On Tue, 2023-01-10 at 14:00 +0100, Thomas Huth wrote:
> On 05/01/2023 15.53, Pierre Morel wrote:
> > The topology information are attributes of the CPU and are
> > specified during the CPU device creation.
> >
> > On hot plug, we gather the topology information on the core,
> > creates a list of topology entries, each entry contains a single
> > core mask of each core with identical topology and finaly we
> > orders the list in topological order.
> > The topological order is, from higher to lower priority:
> > - physical topology
> > - drawer
> > - book
> > - socket
> > - core origin, offset in 64bit increment from core 0.
> > - modifier attributes
> > - CPU type
> > - polarization entitlement
> > - dedication
> >
> > 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 adventage of the CPU topology.
>
> s/adventage/advantage/
>
> > Signed-off-by: Pierre Morel <pmorel@xxxxxxxxxxxxx>
> > ---
> > include/hw/s390x/cpu-topology.h | 48 ++++++
> > hw/s390x/cpu-topology.c | 293 ++++++++++++++++++++++++++++++++
> > hw/s390x/s390-virtio-ccw.c | 10 ++
> > hw/s390x/meson.build | 1 +
> > 4 files changed, 352 insertions(+)
> > create mode 100644 hw/s390x/cpu-topology.c
> >
> > diff --git a/include/hw/s390x/cpu-topology.h b/include/hw/s390x/cpu-topology.h
> > index d945b57fc3..b3fd752d8d 100644
> > --- a/include/hw/s390x/cpu-topology.h
> > +++ b/include/hw/s390x/cpu-topology.h
> >
[...]
> > +typedef struct S390Topology {
> > + QTAILQ_HEAD(, S390TopologyEntry) list;
> > + uint8_t *sockets;
>
> So this "uint8_t" basically is a hidden limit of a maximum of 256 sockets
> that can be used for per book? Do we check that limit somewhere? (I looked
> for it, but I didn't spot such a check)
S390_MAX_CPUS < 256. Might be a good idea to have a build time assert for that.
And one cannot have more sockets that maxcpus.
>
> > + CpuTopology *smp;
> > +} S390Topology;
> > +
> > +#ifdef CONFIG_KVM
> > +bool s390_has_topology(void);
> > +void s390_topology_set_cpu(MachineState *ms, S390CPU *cpu, Error **errp);
> > +#else
> > +static inline bool s390_has_topology(void)
> > +{
> > + return false;
> > +}
> > +static inline void s390_topology_set_cpu(MachineState *ms,
> > + S390CPU *cpu,
> > + Error **errp) {}
> > +#endif
> > +extern S390Topology s390_topology;
> > +
> > #endif
> > diff --git a/hw/s390x/cpu-topology.c b/hw/s390x/cpu-topology.c
> > new file mode 100644
> > index 0000000000..438055c612
> > --- /dev/null
> > +++ b/hw/s390x/cpu-topology.c
> > @@ -0,0 +1,293 @@
> > +/*
> > + * CPU Topology
> > + *
> > + * Copyright IBM Corp. 2022
>
> Want to update to 2023 now?
It's the year of first publication, and I'd guess this is a derivative work of what
was published to the mailing list last year.
>
