Re: [Qemu-devel] [RFC PATCH v0 4/6] spapr: CPU hotplug support

[Bharata B Rao <bharata@linux.vnet.ibm.com>]

On Fri, Feb 26, 2016 at 02:03:57PM +0100, Thomas Huth wrote:
> On 25.02.2016 17:22, Bharata B Rao wrote:
> > Set up device tree entries for the hotplugged CPU core and use the
> > exising EPOW event infrastructure to send CPU hotplug notification to
> > the guest.
> > 
> > Signed-off-by: Bharata B Rao <bharata@linux.vnet.ibm.com>
> > ---
> >  hw/ppc/spapr.c         | 136 ++++++++++++++++++++++++++++++++++++++++++++++++-
> >  hw/ppc/spapr_events.c  |   3 ++
> >  hw/ppc/spapr_rtas.c    |  24 +++++++++
> >  include/hw/ppc/spapr.h |   1 +
> >  4 files changed, 163 insertions(+), 1 deletion(-)
> > 
> > diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> > index 1f0d232..780cd00 100644
> > --- a/hw/ppc/spapr.c
> > +++ b/hw/ppc/spapr.c
> > @@ -603,6 +603,18 @@ static void spapr_populate_cpu_dt(CPUState *cs, void *fdt, int offset,
> >      size_t page_sizes_prop_size;
> >      uint32_t vcpus_per_socket = smp_threads * smp_cores;
> >      uint32_t pft_size_prop[] = {0, cpu_to_be32(spapr->htab_shift)};
> > +    sPAPRMachineClass *smc = SPAPR_MACHINE_GET_CLASS(qdev_get_machine());
> > +    sPAPRDRConnector *drc;
> > +    sPAPRDRConnectorClass *drck;
> > +    int drc_index;
> > +
> > +    if (smc->dr_cpu_enabled) {
> > +        drc = spapr_dr_connector_by_id(SPAPR_DR_CONNECTOR_TYPE_CPU, index);
> > +        g_assert(drc);
> > +        drck = SPAPR_DR_CONNECTOR_GET_CLASS(drc);
> > +        drc_index = drck->get_index(drc);
> > +        _FDT((fdt_setprop_cell(fdt, offset, "ibm,my-drc-index", drc_index)));
> > +    }
> >  
> >      /* Note: we keep CI large pages off for now because a 64K capable guest
> >       * provisioned with large pages might otherwise try to map a qemu
> > @@ -987,6 +999,16 @@ static void spapr_finalize_fdt(sPAPRMachineState *spapr,
> >          _FDT(spapr_drc_populate_dt(fdt, 0, NULL, SPAPR_DR_CONNECTOR_TYPE_LMB));
> >      }
> >  
> > +    if (smc->dr_cpu_enabled) {
> > +        int offset = fdt_path_offset(fdt, "/cpus");
> > +        ret = spapr_drc_populate_dt(fdt, offset, NULL,
> > +                                    SPAPR_DR_CONNECTOR_TYPE_CPU);
> > +        if (ret < 0) {
> > +            fprintf(stderr, "Couldn't set up CPU DR device tree properties\n");
> 
> I think it's better to use error_report() nowadays instead.

Yeah, have been carrying this old hunk, will fix.

