Re: [Qemu-devel] [PATCH v3 21/31] target-arm: Implement AArch64 DAIF system register

[Peter Crosthwaite]

On Sun, Feb 16, 2014 at 2:07 AM, Peter Maydell <address@hidden> wrote:
> Implement the DAIF system register which is a view of the
> DAIF bits in PSTATE.
>
> Signed-off-by: Peter Maydell <address@hidden>
> Reviewed-by: Peter Crosthwaite <address@hidden>
> ---
>  target-arm/helper.c | 24 ++++++++++++++++++++++++
>  1 file changed, 24 insertions(+)
>
> diff --git a/target-arm/helper.c b/target-arm/helper.c
> index 367fbbe..c50ca5a 100644
> --- a/target-arm/helper.c
> +++ b/target-arm/helper.c
> @@ -1589,6 +1589,25 @@ static void aa64_fpsr_write(CPUARMState *env, const 
> ARMCPRegInfo *ri,
>      vfp_set_fpsr(env, value);
>  }
>
> +static CPAccessResult aa64_daif_access(CPUARMState *env, const ARMCPRegInfo 
> *ri)
> +{
> +    if (arm_current_pl(env) == 0 && !(env->cp15.c1_sys & SCTLR_UMA)) {
> +        return CP_ACCESS_TRAP;
> +    }
> +    return CP_ACCESS_OK;
> +}
> +
> +static uint64_t aa64_daif_read(CPUARMState *env, const ARMCPRegInfo *ri)
> +{
> +    return env->daif;
> +}

Is it better to just define the .fieldoffset and do away with the
default-behaving read handler? My understanding is this will avoid a
call out to helper context when running under TCG as well, leading to
a slight perf increase.

Regards,
Peter

> +
> +static void aa64_daif_write(CPUARMState *env, const ARMCPRegInfo *ri,
> +                            uint64_t value)
> +{
> +    env->daif = value & PSTATE_DAIF;
> +}
> +
>  static CPAccessResult aa64_cacheop_access(CPUARMState *env,
>                                            const ARMCPRegInfo *ri)
>  {
> @@ -1632,6 +1651,11 @@ static const ARMCPRegInfo v8_cp_reginfo[] = {
>      { .name = "NZCV", .state = ARM_CP_STATE_AA64,
>        .opc0 = 3, .opc1 = 3, .opc2 = 0, .crn = 4, .crm = 2,
>        .access = PL0_RW, .type = ARM_CP_NZCV },
> +    { .name = "DAIF", .state = ARM_CP_STATE_AA64,
> +      .opc0 = 3, .opc1 = 3, .opc2 = 1, .crn = 4, .crm = 2,
> +      .type = ARM_CP_NO_MIGRATE,
> +      .access = PL0_RW, .accessfn = aa64_daif_access,
> +      .readfn = aa64_daif_read, .writefn = aa64_daif_write },
>      { .name = "FPCR", .state = ARM_CP_STATE_AA64,
>        .opc0 = 3, .opc1 = 3, .opc2 = 0, .crn = 4, .crm = 4,
>        .access = PL0_RW, .readfn = aa64_fpcr_read, .writefn = aa64_fpcr_write 
> },
> --
> 1.8.5
>
>