Re: [PATCH v6 2/2] s390: diagnose 318 info reset and migration support

[Collin Walling]

On 1/27/20 6:36 AM, Thomas Huth wrote:
> On 24/01/2020 23.14, Collin Walling wrote:
>> DIAGNOSE 0x318 (diag318) is a privileged s390x instruction that must
>> be intercepted by SIE and handled via KVM. Let's introduce some
>> functions to communicate between QEMU and KVM via ioctls. These
>> will be used to get/set the diag318 information.
>>
>> The availability of this instruction is determined by byte 134, bit 0
>> of the Read Info block. This coincidentally expands into the space used
>> for CPU entries by taking away one byte, which means VMs running with
>> the diag318 capability will not be able to retrieve information regarding
>> the 248th CPU. This will not effect performance, and VMs can still be
> 
> s/effect/affect/ ?
> 
>> ran with 248 CPUs.
> 
> s/ran/run/ ?
> 
>> In order to simplify the migration and system reset requirements of
>> the diag318 data, let's introduce it as a device class and include
>> a VMStateDescription.
>>
>> Diag318 is set to 0 during modified clear and load normal resets.
>>
>> Signed-off-by: Collin Walling <address@hidden>
>> ---
>>  hw/s390x/Makefile.objs              |  1 +
>>  hw/s390x/diag318.c                  | 85 
>> +++++++++++++++++++++++++++++++++++++
>>  hw/s390x/diag318.h                  | 40 +++++++++++++++++
>>  hw/s390x/s390-virtio-ccw.c          | 17 ++++++++
>>  hw/s390x/sclp.c                     | 13 ++++++
>>  include/hw/s390x/sclp.h             |  2 +
>>  target/s390x/cpu_features.h         |  1 +
>>  target/s390x/cpu_features_def.inc.h |  3 ++
>>  target/s390x/gen-features.c         |  1 +
>>  target/s390x/kvm-stub.c             | 10 +++++
>>  target/s390x/kvm.c                  | 29 +++++++++++++
>>  target/s390x/kvm_s390x.h            |  2 +
>>  12 files changed, 204 insertions(+)
>>  create mode 100644 hw/s390x/diag318.c
>>  create mode 100644 hw/s390x/diag318.h
>>
>> diff --git a/hw/s390x/Makefile.objs b/hw/s390x/Makefile.objs
>> index e02ed80..93621dc 100644
>> --- a/hw/s390x/Makefile.objs
>> +++ b/hw/s390x/Makefile.objs
>> @@ -34,3 +34,4 @@ obj-$(CONFIG_KVM) += s390-stattrib-kvm.o
>>  obj-y += s390-ccw.o
>>  obj-y += ap-device.o
>>  obj-y += ap-bridge.o
>> +obj-y += diag318.o
>> diff --git a/hw/s390x/diag318.c b/hw/s390x/diag318.c
>> new file mode 100644
>> index 0000000..2d30bb2
>> --- /dev/null
>> +++ b/hw/s390x/diag318.c
>> @@ -0,0 +1,85 @@
>> +/*
>> + * DIAGNOSE 0x318 functions for reset and migration
>> + *
>> + * Copyright IBM, Corp. 2019
> 
> Bump to 2020 ?
> 
>> + * Authors:
>> + *  Collin Walling <address@hidden>
>> + *
>> + * This work is licensed under the terms of the GNU GPL, version 2 or (at 
>> your
>> + * option) any later version. See the COPYING file in the top-level 
>> directory.
>> + */
>> +
>> +#include "hw/s390x/diag318.h"
>> +#include "qapi/error.h"
>> +#include "kvm_s390x.h"
>> +#include "sysemu/kvm.h"
>> +
>> +static int diag318_post_load(void *opaque, int version_id)
>> +{
>> +    DIAG318State *d = opaque;
>> +
>> +    if (kvm_enabled())
>> +        kvm_s390_set_diag318_info(d->info);
> 
> QEMU coding style requires curly braces also for single lines.
> 
>> +    return 0;
>> +}
>> +
>> +static int diag318_pre_save(void *opaque)
>> +{
>> +    DIAG318State *d = opaque;
>> +
>> +    if (kvm_enabled())
>> +        kvm_s390_get_diag318_info(&d->info);
> 
> dito
> 
>> +    return 0;
>> +}
>> +
>> +static bool diag318_needed(void *opaque)
>> +{
>> +    return kvm_enabled() ? s390_has_feat(S390_FEAT_DIAG318) : 0;
>> +}
>> +
>> +const VMStateDescription vmstate_diag318 = {
>> +    .name = "vmstate_diag318",
>> +    .post_load = diag318_post_load,
>> +    .pre_save = diag318_pre_save,
>> +    .version_id = 1,
