Re: [Qemu-devel] [PATCH v2 1/1] spapr: Set compat type for CPUs of a core

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

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On Mon, Jun 27, 2016 at 11:49:46AM +0530, Bharata B Rao wrote:
> Compat CPU type is typically specified on -cpu cmdline option like:
> -cpu host,compat=power7 or -cpu POWER8E,compat=power7 etc. When
> compat is specified on -cpu cmdline, apply the same to all the
> CPUs that get created as part of CPU core devices.
> 
> This patch takes care of compat property that is specified with
> -cpu cmdline option only. The other way to specify this property
> is via -global cmdline option and that usage isn't addressed by
> this patch because -global is already broken for some CPU class
> in PowerPC. There are two issues with using -global on CPU class.
> 
> - We specify alias names for CPUs commonly and use of alias names
>   won't work with -global seamlessly. For eg, When "-cpu host" is
>   specified, the actual CPU type that gets created
>   is host-powerpc64-cpu. Hence specifying -global host.compat=power7
>   will not work, so it has to be -global host-powerpc64-cpu.compat=power7.
> 
> - PowerPC class names have . (dot) and opts parsing doesn't like it.
>   Specifying -global POWER8E_v2.1-powerpc64-cpu.compat=power7 will not
>   work as the driver name gets extracted as POWER8E_v2 and hence setting
>   of global property fails.
> 
> The above two aspects could be considered/fixed separately from this
> patch as this patch allows existing uses of -cpu cpuname,compat= to
> work correctly after the introducton of sPAPR CPU cores.
> 
> Signed-off-by: Bharata B Rao <bharata@linux.vnet.ibm.com>
> ---
> Changes in v2:
> - No need for a separate property named compat for cores.
> - Simplified spapr_get_cpu_compat_type() based on David's review.

I'm still not seeing why this is actually necessary.  If the compat
property is specified with -global, it will automatically be
propagated to all threads without core intervention, yes?

So shouldn't we just make the -cpu fallback effectively set the same
-global property, rather than bouncing it through the core object?

> 
> v1: https://lists.gnu.org/archive/html/qemu-devel/2016-06/msg06279.html
> 
>  hw/ppc/spapr_cpu_core.c | 32 ++++++++++++++++++++++++++++++++
>  1 file changed, 32 insertions(+)
> 
> diff --git a/hw/ppc/spapr_cpu_core.c b/hw/ppc/spapr_cpu_core.c
> index 3a5da09..e8873fd 100644
> --- a/hw/ppc/spapr_cpu_core.c
> +++ b/hw/ppc/spapr_cpu_core.c
> @@ -96,6 +96,28 @@ char *spapr_get_cpu_core_type(const char *model)
>      return core_type;
>  }
>  
> +/*
> + * Returns the CPU compat type specified in -cpu @model.
> + */
> +static char *spapr_get_cpu_compat_type(const char *model)
> +{
> +    char *model_str = g_strdup(model);
> +    char *featurestr, *compat = NULL;
> +
> +    featurestr = model_str ? strtok(model_str, ",") : NULL;
> +    while (featurestr) {
> +        if (!strncmp(featurestr, "compat=", 7)) {
> +            compat = g_strdup(featurestr + 7);
> +            goto out;
> +        }
> +        featurestr = strtok(NULL, ",");
> +    }
> +
> +out:
> +    g_free(model_str);
> +    return compat;
> +}
> +
>  static void spapr_core_release(DeviceState *dev, void *opaque)
>  {
>      sPAPRCPUCore *sc = SPAPR_CPU_CORE(OBJECT(dev));
> @@ -285,6 +307,8 @@ static void spapr_cpu_core_realize(DeviceState *dev, Error **errp)
>      CPUCore *cc = CPU_CORE(OBJECT(dev));
>      const char *typename = object_class_get_name(sc->cpu_class);
>      size_t size = object_type_get_instance_size(typename);
> +    MachineState *machine = MACHINE(qdev_get_machine());
> +    char *compat = spapr_get_cpu_compat_type(machine->cpu_model);
>      Error *local_err = NULL;
>      Object *obj;
>      int i;
> @@ -300,11 +324,18 @@ static void spapr_cpu_core_realize(DeviceState *dev, Error **errp)
>          if (local_err) {
>              goto err;
>          }
> +        if (compat) {
> +            object_property_set_str(obj, compat, "compat", &local_err);
> +            if (local_err) {
> +                goto err;
> +            }
> +        }
>      }
>      object_child_foreach(OBJECT(dev), spapr_cpu_core_realize_child, &local_err);
>      if (local_err) {
>          goto err;
>      } else {
> +        g_free(compat);
>          return;
>      }
>  
> @@ -315,6 +346,7 @@ err:
>          i--;
>      }
>      g_free(sc->threads);
> +    g_free(compat);
>      error_propagate(errp, local_err);
>  }
>  

-- 
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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