On Wed, 2023-02-01 at 14:20 +0100, Pierre Morel wrote:
> When the host supports the CPU topology facility, the PTF
> instruction with function code 2 is interpreted by the SIE,
> provided that the userland hypervizor activates the interpretation
> by using the KVM_CAP_S390_CPU_TOPOLOGY KVM extension.
>
> The PTF instructions with function code 0 and 1 are intercepted
> and must be emulated by the userland hypervizor.
>
> During RESET all CPU of the configuration are placed in
> horizontal polarity.
>
> Signed-off-by: Pierre Morel <pmorel@xxxxxxxxxxxxx>
> ---
> include/hw/s390x/s390-virtio-ccw.h | 6 ++
> target/s390x/cpu.h | 1 +
> hw/s390x/cpu-topology.c | 103 +++++++++++++++++++++++++++++
> target/s390x/cpu-sysemu.c | 14 ++++
> target/s390x/kvm/kvm.c | 11 +++
> 5 files changed, 135 insertions(+)
>
[...]
> diff --git a/hw/s390x/cpu-topology.c b/hw/s390x/cpu-topology.c
> index cf63f3dd01..1028bf4476 100644
> --- a/hw/s390x/cpu-topology.c
> +++ b/hw/s390x/cpu-topology.c
> @@ -85,16 +85,104 @@ static void s390_topology_init(MachineState *ms)
> QTAILQ_INSERT_HEAD(&s390_topology.list, entry, next);
> }
>
> +/**
> + * s390_topology_set_cpus_polarity:
> + * @polarity: polarity requested by the caller
> + *
> + * Set all CPU entitlement according to polarity and
> + * dedication.
> + * Default vertical entitlement is POLARITY_VERTICAL_MEDIUM as
> + * it does not require host modification of the CPU provisioning
> + * until the host decide to modify individual CPU provisioning
> + * using QAPI interface.
> + * However a dedicated vCPU will have a POLARITY_VERTICAL_HIGH
> + * entitlement.
> + */
> +static void s390_topology_set_cpus_polarity(int polarity)
Since you set the entitlement field I'd prefer _set_cpus_entitlement or similar.
> +{
> + CPUState *cs;
> +
> + CPU_FOREACH(cs) {
> + if (polarity == POLARITY_HORIZONTAL) {
> + S390_CPU(cs)->env.entitlement = 0;
> + } else if (S390_CPU(cs)->env.dedicated) {
> + S390_CPU(cs)->env.entitlement = POLARITY_VERTICAL_HIGH;
> + } else {
> + S390_CPU(cs)->env.entitlement = POLARITY_VERTICAL_MEDIUM;
> + }
> + }
> +}
> +
[...]
>
> /**
> @@ -137,6 +225,21 @@ static void s390_topology_cpu_default(S390CPU *cpu, Error **errp)
> (smp->books * smp->sockets * smp->cores)) %
> smp->drawers;
> }
Why are the changes below in this patch?
> +
> + /*
> + * Machine polarity is set inside the global s390_topology structure.
> + * In the case the polarity is set as horizontal set the entitlement
> + * to POLARITY_VERTICAL_MEDIUM which is the better equivalent when
> + * machine polarity is set to vertical or POLARITY_VERTICAL_HIGH if
> + * the vCPU is dedicated.
> + */
> + if (s390_topology.polarity && !env->entitlement) {
It'd be more readable if you compared against enum values by name.
I don't see why you check s390_topology.polarity. If it is horizontal
then the value of the entitlement doesn't matter at all, so you can set it
to whatever.
All you want to do is enforce dedicated -> VERTICAL_HIGH, right?
So why don't you just add
+ if (cpu->env.dedicated && cpu->env.entitlement != POLARITY_VERTICAL_HIGH) {
+ error_setg(errp, "A dedicated cpu implies high entitlement");
+ return;
+ }
to s390_topology_check?
> + if (env->dedicated) {
> + env->entitlement = POLARITY_VERTICAL_HIGH;
> + } else {
> + env->entitlement = POLARITY_VERTICAL_MEDIUM;
> + }
If it is horizontal, then setting the entitlement is pointless as it will be
reset to medium on PTF.
So the current polarization is vertical and a cpu is being hotplugged,
but setting the entitlement of the cpu being added is also pointless, because
it's determined by the dedication. That seems weird.
> + }
> }
>
[...]
