Re: [PATCH v3 3/8] qmp: add filtering of statistics by target vCPU

[Markus Armbruster <armbru@redhat.com>]

Paolo Bonzini <pbonzini@redhat.com> writes:

> Introduce a simple filtering of statistics, that allows to retrieve
> statistics for a subset of the guest vCPUs.  This will be used for
> example by the HMP monitor, in order to retrieve the statistics
> for the currently selected CPU.
>
> Example:
> { "execute": "query-stats",
>   "arguments": {
>     "target": "vcpu",
>     "vcpus": [ "/machine/unattached/device[2]",
>                "/machine/unattached/device[4]" ] } }
>
> Extracted from a patch by Mark Kanda.
>
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> ---
>  accel/kvm/kvm-all.c     |  9 +++++++--
>  include/monitor/stats.h |  9 ++++++++-
>  monitor/qmp-cmds.c      | 34 +++++++++++++++++++++++++++++++++-
>  qapi/stats.json         | 20 +++++++++++++++++---
>  4 files changed, 65 insertions(+), 7 deletions(-)
>
> diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c
> index 6a6bbe2994..28f8a45205 100644
> --- a/accel/kvm/kvm-all.c
> +++ b/accel/kvm/kvm-all.c
> @@ -2311,7 +2311,8 @@ bool kvm_dirty_ring_enabled(void)
>      return kvm_state->kvm_dirty_ring_size ? true : false;
>  }
>  
> -static void query_stats_cb(StatsResultList **result, StatsTarget target, Error **errp);
> +static void query_stats_cb(StatsResultList **result, StatsTarget target,
> +                           strList *targets, Error **errp);
>  static void query_stats_schemas_cb(StatsSchemaList **result, Error **errp);
>  
>  static int kvm_init(MachineState *ms)
> @@ -4049,7 +4050,8 @@ static void query_stats_schema_vcpu(CPUState *cpu, run_on_cpu_data data)
>      close(stats_fd);
>  }
>  
> -static void query_stats_cb(StatsResultList **result, StatsTarget target, Error **errp)
> +static void query_stats_cb(StatsResultList **result, StatsTarget target,
> +                           strList *targets, Error **errp)
>  {
>      KVMState *s = kvm_state;
>      CPUState *cpu;
> @@ -4073,6 +4075,9 @@ static void query_stats_cb(StatsResultList **result, StatsTarget target, Error *
>          stats_args.result.stats = result;
>          stats_args.errp = errp;
>          CPU_FOREACH(cpu) {
> +            if (!str_in_list(cpu->parent_obj.canonical_path, targets)) {
> +                continue;
> +            }
>              run_on_cpu(cpu, query_stats_vcpu, RUN_ON_CPU_HOST_PTR(&stats_args));
>          }
>          break;
> diff --git a/include/monitor/stats.h b/include/monitor/stats.h
> index 89552ab06f..92a1df3072 100644
> --- a/include/monitor/stats.h
> +++ b/include/monitor/stats.h
> @@ -10,7 +10,8 @@
>  
>  #include "qapi/qapi-types-stats.h"
>  
> -typedef void StatRetrieveFunc(StatsResultList **result, StatsTarget target, Error **errp);
> +typedef void StatRetrieveFunc(StatsResultList **result, StatsTarget target,
> +                              strList *targets, Error **errp);
>  typedef void SchemaRetrieveFunc(StatsSchemaList **result, Error **errp);
>  
>  /*
> @@ -30,4 +31,10 @@ void add_stats_entry(StatsResultList **, StatsProvider, const char *id,
>  void add_stats_schema(StatsSchemaList **, StatsProvider, StatsTarget,
>                        StatsSchemaValueList *);
>  
> +/*
> + * True if a string matches the filter passed to the stats_fn callabck,
> + * false otherwise.
> + */
> +bool str_in_list(const char *string, strList *list);
> +
>  #endif /* STATS_H */
> diff --git a/monitor/qmp-cmds.c b/monitor/qmp-cmds.c
> index d83faeca88..1ec7409bc2 100644
> --- a/monitor/qmp-cmds.c
> +++ b/monitor/qmp-cmds.c
> @@ -463,13 +463,30 @@ void add_stats_callbacks(StatRetrieveFunc *stats_fn,
>      QTAILQ_INSERT_TAIL(&stats_callbacks, entry, next);
>  }
>  
> +static strList *stats_target_filter(StatsFilter *filter)
> +{
> +    switch (filter->target) {
> +    case STATS_TARGET_VM:
> +        return NULL;
> +    case STATS_TARGET_VCPU:
> +        if (!filter->u.vcpu.has_vcpus) {
> +            return NULL;
> +        }
> +        return filter->u.vcpu.vcpus;
> +        break;
> +    default:
> +        abort();
> +    }
> +}
> +
>  StatsResultList *qmp_query_stats(StatsFilter *filter, Error **errp)
>  {
>      StatsResultList *stats_results = NULL;
> +    strList *targets = stats_target_filter(filter);
>      StatsCallbacks *entry;
>  
>      QTAILQ_FOREACH(entry, &stats_callbacks, next) {
> -        entry->stats_cb(&stats_results, filter->target, errp);
> +        entry->stats_cb(&stats_results, filter->target, targets, errp);
>      }
>  
>      return stats_results;
> @@ -512,3 +529,18 @@ void add_stats_schema(StatsSchemaList **schema_results,
>      entry->stats = stats_list;
>      QAPI_LIST_PREPEND(*schema_results, entry);
>  }
> +
> +bool str_in_list(const char *string, strList *list)
> +{
> +    strList *str_list = NULL;
> +
> +    if (!list) {
> +        return true;

Are you sure the empty list is supposed to contain any string?

> +    }
> +    for (str_list = list; str_list; str_list = str_list->next) {
> +        if (g_str_equal(string, str_list->value)) {
> +            return true;
> +        }
> +    }
> +    return false;
> +}
> diff --git a/qapi/stats.json b/qapi/stats.json
> index 382223e197..859fc0f459 100644
> --- a/qapi/stats.json
> +++ b/qapi/stats.json
> @@ -68,16 +68,30 @@
>  { 'enum': 'StatsTarget',
>    'data': [ 'vm', 'vcpu' ] }
>  
> +##
> +# @StatsVCPUFilter:
> +#
> +# @vcpus: list of QOM paths for the desired vCPU objects.
> +#
> +# Since: 7.1
> +##
> +{ 'struct': 'StatsVCPUFilter',
> +  'data': { '*vcpus': [ 'str' ] } }
> +
>  ##
>  # @StatsFilter:
>  #
>  # The arguments to the query-stats command; specifies a target for which to
> -# request statistics.
> +# request statistics and optionally the required subset of information for
> +# that target:
> +# - which vCPUs to request statistics for
>  #
>  # Since: 7.1
>  ##
> -{ 'struct': 'StatsFilter',
> -  'data': { 'target': 'StatsTarget' } }
> +{ 'union': 'StatsFilter',
> +        'base': { 'target': 'StatsTarget' },
> +  'discriminator': 'target',
> +  'data': { 'vcpu': 'StatsVCPUFilter' } }
>  
>  ##
>  # @StatsValue: