Re: [Qemu-devel] [RFC PATCH v1 08/10] spapr: CPU hotplug support

[Igor Mammedov <imammedo@redhat.com>]

On Tue, 8 Mar 2016 15:27:39 +1100
David Gibson <david@gibson.dropbear.id.au> wrote:

> On Mon, Mar 07, 2016 at 11:59:42AM +0530, Bharata B Rao wrote:
> > On Mon, Mar 07, 2016 at 02:49:06PM +1100, David Gibson wrote:  
> > > On Fri, Mar 04, 2016 at 12:24:19PM +0530, 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                  | 73 ++++++++++++++++++++++++++++++++++++++++-
> > > >  hw/ppc/spapr_cpu_core.c         | 60 +++++++++++++++++++++++++++++++++
> > > >  hw/ppc/spapr_events.c           |  3 ++
> > > >  hw/ppc/spapr_rtas.c             | 24 ++++++++++++++
> > > >  include/hw/ppc/spapr.h          |  4 +++
> > > >  include/hw/ppc/spapr_cpu_core.h |  2 ++
> > > >  6 files changed, 165 insertions(+), 1 deletion(-)
> > > > 
> > > > diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> > > > index 5acb612..6c4ac50 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) {
> > > > +            error_report("Couldn't set up CPU DR device tree properties");
> > > > +            exit(1);
> > > > +        }
> > > > +    }
> > > > +
> > > >      _FDT((fdt_pack(fdt)));
> > > >  
> > > >      if (fdt_totalsize(fdt) > FDT_MAX_SIZE) {
> > > > @@ -1181,7 +1203,7 @@ static void ppc_spapr_reset(void)
> > > >  
> > > >  }
> > > >  
> > > > -static void spapr_cpu_reset(void *opaque)
> > > > +void spapr_cpu_reset(void *opaque)
> > > >  {
> > > >      sPAPRMachineState *spapr = SPAPR_MACHINE(qdev_get_machine());
> > > >      PowerPCCPU *cpu = opaque;
> > > > @@ -1622,6 +1644,8 @@ static void spapr_boot_set(void *opaque, const char *boot_device,
> > > >  void spapr_cpu_init(sPAPRMachineState *spapr, PowerPCCPU *cpu, Error **errp)
> > > >  {
> > > >      CPUPPCState *env = &cpu->env;
> > > > +    CPUState *cs = CPU(cpu);
> > > > +    int i;
> > > >  
> > > >      /* Set time-base frequency to 512 MHz */
> > > >      cpu_ppc_tb_init(env, TIMEBASE_FREQ);
> > > > @@ -1646,6 +1670,14 @@ void spapr_cpu_init(sPAPRMachineState *spapr, PowerPCCPU *cpu, Error **errp)
> > > >          }
> > > >      }
> > > >  
> > > > +    /* Set NUMA node for the added CPUs  */
> > > > +    for (i = 0; i < nb_numa_nodes; i++) {
> > > > +        if (test_bit(cs->cpu_index, numa_info[i].node_cpu)) {
> > > > +            cs->numa_node = i;
> > > > +            break;
> > > > +        }
> > > > +    }
> > > > +  
> > > 
> > > This hunk seems like it belongs in a different patch.  
> > 
> > It appears that this would be needed by other archs also to set the
> > NUMA node for the hot-plugged CPU. How about make an API out of this
> > and use this something like below ? Igor ?  
> 
> Is there a way we could put this in the the CPU thread initialization
> itself?  Rather than requiring every platform to call a helper.
I'd suggest hotplugable CPU entity to have 'node' property, like we have
in pc-dimm.

However machine owns numa mapping, so setting it from thread
initialization seems to be wrong.
Could that be done from machine's plug() handler (spapr_core_plug)?

Also I notice that there is in no way to check/set 'address' properties
at machine level before calling cpu->realize(), which makes us
to attempt checking them inside cpu->realize() or at post realize time
in HotplugHandler(machine)->plug() hook with following full rollback
in case of failure.
Maybe we need add an HotplugHandler->pre_realize() hook to allow machine
verify/set properties of CPU before it's realized.

