Re: [PULL 03/25] s390x/cpu topology: add topology entries on CPU hotplug

[Nina Schoetterl-Glausch]

On Wed, 2023-10-18 at 15:06 +0200, Thomas Huth wrote:
> From: Pierre Morel <pmorel@linux.ibm.com>
> 
> The topology information are attributes of the CPU and are
> specified during the CPU device creation.
> 
> On hot plug we:
> - calculate the default values for the topology for drawers,
>   books and sockets in the case they are not specified.
> - verify the CPU attributes
> - check that we have still room on the desired socket
> 
> The possibility to insert a CPU in a mask is dependent on the
> number of cores allowed in a socket, a book or a drawer, the
> checking is done during the hot plug of the CPU to have an
> immediate answer.
> 
> If the complete topology is not specified, the core is added
> in the physical topology based on its core ID and it gets
> defaults values for the modifier attributes.
> 
> This way, starting QEMU without specifying the topology can
> still get some advantage of the CPU topology.
> 
> Signed-off-by: Pierre Morel <pmorel@linux.ibm.com>
> Reviewed-by: Nina Schoetterl-Glausch <nsg@linux.ibm.com>
> Co-developed-by: Nina Schoetterl-Glausch <nsg@linux.ibm.com>
> Reviewed-by: Thomas Huth <thuth@redhat.com>
> Signed-off-by: Nina Schoetterl-Glausch <nsg@linux.ibm.com>
> Message-ID: <20231016183925.2384704-4-nsg@linux.ibm.com>
> Signed-off-by: Thomas Huth <thuth@redhat.com>
> ---
>  MAINTAINERS                     |   6 +
>  include/hw/s390x/cpu-topology.h |  54 +++++++
>  hw/s390x/cpu-topology.c         | 259 ++++++++++++++++++++++++++++++++
>  hw/s390x/s390-virtio-ccw.c      |  22 ++-
>  hw/s390x/meson.build            |   1 +
>  5 files changed, 340 insertions(+), 2 deletions(-)
>  create mode 100644 include/hw/s390x/cpu-topology.h
>  create mode 100644 hw/s390x/cpu-topology.c

[...]

> --- /dev/null
> +++ b/include/hw/s390x/cpu-topology.h
> @@ -0,0 +1,54 @@
> +/* SPDX-License-Identifier: GPL-2.0-or-later */
> +/*
> + * CPU Topology
> + *
> + * Copyright IBM Corp. 2022, 2023
> + * Author(s): Pierre Morel <pmorel@linux.ibm.com>
> + *
> + */
> +#ifndef HW_S390X_CPU_TOPOLOGY_H
> +#define HW_S390X_CPU_TOPOLOGY_H
> +
> +#ifndef CONFIG_USER_ONLY
> +
> +#include "qemu/queue.h"
> +#include "hw/boards.h"
> +#include "qapi/qapi-types-machine-target.h"
> +
> +typedef struct S390Topology {
> +    uint8_t *cores_per_socket;
> +} S390Topology;
> +
> +#ifdef CONFIG_KVM
> +bool s390_has_topology(void);
> +void s390_topology_setup_cpu(MachineState *ms, S390CPU *cpu, Error **errp);
> +#else
> +static inline bool s390_has_topology(void)
> +{
> +       return false;

Just noticed that the indent is off here :(

> +}

[...]