Re: [Qemu-devel] [PATCH for-2.9 17/17] target-i386: Implement query-cpu-model-expansion QMP command

[Eduardo Habkost]

On Tue, Dec 13, 2016 at 11:16:01AM +0100, Markus Armbruster wrote:
> Eduardo Habkost <address@hidden> writes:
> 
> > Implement query-cpu-model-expansion for target-i386.
> >
> > The code needs to be careful to handle non-migration-safe
> > features ("pmu" and "host-cache-info") according to the expansion
> > type.
> >
> > Cc: address@hidden
> > Cc: Jiri Denemark <address@hidden>
> > Signed-off-by: Eduardo Habkost <address@hidden>
> > ---
> >  tests/Makefile.include |   3 +
> >  monitor.c              |   4 +-
> >  target-i386/cpu.c      | 195 
> > ++++++++++++++++++++++++++++++++++++++++++++++++-
> >  3 files changed, 200 insertions(+), 2 deletions(-)
> >
> > diff --git a/tests/Makefile.include b/tests/Makefile.include
> > index 63c4347..c7bbfca 100644
> > --- a/tests/Makefile.include
> > +++ b/tests/Makefile.include
> > @@ -251,6 +251,9 @@ check-qtest-x86_64-y += $(check-qtest-i386-y)
> >  gcov-files-i386-y += i386-softmmu/hw/timer/mc146818rtc.c
> >  gcov-files-x86_64-y = $(subst 
> > i386-softmmu/,x86_64-softmmu/,$(gcov-files-i386-y))
> >  
> > +check-simpleqtest-x86_64-y += $(SRC_PATH)/tests/query-cpu-model-test.py
> > +check-simpleqtest-i386-y += $(SRC_PATH)/tests/query-cpu-model-test.py
> > +
> >  check-qtest-alpha-y = tests/boot-serial-test$(EXESUF)
> >  
> >  check-qtest-mips-y = tests/endianness-test$(EXESUF)
> > diff --git a/monitor.c b/monitor.c
> > index 0841d43..90c12b3 100644
> > --- a/monitor.c
> > +++ b/monitor.c
> > @@ -983,8 +983,10 @@ static void qmp_unregister_commands_hack(void)
> >  #ifndef TARGET_ARM
> >      qmp_unregister_command("query-gic-capabilities");
> >  #endif
> > -#if !defined(TARGET_S390X)
> > +#if !defined(TARGET_S390X) && !defined(TARGET_I386)
> >      qmp_unregister_command("query-cpu-model-expansion");
> > +#endif
> > +#if !defined(TARGET_S390X)
> >      qmp_unregister_command("query-cpu-model-baseline");
> >      qmp_unregister_command("query-cpu-model-comparison");
> >  #endif
> > diff --git a/target-i386/cpu.c b/target-i386/cpu.c
> > index bf4ac09..198014a 100644
> > --- a/target-i386/cpu.c
> > +++ b/target-i386/cpu.c
> > @@ -29,10 +29,14 @@
> >  #include "qemu/option.h"
> >  #include "qemu/config-file.h"
> >  #include "qapi/qmp/qerror.h"
> > +#include "qapi/qmp/qstring.h"
> > +#include "qapi/qmp/qdict.h"
> > +#include "qapi/qmp/qbool.h"
> >  
> >  #include "qapi-types.h"
> >  #include "qapi-visit.h"
> >  #include "qapi/visitor.h"
> > +#include "qom/qom-qobject.h"
> >  #include "sysemu/arch_init.h"
> >  
> >  #if defined(CONFIG_KVM)
> > @@ -2259,7 +2263,7 @@ static void x86_cpu_apply_props(X86CPU *cpu, 
> > PropValue *props)
> >      }
> >  }
> >  
> > -/* Load data from X86CPUDefinition
> > +/* Load data from X86CPUDefinition into a X86CPU object
> >   */
> >  static void x86_cpu_load_def(X86CPU *cpu, X86CPUDefinition *def, Error 
> > **errp)
> >  {
> > @@ -2268,6 +2272,11 @@ static void x86_cpu_load_def(X86CPU *cpu, 
> > X86CPUDefinition *def, Error **errp)
> >      char host_vendor[CPUID_VENDOR_SZ + 1];
> >      FeatureWord w;
> >  
> > +    /*NOTE: any property set by this function should be returned by
> 
> Space between /* and comment text, please.
> 
> Also, consider adding wings to both ends of multi-line comments.

Will do.

> 
> > +     * x86_cpu_to_dict(), so CPU model data returned by
> > +     * query-cpu-model-expansion is always complete.
> > +     */
> > +
> >      /* CPU models only set _minimum_ values for level/xlevel: */
> >      object_property_set_int(OBJECT(cpu), def->level, "min-level", errp);
> >      object_property_set_int(OBJECT(cpu), def->xlevel, "min-xlevel", errp);
> > @@ -2312,6 +2321,190 @@ static void x86_cpu_load_def(X86CPU *cpu, 
> > X86CPUDefinition *def, Error **errp)
> >  
> >  }
> >  
> > +/* Convert CPU model data from X86CPU object to a property dictionary
> > + * that can recreate exactly the same CPU model.
> > + *
> > + * This function does the opposite of x86_cpu_load_def(). Any
> > + * property changed by x86_cpu_load_def() or instance_init
> > + * methods should be returned by this function too.
> > + */
> > +static void x86_cpu_to_dict(X86CPU *cpu, QDict *props, Error **errp)
> > +{
> > +    Object *obj = OBJECT(cpu);
> > +    FeatureWord w;
> > +    PropValue *pv;
> > +
> > +    /* This code could simply iterate over all writeable properties in the
> > +     * CPU object, and return all of them. But then the aliases properties
> 
> "alias properties"?

Will fix it.

> 
> > +     * would be returned as well. Returning only the known features
> > +     * is more reliable.
> > +     */
> > +    qdict_put_obj(props, "min-level",
> > +                  object_property_get_qobject(obj, "min-level", errp));
> > +    qdict_put_obj(props, "min-xlevel",
> > +                  object_property_get_qobject(obj, "min-xlevel", errp));
> > +
> > +    qdict_put_obj(props, "family",
> > +                  object_property_get_qobject(obj, "family", errp));
> > +    qdict_put_obj(props, "model",
> > +                  object_property_get_qobject(obj, "model", errp));
> > +    qdict_put_obj(props, "stepping",
> > +                  object_property_get_qobject(obj, "stepping", errp));
> > +    qdict_put_obj(props, "model-id",
> > +                  object_property_get_qobject(obj, "model-id", errp));
> 
> Incorrect use of the error API: if more than one call fails, the second
> failure will trip the assertion in error_setv().
> 
> If errors should not happen here, use &error_abort.
> 
> If errors need to be handled, see "Receive and accumulate multiple
> errors" in error.h.
> 

Oops. I will fix it.

> Consider "more than four, use a for":
> 
>        static char *prop_name[] = {
>            "min-level", "min-xlevel", "family", "model", "stepping",
>            "model-id", NULL
>        };
> 
>        for (pname = prop_name; *pname, pname++) {
>            qdict_put_obj(props, *pname,
>                          object_property_get_qobject(obj, *pname,
>                                                      &error_abort));
>        }

Good idea, I will do it.

> 
> > +
> > +    for (w = 0; w < FEATURE_WORDS; w++) {
> > +        FeatureWordInfo *fi = &feature_word_info[w];
> > +        int bit;
> > +        for (bit = 0; bit < 32; bit++) {
> > +            if (!fi->feat_names[bit]) {
> > +                continue;
> > +            }
> > +            qdict_put_obj(props, fi->feat_names[bit],
> > +                          object_property_get_qobject(obj, 
> > fi->feat_names[bit],
> > +                                                      errp));
> > +        }
> > +    }
> > +
> > +    for (pv = kvm_default_props; pv->prop; pv++) {
> > +        qdict_put_obj(props, pv->prop,
> > +                      object_property_get_qobject(obj, pv->prop, errp));
> > +    }
> > +    for (pv = tcg_default_props; pv->prop; pv++) {
> > +        qdict_put_obj(props, pv->prop,
> > +                      object_property_get_qobject(obj, pv->prop, errp));
> > +    }
> > +
> > +    qdict_put_obj(props, "vendor",
> > +                  object_property_get_qobject(obj, "vendor", errp));
> > +
> > +    /* Set by "host": */
> > +    qdict_put_obj(props, "lmce",
> > +                  object_property_get_qobject(obj, "lmce", errp));
> > +    qdict_put_obj(props, "pmu",
> > +                  object_property_get_qobject(obj, "pmu", errp));
> > +
> > +
> > +    /* Other properties configurable by the user: */
> > +    qdict_put_obj(props, "host-cache-info",
> > +                  object_property_get_qobject(obj, "host-cache-info", 
> > errp));
> > +}
> > +
> > +static void object_apply_props(Object *obj, QDict *props, Error **errp)
> > +{
> > +    const QDictEntry *prop;
> > +    Error *err = NULL;
> > +
> > +    for (prop = qdict_first(props); prop; prop = qdict_next(props, prop)) {
> > +        object_property_set_qobject(obj, qdict_entry_value(prop),
> > +                                         qdict_entry_key(prop), &err);
> > +        if (err) {
> > +            break;
> > +        }
> > +    }
> > +
> > +    error_propagate(errp, err);
> > +}
> > +
> > +static X86CPU *x86_cpu_from_model(CpuModelInfo *model, Error **errp)
> > +{
> > +    X86CPU *xc = NULL;
> > +    X86CPUClass *xcc;
> > +    Error *err = NULL;
> > +
> > +    xcc = X86_CPU_CLASS(cpu_class_by_name(TYPE_X86_CPU, model->name));
> > +    if (xcc == NULL) {
> > +        error_setg(&err, "CPU model '%s' not found", model->name);
> > +        goto out;
> > +    }
> > +
> > +    xc = X86_CPU(object_new(object_class_get_name(OBJECT_CLASS(xcc))));
> > +    if (model->has_props) {
> > +        QDict *d = qobject_to_qdict(model->props);
> > +        if (!d) {
> > +            error_setg(&err, "model.props must be a dictionary");
> > +            goto out;
> 
> How can this happen?

'props' is 'any' in the QAPI schema, because (it looks like) QAPI
doesn't have a 'dict' type.

> 
> > +        }
> > +        object_apply_props(OBJECT(xc), d, &err);
> > +        if (err) {
> > +            goto out;
> > +        }
> > +    }
> > +
> > +    x86_cpu_expand_features(xc, &err);
> > +    if (err) {
> > +        goto out;
> > +    }
> > +
> > +out:
> > +    if (err) {
> > +        error_propagate(errp, err);
> > +        object_unref(OBJECT(xc));
> > +        xc = NULL;
> > +    }
> > +    return xc;
> > +}
> > +
> > +CpuModelExpansionInfo 
> > *arch_query_cpu_model_expansion(CpuModelExpansionType type,
> > +                                                      CpuModelInfo *model,
> > +                                                      Error **errp)
> > +{
> > +    X86CPU *xc = NULL;
> > +    Error *err = NULL;
> > +    CpuModelExpansionInfo *ret = g_new0(CpuModelExpansionInfo, 1);
> > +    QDict *props;
> > +
> > +    xc = x86_cpu_from_model(model, &err);
> > +    if (err) {
> > +        goto out;
> > +    }
> > +
> > +    /* We currently always do full expansion */
> 
> This comment made me go "wait, we do full expansion even when @type is
> CPU_MODEL_EXPANSION_TYPE_STATIC?"  Looks like we first to full
> expansion, then correct the result according to type.

The comment is a leftover from a previous version where we didn't
even check expansion type. I will remove it (or clarify it).

> 
> > +    ret->model = g_new0(CpuModelInfo, 1);
> > +    ret->model->name = g_strdup("base"); /* the only static model */
> > +    props = qdict_new();
> > +    ret->model->props = QOBJECT(props);
> > +    ret->model->has_props = true;
> > +    x86_cpu_to_dict(xc, props, &err);
> > +
> > +    /* Some features (pmu, host-cache-info) are not migration-safe,
> > +     * and are handled differently depending on expansion type:
> > +     */
> > +    if (type ==  CPU_MODEL_EXPANSION_TYPE_STATIC) {
> 
> Single space after ==, please.

Will fix.

> 
> > +        /* static expansion force migration-unsafe features off: */
> > +        ret->q_static = ret->migration_safe = true;
> > +        qdict_del(props, "pmu");
> > +        qdict_del(props, "host-cache-info");
> > +    } else if (type == CPU_MODEL_EXPANSION_TYPE_FULL) {
> > +        QObject *o;
> > +        /* full expansion clear the static/migration-safe flags
> > +         * to indicate migration-unsafe features are on:
> > +         */
> > +        ret->q_static = true;
> > +        ret->migration_safe = true;
> > +
> > +        o = qdict_get(props, "pmu");
> > +        if (o && qbool_get_bool(qobject_to_qbool(o))) {
> > +            ret->q_static = ret->migration_safe = false;
> > +        }
> > +        o = qdict_get(props, "host-cache-info");
> > +        if (o && qbool_get_bool(qobject_to_qbool(o))) {
> > +            ret->q_static = ret->migration_safe = false;
> > +        }
> > +    } else {
> > +        error_setg(&err, "The requested expansion type is not supported.");
> 
> How can this happen?
> 
> If it can, it bombs when x86_cpu_to_dict() already set an error (see
> "use of the error API" above).

This can happen if we change the QAPI schema to support another
expansion type in the future.

> 
> > +    }
> > +
> > +out:
> > +    object_unref(OBJECT(xc));
> > +    if (err) {
> > +        error_propagate(errp, err);
> > +        qapi_free_CpuModelExpansionInfo(ret);
> > +        ret = NULL;
> > +    }
> > +    return ret;
> > +}
> > +
> >  X86CPU *cpu_x86_init(const char *cpu_model)
> >  {
> >      return X86_CPU(cpu_generic_init(TYPE_X86_CPU, cpu_model));

-- 
Eduardo