Re: [Qemu-devel] [PATCH v2] numa: improve cpu hotplug error message with a wrong node-id

[David Gibson <david@gibson.dropbear.id.au>]

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On Tue, May 21, 2019 at 09:33:48AM +0200, Laurent Vivier wrote:
> On pseries, core-ids are strongly binded to a node-id by the command
> line option. If an user tries to add a CPU to the wrong node, he has
> an error but it is not really helpful:
> 
>   qemu-system-ppc64 ... -smp 1,maxcpus=64,cores=1,threads=1,sockets=1 \
>                         -numa node,nodeid=0 -numa node,nodeid=1 ...
> 
>   (qemu) device_add power9_v2.0-spapr-cpu-core,core-id=30,node-id=1
>   Error: node-id=1 must match numa node specified with -numa option
> 
> This patch improves this error message by giving to the user the good
> topology information (node-id, socket-id and thread-id if they are
> available) to use with the core-id he's providing:
> 
>   Error: core-id 30 can only be plugged into node-id 0
> 
> Signed-off-by: Laurent Vivier <lvivier@redhat.com>

LGTM,

Reviewed-by: David Gibson <david@gibson.dropbear.id.au>

> ---
> 
> Notes:
>     v2: display full topology in the error message
> 
>  numa.c | 28 ++++++++++++++++++++++++++--
>  1 file changed, 26 insertions(+), 2 deletions(-)
> 
> diff --git a/numa.c b/numa.c
> index 3875e1efda3a..7413f821e2bb 100644
> --- a/numa.c
> +++ b/numa.c
> @@ -458,6 +458,27 @@ void qmp_set_numa_node(NumaOptions *cmd, Error **errp)
>      set_numa_options(MACHINE(qdev_get_machine()), cmd, errp);
>  }
>  
> +static char *cpu_topology_to_string(const CPUArchId *cpu)
> +{
> +    GString *s = g_string_new(NULL);
> +    if (cpu->props.has_socket_id) {
> +        g_string_append_printf(s, "socket-id %"PRId64, cpu->props.socket_id);
> +    }
> +    if (cpu->props.has_node_id) {
> +        if (s->len) {
> +            g_string_append_printf(s, ", ");
> +        }
> +        g_string_append_printf(s, "node-id %"PRId64, cpu->props.node_id);
> +    }
> +    if (cpu->props.has_thread_id) {
> +        if (s->len) {
> +            g_string_append_printf(s, ", ");
> +        }
> +        g_string_append_printf(s, "thread-id %"PRId64, cpu->props.thread_id);
> +    }
> +    return g_string_free(s, false);
> +}
> +
>  void numa_cpu_pre_plug(const CPUArchId *slot, DeviceState *dev, Error **errp)
>  {
>      int node_id = object_property_get_int(OBJECT(dev), "node-id", &error_abort);
> @@ -470,8 +491,11 @@ void numa_cpu_pre_plug(const CPUArchId *slot, DeviceState *dev, Error **errp)
>                                      "node-id", errp);
>          }
>      } else if (node_id != slot->props.node_id) {
> -        error_setg(errp, "node-id=%d must match numa node specified "
> -                   "with -numa option", node_id);
> +        char *topology = cpu_topology_to_string(slot);
> +        error_setg(errp,
> +                   "core-id %"PRId64" can only be plugged into %s",
> +                   slot->props.core_id, topology);
> +        g_free(topology);
>      }
>  }
>  

-- 
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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