Re: [PATCH 01/19] target/ppc: add exclusive Book3S PMU reg read/write functions

[Daniel Henrique Barboza]

On 8/10/21 12:19 AM, David Gibson wrote:
> On Mon, Aug 09, 2021 at 10:10:39AM -0300, Daniel Henrique Barboza wrote:
> > The PowerPC PMU, as described by PowerISA v3.1, has a lot of functions
> > that freezes, resets and sets counters to specific values depending on
> > the circuntances. Some of these are trigged based on read/value of the
> > PMU registers (MMCR0, MMCR1, MMCR2, MMCRA and PMC counters).
> >
> > Having to handle the PMU logic using the generic read/write functions
> > can impact all other registers that has nothing to do with the PMU that
> > uses these functions. This patch creates two new functions,
> > spr_read_pmu_generic() and spr_write_pmu_generic, that will be used later
> > on to handle PMU logic together with the read/write of PMU registers.
> >
> > We're not ready to add specific PMU logic in these new functions yet, so
> > for now these are just stubs that calls spr_read/write_generic(). No
> > functional change is made.
> >
> > Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com>
> > ---
> >   target/ppc/cpu_init.c  | 24 ++++++++++++------------
> >   target/ppc/spr_tcg.h   |  2 ++
> >   target/ppc/translate.c | 12 ++++++++++++
> >   3 files changed, 26 insertions(+), 12 deletions(-)
> >
> > diff --git a/target/ppc/cpu_init.c b/target/ppc/cpu_init.c
> > index 505a0ed6ac..021c1bc750 100644
> > --- a/target/ppc/cpu_init.c
> > +++ b/target/ppc/cpu_init.c
> > @@ -6821,47 +6821,47 @@ static void register_book3s_pmu_sup_sprs(CPUPPCState 
> > *env)
> >   {
> >       spr_register_kvm(env, SPR_POWER_MMCR0, "MMCR0",
> >                        SPR_NOACCESS, SPR_NOACCESS,
> > -                     &spr_read_generic, &spr_write_generic,
> > +                     &spr_read_pmu_generic, &spr_write_pmu_generic,
>
> So... this seems dubiousd to me.  Surely when you go to implement the
> specifics of these registers you'll need separate logic for each of
> them.
>
> Why call a common "read_pmu" function that will then have to multiplex
> to different logic for each register, when you could just dispatch
> directly to a helper for that specific register.

Now that I have an idea of which registers I'll end up reading/writing,
I believe that we can cut a few of those early patches and expose the
logic in a "register-centric" manner.


