linux-kernel - [RFT][PATCH v1 3/8] cpufreq/sched: Allow .setpolicy() cpufreq drivers to enable EAS

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <8554829.NyiUUSuA9g@rjwysocki.net>
Date: Wed, 16 Apr 2025 20:01:06 +0200
From: "Rafael J. Wysocki" <rjw@...ysocki.net>
To: Linux PM <linux-pm@...r.kernel.org>
Cc: LKML <linux-kernel@...r.kernel.org>, Lukasz Luba <lukasz.luba@....com>,
 Peter Zijlstra <peterz@...radead.org>,
 Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
 Dietmar Eggemann <dietmar.eggemann@....com>,
 Morten Rasmussen <morten.rasmussen@....com>,
 Vincent Guittot <vincent.guittot@...aro.org>,
 Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>,
 Pierre Gondois <pierre.gondois@....com>,
 Christian Loehle <christian.loehle@....com>
Subject:
 [RFT][PATCH v1 3/8] cpufreq/sched: Allow .setpolicy() cpufreq drivers to
 enable EAS

From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>

Some cpufreq drivers, like intel_pstate, have built-in governors that
are used instead of regular cpufreq governors, schedutil in particular,
but they can work with EAS just fine, so allow EAS to be used with
those drivers.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
---

v0.3 -> v1
     * Rebase on top of the new [1-2/8].
     * Update the diagnostic message printed if the conditions are not met.

This patch is regarded as a cleanup for 6.16.

---
 drivers/cpufreq/cpufreq.c |   13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -3054,7 +3054,16 @@

 	guard(cpufreq_policy_read)(policy);

-	return sugov_is_governor(policy);
+	/*
+	 * For EAS compatibility, require that either schedutil is the policy
+	 * governor or the policy is governed directly by the cpufreq driver.
+	 *
+	 * In the latter case, it is assumed that EAS can only be enabled by the
+	 * cpufreq driver itself which will not enable EAS if it does not meet
+	 * the EAS' expectations regarding performance scaling response.
+	 */
+	return sugov_is_governor(policy) || (!policy->governor &&
+		policy->policy != CPUFREQ_POLICY_UNKNOWN);
 }

 bool cpufreq_ready_for_eas(const struct cpumask *cpu_mask)
@@ -3064,7 +3073,7 @@
 	/* Do not attempt EAS if schedutil is not being used. */
 	for_each_cpu(cpu, cpu_mask) {
 		if (!cpufreq_policy_is_good_for_eas(cpu)) {
-			pr_debug("rd %*pbl: schedutil is mandatory for EAS\n",
+			pr_debug("rd %*pbl: EAS requirements not met\n",
 				 cpumask_pr_args(cpu_mask));
 			return false;
 		}