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Mon, 10 Apr 2023 09:53:27 +0000 X-MS-Exchange-Authentication-Results: spf=pass (sender IP is 165.204.84.17) smtp.mailfrom=amd.com; dkim=none (message not signed) header.d=none;dmarc=pass action=none header.from=amd.com; Received-SPF: Pass (protection.outlook.com: domain of amd.com designates 165.204.84.17 as permitted sender) receiver=protection.outlook.com; client-ip=165.204.84.17; helo=SATLEXMB04.amd.com; pr=C Received: from SATLEXMB04.amd.com (165.204.84.17) by CO1NAM11FT066.mail.protection.outlook.com (10.13.175.18) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.20.6298.25 via Frontend Transport; Mon, 10 Apr 2023 09:53:27 +0000 Received: from beas.amd.com (10.180.168.240) by SATLEXMB04.amd.com (10.181.40.145) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.34; Mon, 10 Apr 2023 04:53:18 -0500 From: Wyes Karny To: , , CC: , , , , , , , , , , , , , , Wyes Karny , Subject: [PATCH 1/2] cpufreq/schedutil: Add fast_switch callback check Date: Mon, 10 Apr 2023 09:52:50 +0000 Message-ID: <20230410095250.14908-1-wyes.karny@amd.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20230410095045.14872-1-wyes.karny@amd.com> References: <20230410095045.14872-1-wyes.karny@amd.com> MIME-Version: 1.0 X-Originating-IP: [10.180.168.240] X-ClientProxiedBy: SATLEXMB04.amd.com (10.181.40.145) To SATLEXMB04.amd.com (10.181.40.145) X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: CO1NAM11FT066:EE_|PH7PR12MB6537:EE_ X-MS-Office365-Filtering-Correlation-Id: 0c5b243e-a9ab-4785-d60c-08db39a96ea9 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; 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X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 10 Apr 2023 09:53:27.0375 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 0c5b243e-a9ab-4785-d60c-08db39a96ea9 X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=3dd8961f-e488-4e60-8e11-a82d994e183d;Ip=[165.204.84.17];Helo=[SATLEXMB04.amd.com] X-MS-Exchange-CrossTenant-AuthSource: CO1NAM11FT066.eop-nam11.prod.protection.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: PH7PR12MB6537 Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org The set value of `fast_switch_enabled` flag doesn't guarantee that fast_switch callback is set. For some drivers such as amd_pstate, the adjust_perf callback is used but it still sets `fast_switch_possible` flag. This is not wrong because this flag doesn't imply fast_switch callback is set, it implies whether the driver can guarantee that frequency can be changed on any CPU sharing the policy and that the change will affect all of the policy CPUs without the need to send any IPIs or issue callbacks from the notifier chain. Therefore add an extra NULL check before calling fast_switch in sugov_update_single_freq function. Ideally `sugov_update_single_freq` function should not be called with amd_pstate. But in a corner case scenario, when aperf/mperf overflow occurs, kernel disables frequency invariance calculation which causes schedutil to fallback to sugov_update_single_freq which currently relies on the fast_switch callback. Normal flow: sugov_update_single_perf cpufreq_driver_adjust_perf cpufreq_driver->adjust_perf Error case flow: sugov_update_single_perf sugov_update_single_freq <-- This is chosen because the freq invariant is disabled due to aperf/mperf overflow cpufreq_driver_fast_switch cpufreq_driver->fast_switch <-- Here NULL pointer dereference is happening, because fast_switch is not set Fix this NULL pointer dereference issue by doing a NULL check. Fixes: a61dec744745 ("cpufreq: schedutil: Avoid missing updates for one-CPU policies") Signed-off-by: Wyes Karny Cc: "Rafael J. Wysocki" Cc: stable@vger.kernel.org --- drivers/cpufreq/cpufreq.c | 11 +++++++++++ include/linux/cpufreq.h | 1 + kernel/sched/cpufreq_schedutil.c | 2 +- 3 files changed, 13 insertions(+), 1 deletion(-) diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c index 6d8fd3b8dcb5..364d31b55380 100644 --- a/drivers/cpufreq/cpufreq.c +++ b/drivers/cpufreq/cpufreq.c @@ -2138,6 +2138,17 @@ unsigned int cpufreq_driver_fast_switch(struct cpufreq_policy *policy, } EXPORT_SYMBOL_GPL(cpufreq_driver_fast_switch); +/** + * cpufreq_driver_has_fast_switch - Check "fast switch" callback. + * + * Return 'true' if the ->fast_switch callback is present for the + * current driver or 'false' otherwise. + */ +bool cpufreq_driver_has_fast_switch(void) +{ + return !!cpufreq_driver->fast_switch; +} + /** * cpufreq_driver_adjust_perf - Adjust CPU performance level in one go. * @cpu: Target CPU. diff --git a/include/linux/cpufreq.h b/include/linux/cpufreq.h index 65623233ab2f..8a9286fc718b 100644 --- a/include/linux/cpufreq.h +++ b/include/linux/cpufreq.h @@ -604,6 +604,7 @@ struct cpufreq_governor { /* Pass a target to the cpufreq driver */ unsigned int cpufreq_driver_fast_switch(struct cpufreq_policy *policy, unsigned int target_freq); +bool cpufreq_driver_has_fast_switch(void); void cpufreq_driver_adjust_perf(unsigned int cpu, unsigned long min_perf, unsigned long target_perf, diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c index e3211455b203..a1c449525ac2 100644 --- a/kernel/sched/cpufreq_schedutil.c +++ b/kernel/sched/cpufreq_schedutil.c @@ -364,7 +364,7 @@ static void