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

[Thomas Huth <thuth@redhat.com>]

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 <walling@linux.ibm.com>
> ---
>  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 <walling@linux.ibm.com>
> + *
> + * 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 <walling@linux.ibm.com>
> + *
> + * 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