Re: [Qemu-devel] [PATCH 13/17] ppc: Add POWER8 IAMR register

[Thomas Huth]

On 14.03.2016 17:56, Cédric Le Goater wrote:
> From: Benjamin Herrenschmidt <address@hidden>
> 
> With appropriate AMR-like masks. Not actually used by the translation
> logic at that point
> 
> Signed-off-by: Benjamin Herrenschmidt <address@hidden>
> [clg: add the use of spr_register_kvm_hv()]
> Signed-off-by: Cédric Le Goater <address@hidden>
> ---
>  target-ppc/cpu.h            |  1 +
>  target-ppc/translate_init.c | 38 ++++++++++++++++++++++++++++++++++++++
>  2 files changed, 39 insertions(+)
> 
> diff --git a/target-ppc/cpu.h b/target-ppc/cpu.h
> index 6952d789e518..81a3e6b5ed29 100644
> --- a/target-ppc/cpu.h
> +++ b/target-ppc/cpu.h
> @@ -1364,6 +1364,7 @@ static inline int cpu_mmu_index (CPUPPCState *env, bool 
> ifetch)
>  #define SPR_BOOKE_CSRR0       (0x03A)
>  #define SPR_BOOKE_CSRR1       (0x03B)
>  #define SPR_BOOKE_DEAR        (0x03D)
> +#define SPR_IAMR              (0x03D)
>  #define SPR_BOOKE_ESR         (0x03E)
>  #define SPR_BOOKE_IVPR        (0x03F)
>  #define SPR_MPC_EIE           (0x050)
> diff --git a/target-ppc/translate_init.c b/target-ppc/translate_init.c
> index f2eb5f041ecd..2fac6ea58698 100644
> --- a/target-ppc/translate_init.c
> +++ b/target-ppc/translate_init.c
> @@ -1133,6 +1133,36 @@ static void spr_write_uamor(DisasContext *ctx, int 
> sprn, int gprn)
>      tcg_temp_free(t1);
>      tcg_temp_free(t2);
>  }
> +
> +static void spr_write_iamr(DisasContext *ctx, int sprn, int gprn)
> +{
> +    TCGv t0 = tcg_temp_new();
> +    TCGv t1 = tcg_temp_new();
> +    TCGv t2 = tcg_temp_new();
> +
> +    /* Note, the HV=1 case is handled earlier by simply using
> +     * spr_write_generic for HV mode in the SPR table
> +     */
> +
> +    /* Build insertion mask into t1 based on context */
> +    gen_load_spr(t1, SPR_AMOR);
> +
> +    /* Mask new bits into t2 */
> +    tcg_gen_and_tl(t2, t1, cpu_gpr[gprn]);
> +
> +    /* Load AMR and clear new bits in t0 */
> +    gen_load_spr(t0, SPR_IAMR);
> +    tcg_gen_andc_tl(t0, t0, t1);
> +
> +    /* Or'in new bits and write it out */
> +    tcg_gen_or_tl(t0, t0, t2);
> +    gen_store_spr(SPR_IAMR, t0);
> +    spr_store_dump_spr(SPR_IAMR);
> +
> +    tcg_temp_free(t0);
> +    tcg_temp_free(t1);
> +    tcg_temp_free(t2);
> +}
>  #endif /* CONFIG_USER_ONLY */
>  
>  static void gen_spr_amr(CPUPPCState *env, bool has_iamr)
> @@ -1161,6 +1191,14 @@ static void gen_spr_amr(CPUPPCState *env, bool 
> has_iamr)
>                      SPR_NOACCESS, SPR_NOACCESS,
>                      &spr_read_generic, &spr_write_generic,
>                      0);
> +    if (!has_iamr) {
> +        return;
> +    }
> +    spr_register_kvm_hv(env, SPR_IAMR, "IAMR",
> +                        SPR_NOACCESS, SPR_NOACCESS,
> +                        &spr_read_generic, &spr_write_iamr,
> +                        &spr_read_generic, &spr_write_generic,
> +                        KVM_REG_PPC_IAMR, 0);

In case you rework this patch (e.g. by putting the has_iamr parameter
from the last patch in here), I think I'd also rather write this as:

    if (has_iamr) {
        spr_register_kvm_hv(...
    }

That would be slightly easier to read.

Apart from that, the patch looks fine to me.

 Thomas