> 
> > -------------------------------------------------------------------
> > diff --git a/hw/i386/pc.c b/hw/i386/pc.c
> > index 0aeefd2..8347234 100644
> > --- a/hw/i386/pc.c
> > +++ b/hw/i386/pc.c
> > @@ -1112,6 +1112,7 @@ void pc_hot_add_cpu(const int64_t id, Error **errp)
> >          error_propagate(errp, local_err);
> >          return;
> >      }
> > +    numa_set_cpu(CPU(cpu));
> >      object_unref(OBJECT(cpu));
> >  }
> >  
> > diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> > index a42f8c0..f2b3b67 100644
> > --- a/hw/ppc/spapr.c
> > +++ b/hw/ppc/spapr.c
> > @@ -1645,7 +1645,6 @@ void spapr_cpu_init(sPAPRMachineState *spapr, PowerPCCPU *cpu, Error **errp)
> >  {
> >      CPUPPCState *env = &cpu->env;
> >      CPUState *cs = CPU(cpu);
> > -    int i;
> >  
> >      /* Set time-base frequency to 512 MHz */
> >      cpu_ppc_tb_init(env, TIMEBASE_FREQ);
> > @@ -1671,12 +1670,7 @@ void spapr_cpu_init(sPAPRMachineState *spapr, PowerPCCPU *cpu, Error **errp)
> >      }
> >  
> >      /* Set NUMA node for the added CPUs  */
> > -    for (i = 0; i < nb_numa_nodes; i++) {
> > -        if (test_bit(cs->cpu_index, numa_info[i].node_cpu)) {
> > -            cs->numa_node = i;
> > -            break;
> > -        }
> > -    }
> > +    numa_set_cpu(cs);
> >  
> >      xics_cpu_setup(spapr->icp, cpu);
> >      qemu_register_reset(spapr_cpu_reset, cpu);
> > diff --git a/include/sysemu/numa.h b/include/sysemu/numa.h
> > index bb184c9..648d68b 100644
> > --- a/include/sysemu/numa.h
> > +++ b/include/sysemu/numa.h
> > @@ -31,5 +31,6 @@ extern QemuOptsList qemu_numa_opts;
> >  void numa_set_mem_node_id(ram_addr_t addr, uint64_t size, uint32_t node);
> >  void numa_unset_mem_node_id(ram_addr_t addr, uint64_t size, uint32_t node);
> >  uint32_t numa_get_node(ram_addr_t addr, Error **errp);
> > +void numa_set_cpu(CPUState *cpu);
> >  
> >  #endif
> > diff --git a/numa.c b/numa.c
> > index 4c4f7f5..1b47c15 100644
> > --- a/numa.c
> > +++ b/numa.c
> > @@ -396,20 +396,32 @@ void parse_numa_opts(MachineClass *mc)
> >      }
> >  }
> >  
> > +static void numa_set_cpu_numa_node(CPUState *cpu)
> > +{
> > +    int i;
> > +
> > +    for (i = 0; i < nb_numa_nodes; i++) {
> > +        if (test_bit(cpu->cpu_index, numa_info[i].node_cpu)) {
> > +            cpu->numa_node = i;
> > +            break;
> > +        }
> > +    }
> > +}
> > +
> >  void numa_post_machine_init(void)
> >  {
> >      CPUState *cpu;
> > -    int i;
> >  
> >      CPU_FOREACH(cpu) {
> > -        for (i = 0; i < nb_numa_nodes; i++) {
> > -            if (test_bit(cpu->cpu_index, numa_info[i].node_cpu)) {
> > -                cpu->numa_node = i;
> > -            }
> > -        }
> > +        numa_set_cpu_numa_node(cpu);
> >      }
> >  }
> >  
> > +void numa_set_cpu(CPUState *cpu)
> > +{
> > +    numa_set_cpu_numa_node(cpu);
> > +}
> > +
> >  static void allocate_system_memory_nonnuma(MemoryRegion *mr, Object *owner,
> >                                             const char *name,
> >                                             uint64_t ram_size)
> > 
> > -------------------------------------------------------------------  
> > >   
> > > >      xics_cpu_setup(spapr->icp, cpu);
> > > >      qemu_register_reset(spapr_cpu_reset, cpu);
> > > >  }
> > > > @@ -1768,6 +1800,7 @@ 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();
> > > >  
> > > >      if (smp_cpus % smp_threads) {
> > > >          error_report("smp_cpus (%u) must be multiple of threads (%u)",
> > > > @@ -1834,6 +1867,15 @@ 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);
