist)
> diff --git a/hw/s390x/s390-virtio-ccw.c b/hw/s390x/s390-virtio-ccw.c
> index cc3097bfee..70229b102b 100644
> --- a/hw/s390x/s390-virtio-ccw.c
> +++ b/hw/s390x/s390-virtio-ccw.c
> @@ -645,6 +645,21 @@ static inline void machine_set_dea_key_wrap(Object *obj, bool value,
>       ms->dea_key_wrap = value;
>   }
>   
> +static inline bool machine_get_zpcii_disable(Object *obj, Error **errp)
> +{
> +    S390CcwMachineState *ms = S390_CCW_MACHINE(obj);
> +
> +    return ms->zpcii_disable;
> +}
> +
> +static inline void machine_set_zpcii_disable(Object *obj, bool value,
> +                                             Error **errp)
> +{
> +    S390CcwMachineState *ms = S390_CCW_MACHINE(obj);
> +
> +    ms->zpcii_disable = value;
> +}
> +
>   static S390CcwMachineClass *current_mc;
>   
>   /*
> @@ -740,6 +755,13 @@ static inline void s390_machine_initfn(Object *obj)
>               "Up to 8 chars in set of [A-Za-z0-9. ] (lower case chars converted"
>               " to upper case) to pass to machine loader, boot manager,"
>               " and guest kernel");
> +
> +    object_property_add_bool(obj, "zpcii-disable",
> +                             machine_get_zpcii_disable,
> +                             machine_set_zpcii_disable);
> +    object_property_set_description(obj, "zpcii-disable",
> +            "disable zPCI interpretation facilties");
> +    object_property_set_bool(obj, "zpcii-disable", false, NULL);
>   }
>   
>   static const TypeInfo ccw_machine_info = {
> @@ -804,9 +826,11 @@ DEFINE_CCW_MACHINE(7_1, "7.1", true);
>   static void ccw_machine_7_0_instance_options(MachineState *machine)
>   {
>       static const S390FeatInit qemu_cpu_feat = { S390_FEAT_LIST_QEMU_V7_0 };
> +    S390CcwMachineState *ms = S390_CCW_MACHINE(machine);
>   
>       ccw_machine_7_1_instance_options(machine);
>       s390_set_qemu_cpu_model(0x8561, 15, 1, qemu_cpu_feat);
> +    ms->zpcii_disable = true;
>   }
>   
>   static void ccw_machine_7_0_class_options(MachineClass *mc)
> diff --git a/include/hw/s390x/s390-virtio-ccw.h b/include/hw/s390x/s390-virtio-ccw.h
> index 3331990e02..8a0090a071 100644
> --- a/include/hw/s390x/s390-virtio-ccw.h
> +++ b/include/hw/s390x/s390-virtio-ccw.h
> @@ -27,6 +27,7 @@ struct S390CcwMachineState {
>       bool aes_key_wrap;
>       bool dea_key_wrap;
>       bool pv;
> +    bool zpcii_disable;
>       uint8_t loadparm[8];
>   };
>   
> diff --git a/qemu-options.hx b/qemu-options.hx
> index 60cf188da4..fafe335b4a 100644
> --- a/qemu-options.hx
> +++ b/qemu-options.hx
> @@ -36,7 +36,8 @@ DEF("machine", HAS_ARG, QEMU_OPTION_machine, \
>       "                nvdimm=on|off controls NVDIMM support (default=off)\n"
>       "                memory-encryption=@var{} memory encryption object to use (default=none)\n"
>       "                hmat=on|off controls ACPI HMAT support (default=off)\n"
> -    "                memory-backend='backend-id' specifies explicitly provided backend for main RAM (default=none)\n",
> +    "                memory-backend='backend-id' specifies explicitly provided backend for main RAM (default=none)\n"
> +    "                zpcii-disable=on|off disables zPCI interpretation facilities (default=off)\n",
>       QEMU_ARCH_ALL)
>   SRST
>   ``-machine [type=]name[,prop=value[,...]]``
> @@ -124,6 +125,11 @@ SRST
>               -object memory-backend-ram,id=pc.ram,size=512M,x-use-canonical-path-for-ramblock-id=off
>               -machine memory-backend=pc.ram
>               -m 512M
> +
> +    ``zpcii-disable=on|off``
> +        Disables zPCI interpretation facilties on s390-ccw hosts.

s/facilties/facility/

> +        This feature can be used to disable hardware virtual assists
> +        related to zPCI devices. The default is off.
>   ERST
>   
>   DEF("M", HAS_ARG, QEMU_OPTION_M,
> diff --git a/util/qemu-config.c b/util/qemu-config.c
> index 433488aa56..5325f6bf80 100644
> --- a/util/qemu-config.c
> +++ b/util/qemu-config.c
> @@ -236,6 +236,10 @@ static QemuOptsList machine_opts = {
>               .help = "Up to 8 chars in set of [A-Za-z0-9. ](lower case chars"
>                       " converted to upper case) to pass to machine"
>                       " loader, boot manager, and guest kernel",
> +        },{
> +            .name = "zpcii-disable",
> +            .type = QEMU_OPT_BOOL,
> +            .help = "disable zPCI interpretation facilities",
>           },
>           { /* End of list */ }
>       }
> 

-- 
Pierre Morel
IBM Lab Boeblingen