Re: [Qemu-devel] [Qemu-ppc] [RFC 03/17] pseries: Always use core objects for CPU construction

[Greg Kurz <groug@kaod.org>]

On Thu, 3 Nov 2016 19:11:48 +1100
Alexey Kardashevskiy <aik@ozlabs.ru> wrote:

> On 30/10/16 22:11, David Gibson wrote:
> > Currently the pseries machine has two paths for constructing CPUs.  On
> > newer machine type versions, which support cpu hotplug, it constructs
> > cpu core objects, which in turn construct CPU threads.  For older machine
> > versions it individually constructs the CPU threads.
> > 
> > This division is going to make some future changes to the cpu construction
> > harder, so this patch unifies them.  Now cpu core objects are always
> > created.  This requires some updates to allow core objects to be created
> > without a full complement of threads (since older versions allowed a
> > number of cpus not a multiple of the threads-per-core).  Likewise it needs
> > some changes to the cpu core hot/cold plug path so as not to choke on the
> > old machine types without hotplug support.
> > 
> > For good measure, we move the cpu construction to its own subfunction,
> > spapr_init_cpus().
> > 
> > Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
> > ---
> >  hw/ppc/spapr.c          | 125 +++++++++++++++++++++++++++---------------------
> >  hw/ppc/spapr_cpu_core.c |  30 +++++++-----
> >  include/hw/ppc/spapr.h  |   1 -
> >  3 files changed, 89 insertions(+), 67 deletions(-)
> > 
> > diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> > index c8e2921..ad68a9d 100644
> > --- a/hw/ppc/spapr.c
> > +++ b/hw/ppc/spapr.c
> > @@ -1688,11 +1688,80 @@ static void spapr_validate_node_memory(MachineState *machine, Error **errp)
> >      }
> >  }
> >  
> > +static void spapr_init_cpus(sPAPRMachineState *spapr)
> > +{
> > +    MachineState *machine = MACHINE(spapr);
> > +    MachineClass *mc = MACHINE_GET_CLASS(machine);
> > +    char *type = spapr_get_cpu_core_type(machine->cpu_model);
> > +    int smt = kvmppc_smt_threads();
> > +    int spapr_max_cores, spapr_cores;
> > +    int i;
> > +
> > +    if (!type) {
> > +        error_report("Unable to find sPAPR CPU Core definition");
> > +        exit(1);
> > +    }
> > +
> > +    if (mc->query_hotpluggable_cpus) {
> > +        if (smp_cpus % smp_threads) {
> > +            error_report("smp_cpus (%u) must be multiple of threads (%u)",
> > +                         smp_cpus, smp_threads);
> > +            exit(1);
> > +        }
> > +        if (max_cpus % smp_threads) {
> > +            error_report("max_cpus (%u) must be multiple of threads (%u)",
> > +                         max_cpus, smp_threads);
> > +            exit(1);
> > +        }
> > +
> > +        spapr_max_cores = max_cpus / smp_threads;
> > +        spapr_cores = smp_cpus / smp_threads;
> > +    } else {
> > +        if (max_cpus != smp_cpus) {
> > +            error_report("This machine version does not support CPU hotplug");
> > +            exit(1);
> > +        }
> > +
> > +        spapr_max_cores = QEMU_ALIGN_UP(smp_cpus, smp_threads) / smp_threads;
> > +        spapr_cores = spapr_max_cores;
> > +    }
> > +
> > +    spapr->cores = g_new0(Object *, spapr_max_cores);
> > +    for (i = 0; i < spapr_max_cores; i++) {
> > +        int core_id = i * smp_threads;
> > +
> > +        if (mc->query_hotpluggable_cpus) {
> > +            sPAPRDRConnector *drc =
> > +                spapr_dr_connector_new(OBJECT(spapr),
> > +                                       SPAPR_DR_CONNECTOR_TYPE_CPU,
> > +                                       (core_id / smp_threads) * smt);
> > +
> > +            qemu_register_reset(spapr_drc_reset, drc);
> > +        }
> > +
> > +        if (i < spapr_cores) {
> > +            Object *core  = object_new(type);
> > +            int nr_threads = smp_threads;
> > +
> > +            /* Handle the partially filled core for older machine types */
> > +            if ((i + 1) * smp_threads >= smp_cpus) {
> > +                nr_threads = smp_cpus - i * smp_threads;
> > +            }  
> 
> 
> What is this exactly for? Older machines report "qemu-system-ppc64: threads
> must be 8" when I do "-smp 12,threads=8 -machine pseries-2.2".
> 

IIUC, this lowers nr_threads for the last core to end up with the requested
number of vCPUs... but spapr_core_pre_plug() doesn't like partially filled
cores.

    if (cc->nr_threads != smp_threads) {
        error_setg(&local_err, "threads must be %d", smp_threads);
        goto out;
    }

BTW, this error message looks weird when ones has passed "-smp threads=8"...
It should better reads:

    "unsupported partially filled core (%d threads, should have %d)"

If this check is removed, then we hit:

qemu-system-ppc64: core id 8 out of range

because of:

    int spapr_max_cores = max_cpus / smp_threads;

    index = cc->core_id / smp_threads;
    if (index < 0 || index >= spapr_max_cores) {
        error_setg(&local_err, "core id %d out of range", cc->core_id);
        goto out;
    }

Since the cc->core_id / smp_threads pattern is only used on the plug/unplug
paths, maybe these checks in spapr_core_pre_plug() should only be done
when mc->query_hotpluggable_cpus != NULL ?

