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

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

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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.

>                       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)
>  {

-- 
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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