Daniel





> >                        KVM_REG_PPC_MMCR0, 0x00000000);
> >       spr_register_kvm(env, SPR_POWER_MMCR1, "MMCR1",
> >                        SPR_NOACCESS, SPR_NOACCESS,
> > -                     &spr_read_generic, &spr_write_generic,
> > +                     &spr_read_pmu_generic, &spr_write_pmu_generic,
> >                        KVM_REG_PPC_MMCR1, 0x00000000);
> >       spr_register_kvm(env, SPR_POWER_MMCRA, "MMCRA",
> >                        SPR_NOACCESS, SPR_NOACCESS,
> > -                     &spr_read_generic, &spr_write_generic,
> > +                     &spr_read_pmu_generic, &spr_write_pmu_generic,
> >                        KVM_REG_PPC_MMCRA, 0x00000000);
> >       spr_register_kvm(env, SPR_POWER_PMC1, "PMC1",
> >                        SPR_NOACCESS, SPR_NOACCESS,
> > -                     &spr_read_generic, &spr_write_generic,
> > +                     &spr_read_pmu_generic, &spr_write_pmu_generic,
> >                        KVM_REG_PPC_PMC1, 0x00000000);
> >       spr_register_kvm(env, SPR_POWER_PMC2, "PMC2",
> >                        SPR_NOACCESS, SPR_NOACCESS,
> > -                     &spr_read_generic, &spr_write_generic,
> > +                     &spr_read_pmu_generic, &spr_write_pmu_generic,
> >                        KVM_REG_PPC_PMC2, 0x00000000);
> >       spr_register_kvm(env, SPR_POWER_PMC3, "PMC3",
> >                        SPR_NOACCESS, SPR_NOACCESS,
> > -                     &spr_read_generic, &spr_write_generic,
> > +                     &spr_read_pmu_generic, &spr_write_pmu_generic,
> >                        KVM_REG_PPC_PMC3, 0x00000000);
> >       spr_register_kvm(env, SPR_POWER_PMC4, "PMC4",
> >                        SPR_NOACCESS, SPR_NOACCESS,
> > -                     &spr_read_generic, &spr_write_generic,
> > +                     &spr_read_pmu_generic, &spr_write_pmu_generic,
> >                        KVM_REG_PPC_PMC4, 0x00000000);
> >       spr_register_kvm(env, SPR_POWER_PMC5, "PMC5",
> >                        SPR_NOACCESS, SPR_NOACCESS,
> > -                     &spr_read_generic, &spr_write_generic,
> > +                     &spr_read_pmu_generic, spr_write_pmu_generic,
> >                        KVM_REG_PPC_PMC5, 0x00000000);
> >       spr_register_kvm(env, SPR_POWER_PMC6, "PMC6",
> >                        SPR_NOACCESS, SPR_NOACCESS,
> > -                     &spr_read_generic, &spr_write_generic,
> > +                     &spr_read_pmu_generic, &spr_write_pmu_generic,
> >                        KVM_REG_PPC_PMC6, 0x00000000);
> >       spr_register_kvm(env, SPR_POWER_SIAR, "SIAR",
> >                        SPR_NOACCESS, SPR_NOACCESS,
> > -                     &spr_read_generic, &spr_write_generic,
> > +                     &spr_read_pmu_generic, &spr_write_pmu_generic,
> >                        KVM_REG_PPC_SIAR, 0x00000000);
> >       spr_register_kvm(env, SPR_POWER_SDAR, "SDAR",
> >                        SPR_NOACCESS, SPR_NOACCESS,
> > -                     &spr_read_generic, &spr_write_generic,
> > +                     &spr_read_pmu_generic, &spr_write_pmu_generic,
> >                        KVM_REG_PPC_SDAR, 0x00000000);
> >   }
> >   
> > @@ -6941,7 +6941,7 @@ static void register_power8_pmu_sup_sprs(CPUPPCState *env)
> >   {
> >       spr_register_kvm(env, SPR_POWER_MMCR2, "MMCR2",
> >                        SPR_NOACCESS, SPR_NOACCESS,
> > -                     &spr_read_generic, &spr_write_generic,
> > +                     &spr_read_pmu_generic, &spr_write_pmu_generic,
> >                        KVM_REG_PPC_MMCR2, 0x00000000);
> >       spr_register_kvm(env, SPR_POWER_MMCRS, "MMCRS",
> >                        SPR_NOACCESS, SPR_NOACCESS,
> > diff --git a/target/ppc/spr_tcg.h b/target/ppc/spr_tcg.h
> > index 0be5f347d5..2aab5878a0 100644
> > --- a/target/ppc/spr_tcg.h
> > +++ b/target/ppc/spr_tcg.h
> > @@ -25,6 +25,8 @@
> >   void spr_noaccess(DisasContext *ctx, int gprn, int sprn);
> >   void spr_read_generic(DisasContext *ctx, int gprn, int sprn);
> >   void spr_write_generic(DisasContext *ctx, int sprn, int gprn);
> > +void spr_read_pmu_generic(DisasContext *ctx, int gprn, int sprn);
> > +void spr_write_pmu_generic(DisasContext *ctx, int sprn, int gprn);
> >   void spr_read_xer(DisasContext *ctx, int gprn, int sprn);
> >   void spr_write_xer(DisasContext *ctx, int sprn, int gprn);
> >   void spr_read_lr(DisasContext *ctx, int gprn, int sprn);
> > diff --git a/target/ppc/translate.c b/target/ppc/translate.c
> > index 171b216e17..c8f3878002 100644
> > --- a/target/ppc/translate.c
> > +++ b/target/ppc/translate.c
> > @@ -385,6 +385,12 @@ void spr_read_generic(DisasContext *ctx, int gprn, int 
> > sprn)
> >       spr_load_dump_spr(sprn);
> >   }
> >   
> > +void spr_read_pmu_generic(DisasContext *ctx, int gprn, int sprn)
> > +{
> > +    /* For now it's just a call to spr_read_generic() */
> > +    spr_read_generic(ctx, gprn, sprn);
> > +}
> > +
> >   static void spr_store_dump_spr(int sprn)
> >   {
> >   #ifdef PPC_DUMP_SPR_ACCESSES
> > @@ -400,6 +406,12 @@ void spr_write_generic(DisasContext *ctx, int sprn, int 
> > gprn)
> >       spr_store_dump_spr(sprn);
> >   }
> >   
> > +void spr_write_pmu_generic(DisasContext *ctx, int sprn, int gprn)
> > +{
> > +    /* For now it's just a call to spr_write_generic() */
> > +    spr_write_generic(ctx, sprn, gprn);
> > +}
> > +
> >   #if !defined(CONFIG_USER_ONLY)
> >   void spr_write_generic32(DisasContext *ctx, int sprn, int gprn)
> >   {