On Tue, 2023-04-25 at 18:14 +0200, Pierre Morel wrote:
> When the guest asks to change the polarization this change
> is forwarded to the upper layer using QAPI.
> The upper layer is supposed to take according decisions concerning
> CPU provisioning.
>
> Signed-off-by: Pierre Morel <pmorel@xxxxxxxxxxxxx>
> ---
> qapi/machine-target.json | 33 +++++++++++++++++++++++++++++++++
> hw/s390x/cpu-topology.c | 2 ++
> 2 files changed, 35 insertions(+)
>
> diff --git a/qapi/machine-target.json b/qapi/machine-target.json
> index 3b7a0b77f4..ffde2e9cbd 100644
> --- a/qapi/machine-target.json
> +++ b/qapi/machine-target.json
> @@ -391,3 +391,36 @@
> 'features': [ 'unstable' ],
> 'if': { 'all': [ 'TARGET_S390X' , 'CONFIG_KVM' ] }
> }
> +
> +##
> +# @CPU_POLARIZATION_CHANGE:
> +#
> +# Emitted when the guest asks to change the polarization.
> +#
> +# @polarization: polarization specified by the guest
> +#
> +# Features:
> +# @unstable: This command may still be modified.
> +#
> +# The guest can tell the host (via the PTF instruction) whether the
> +# CPUs should be provisioned using horizontal or vertical polarization.
> +#
> +# On horizontal polarization the host is expected to provision all vCPUs
> +# equally.
> +# On vertical polarization the host can provision each vCPU differently.
> +# The guest will get information on the details of the provisioning
> +# the next time it uses the STSI(15) instruction.
> +#
> +# Since: 8.1
> +#
> +# Example:
> +#
> +# <- { "event": "CPU_POLARIZATION_CHANGE",
> +# "data": { "polarization": 0 },
I think you'd be getting "horizontal" instead of 0.
> +# "timestamp": { "seconds": 1401385907, "microseconds": 422329 } }
> +##
> +{ 'event': 'CPU_POLARIZATION_CHANGE',
> + 'data': { 'polarization': 'CpuS390Polarization' },
> + 'features': [ 'unstable' ],
> + 'if': { 'all': [ 'TARGET_S390X', 'CONFIG_KVM' ] }
> +}
> diff --git a/hw/s390x/cpu-topology.c b/hw/s390x/cpu-topology.c
> index e5fb976594..e8b140d623 100644
> --- a/hw/s390x/cpu-topology.c
> +++ b/hw/s390x/cpu-topology.c
> @@ -17,6 +17,7 @@
> #include "hw/s390x/s390-virtio-ccw.h"
> #include "hw/s390x/cpu-topology.h"
> #include "qapi/qapi-commands-machine-target.h"
> +#include "qapi/qapi-events-machine-target.h"
>
> /*
> * s390_topology is used to keep the topology information.
> @@ -138,6 +139,7 @@ void s390_handle_ptf(S390CPU *cpu, uint8_t r1, uintptr_t ra)
> } else {
> s390_topology.vertical_polarization = !!fc;
> s390_cpu_topology_set_changed(true);
> + qapi_event_send_cpu_polarization_change(fc);
I'm not sure I like the implicit conversation of the function code to the enum value.
How about you do qapi_event_send_cpu_polarization_change(s390_topology.polarization);
and rename vertical_polarization and change it's type to the enum.
You can then also do
+ CpuS390Polarization polarization = S390_CPU_POLARIZATION_HORIZONTAL;
+ switch (fc) {
+ case S390_CPU_POLARIZATION_VERTICAL:
+ polarization = S390_CPU_POLARIZATION_VERTICAL;
+ /* fallthrough */
+ case S390_CPU_POLARIZATION_HORIZONTAL:
+ if (s390_topology.polarization == polarization) {
and use the value for the assignment further down, too.
> setcc(cpu, 0);
> }
> break;
