Re: [PATCH v5 18/18] xen/cpufreq: Adapt SET/GET_CPUFREQ_CPPC xen_sysctl_pm_op for amd-cppc driver

[Jan Beulich <jbeulich@xxxxxxxx>]

On 27.05.2025 10:48, Penny Zheng wrote:
> +int set_amd_cppc_para(struct cpufreq_policy *policy,
> +                      const struct xen_set_cppc_para *set_cppc)
> +{
> +    unsigned int cpu = policy->cpu;
> +    struct amd_cppc_drv_data *data = per_cpu(amd_cppc_drv_data, cpu);
> +    uint8_t max_perf, min_perf, des_perf = 0, epp;
> +
> +    if ( data == NULL )
> +        return -ENOENT;
> +
> +    /* Validate all parameters */
> +    if ( set_cppc->minimum > UINT8_MAX || set_cppc->maximum > UINT8_MAX ||
> +         set_cppc->desired > UINT8_MAX || set_cppc->energy_perf > UINT8_MAX )
> +        return -EINVAL;
> +
> +    /* Only allow values if params bit is set. */
> +    if ( (!(set_cppc->set_params & XEN_SYSCTL_CPPC_SET_DESIRED) &&
> +          set_cppc->desired) ||
> +         (!(set_cppc->set_params & XEN_SYSCTL_CPPC_SET_MINIMUM) &&
> +          set_cppc->minimum) ||
> +         (!(set_cppc->set_params & XEN_SYSCTL_CPPC_SET_MAXIMUM) &&
> +          set_cppc->maximum) ||
> +         (!(set_cppc->set_params & XEN_SYSCTL_CPPC_SET_ENERGY_PERF) &&
> +          set_cppc->energy_perf) )
> +        return -EINVAL;
> +
> +    /* Activity window not supported in MSR */
> +    if ( set_cppc->set_params & XEN_SYSCTL_CPPC_SET_ACT_WINDOW )
> +        return -EOPNOTSUPP;
> +
> +    /* Return if there is nothing to do. */
> +    if ( set_cppc->set_params == 0 )
> +        return 0;
> +
> +    epp = per_cpu(epp_init, cpu);
> +    /*
> +     * Apply presets:
> +     * XEN_SYSCTL_CPPC_SET_DESIRED reflects whether desired perf is set, 
> which
> +     * is also the flag to distinguish between passive mode and active mode.
> +     * When it is set, CPPC in passive mode, only
> +     * XEN_SYSCTL_CPPC_SET_PRESET_NONE could be chosen.
> +     * when it is not set, CPPC in active mode, three different profile
> +     * XEN_SYSCTL_CPPC_SET_PRESET_POWERSAVE/PERFORMANCE/BALANCE are provided,
> +     */
> +    switch ( set_cppc->set_params & XEN_SYSCTL_CPPC_SET_PRESET_MASK )
> +    {
> +    case XEN_SYSCTL_CPPC_SET_PRESET_POWERSAVE:
> +        if ( set_cppc->set_params & XEN_SYSCTL_CPPC_SET_DESIRED )
> +            return -EINVAL;
> +        policy->policy = CPUFREQ_POLICY_POWERSAVE;
> +        min_perf = data->caps.lowest_perf;
> +        /* Lower max frequency to lowest */
> +        max_perf = data->caps.lowest_perf;
> +        epp = CPPC_ENERGY_PERF_MAX_POWERSAVE;
> +        break;
> +
> +    case XEN_SYSCTL_CPPC_SET_PRESET_PERFORMANCE:
> +        if ( set_cppc->set_params & XEN_SYSCTL_CPPC_SET_DESIRED )
> +            return -EINVAL;
> +        /* Increase idle frequency to highest */
> +        policy->policy = CPUFREQ_POLICY_PERFORMANCE;
> +        min_perf = data->caps.highest_perf;
> +        max_perf = data->caps.highest_perf;
> +        epp = CPPC_ENERGY_PERF_MAX_PERFORMANCE;
> +        break;
> +
> +    case XEN_SYSCTL_CPPC_SET_PRESET_BALANCE:
> +        if ( set_cppc->set_params & XEN_SYSCTL_CPPC_SET_DESIRED )
> +            return -EINVAL;
> +        policy->policy = CPUFREQ_POLICY_BALANCE;
> +        min_perf = data->caps.lowest_perf;
> +        max_perf = data->caps.highest_perf;
> +        epp = CPPC_ENERGY_PERF_BALANCE;
> +        break;
> +
> +    case XEN_SYSCTL_CPPC_SET_PRESET_NONE:
> +        /*
> +         * In paasive mode, Xen governor is responsible for perfomance 
> tuning.
> +         * we shall set lowest_perf with "lowest_nonlinear_perf" to ensure
> +         * governoring performance in P-states range.
> +         */
> +        min_perf = data->caps.lowest_nonlinear_perf;
> +        max_perf = data->caps.highest_perf;
> +        break;

Oh, also - can you really leave policy->policy unaltered here?

Jan