Re: [PATCH V1 2/6] cpufreq: amd-pstate: Enable AMD Pstate Preferred Core Supporting.

From: Peter Zijlstra <peterz@infradead.org>
To: Meng Li <li.meng@amd.com>
Cc: "Rafael J . Wysocki" <rafael.j.wysocki@intel.com>,
	Huang Rui <ray.huang@amd.com>,
	linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org,
	x86@kernel.org, linux-acpi@vger.kernel.org,
	Shuah Khan <skhan@linuxfoundation.org>,
	linux-kselftest@vger.kernel.org,
	Nathan Fontenot <nathan.fontenot@amd.com>,
	Deepak Sharma <deepak.sharma@amd.com>,
	Alex Deucher <alexander.deucher@amd.com>,
	Mario Limonciello <mario.limonciello@amd.com>,
	Shimmer Huang <shimmer.huang@amd.com>,
	Perry Yuan <Perry.Yuan@amd.com>,
	Xiaojian Du <Xiaojian.Du@amd.com>,
	Viresh Kumar <viresh.kumar@linaro.org>,
	Borislav Petkov <bp@alien8.de>
Subject: Re: [PATCH V1 2/6] cpufreq: amd-pstate: Enable AMD Pstate Preferred Core Supporting.
Date: Tue, 8 Aug 2023 11:06:41 +0200	[thread overview]
Message-ID: <20230808090641.GV212435@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20230808081001.2215240-3-li.meng@amd.com>

On Tue, Aug 08, 2023 at 04:09:57PM +0800, Meng Li wrote:

> +static int amd_pstate_get_highest_perf(int cpu, u64 *highest_perf)
> +{
> +       int ret;
> +
> +       if (boot_cpu_has(X86_FEATURE_CPPC)) {
> +               u64 cap1;
> +
> +               ret = rdmsrl_safe_on_cpu(cpu, MSR_AMD_CPPC_CAP1, &cap1);
> +               if (ret)
> +                       return ret;
> +               WRITE_ONCE(*highest_perf, AMD_CPPC_HIGHEST_PERF(cap1));
> +       } else {
> +               ret = cppc_get_highest_perf(cpu, highest_perf);
> +       }
> +
> +       return (ret);
> +}
> +
> +static void amd_pstate_init_prefcore(void)
> +{
> +	int cpu, ret;
> +	u64 highest_perf;
> +
> +	if (no_prefcore)
> +		return;
> +
> +	for_each_possible_cpu(cpu) {
> +		ret = amd_pstate_get_highest_perf(cpu, &highest_perf);
> +		if (ret)
> +			break;

So what is the intended behaviour when online != possible ?

> +		sched_set_itmt_core_prio(highest_perf, cpu);
> +	}
> +
> +	/*
> +	 * This code can be run during CPU online under the
> +	 * CPU hotplug locks, so sched_set_amd_prefcore_support()
> +	 * cannot be called from here.  Queue up a work item
> +	 * to invoke it.
> +	 */
> +	schedule_work(&sched_prefcore_work);
> +}