Re: [Qemu-arm] [PATCH 08/10] cpu: use CPUClass->parse_features() as convertor to global properties

[Eduardo Habkost]

On Mon, Jun 06, 2016 at 05:16:50PM +0200, Igor Mammedov wrote:
> Currently CPUClass->parse_features() is used to parse
> -cpu features string and set properties on created CPU
> instances.
> 
> But considering that features specified by -cpu apply to
> every created CPU instance, it doesn't make sence to
> parse the same features string for every CPU created.
> It also makes every target that cares about parsing
> features string explicitly call CPUClass->parse_features()
> parser, which gets in a way if we consider using
> generic device_add for CPU hotplug as device_add
> has not a clue about CPU specific hooks.
> 
> Turns out we can use global properties mechanism to set
> properties on every created CPU instance for a given
> type. That way it's possible to convert CPU features
> into a set of global properties for CPU type specified
> by -cpu cpu_model and common Device.device_post_init()
> will apply them to CPU of given type automatically
> regardless whether it's manually created CPU or CPU
> created with help of device_add.
> 
> Signed-off-by: Igor Mammedov <address@hidden>
> ---
> This patch only make CPUClass->parse_features()
> a global properties convertor and follow up patches
> will switch individual users to new behaviour

Considering that we won't fix all callers to not call it multiple
times in the same series, can we add TODO notes to the
->parse_features() callers that are still need to be fixed?

Additional comments (and TODO notes suggestions) below:

> ---
>  hw/arm/virt.c     |  7 ++++---
>  include/qom/cpu.h |  2 +-
>  qom/cpu.c         | 29 +++++++++++++++++------------
>  target-i386/cpu.c | 30 ++++++++++++++++++++----------
>  4 files changed, 42 insertions(+), 26 deletions(-)
> 
> diff --git a/hw/arm/virt.c b/hw/arm/virt.c
> index e77ed88..473e439 100644
> --- a/hw/arm/virt.c
> +++ b/hw/arm/virt.c
> @@ -1193,6 +1193,7 @@ static void machvirt_init(MachineState *machine)
>  
>      for (n = 0; n < smp_cpus; n++) {
>          ObjectClass *oc = cpu_class_by_name(TYPE_ARM_CPU, cpustr[0]);
> +        const char *typename = object_class_get_name(oc);
>          CPUClass *cc = CPU_CLASS(oc);
>          Object *cpuobj;
>          Error *err = NULL;
> @@ -1202,10 +1203,10 @@ static void machvirt_init(MachineState *machine)
>              error_report("Unable to find CPU definition");
>              exit(1);
>          }
> -        cpuobj = object_new(object_class_get_name(oc));
> +        /* convert -smp CPU options specified by the user into global props 
> */
> +        cc->parse_features(typename, cpuopts, &err);

/*TODO: call cc->parse_features() only once */

> +        cpuobj = object_new(typename);
>  
> -        /* Handle any CPU options specified by the user */
> -        cc->parse_features(CPU(cpuobj), cpuopts, &err);
>          g_free(cpuopts);
>          if (err) {
>              error_report_err(err);
> diff --git a/include/qom/cpu.h b/include/qom/cpu.h
> index 32f3af3..cacb100 100644
> --- a/include/qom/cpu.h
> +++ b/include/qom/cpu.h
> @@ -134,7 +134,7 @@ typedef struct CPUClass {
>      /*< public >*/
>  
>      ObjectClass *(*class_by_name)(const char *cpu_model);
> -    void (*parse_features)(CPUState *cpu, char *str, Error **errp);
> +    void (*parse_features)(const char *typename, char *str, Error **errp);
>  
>      void (*reset)(CPUState *cpu);
>      int reset_dump_flags;
> diff --git a/qom/cpu.c b/qom/cpu.c
> index 751e992..f3e3c02 100644
> --- a/qom/cpu.c
> +++ b/qom/cpu.c
> @@ -28,6 +28,7 @@
>  #include "exec/log.h"
>  #include "qemu/error-report.h"
>  #include "sysemu/sysemu.h"
> +#include "hw/qdev-properties.h"
>  
>  bool cpu_exists(int64_t id)
>  {
> @@ -46,7 +47,7 @@ bool cpu_exists(int64_t id)
>  CPUState *cpu_generic_init(const char *typename, const char *cpu_model)
>  {
>      char *str, *name, *featurestr;
> -    CPUState *cpu;
> +    CPUState *cpu = NULL;
>      ObjectClass *oc;
>      CPUClass *cc;
>      Error *err = NULL;
> @@ -60,16 +61,15 @@ CPUState *cpu_generic_init(const char *typename, const 
> char *cpu_model)
>          return NULL;
>      }
>  
> -    cpu = CPU(object_new(object_class_get_name(oc)));
> -    cc = CPU_GET_CLASS(cpu);
> -
> +    cc = CPU_CLASS(oc);
>      featurestr = strtok(NULL, ",");
> -    cc->parse_features(cpu, featurestr, &err);
> +    cc->parse_features(object_class_get_name(oc), featurestr, &err);

/*TODO: all callers of cpu_generic_init() need to be converted to
 * call parse_features() only once, before calling cpu_generic_init().
 */