> > > > +        }
> > > > +    }
> > > > +  
> > > 
> > > Nit: would this be cleaner to include in the same loop that constructs
> > > the (empty) links and boot-time cpu cores?  
> > 
> > Seems possible, will change.
> >   
> > >   
> > > >      /* init CPUs */
> > > >      if (machine->cpu_model == NULL) {
> > > >          machine->cpu_model = kvm_enabled() ? "host" : "POWER7";
> > > > @@ -2267,6 +2309,27 @@ out:
> > > >      error_propagate(errp, local_err);
> > > >  }
> > > >  
> > > > +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_machine_device_plug(HotplugHandler *hotplug_dev,
> > > >                                        DeviceState *dev, Error **errp)
> > > >  {
> > > > @@ -2307,6 +2370,12 @@ static void spapr_machine_device_plug(HotplugHandler *hotplug_dev,
> > > >          }
> > > >  
> > > >          spapr_memory_plug(hotplug_dev, dev, node, errp);
> > > > +    } else if (object_dynamic_cast(OBJECT(dev), TYPE_SPAPR_CPU_CORE)) {
> > > > +        if (!smc->dr_cpu_enabled && dev->hotplugged) {
> > > > +            error_setg(errp, "CPU hotplug not supported for this machine");
> > > > +            return;
> > > > +        }
> > > > +        spapr_core_plug(hotplug_dev, dev, errp);
> > > >      }
> > > >  }
> > > >  
> > > > @@ -2366,6 +2435,7 @@ static void spapr_machine_class_init(ObjectClass *oc, void *data)
> > > >      mc->cpu_index_to_socket_id = spapr_cpu_index_to_socket_id;
> > > >  
> > > >      smc->dr_lmb_enabled = true;
> > > > +    smc->dr_cpu_enabled = true;
> > > >      fwc->get_dev_path = spapr_get_fw_dev_path;
> > > >      nc->nmi_monitor_handler = spapr_nmi;
> > > >  }
> > > > @@ -2445,6 +2515,7 @@ static void spapr_machine_2_5_class_options(MachineClass *mc)
> > > >  
> > > >      spapr_machine_2_6_class_options(mc);
> > > >      smc->use_ohci_by_default = true;
> > > > +    smc->dr_cpu_enabled = false;
> > > >      SET_MACHINE_COMPAT(mc, SPAPR_COMPAT_2_5);
> > > >  }
> > > >  
> > > > diff --git a/hw/ppc/spapr_cpu_core.c b/hw/ppc/spapr_cpu_core.c
> > > > index 9ddf3ce..4c233d7 100644
> > > > --- a/hw/ppc/spapr_cpu_core.c
> > > > +++ b/hw/ppc/spapr_cpu_core.c
> > > > @@ -14,6 +14,65 @@
> > > >  #include "qapi/visitor.h"
> > > >  #include <sysemu/cpus.h>
> > > >  
> > > > +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;
> > > > +    }
> > > > +
> > > > +    drck = SPAPR_DR_CONNECTOR_GET_CLASS(drc);
> > > > +    drck->attach(drc, dev, fdt, fdt_offset, !dev->hotplugged, &local_err);
> > > > +    if (local_err) {
> > > > +        g_free(fdt);
> > > > +        error_propagate(errp, local_err);
> > > > +        return;
> > > > +    }
> > > > +
> > > > +    if (dev->hotplugged) {
> > > > +        /*
> > > > +         * Send hotplug notification interrupt to the guest only in case
> > > > +         * of hotplugged CPUs.
> > > > +         */
> > > > +        spapr_hotplug_req_add_by_index(drc);
> > > > +    } else {
> > > > +        /*
> > > > +         * 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);
> > > > +    }
> > > > +}
> > > > +
> > > >  static int spapr_cpu_core_realize_child(Object *child, void *opaque)
> > > >  {
> > > >      Error **errp = opaque;
> > > > @@ -30,6 +89,7 @@ static int spapr_cpu_core_realize_child(Object *child, void *opaque)
> > > >      if (*errp) {
> > > >          return 1;
> > > >      }
> > > > +    spapr_cpu_reset(cpu);  
> > > 
> > > This also looks like it belongs in a different patch.  
> > 
> > You mean a separate patch for this or push this around to an existing
> > patch of the series ?
> > 
> > Regards,
> > Bharata.
> >   
>