> 
> 
> > +
> > +            object_property_set_int(core, nr_threads, "nr-threads",
> > +                                    &error_fatal);
> > +            object_property_set_int(core, core_id, CPU_CORE_PROP_CORE_ID,
> > +                                    &error_fatal);
> > +            object_property_set_bool(core, true, "realized", &error_fatal);
> > +        }
> > +    }
> > +    g_free(type);
> > +}
> > +
> >  /* pSeries LPAR / sPAPR hardware init */
> >  static void ppc_spapr_init(MachineState *machine)
> >  {
> >      sPAPRMachineState *spapr = SPAPR_MACHINE(machine);
> > -    MachineClass *mc = MACHINE_GET_CLASS(machine);
> >      sPAPRMachineClass *smc = SPAPR_MACHINE_GET_CLASS(machine);
> >      const char *kernel_filename = machine->kernel_filename;
> >      const char *initrd_filename = machine->initrd_filename;
> > @@ -1707,21 +1776,6 @@ static void ppc_spapr_init(MachineState *machine)
> >      long load_limit, fw_size;
> >      char *filename;
> >      int smt = kvmppc_smt_threads();
> > -    int spapr_cores = smp_cpus / smp_threads;
> > -    int spapr_max_cores = max_cpus / smp_threads;
> > -
> > -    if (mc->query_hotpluggable_cpus) {
> > -        if (smp_cpus % smp_threads) {
> > -            error_report("smp_cpus (%u) must be multiple of threads (%u)",
> > -                         smp_cpus, smp_threads);
> > -            exit(1);
> > -        }
> > -        if (max_cpus % smp_threads) {
> > -            error_report("max_cpus (%u) must be multiple of threads (%u)",
> > -                         max_cpus, smp_threads);
> > -            exit(1);
> > -        }
> > -    }
> >  
> >      msi_nonbroken = true;
> >  
> > @@ -1801,44 +1855,7 @@ static void ppc_spapr_init(MachineState *machine)
> >  
> >      ppc_cpu_parse_features(machine->cpu_model);
> >  
> > -    if (mc->query_hotpluggable_cpus) {
> > -        char *type = spapr_get_cpu_core_type(machine->cpu_model);
> > -
> > -        if (type == NULL) {
> > -            error_report("Unable to find sPAPR CPU Core definition");
> > -            exit(1);
> > -        }
> > -
> > -        spapr->cores = g_new0(Object *, spapr_max_cores);
> > -        for (i = 0; i < spapr_max_cores; i++) {
> > -            int core_id = i * smp_threads;
> > -            sPAPRDRConnector *drc =
> > -                spapr_dr_connector_new(OBJECT(spapr),
> > -                                       SPAPR_DR_CONNECTOR_TYPE_CPU,
> > -                                       (core_id / smp_threads) * smt);
> > -
> > -            qemu_register_reset(spapr_drc_reset, drc);
> > -
> > -            if (i < spapr_cores) {
> > -                Object *core  = object_new(type);
> > -                object_property_set_int(core, smp_threads, "nr-threads",
> > -                                        &error_fatal);
> > -                object_property_set_int(core, core_id, CPU_CORE_PROP_CORE_ID,
> > -                                        &error_fatal);
> > -                object_property_set_bool(core, true, "realized", &error_fatal);
> > -            }
> > -        }
> > -        g_free(type);
> > -    } else {
> > -        for (i = 0; i < smp_cpus; i++) {
> > -            PowerPCCPU *cpu = cpu_ppc_init(machine->cpu_model);
> > -            if (cpu == NULL) {
> > -                error_report("Unable to find PowerPC CPU definition");
> > -                exit(1);
> > -            }
> > -            spapr_cpu_init(spapr, cpu, &error_fatal);
> > -       }
> > -    }
> > +    spapr_init_cpus(spapr);
> >  
> >      if (kvm_enabled()) {
> >          /* Enable H_LOGICAL_CI_* so SLOF can talk to in-kernel devices */
> > diff --git a/hw/ppc/spapr_cpu_core.c b/hw/ppc/spapr_cpu_core.c
> > index e0c14f6..1357293 100644
> > --- a/hw/ppc/spapr_cpu_core.c
> > +++ b/hw/ppc/spapr_cpu_core.c
> > @@ -46,7 +46,8 @@ static void spapr_cpu_destroy(PowerPCCPU *cpu)
