On 02.05.19 00:31, 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 related information (also known
> as the "Control Program Code" or "CPC"), as well as check the system
> if KVM supports handling this instruction.
>
> 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, which means VMs running with the diag318 capability
> will have a reduced maximum CPU count. To alleviate this, let's calculate
> the actual max CPU entry space by subtracting the size of Read Info from
> the SCCB size then dividing that number by the size of a CPU entry. If
> this value is less than the value denoted by S390_MAX_CPUS, then let's
> reduce the max cpus for s390 from 248 to 240 in an effort to anticipate
> this potentially happening again in the future.
>
> 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 reset on during modified clear and load normal.
>
> Signed-off-by: Collin Walling <wall...@linux.ibm.com>
> ---
> hw/s390x/Makefile.objs | 1 +
> hw/s390x/diag318.c | 100
> +++++++++++++++++++++++++++++++++++++++++++
> hw/s390x/diag318.h | 39 +++++++++++++++++
> hw/s390x/s390-virtio-ccw.c | 23 ++++++++++
> hw/s390x/sclp.c | 5 +++
> include/hw/s390x/sclp.h | 2 +
> linux-headers/asm-s390/kvm.h | 4 ++
> target/s390x/kvm-stub.c | 15 +++++++
> target/s390x/kvm.c | 32 ++++++++++++++
> target/s390x/kvm_s390x.h | 3 ++
> 10 files changed, 224 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..94b44da
> --- /dev/null
> +++ b/hw/s390x/diag318.c
> @@ -0,0 +1,100 @@
> +/*
> + * DIAGNOSE 0x318 functions for reset and migration
> + *
> + * Copyright IBM, Corp. 2019
> + *
> + * Authors:
> + * Collin Walling <wall...@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;
> +
> + kvm_s390_set_cpc(d->cpc);
> +
> + /* It is not necessary to retain a copy of the cpc after migration. */
> + d->cpc = 0;
> +
> + return 0;
> +}
> +
> +static int diag318_pre_save(void *opaque)
> +{
> + DIAG318State *d = opaque;
> +
> + kvm_s390_get_cpc(&d->cpc);
> + return 0;
> +}
> +
> +static bool diag318_needed(void *opaque)
> +{
> + DIAG318State *d = opaque;
> +
> + return d->enabled;
> +}
> +
> +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(cpc, DIAG318State),
> + VMSTATE_END_OF_LIST()
> + }
> +};
> +
> +static void s390_diag318_realize(DeviceState *dev, Error **errp)
> +{
> + DIAG318State *d = DIAG318(dev);
> +
> + if (kvm_s390_has_diag318()) {
> + d->enabled = true;
> + }
> +}
> +
> +static void s390_diag318_reset(DeviceState *dev)
> +{
> + DIAG318State *d = DIAG318(dev);
> +
> + if (d->enabled) {
> + kvm_s390_set_cpc(0);
> + }
> +}
> +
> +static void s390_diag318_class_init(ObjectClass *klass, void *data)
> +{
> + DeviceClass *dc = DEVICE_CLASS(klass);
> +
> + dc->realize = s390_diag318_realize;
> + dc->reset = s390_diag318_reset;
> + dc->vmsd = &vmstate_diag318;
> + dc->hotpluggable = false;
> + /* Reason: Set automatically during IPL */
> + 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..c154b0a
> --- /dev/null
> +++ b/hw/s390x/diag318.h
> @@ -0,0 +1,39 @@
> +/*
> + * DIAGNOSE 0x318 functions for reset and migration
> + *
> + * Copyright IBM, Corp. 2019
> + *
> + * Authors:
> + * Collin Walling <wall...@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 DIAG318_H
> + #define DIAG318_H
> +
> +#include "qemu/osdep.h"
> +#include "hw/qdev.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 cpc;
> + bool enabled;
> +} DIAG318State;
> +
> +typedef struct DIAG318Class {
> + /*< private >*/
> + DeviceClass parent_class;
> +
> + /*< public >*/
> +} DIAG318Class;
> +
> +#endif /* DIAG318_H */
> diff --git a/hw/s390x/s390-virtio-ccw.c b/hw/s390x/s390-virtio-ccw.c
> index d11069b..44a424b 100644
> --- a/hw/s390x/s390-virtio-ccw.c
> +++ b/hw/s390x/s390-virtio-ccw.c
> @@ -36,6 +36,7 @@
> #include "cpu_models.h"
> #include "hw/nmi.h"
> #include "hw/s390x/tod.h"
> +#include "hw/s390x/diag318.h"
>
> S390CPU *s390_cpu_addr2state(uint16_t cpu_addr)
> {
> @@ -92,6 +93,7 @@ static const char *const reset_dev_types[] = {
> "s390-sclp-event-facility",
> "s390-flic",
> "diag288",
> + TYPE_S390_DIAG318,
> };
>
> static void subsystem_reset(void)
> @@ -246,6 +248,17 @@ 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);
> + DeviceState *dev = DEVICE(new);
> +
> + object_property_add_child(qdev_get_machine(), TYPE_S390_DIAG318,
> + new, NULL);
> + object_unref(new);
> + qdev_init_nofail(dev);
> +}
> +
> static void ccw_init(MachineState *machine)
> {
> int ret;
> @@ -302,6 +315,8 @@ static void ccw_init(MachineState *machine)
>
> /* init the TOD clock */
> s390_init_tod();
> +
> + s390_init_diag318();
> }
>
> static void s390_cpu_plug(HotplugHandler *hotplug_dev,
> @@ -570,6 +585,7 @@ static void machine_set_loadparm(Object *obj, const char
> *val, Error **errp)
> ms->loadparm[i] = ' '; /* pad right with spaces */
> }
> }
> +
> static inline void s390_machine_initfn(Object *obj)
> {
> object_property_add_bool(obj, "aes-key-wrap",
> @@ -652,6 +668,13 @@ static void
> ccw_machine_4_0_instance_options(MachineState *machine)
>
> static void ccw_machine_4_0_class_options(MachineClass *mc)
> {
> + /*
> + * Read Info might reveal more bytes used to detect facilities, thus
> + * reducing the number of CPU entries. Let's reduce the max CPUs by
> + * an arbitrary number in effort to anticipate future facility bytes.
> + */
> + if ((SCCB_SIZE - sizeof(ReadInfo)) / sizeof(CPUEntry) < S390_MAX_CPUS)
> + mc->max_cpus = S390_MAX_CPUS - 8;
This is too complicated, just set it always to 240.
However, I am still not sure how to best handle this scenario. One
solution is
1. Set it statically to 240 for machine > 4.1
2. Keep the old machines unmodifed
3. Don't indicate the CPU feature for machines <= 4.0
#3 is the problematic part, as it mixes host CPU features and machines.
Bad. The host CPU model should always look the same on all machines. I
don't like this.
--
Thanks,
David / dhildenb
