Re: [Qemu-devel] [RFC PATCH 2/2] numa: Add node_id data in query-hotpluggable-cpus

[David Gibson <dgibson@redhat.com>]

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On Thu,  7 Jul 2016 17:17:14 +0200
Peter Krempa <pkrempa@redhat.com> wrote:

> Add a helper that looks up the NUMA node for a given CPU and use it to
> fill the node_id in the PPC and X86 impls of query-hotpluggable-cpus.


IIUC how the query thing works this means that the node id issued by
query-hotpluggable-cpus will be echoed back to device add by libvirt.
I'm not sure we actually process that information in the core at
present, so I don't know that that's right.

We need to be clear on which direction information is flowing here.
Does query-hotpluggable-cpus *define* the NUMA node allocation which is
then passed to the core device which implements it.  Or is the NUMA
allocation defined elsewhere, and query-hotpluggable-cpus just reports
it.

> Signed-off-by: Peter Krempa <pkrempa@redhat.com>
> ---
>  hw/i386/pc.c          |  7 +++++++
>  hw/ppc/spapr.c        |  8 ++++++--
>  include/sysemu/numa.h |  1 +
>  numa.c                | 13 +++++++++++++
>  4 files changed, 27 insertions(+), 2 deletions(-)
> 
> diff --git a/hw/i386/pc.c b/hw/i386/pc.c
> index 4ba02c4..a0b9507 100644
> --- a/hw/i386/pc.c
> +++ b/hw/i386/pc.c
> @@ -2115,6 +2115,7 @@ static HotpluggableCPUList *pc_query_hotpluggable_cpus(MachineState *machine)
>      HotpluggableCPUList *head = NULL;
>      PCMachineState *pcms = PC_MACHINE(machine);
>      const char *cpu_type;
> +    int node_id;
> 
>      cpu = pcms->possible_cpus->cpus[0].cpu;
>      assert(cpu); /* BSP is always present */
> @@ -2138,6 +2139,12 @@ static HotpluggableCPUList *pc_query_hotpluggable_cpus(MachineState *machine)
>          cpu_props->core_id = topo.core_id;
>          cpu_props->has_thread_id = true;
>          cpu_props->thread_id = topo.smt_id;
> +
> +        if ((node_id = numa_node_get_by_cpu_index(i)) >= 0) {
> +            cpu_props->has_node_id = true;
> +            cpu_props->node_id = node_id;
> +        }
> +
>          cpu_item->props = cpu_props;
> 
>          cpu = pcms->possible_cpus->cpus[i].cpu;
> diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> index d1f5195..06ba7fc 100644
> --- a/hw/ppc/spapr.c
> +++ b/hw/ppc/spapr.c
> @@ -2370,6 +2370,7 @@ static HotpluggableCPUList *spapr_query_hotpluggable_cpus(MachineState *machine)
>      sPAPRMachineState *spapr = SPAPR_MACHINE(machine);
>      int spapr_max_cores = max_cpus / smp_threads;
>      int smt = kvmppc_smt_threads();
> +    int node_id;
> 
>      for (i = 0; i < spapr_max_cores; i++) {
>          HotpluggableCPUList *list_item = g_new0(typeof(*list_item), 1);
> @@ -2381,8 +2382,11 @@ static HotpluggableCPUList *spapr_query_hotpluggable_cpus(MachineState *machine)
>          cpu_item->vcpu_id = i;
>          cpu_props->has_core_id = true;
>          cpu_props->core_id = i * smt;
> -        /* TODO: add 'has_node/node' here to describe
> -           to which node core belongs */
> +
> +        if ((node_id = numa_node_get_by_cpu_index(i)) >= 0) {

As with the previous patch this is incorrect, becauyse
numa_node_get_by_cpu_index() is working from a vcpu (i.e. thread)
index, but you're passing a core index.

> +            cpu_props->has_node_id = true;
> +            cpu_props->node_id = node_id;
> +        }
> 
>          cpu_item->props = cpu_props;
>          if (spapr->cores[i]) {
> diff --git a/include/sysemu/numa.h b/include/sysemu/numa.h
> index bb184c9..04d7097 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);
> +int numa_node_get_by_cpu_index(int cpu_index);
> 
>  #endif
> diff --git a/numa.c b/numa.c
> index cbae430..365738a 100644
> --- a/numa.c
> +++ b/numa.c
> @@ -506,6 +506,19 @@ void query_numa_node_mem(uint64_t node_mem[])
>      }
>  }
> 
> +int numa_node_get_by_cpu_index(int cpu_index)
> +{
> +    int i;
> +
> +    for (i = 0; i < nb_numa_nodes; i++) {
> +        if (test_bit(cpu_index, numa_info[i].node_cpu)) {
> +            return i;
> +        }
> +    }
> +
> +    return -1;
> +}
> +
>  static int query_memdev(Object *obj, void *opaque)
>  {
>      MemdevList **list = opaque;
> -- 
> 2.9.0
> 


-- 
David Gibson <dgibson@redhat.com>
Senior Software Engineer, Virtualization, Red Hat

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