> >      qemu_unregister_reset(spapr_cpu_reset, cpu);
> >  }
> >  
> > -void spapr_cpu_init(sPAPRMachineState *spapr, PowerPCCPU *cpu, Error **errp)
> > +static void spapr_cpu_init(sPAPRMachineState *spapr, PowerPCCPU *cpu,
> > +                           Error **errp)
> >  {
> >      CPUPPCState *env = &cpu->env;
> >      CPUState *cs = CPU(cpu);
> > @@ -166,6 +167,7 @@ void spapr_core_plug(HotplugHandler *hotplug_dev, DeviceState *dev,
> >                       Error **errp)
> >  {
> >      sPAPRMachineState *spapr = SPAPR_MACHINE(OBJECT(hotplug_dev));
> > +    MachineClass *mc = MACHINE_GET_CLASS(spapr);
> >      sPAPRCPUCore *core = SPAPR_CPU_CORE(OBJECT(dev));
> >      CPUCore *cc = CPU_CORE(dev);
> >      CPUState *cs = CPU(core->threads);
> > @@ -180,7 +182,7 @@ void spapr_core_plug(HotplugHandler *hotplug_dev, DeviceState *dev,
> >      drc = spapr_dr_connector_by_id(SPAPR_DR_CONNECTOR_TYPE_CPU, index * smt);
> >      spapr->cores[index] = OBJECT(dev);
> >  
> > -    g_assert(drc);
> > +    g_assert(drc || !mc->query_hotpluggable_cpus);
> >  
> >      /*
> >       * Setup CPU DT entries only for hotplugged CPUs. For boot time or
> > @@ -190,13 +192,15 @@ void spapr_core_plug(HotplugHandler *hotplug_dev, DeviceState *dev,
> >          fdt = spapr_populate_hotplug_cpu_dt(cs, &fdt_offset, spapr);
> >      }
> >  
> > -    drck = SPAPR_DR_CONNECTOR_GET_CLASS(drc);
> > -    drck->attach(drc, dev, fdt, fdt_offset, !dev->hotplugged, &local_err);
> > -    if (local_err) {
> > -        g_free(fdt);
> > -        spapr->cores[index] = NULL;
> > -        error_propagate(errp, local_err);
> > -        return;
> > +    if (drc) {
> > +        drck = SPAPR_DR_CONNECTOR_GET_CLASS(drc);
> > +        drck->attach(drc, dev, fdt, fdt_offset, !dev->hotplugged, &local_err);
> > +        if (local_err) {
> > +            g_free(fdt);
> > +            spapr->cores[index] = NULL;
> > +            error_propagate(errp, local_err);
> > +            return;
> > +        }
> >      }
> >  
> >      if (dev->hotplugged) {
> > @@ -209,8 +213,10 @@ void spapr_core_plug(HotplugHandler *hotplug_dev, DeviceState *dev,
> >          /*
> >           * Set the right DRC states for cold plugged CPU.
> >           */
> > -        drck->set_allocation_state(drc, SPAPR_DR_ALLOCATION_STATE_USABLE);
> > -        drck->set_isolation_state(drc, SPAPR_DR_ISOLATION_STATE_UNISOLATED);
> > +        if (drc) {
> > +            drck->set_allocation_state(drc, SPAPR_DR_ALLOCATION_STATE_USABLE);
> > +            drck->set_isolation_state(drc, SPAPR_DR_ISOLATION_STATE_UNISOLATED);
> > +        }
> >      }
> >  }
> >  
> > @@ -227,7 +233,7 @@ void spapr_core_pre_plug(HotplugHandler *hotplug_dev, DeviceState *dev,
> >      char *base_core_type = spapr_get_cpu_core_type(machine->cpu_model);
> >      const char *type = object_get_typename(OBJECT(dev));
> >  
> > -    if (!mc->query_hotpluggable_cpus) {
> > +    if (dev->hotplugged && !mc->query_hotpluggable_cpus) {
> >          error_setg(&local_err, "CPU hotplug not supported for this machine");
> >          goto out;
> >      }
> > diff --git a/include/hw/ppc/spapr.h b/include/hw/ppc/spapr.h
> > index bd5bcf7..f8d444d 100644
> > --- a/include/hw/ppc/spapr.h
> > +++ b/include/hw/ppc/spapr.h
> > @@ -614,7 +614,6 @@ void spapr_hotplug_req_add_by_count_indexed(sPAPRDRConnectorType drc_type,
> >                                              uint32_t count, uint32_t index);
> >  void spapr_hotplug_req_remove_by_count_indexed(sPAPRDRConnectorType drc_type,
> >                                                 uint32_t count, uint32_t index);
> > -void spapr_cpu_init(sPAPRMachineState *spapr, PowerPCCPU *cpu, Error **errp);
> >  void *spapr_populate_hotplug_cpu_dt(CPUState *cs, int *fdt_offset,
> >                                      sPAPRMachineState *spapr);
> >  
> >   
> 
>