>      g_free(str);
>      if (err != NULL) {
>          goto out;
>      }
>  
> +    cpu = CPU(object_new(object_class_get_name(oc)));
>      object_property_set_bool(OBJECT(cpu), true, "realized", &err);
>  
>  out:
> @@ -282,25 +282,29 @@ static ObjectClass *cpu_common_class_by_name(const char 
> *cpu_model)
>      return NULL;
>  }
>  
> -static void cpu_common_parse_features(CPUState *cpu, char *features,
> +static void cpu_common_parse_features(const char *typename, char *features,
>                                        Error **errp)
>  {
>      char *featurestr; /* Single "key=value" string being parsed */
>      char *val;
> -    Error *err = NULL;
> +    static bool cpu_globals_initialized;
> +

/*TODO: all callers of ->parse_features() need to be changed to
 * call it only once, so we can remove this check (or change it
 * to assert(!cpu_globals_initialized).
 * Current callers of ->parse_features() are:
 * - machvirt_init()
 * - cpu_generic_init()
 * - cpu_x86_create()
 */

As far as I can see, after applying the whole series, only
cpu_x86_create() will remain.

> +    if (cpu_globals_initialized) {
> +        return;
> +    }
>  
>      featurestr = features ? strtok(features, ",") : NULL;
>  
>      while (featurestr) {
>          val = strchr(featurestr, '=');
>          if (val) {
> +            GlobalProperty *prop = g_new0(typeof(*prop), 1);
>              *val = 0;
>              val++;
> -            object_property_parse(OBJECT(cpu), val, featurestr, &err);
> -            if (err) {
> -                error_propagate(errp, err);
> -                return;
> -            }
> +            prop->driver = typename;
> +            prop->property = g_strdup(featurestr);
> +            prop->value = g_strdup(val);
> +            qdev_prop_register_global(prop);
>          } else {
>              error_setg(errp, "Expected key=value format, found %s.",
>                         featurestr);
> @@ -308,6 +312,7 @@ static void cpu_common_parse_features(CPUState *cpu, char 
> *features,
>          }
>          featurestr = strtok(NULL, ",");
>      }
> +    cpu_globals_initialized = true;

This will register globals multiple times if called with
"foo=x,bar". Easier to just set cpu_globals_initialized=true
earlier, and report errors only on the first ->parse_features()
call?

(The same comment applies to x86_cpu_parse_featurestr() below)

>  }
>  
>  static void cpu_common_realizefn(DeviceState *dev, Error **errp)
> diff --git a/target-i386/cpu.c b/target-i386/cpu.c
> index 31e5e6f..43b22e6 100644
> --- a/target-i386/cpu.c
> +++ b/target-i386/cpu.c
> @@ -1950,12 +1950,16 @@ static FeatureWordArray minus_features = { 0 };
>  
>  /* Parse "+feature,-feature,feature=foo" CPU feature string
>   */
> -static void x86_cpu_parse_featurestr(CPUState *cs, char *features,
> +static void x86_cpu_parse_featurestr(const char *typename, char *features,
>                                       Error **errp)
>  {
> -    X86CPU *cpu = X86_CPU(cs);
>      char *featurestr; /* Single 'key=value" string being parsed */
>      Error *local_err = NULL;
> +    static bool cpu_globals_initialized;
> +
> +    if (cpu_globals_initialized) {
> +        return;
> +    }
>  
>      if (!features) {
>          return;
> @@ -1967,6 +1971,7 @@ static void x86_cpu_parse_featurestr(CPUState *cs, char 
> *features,
>          const char *name;
>          const char *val = NULL;
>          char *eq = NULL;
> +        GlobalProperty *prop;
>  
>          /* Compatibility syntax: */
>          if (featurestr[0] == '+') {
> @@ -2019,12 +2024,14 @@ static void x86_cpu_parse_featurestr(CPUState *cs, 
> char *features,
>              name = "tsc-frequency";
>          }
>  
> -        object_property_parse(OBJECT(cpu), val, name, &local_err);
> -        if (local_err) {
> -            error_propagate(errp, local_err);
> -            return;
> -        }
> +        prop = g_new0(typeof(*prop), 1);
> +        prop->driver = typename;
> +        prop->property = g_strdup(name);
> +        prop->value = g_strdup(val);
> +        qdev_prop_register_global(prop);
>      }
> +
> +    cpu_globals_initialized = true;
>  }
>  
>  /* Print all cpuid feature names in featureset
> @@ -2208,9 +2215,11 @@ X86CPU *cpu_x86_create(const char *cpu_model, Error 
> **errp)
>  {
>      X86CPU *cpu = NULL;
>      ObjectClass *oc;
> +    CPUClass *cc;
>      gchar **model_pieces;
>      char *name, *features;
>      Error *error = NULL;
> +    const char *typename;
>  
>      model_pieces = g_strsplit(cpu_model, ",", 2);
>      if (!model_pieces[0]) {
> @@ -2225,10 +2234,11 @@ X86CPU *cpu_x86_create(const char *cpu_model, Error 
> **errp)
>          error_setg(&error, "Unable to find CPU definition: %s", name);
>          goto out;
>      }
> +    cc = CPU_CLASS(oc);
> +    typename = object_class_get_name(oc);
>  
> -    cpu = X86_CPU(object_new(object_class_get_name(oc)));
> -
> -    x86_cpu_parse_featurestr(CPU(cpu), features, &error);
> +    cc->parse_features(typename, features, &error);

/*TODO: call cc->parse_features() only once, before calling cpu_x86_create() */

> +    cpu = X86_CPU(object_new(typename));
>      if (error) {
>          goto out;
>      }
> -- 
> 1.8.3.1
> 

-- 
Eduardo