linux-kernel - Re: [PATCH v2 3/6] powerpc/smp: Move shared

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Message-ID: <20231019130843.GI2194132@linux.vnet.ibm.com>
Date:   Thu, 19 Oct 2023 18:38:43 +0530
From:   Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
To:     Michael Ellerman <mpe@...erman.id.au>
Cc:     linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>,
        Christophe Leroy <christophe.leroy@...roup.eu>,
        Nicholas Piggin <npiggin@...il.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Rohan McLure <rmclure@...ux.ibm.com>,
        Valentin Schneider <vschneid@...hat.com>,
        Ajay Kaher <akaher@...are.com>,
        Alexey Makhalov <amakhalov@...are.com>,
        VMware PV-Drivers Reviewers <pv-drivers@...are.com>,
        Josh Poimboeuf <jpoimboe@...nel.org>,
        virtualization@...ts.linux-foundation.org, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 3/6] powerpc/smp: Move shared_processor static key to
 smp.h

* Michael Ellerman <mpe@...erman.id.au> [2023-10-19 15:41:40]:

> Srikar Dronamraju <srikar@...ux.vnet.ibm.com> writes:
> > The ability to detect if the system is running in a shared processor
> > mode is helpful in few more generic cases not just in
> > paravirtualization.
> > For example: At boot time, different scheduler/ topology flags may be
> > set based on the processor mode. Hence move it to a more generic file.
> 
> I'd rather you just included paravirt.h in the few files where you need it.


I thought, detecting if a Processor was shared or not was more a
smp/processor related than a paravirt related.

Will drop as suggested.

> 
> cheers
> 
> > diff --git a/arch/powerpc/include/asm/paravirt.h b/arch/powerpc/include/asm/paravirt.h
> > index 0372b0093f72..cf83e837a571 100644
> > --- a/arch/powerpc/include/asm/paravirt.h
> > +++ b/arch/powerpc/include/asm/paravirt.h
> > @@ -15,13 +15,6 @@
> >  #include <asm/kvm_guest.h>
> >  #include <asm/cputhreads.h>
> >  
> > -DECLARE_STATIC_KEY_FALSE(shared_processor);
> > -
> > -static inline bool is_shared_processor(void)
> > -{
> > -	return static_branch_unlikely(&shared_processor);
> > -}
> > -
> >  #ifdef CONFIG_PARAVIRT_TIME_ACCOUNTING
> >  extern struct static_key paravirt_steal_enabled;
> >  extern struct static_key paravirt_steal_rq_enabled;
> > @@ -77,11 +70,6 @@ static inline bool is_vcpu_idle(int vcpu)
> >  	return lppaca_of(vcpu).idle;
> >  }
> >  #else
> > -static inline bool is_shared_processor(void)
> > -{
> > -	return false;
> > -}
> > -
> >  static inline u32 yield_count_of(int cpu)
> >  {
> >  	return 0;
> > diff --git a/arch/powerpc/include/asm/smp.h b/arch/powerpc/include/asm/smp.h
> > index aaaa576d0e15..08631b2a4528 100644
> > --- a/arch/powerpc/include/asm/smp.h
> > +++ b/arch/powerpc/include/asm/smp.h
> > @@ -34,6 +34,20 @@ extern bool coregroup_enabled;
> >  extern int cpu_to_chip_id(int cpu);
> >  extern int *chip_id_lookup_table;
> >  
> > +#ifdef CONFIG_PPC_SPLPAR
> > +DECLARE_STATIC_KEY_FALSE(shared_processor);
> > +
> > +static inline bool is_shared_processor(void)
> > +{
> > +	return static_branch_unlikely(&shared_processor);
> > +}
> > +#else
> > +static inline bool is_shared_processor(void)
> > +{
> > +	return false;
> > +}
> > +#endif
> > +
> >  DECLARE_PER_CPU(cpumask_var_t, thread_group_l1_cache_map);
> >  DECLARE_PER_CPU(cpumask_var_t, thread_group_l2_cache_map);
> >  DECLARE_PER_CPU(cpumask_var_t, thread_group_l3_cache_map);
> > -- 
> > 2.31.1

-- 
Thanks and Regards
Srikar Dronamraju