> 
> > +            exit(1);
> > +        }
> > +    }
> > +
> >      _FDT((fdt_pack(fdt)));
> >  
> >      if (fdt_totalsize(fdt) > FDT_MAX_SIZE) {
> > @@ -1759,6 +1781,7 @@ static void ppc_spapr_init(MachineState *machine)
> >      char *filename;
> >      int spapr_cores = smp_cpus / smp_threads;
> >      int spapr_max_cores = max_cpus / smp_threads;
> > +    int smt = kvmppc_smt_threads();
> >  
> >      msi_supported = true;
> >  
> > @@ -1813,6 +1836,15 @@ static void ppc_spapr_init(MachineState *machine)
> >          spapr_validate_node_memory(machine, &error_fatal);
> >      }
> >  
> > +    if (smc->dr_cpu_enabled) {
> > +        for (i = 0; i < spapr_max_cores; i++) {
> > +            sPAPRDRConnector *drc =
> > +                spapr_dr_connector_new(OBJECT(spapr),
> > +                                       SPAPR_DR_CONNECTOR_TYPE_CPU, i * smt);
> > +            qemu_register_reset(spapr_drc_reset, drc);
> > +        }
> > +    }
> > +
> >      /* init CPUs */
> >      if (machine->cpu_model == NULL) {
> >          machine->cpu_model = kvm_enabled() ? "host" : "POWER7";
> > @@ -2247,6 +2279,88 @@ out:
> >      error_propagate(errp, local_err);
> >  }
> >  
> > +static void *spapr_populate_hotplug_cpu_dt(DeviceState *dev, CPUState *cs,
> > +                                           int *fdt_offset,
> > +                                           sPAPRMachineState *spapr)
> > +{
> > +    PowerPCCPU *cpu = POWERPC_CPU(cs);
> > +    DeviceClass *dc = DEVICE_GET_CLASS(cs);
> > +    int id = ppc_get_vcpu_dt_id(cpu);
> > +    void *fdt;
> > +    int offset, fdt_size;
> > +    char *nodename;
> > +
> > +    fdt = create_device_tree(&fdt_size);
> > +    nodename = g_strdup_printf("%s@%x", dc->fw_name, id);
> > +    offset = fdt_add_subnode(fdt, 0, nodename);
> > +
> > +    spapr_populate_cpu_dt(cs, fdt, offset, spapr);
> > +    g_free(nodename);
> > +
> > +    *fdt_offset = offset;
> > +    return fdt;
> > +}
> > +
> > +static void spapr_core_plug(HotplugHandler *hotplug_dev, DeviceState *dev,
> > +                            Error **errp)
> > +{
> > +    sPAPRMachineClass *smc = SPAPR_MACHINE_GET_CLASS(qdev_get_machine());
> > +    sPAPRMachineState *ms = SPAPR_MACHINE(qdev_get_machine());
> > +    sPAPRCPUCore *core = SPAPR_CPU_CORE(OBJECT(dev));
> > +    PowerPCCPU *cpu = &core->threads[0];
> > +    CPUState *cs = CPU(cpu);
> > +    int id = ppc_get_vcpu_dt_id(cpu);
> > +    sPAPRDRConnector *drc =
> > +        spapr_dr_connector_by_id(SPAPR_DR_CONNECTOR_TYPE_CPU, id);
> > +    sPAPRDRConnectorClass *drck;
> > +    Error *local_err = NULL;
> > +    void *fdt = NULL;
> > +    int fdt_offset = 0;
> > +
> > +    if (!smc->dr_cpu_enabled) {
> > +        /*
> > +         * This is a cold plugged CPU core but the machine doesn't support
> > +         * DR. So skip the hotplug path ensuring that the core is brought
> > +         * up online with out an associated DR connector.
> > +         */
> > +        return;
> > +    }
> > +
> > +    g_assert(drc);
> > +
> > +    /*
> > +     * Setup CPU DT entries only for hotplugged CPUs. For boot time or
> > +     * coldplugged CPUs DT entries are setup in spapr_finalize_fdt().
> > +     */
> > +    if (dev->hotplugged) {
> > +        fdt = spapr_populate_hotplug_cpu_dt(dev, cs, &fdt_offset, ms);
> > +        dev->hotplugged = true;
> 
> That looks strange ... why "dev->hotplugged = true" after you've already
> checked that with the above if-statement?

Yeah this is a remnant of the implmentation that was based on David's proposal
where all the devices were pre-created and I had to set dev->hotplugged
manually here. Will remove as it is not needed here in this device_add
based implementation.

Regards,
Bharata.