Re: [Qemu-devel] [PATCH 2/4] target/arm: Allow M-profile CPUs to disable the DSP extension via CPU property

["Philippe Mathieu-Daudé" <philmd@redhat.com>]

On 5/17/19 7:40 PM, Peter Maydell wrote:
> Allow the DSP extension to be disabled via a CPU property for
> M-profile CPUs. (A and R-profile CPUs don't have this extension
> as a defined separate optional architecture extension, so
> they don't need the property.)
> 
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> ---
>  target/arm/cpu.h |  2 ++
>  target/arm/cpu.c | 29 +++++++++++++++++++++++++++++
>  2 files changed, 31 insertions(+)
> 
> diff --git a/target/arm/cpu.h b/target/arm/cpu.h
> index 778fb293e7c..b1c7ab3ee94 100644
> --- a/target/arm/cpu.h
> +++ b/target/arm/cpu.h
> @@ -801,6 +801,8 @@ struct ARMCPU {
>      bool has_vfp;
>      /* CPU has Neon */
>      bool has_neon;
> +    /* CPU has M-profile DSP extension */
> +    bool has_dsp;
>  
>      /* CPU has memory protection unit */
>      bool has_mpu;
> diff --git a/target/arm/cpu.c b/target/arm/cpu.c
> index 406fd360a2a..c43139ba897 100644
> --- a/target/arm/cpu.c
> +++ b/target/arm/cpu.c
> @@ -769,6 +769,9 @@ static Property arm_cpu_has_vfp_property =
>  static Property arm_cpu_has_neon_property =
>              DEFINE_PROP_BOOL("neon", ARMCPU, has_neon, true);
>  
> +static Property arm_cpu_has_dsp_property =
> +            DEFINE_PROP_BOOL("dsp", ARMCPU, has_dsp, true);
> +
>  static Property arm_cpu_has_mpu_property =
>              DEFINE_PROP_BOOL("has-mpu", ARMCPU, has_mpu, true);
>  
> @@ -881,6 +884,12 @@ void arm_cpu_post_init(Object *obj)
>          }
>      }
>  
> +    if (arm_feature(&cpu->env, ARM_FEATURE_M) &&
> +        arm_feature(&cpu->env, ARM_FEATURE_THUMB_DSP)) {
> +        qdev_property_add_static(DEVICE(obj), &arm_cpu_has_dsp_property,
> +                                 &error_abort);

TIL qdev_property_add_static, clean.
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>

> +    }
> +
>      if (arm_feature(&cpu->env, ARM_FEATURE_PMSA)) {
>          qdev_property_add_static(DEVICE(obj), &arm_cpu_has_mpu_property,
>                                   &error_abort);
> @@ -1100,6 +1109,26 @@ static void arm_cpu_realizefn(DeviceState *dev, Error **errp)
>          cpu->isar.mvfr0 = u;
>      }
>  
> +    if (arm_feature(env, ARM_FEATURE_M) && !cpu->has_dsp) {
> +        uint32_t u;
> +
> +        unset_feature(env, ARM_FEATURE_THUMB_DSP);
> +
> +        u = cpu->isar.id_isar1;
> +        u = FIELD_DP32(u, ID_ISAR1, EXTEND, 1);
> +        cpu->isar.id_isar1 = u;
> +
> +        u = cpu->isar.id_isar2;
> +        u = FIELD_DP32(u, ID_ISAR2, MULTU, 1);
> +        u = FIELD_DP32(u, ID_ISAR2, MULTS, 1);
> +        cpu->isar.id_isar2 = u;
> +
> +        u = cpu->isar.id_isar3;
> +        u = FIELD_DP32(u, ID_ISAR3, SIMD, 1);
> +        u = FIELD_DP32(u, ID_ISAR3, SATURATE, 0);
> +        cpu->isar.id_isar3 = u;
> +    }
> +
>      /* Some features automatically imply others: */
>      if (arm_feature(env, ARM_FEATURE_V8)) {
>          if (arm_feature(env, ARM_FEATURE_M)) {
>