sugov_update_single_freq(struct update_util_data *hook, u64 time, * concurrently on two different CPUs for the same target and it is not * necessary to acquire the lock in the fast switch case. */ - if (sg_policy->policy->fast_switch_enabled) { + if (sg_policy->policy->fast_switch_enabled && cpufreq_driver_has_fast_switch()) { cpufreq_driver_fast_switch(sg_policy->policy, next_f); } else { raw_spin_lock(&sg_policy->update_lock); From patchwork Mon Apr 10 09:53:39 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Wyes Karny X-Patchwork-Id: 13206234 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 45304C76196 for ; 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Received-SPF: Pass (protection.outlook.com: domain of amd.com designates 165.204.84.17 as permitted sender) receiver=protection.outlook.com; client-ip=165.204.84.17; helo=SATLEXMB04.amd.com; pr=C Received: from SATLEXMB04.amd.com (165.204.84.17) by CO1NAM11FT063.mail.protection.outlook.com (10.13.175.37) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.20.6298.21 via Frontend Transport; Mon, 10 Apr 2023 09:54:09 +0000 Received: from beas.amd.com (10.180.168.240) by SATLEXMB04.amd.com (10.181.40.145) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.34; Mon, 10 Apr 2023 04:54:01 -0500 From: Wyes Karny To: , , CC: , , , , , , , , , , , , , , Wyes Karny Subject: [PATCH 2/2] amd_pstate: Add ->fast_switch() callback Date: Mon, 10 Apr 2023 09:53:39 +0000 Message-ID: <20230410095339.14923-1-wyes.karny@amd.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20230410095045.14872-1-wyes.karny@amd.com> References: <20230410095045.14872-1-wyes.karny@amd.com> MIME-Version: 1.0 X-Originating-IP: [10.180.168.240] X-ClientProxiedBy: SATLEXMB04.amd.com (10.181.40.145) To SATLEXMB04.amd.com (10.181.40.145) X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: CO1NAM11FT063:EE_|PH0PR12MB8176:EE_ X-MS-Office365-Filtering-Correlation-Id: d590cda1-7a4c-48a4-3ea4-08db39a98833 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; 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X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 10 Apr 2023 09:54:09.8810 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: d590cda1-7a4c-48a4-3ea4-08db39a98833 X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=3dd8961f-e488-4e60-8e11-a82d994e183d;Ip=[165.204.84.17];Helo=[SATLEXMB04.amd.com] X-MS-Exchange-CrossTenant-AuthSource: CO1NAM11FT063.eop-nam11.prod.protection.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: PH0PR12MB8176 Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org From: "Gautham R. Shenoy" Schedutil normally calls the adjust_perf callback for drivers with adjust_perf callback available and fast_switch_possible flag set. However, when frequency invariance is disabled and schedutil tries to invoke fast_switch, and that callback is NULL, it schedules a kthread to invoke the target() callback, which could slow down the frequency update. Prevent the frequency update slow down by implementing the fast_switch callback for amd_pstate. Signed-off-by: Wyes Karny Signed-off-by: Gautham R. Shenoy --- drivers/cpufreq/amd-pstate.c | 33 +++++++++++++++++++++++++++------ 1 file changed, 27 insertions(+), 6 deletions(-) diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c index 73c7643b2697..b3d594b35c65 100644 --- a/drivers/cpufreq/amd-pstate.c +++ b/drivers/cpufreq/amd-pstate.c @@ -422,9 +422,8 @@ static int amd_pstate_verify(struct cpufreq_policy_data *policy) return 0; } -static int amd_pstate_target(struct cpufreq_policy *policy, - unsigned int target_freq, - unsigned int relation) +static int amd_pstate_update_freq(struct cpufreq_policy *policy, + unsigned int target_freq, bool fast_switch) { struct cpufreq_freqs freqs; struct amd_cpudata *cpudata = policy->driver_data; @@ -443,14 +442,35 @@ static int amd_pstate_target(struct cpufreq_policy *policy, des_perf = DIV_ROUND_CLOSEST(target_freq * cap_perf, cpudata->max_freq); - cpufreq_freq_transition_begin(policy, &freqs); + WARN_ON(fast_switch && !policy->fast_switch_enabled); + /* + * If fast_switch is desired, then there aren't any registered + * transition notifiers. See comment for + * cpufreq_enable_fast_switch(). + */ + if (!fast_switch) + cpufreq_freq_transition_begin(policy, &freqs); amd_pstate_update(cpudata, min_perf, des_perf, - max_perf, false); - cpufreq_freq_transition_end(policy, &freqs, false); + max_perf, fast_switch); + if (!fast_switch) + cpufreq_freq_transition_end(policy, &freqs, false); return 0; } +static int amd_pstate_target(struct cpufreq_policy *policy, + unsigned int target_freq, + unsigned int relation) +{ + return amd_pstate_update_freq(policy, target_freq, false); +} + +static unsigned int amd_pstate_fast_switch(struct cpufreq_policy *policy, + unsigned int target_freq) +{ + return amd_pstate_update_freq(policy, target_freq, true); +} + static void amd_pstate_adjust_perf(unsigned int cpu, unsigned long _min_perf, unsigned long target_perf, @@ -1228,6 +1248,7 @@ static struct cpufreq_driver amd_pstate_driver = { .flags = CPUFREQ_CONST_LOOPS | CPUFREQ_NEED_UPDATE_LIMITS, .verify = amd_pstate_verify, .target = amd_pstate_target, + .fast_switch = amd_pstate_fast_switch, .init = amd_pstate_cpu_init, .exit = amd_pstate_cpu_exit, .suspend = amd_pstate_cpu_suspend,