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Re: [Qemu-devel] [RFC PATCH v0 1/1] spapr: Support setting of compat CPU


From: Eduardo Habkost
Subject: Re: [Qemu-devel] [RFC PATCH v0 1/1] spapr: Support setting of compat CPU type for CPU cores
Date: Thu, 23 Jun 2016 12:55:36 -0300
User-agent: Mutt/1.6.1 (2016-04-27)

On Wed, Jun 22, 2016 at 09:09:46AM +0200, Igor Mammedov wrote:
> On Wed, 22 Jun 2016 08:00:28 +0530
> Bharata B Rao <address@hidden> wrote:
> 
> > On Tue, Jun 21, 2016 at 09:09:57AM +0200, Igor Mammedov wrote:
> > > On Sat, 18 Jun 2016 14:04:06 +0530
> > > Bharata B Rao <address@hidden> wrote:
> > > 
> > > > Compat CPU type is typically specified on -cpu cmdline option
> > > > like: -cpu host,compat=power7 or -cpu POWER8E,compat=power7 etc.
> > > > With the introduction of sPAPR CPU core devices, we need to
> > > > support the same for core devices too.
> > > > 
> > > > Support the specification of CPU compat type on device_add
> > > > command for sPAPRCPUCore devices like:
> > > > (qemu) device_add
> > > > POWER8E-spapr-cpu-core,id=core3,compat=power7,core-id=24
> > > > 
> > > > Signed-off-by: Bharata B Rao <address@hidden>
> > > > ---
> > > > Applies on ppc-for-2.7 branch of David Gibson's tree.
> > > > 
> > > >  hw/ppc/spapr.c                  |  8 +++++
> > > >  hw/ppc/spapr_cpu_core.c         | 73
> > > > +++++++++++++++++++++++++++++++++++++++++
> > > > include/hw/ppc/spapr_cpu_core.h |  2 ++ 3 files changed, 83
> > > > insertions(+)
> > > > 
> > > > diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> > > > index 778fa25..2049d7d 100644
> > > > --- a/hw/ppc/spapr.c
> > > > +++ b/hw/ppc/spapr.c
> > > > @@ -1807,6 +1807,7 @@ static void ppc_spapr_init(MachineState
> > > > *machine) if (i < spapr_cores) {
> > > >                  char *type =
> > > > spapr_get_cpu_core_type(machine->cpu_model); Object *core;
> > > > +                char *compat;
> > > >  
> > > >                  if (!object_class_by_name(type)) {
> > > >                      error_report("Unable to find sPAPR CPU Core
> > > > definition"); @@ -1818,6 +1819,13 @@ static void
> > > > ppc_spapr_init(MachineState *machine) &error_fatal);
> > > >                  object_property_set_int(core, core_dt_id,
> > > > CPU_CORE_PROP_CORE_ID, &error_fatal);
> > > > +                compat =
> > > > spapr_get_cpu_compat_type(machine->cpu_model);
> > > > +                if (compat) {
> > > > +                    object_property_set_str(core, compat,
> > > > "compat",
> > > > +                                            &error_fatal);
> > > > +                    g_free(compat);
> > > > +                }
> > > > +
> > > >                  object_property_set_bool(core, true, "realized",
> > > > &error_fatal); }
> > > >          }
> > > > diff --git a/hw/ppc/spapr_cpu_core.c b/hw/ppc/spapr_cpu_core.c
> > > > index 3a5da09..9eb63cc 100644
> > > > --- a/hw/ppc/spapr_cpu_core.c
> > > > +++ b/hw/ppc/spapr_cpu_core.c
> > > > @@ -96,6 +96,24 @@ char *spapr_get_cpu_core_type(const char
> > > > *model) return core_type;
> > > >  }
> > > >  
> > > > +/*
> > > > + * Returns the CPU compat type specified in -cpu @model.
> > > > + */
> > > > +char *spapr_get_cpu_compat_type(const char *model)
> > > CPUClass already has such parser and hook to override it in case of
> > > target does legacy parsing, see CPUClass->parse_features.
> > > Maybe extending generic core in similar way and reusing generic
> > > parser will do the job.
> > 
> > In fact, I am already using CPUClass->parse_features() to set the
> > feature properties (which right now is only compat= for us) for core
> > device.
> > 
> > What I need in the above routine spapr_get_cpu_compat_type() is to
> > extract "compat=", so that I can verify that the compat type specified
> > with -device matches with what was specified with -cpu.
> > 
> > > 
> > > However we are in progress [1] of converting legacy
> > >  -cpu cpuname,feat1=x,feat2=y,...
> > > into a set of global properties
> > >  -global cputype.feat1=x ...
> > > 
> > > it would be better if you wouldn't start using -cpu for features
> > > but use directly -global mechanism,
> > > for that you need only have a corresponding property in spapr_core
> > > type.
> > 
> > Will this work be part of 2.7 ? If not, we will have to use -cpu to
> > extract the compat type since powerpc core hotplug is already
> > upstream.
> You can use -global without that work but so far it looks like it will
> make into 2.7.

I expect the -cpu => globals series to be included soon, unless
there are objections by others.

But as Igor said, globals are already supported. If you want to
set a property in the CPU core objects, you just need to use:

  -global spapr-cpu-core.compat=XXX

The conflict here seems to be that you want the "-cpu" option to
affect the cpu-core objects, not just the VCPU/thread objects.
But we have been assuming that "-cpu" would only affect the
VCPU/thread objects.

What if you just call the cpu_common_parse_features() function
from Igor's series using "spapr-cpu-core" as the typename? This
way all the "-cpu" options would be simply translated to
spapr-cpu-core global properties.

Is "core" the only property in TYPE_POWERPC_CPU, currently?

-- 
Eduardo



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