>> +    .minimum_version_id = 1,
>> +    .needed = diag318_needed,
>> +    .fields = (VMStateField[]) {
>> +        VMSTATE_UINT64(info, DIAG318State),
>> +        VMSTATE_END_OF_LIST()
>> +    }
>> +};
>> +
>> +static void s390_diag318_reset(DeviceState *dev)
>> +{
>> +    if (kvm_enabled())
>> +        kvm_s390_set_diag318_info(0);
> 
> dito
> 
>> +}
>> +
>> +static void s390_diag318_class_init(ObjectClass *klass, void *data)
>> +{
>> +    DeviceClass *dc = DEVICE_CLASS(klass);
>> +
>> +    dc->reset = s390_diag318_reset;
>> +    dc->vmsd = &vmstate_diag318;
>> +    dc->hotpluggable = false;
>> +    /* Reason: Created automatically during machine instantiation */
>> +    dc->user_creatable = false;
>> +}
>> +
>> +static const TypeInfo s390_diag318_info = {
>> +    .class_init = s390_diag318_class_init,
>> +    .parent = TYPE_DEVICE,
>> +    .name = TYPE_S390_DIAG318,
>> +    .instance_size = sizeof(DIAG318State),
>> +};
>> +
>> +static void s390_diag318_register_types(void)
>> +{
>> +    type_register_static(&s390_diag318_info);
>> +}
>> +
>> +type_init(s390_diag318_register_types)
>> diff --git a/hw/s390x/diag318.h b/hw/s390x/diag318.h
>> new file mode 100644
>> index 0000000..06d9f67
>> --- /dev/null
>> +++ b/hw/s390x/diag318.h
>> @@ -0,0 +1,40 @@
>> +/*
>> + * DIAGNOSE 0x318 functions for reset and migration
>> + *
>> + * Copyright IBM, Corp. 2019
> 
> 2020 ?
> 
>> + * Authors:
>> + *  Collin Walling <address@hidden>
>> + *
>> + * This work is licensed under the terms of the GNU GPL, version 2 or (at 
>> your
>> + * option) any later version. See the COPYING file in the top-level 
>> directory.
>> + */
>> +
>> +#ifndef HW_DIAG318_H
>> +#define HW_DIAG318_H
>> +
>> +#include "qemu/osdep.h"
>> +#include "migration/vmstate.h"
>> +#include "qom/object.h"
>> +#include "hw/qdev-core.h"
>> +
>> +#define TYPE_S390_DIAG318 "diag318"
>> +#define DIAG318(obj) \
>> +    OBJECT_CHECK(DIAG318State, (obj), TYPE_S390_DIAG318)
>> +
>> +typedef struct DIAG318State {
>> +    /*< private >*/
>> +    DeviceState parent_obj;
>> +
>> +    /*< public >*/
>> +    uint64_t info;
>> +} DIAG318State;
>> +
>> +typedef struct DIAG318Class {
>> +    /*< private >*/
>> +    DeviceClass parent_class;
>> +
>> +    /*< public >*/
>> +} DIAG318Class;
> 
> You don't use DIAG318Class anywhere. Please drop it.
> 
>> +#endif /* HW_DIAG318_H */
>> \ No newline at end of file
>> diff --git a/hw/s390x/s390-virtio-ccw.c b/hw/s390x/s390-virtio-ccw.c
>> index e0e2813..d5b7a33 100644
>> --- a/hw/s390x/s390-virtio-ccw.c
>> +++ b/hw/s390x/s390-virtio-ccw.c
>> @@ -41,6 +41,7 @@
>>  #include "hw/qdev-properties.h"
>>  #include "hw/s390x/tod.h"
>>  #include "sysemu/sysemu.h"
>> +#include "hw/s390x/diag318.h"
>>  
>>  S390CPU *s390_cpu_addr2state(uint16_t cpu_addr)
>>  {
>> @@ -97,6 +98,7 @@ static const char *const reset_dev_types[] = {
>>      "s390-sclp-event-facility",
>>      "s390-flic",
>>      "diag288",
>> +    TYPE_S390_DIAG318,
>>  };
>>  
>>  static void subsystem_reset(void)
>> @@ -237,6 +239,17 @@ static void s390_create_sclpconsole(const char *type, 
>> Chardev *chardev)
>>      qdev_init_nofail(dev);
>>  }
>>  
>> +static void s390_init_diag318(void)
>> +{
>> +    Object *new = object_new(TYPE_S390_DIAG318);
> 
> For the very unlikely case that we ever switch QEMU to C++ ... could you
> maybe use a different variable name than "new" ? Simply "obj" maybe?
> 
>> +    DeviceState *dev = DEVICE(new);
>> +
>> +    object_property_add_child(qdev_get_machine(), TYPE_S390_DIAG318,
>> +                              new, NULL);
>> +    object_unref(new);
>> +    qdev_init_nofail(dev);
>> +}
>> +
> 
>  Thomas
> 

Noted your comments. Thanks for the review! I'll remember to run checkpatch
next time ;)

-- 
Respectfully,
- Collin Walling