Re: [Qemu-ppc] [RFC PATCH v3 12/24] spapr: CPU hotplug support

[David Gibson]

On Fri, Apr 24, 2015 at 12:17:34PM +0530, Bharata B Rao wrote:
> Support CPU hotplug via device-add command. 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.
> 
> Also support cold plugged CPUs that are specified by -device option
> on cmdline.
> 
> Signed-off-by: Bharata B Rao <address@hidden>
> ---
>  hw/ppc/spapr.c        | 129 
> ++++++++++++++++++++++++++++++++++++++++++++++++++
>  hw/ppc/spapr_events.c |   8 ++--
>  hw/ppc/spapr_rtas.c   |  11 +++++
>  3 files changed, 145 insertions(+), 3 deletions(-)
> 
> diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> index b526b7d..9b0701c 100644
> --- a/hw/ppc/spapr.c
> +++ b/hw/ppc/spapr.c
> @@ -33,6 +33,7 @@
>  #include "sysemu/block-backend.h"
>  #include "sysemu/cpus.h"
>  #include "sysemu/kvm.h"
> +#include "sysemu/device_tree.h"
>  #include "kvm_ppc.h"
>  #include "mmu-hash64.h"
>  #include "qom/cpu.h"
> @@ -662,6 +663,17 @@ static void spapr_populate_cpu_dt(CPUState *cs, void 
> *fdt, int offset)
>      unsigned sockets = opts ? qemu_opt_get_number(opts, "sockets", 0) : 0;
>      uint32_t cpus_per_socket = sockets ? (smp_cpus / sockets) : 1;
>      uint32_t pft_size_prop[] = {0, cpu_to_be32(spapr->htab_shift)};
> +    sPAPRDRConnector *drc;
> +    sPAPRDRConnectorClass *drck;
> +    int drc_index;
> +
> +    if (spapr->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)));
> +    }
>  
>      _FDT((fdt_setprop_cell(fdt, offset, "reg", index)));
>      _FDT((fdt_setprop_string(fdt, offset, "device_type", "cpu")));
> @@ -1850,6 +1862,114 @@ static void spapr_nmi(NMIState *n, int cpu_index, 
> Error **errp)
>      }
>  }
>  
> +static void *spapr_populate_hotplug_cpu_dt(DeviceState *dev, CPUState *cs,
> +                                            int *fdt_offset)
> +{
> +    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("address@hidden", dc->fw_name, id);
> +    offset = fdt_add_subnode(fdt, 0, nodename);
> +
> +    spapr_populate_cpu_dt(cs, fdt, offset);
> +    g_free(nodename);
> +
> +    *fdt_offset = offset;
> +    return fdt;
> +}
> +
> +static void spapr_cpu_plug(HotplugHandler *hotplug_dev, DeviceState *dev,
> +                            Error **errp)
> +{
> +    CPUState *cs = CPU(dev);
> +    PowerPCCPU *cpu = POWERPC_CPU(cs);
> +    int id = ppc_get_vcpu_dt_id(cpu);
> +    sPAPRDRConnector *drc =
> +        spapr_dr_connector_by_id(SPAPR_DR_CONNECTOR_TYPE_CPU, id);
> +    sPAPRDRConnectorClass *drck;
> +    int smt = kvmppc_smt_threads();
> +    Error *local_err = NULL;
> +    void *fdt = NULL;
> +    int i, fdt_offset = 0;
> +
> +    /* 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;
> +        }
> +    }
> +
> +    /*
> +     * SMT threads return from here, only main thread (core) will
> +     * continue and signal hotplug event to the guest.
> +     */
> +    if ((id % smt) != 0) {
> +        return;
> +    }

Couldn't you avoid this by attaching this call to the core device,
rather than the individual vcpu thread objects?


