Re: [PATCH v2 03/16] target/ppc: add exclusive user write function for MMCR0

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

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On Tue, Aug 24, 2021 at 01:30:19PM -0300, Daniel Henrique Barboza wrote:
> From: Gustavo Romero <gromero@linux.ibm.com>
> 
> Similar to the previous patch, user write on some PowerPC
> PMU regs, in this case, MMCR0, is limited. Create a new
> function to handle that.

Ok.. ok, this fixes my concern on the previous patch.  Best to avoid
the confusing interim step though.  I'm not sure there's a lot of use
adding the general "group A" helper if you're going to replace them
with more specific functions shortly afterwards.

> 
> CC: Gustavo Romero <gustavo.romero@linaro.org>
> Signed-off-by: Gustavo Romero <gromero@linux.ibm.com>
> Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com>
> ---
>  target/ppc/cpu_init.c  |  2 +-
>  target/ppc/spr_tcg.h   |  1 +
>  target/ppc/translate.c | 38 ++++++++++++++++++++++++++++++++++++++
>  3 files changed, 40 insertions(+), 1 deletion(-)
> 
> diff --git a/target/ppc/cpu_init.c b/target/ppc/cpu_init.c
> index 5510c3799f..860716da18 100644
> --- a/target/ppc/cpu_init.c
> +++ b/target/ppc/cpu_init.c
> @@ -6868,7 +6868,7 @@ static void register_book3s_pmu_sup_sprs(CPUPPCState *env)
>  static void register_book3s_pmu_user_sprs(CPUPPCState *env)
>  {
>      spr_register(env, SPR_POWER_UMMCR0, "UMMCR0",
> -                 &spr_read_MMCR0_ureg, &spr_write_PMU_groupA_ureg,
> +                 &spr_read_MMCR0_ureg, &spr_write_MMCR0_ureg,
>                   &spr_read_ureg, &spr_write_ureg,
>                   0x00000000);
>      spr_register(env, SPR_POWER_UMMCR1, "UMMCR1",
> diff --git a/target/ppc/spr_tcg.h b/target/ppc/spr_tcg.h
> index 64ef2cd089..5c383dae3d 100644
> --- a/target/ppc/spr_tcg.h
> +++ b/target/ppc/spr_tcg.h
> @@ -43,6 +43,7 @@ void spr_read_601_rtcu(DisasContext *ctx, int gprn, int sprn);
>  void spr_read_spefscr(DisasContext *ctx, int gprn, int sprn);
>  void spr_write_spefscr(DisasContext *ctx, int sprn, int gprn);
>  void spr_write_PMU_groupA_ureg(DisasContext *ctx, int sprn, int gprn);
> +void spr_write_MMCR0_ureg(DisasContext *ctx, int sprn, int gprn);
>  
>  #ifndef CONFIG_USER_ONLY
>  void spr_write_generic32(DisasContext *ctx, int sprn, int gprn);
> diff --git a/target/ppc/translate.c b/target/ppc/translate.c
> index ec4160378d..b48eec83e3 100644
> --- a/target/ppc/translate.c
> +++ b/target/ppc/translate.c
> @@ -592,11 +592,49 @@ void spr_write_PMU_groupA_ureg(DisasContext *ctx, int sprn, int gprn)
>      }
>      spr_write_ureg(ctx, sprn, gprn);
>  }
> +
> +void spr_write_MMCR0_ureg(DisasContext *ctx, int sprn, int gprn)
> +{
> +    TCGv t0, t1;
> +
> +    /*
> +     * MMCR0 is a Group A SPR. The same write access control
> +     * done in spr_write_PMU_groupA_ureg() applies.
> +     */
> +    if (ctx->pmcc_clear) {
> +        gen_hvpriv_exception(ctx, POWERPC_EXCP_INVAL_SPR);
> +        return;
> +    }
> +
> +    t0 = tcg_temp_new();
> +    t1 = tcg_temp_new();
> +
> +    /*
> +     * Filter out all bits but FC, PMAO, and PMAE, according
> +     * to ISA v3.1, in 10.4.4 Monitor Mode Control Register 0,
> +     * fourth paragraph.
> +     */
> +    tcg_gen_andi_tl(t0, cpu_gpr[gprn],
> +                    MMCR0_FC | MMCR0_PMAO | MMCR0_PMAE);
> +    gen_load_spr(t1, SPR_POWER_MMCR0);
> +    tcg_gen_andi_tl(t1, t1, ~(MMCR0_FC | MMCR0_PMAO | MMCR0_PMAE));

Since you're reusing them again here, definitely want a #define for
this mask.

> +    /* Keep all other bits intact */
> +    tcg_gen_or_tl(t1, t1, t0);
> +    gen_store_spr(SPR_POWER_MMCR0, t1);
> +
> +    tcg_temp_free(t0);
> +    tcg_temp_free(t1);
> +}
>  #else
>  void spr_write_PMU_groupA_ureg(DisasContext *ctx, int sprn, int gprn)
>  {
>      spr_noaccess(ctx, gprn, sprn);
>  }
> +
> +void spr_write_MMCR0_ureg(DisasContext *ctx, int sprn, int gprn)
> +{
> +    spr_noaccess(ctx, gprn, sprn);
> +}
>  #endif
>  
>  /* SPR common to all non-embedded PowerPC */

-- 
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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