Re: [PATCH v9 02/10] s390x/cpu topology: core_id sets s390x CPU topology

[Janis Schoetterl-Glausch]

On Fri, 2022-09-02 at 09:55 +0200, Pierre Morel wrote:
> In the S390x CPU topology the core_id specifies the CPU address
> and the position of the core withing the topology.
> 
> Let's build the topology based on the core_id.
> 
> Signed-off-by: Pierre Morel <pmorel@linux.ibm.com>
> ---
>  hw/s390x/cpu-topology.c         | 135 ++++++++++++++++++++++++++++++++
>  hw/s390x/meson.build            |   1 +
>  hw/s390x/s390-virtio-ccw.c      |  10 +++
>  include/hw/s390x/cpu-topology.h |  42 ++++++++++
>  4 files changed, 188 insertions(+)
>  create mode 100644 hw/s390x/cpu-topology.c
>  create mode 100644 include/hw/s390x/cpu-topology.h
> 
> diff --git a/hw/s390x/cpu-topology.c b/hw/s390x/cpu-topology.c
> 
[...]

> +/**
> + * s390_topology_realize:
> + * @dev: the device state
> + * @errp: the error pointer (not used)
> + *
> + * During realize the machine CPU topology is initialized with the
> + * QEMU -smp parameters.
> + * The maximum count of CPU TLE in the all Topology can not be greater
> + * than the maximum CPUs.
> + */
> +static void s390_topology_realize(DeviceState *dev, Error **errp)
> +{
> +    MachineState *ms = MACHINE(qdev_get_machine());
> +    S390Topology *topo = S390_CPU_TOPOLOGY(dev);
> +    int n;
> +
> +    topo->sockets = ms->smp.sockets;
> +    topo->cores = ms->smp.cores;
> +    topo->tles = ms->smp.max_cpus;
> +
> +    n = topo->sockets;
> +    topo->socket = g_malloc0(n * sizeof(S390TopoContainer));
> +    topo->tle = g_malloc0(topo->tles * sizeof(S390TopoTLE));

Seems like a good use case for g_new0.

[...]
> 
> diff --git a/include/hw/s390x/cpu-topology.h b/include/hw/s390x/cpu-topology.h
> new file mode 100644
> index 0000000000..6911f975f4
> --- /dev/null
> +++ b/include/hw/s390x/cpu-topology.h
> @@ -0,0 +1,42 @@
> +/*
> + * CPU Topology
> + *
> + * Copyright 2022 IBM Corp.
> + *
> + * 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_S390X_CPU_TOPOLOGY_H
> +#define HW_S390X_CPU_TOPOLOGY_H

Is there a reason this is before the includes?
> +
> +typedef struct S390TopoContainer {
> +    int active_count;
> +} S390TopoContainer;
> +
> +#define S390_TOPOLOGY_MAX_ORIGIN (1 + S390_MAX_CPUS / 64)

This is correct because cpu_id == core_id for s390, right?
So the cpu limit also applies to the core id.
You could do ((S390_MAX_CPUS + 63) / 64) instead.
But if you chose this for simplicity's sake, I'm fine with it.

> +typedef struct S390TopoTLE {
> +    int active_count;

Do you use (read) this field somewhere?
Is this in anticipation of there being multiple TLE arrays, for
different polarizations, etc? If so I would defer this for later.

> +    uint64_t mask[S390_TOPOLOGY_MAX_ORIGIN];
> +} S390TopoTLE;
> +
> +#include "hw/qdev-core.h"
> +#include "qom/object.h"
> +
> +struct S390Topology {
> +    SysBusDevice parent_obj;
> +    int sockets;
> +    int cores;

These are just cached values from machine_state.smp, right?
Not sure if I like the redundancy, it doesn't aid in comprehension.

> +    int tles;
> +    S390TopoContainer *socket;
> +    S390TopoTLE *tle;
> +};
> +typedef struct S390Topology S390Topology;

The DECLARE macro takes care of this typedef.

> +
> +#define TYPE_S390_CPU_TOPOLOGY "s390-topology"
> +OBJECT_DECLARE_SIMPLE_TYPE(S390Topology, S390_CPU_TOPOLOGY)
> +
> +S390Topology *s390_get_topology(void);
> +void s390_topology_new_cpu(int core_id);
> +
> +#endif