> +    if (!spapr->dr_cpu_enabled) {
> +        /*
> +         * This is a cold plugged CPU but the machine doesn't support
> +         * DR. So skip the hotplug path ensuring that the CPU 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);
> +    }
> +
> +    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;
> +    }
> +
> +    /*
> +     * We send hotplug notification interrupt to the guest only in case
> +     * of hotplugged CPUs.
> +     */
> +    if (dev->hotplugged) {
> +        spapr_hotplug_req_add_event(drc);
> +    } else {
> +        /*
> +         * HACK to support removal of hotplugged CPU after VM migration:
> +         *
> +         * Since we want to be able to hot-remove those coldplugged CPUs
> +         * started at boot time using -device option at the target VM, we set
> +         * the right allocation_state and isolation_state for them, which for
> +         * the hotplugged CPUs would be set via RTAS calls done from the
> +         * guest during hotplug.
> +         *
> +         * This allows the coldplugged CPUs started using -device option to
> +         * have the right isolation and allocation states as expected by the
> +         * CPU hot removal code.
> +         *
> +         * This hack will be removed once we have DRC states migrated as part
> +         * of VM migration.
> +         */
> +        drck->set_allocation_state(drc, SPAPR_DR_ALLOCATION_STATE_USABLE);
> +        drck->set_isolation_state(drc, SPAPR_DR_ISOLATION_STATE_UNISOLATED);
> +    }
> +
> +    return;
> +}
> +
>  static void spapr_machine_device_plug(HotplugHandler *hotplug_dev,
>                                        DeviceState *dev, Error **errp)
>  {
> @@ -1858,6 +1978,15 @@ static void spapr_machine_device_plug(HotplugHandler 
> *hotplug_dev,
>          PowerPCCPU *cpu = POWERPC_CPU(cs);
>  
>          spapr_cpu_init(cpu);
> +        spapr_cpu_reset(cpu);

I'm a little surprised these get called here, rather than in the
creation / realize path of the core qdev.

> +        /*
> +         * Fail hotplug on machines where CPU DR isn't enabled.
> +         */
> +        if (!spapr->dr_cpu_enabled && dev->hotplugged) {
> +            return;
> +        }
> +        spapr_cpu_plug(hotplug_dev, dev, errp);
>      }
>  }
>  
> diff --git a/hw/ppc/spapr_events.c b/hw/ppc/spapr_events.c
> index be82815..4ae818a 100644
> --- a/hw/ppc/spapr_events.c
> +++ b/hw/ppc/spapr_events.c
> @@ -421,14 +421,16 @@ static void spapr_hotplug_req_event(sPAPRDRConnector 
> *drc, uint8_t hp_action)
>      hp->hdr.section_length = cpu_to_be16(sizeof(*hp));
>      hp->hdr.section_version = 1; /* includes extended modifier */
>      hp->hotplug_action = hp_action;
> -
> +    hp->drc.index = cpu_to_be32(drck->get_index(drc));
> +    hp->hotplug_identifier = RTAS_LOG_V6_HP_ID_DRC_INDEX;
>  
>      switch (drc_type) {
>      case SPAPR_DR_CONNECTOR_TYPE_PCI:
> -        hp->drc.index = cpu_to_be32(drck->get_index(drc));
> -        hp->hotplug_identifier = RTAS_LOG_V6_HP_ID_DRC_INDEX;
>          hp->hotplug_type = RTAS_LOG_V6_HP_TYPE_PCI;
>          break;
> +    case SPAPR_DR_CONNECTOR_TYPE_CPU:
> +        hp->hotplug_type = RTAS_LOG_V6_HP_TYPE_CPU;
> +        break;
>      default:
>          /* we shouldn't be signaling hotplug events for resources
>           * that don't support them
> diff --git a/hw/ppc/spapr_rtas.c b/hw/ppc/spapr_rtas.c
> index 57ec97a..48aeb86 100644
> --- a/hw/ppc/spapr_rtas.c
> +++ b/hw/ppc/spapr_rtas.c
> @@ -121,6 +121,16 @@ static void rtas_query_cpu_stopped_state(PowerPCCPU 
> *cpu_,
>      rtas_st(rets, 0, RTAS_OUT_PARAM_ERROR);
>  }
>  
> +static void spapr_cpu_set_endianness(PowerPCCPU *cpu)
> +{
> +    PowerPCCPU *fcpu = POWERPC_CPU(first_cpu);
> +    PowerPCCPUClass *pcc = POWERPC_CPU_GET_CLASS(fcpu);
> +
> +    if (!(*pcc->interrupts_big_endian)(fcpu)) {
> +        cpu->env.spr[SPR_LPCR] |= LPCR_ILE;
> +    }
> +}
> +
>  static void rtas_start_cpu(PowerPCCPU *cpu_, sPAPREnvironment *spapr,
>                             uint32_t token, uint32_t nargs,
>                             target_ulong args,
> @@ -157,6 +167,7 @@ static void rtas_start_cpu(PowerPCCPU *cpu_, 
> sPAPREnvironment *spapr,
>          env->nip = start;
>          env->gpr[3] = r3;
>          cs->halted = 0;
> +        spapr_cpu_set_endianness(cpu);
>  
>          qemu_cpu_kick(cs);
>  

-- 
David Gibson                    | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au  | minimalist, thank you.  NOT _the_ _other_
                                | _way_ _around_!
http://www.ozlabs.org/~dgibson

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