Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
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
From:   Wyes Karny <wyes.karny@amd.com>
To:     <ray.huang@amd.com>, <rafael@kernel.org>, <viresh.kumar@linaro.org>
CC:     <mingo@redhat.com>, <peterz@infradead.org>,
        <juri.lelli@redhat.com>, <vincent.guittot@linaro.org>,
        <dietmar.eggemann@arm.com>, <rostedt@goodmis.org>,
        <bsegall@google.com>, <mgorman@suse.de>, <bristot@redhat.com>,
        <vschneid@redhat.com>, <joel@joelfernandes.org>,
        <gautham.shenoy@amd.com>, <linux-pm@vger.kernel.org>,
        <linux-kernel@vger.kernel.org>, Wyes Karny <wyes.karny@amd.com>
Subject: [PATCH 0/2] cpufreq/schedutil: Fix null pointer dereference in sugov_update_single_freq
Date:   Mon, 10 Apr 2023 09:50:43 +0000
Message-ID: <20230410095045.14872-1-wyes.karny@amd.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Content-Type: text/plain
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 10 Apr 2023 09:51:13.6318
 (UTC)
X-MS-Exchange-CrossTenant-Network-Message-Id: 921fe078-ff79-42e8-bef1-08db39a91f25
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: CO1NAM11FT029.eop-nam11.prod.protection.outlook.com
X-MS-Exchange-CrossTenant-AuthAs: Anonymous
X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem
X-MS-Exchange-Transport-CrossTenantHeadersStamped: BN9PR12MB5225
X-Spam-Status: No, score=0.8 required=5.0 tests=DKIM_SIGNED,DKIM_VALID,
        DKIM_VALID_AU,DKIM_VALID_EF,FORGED_SPF_HELO,RCVD_IN_DNSWL_NONE,
        RCVD_IN_MSPIKE_H2,SPF_HELO_PASS,SPF_NONE autolearn=no
        autolearn_force=no version=3.4.6
X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on
        lindbergh.monkeyblade.net
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

Currently, amd_pstate only uses `adjust_perf` and `target` callback
functions to get the frequency/effective utilization data from scaling
governors.  Schedutil generally avoids calling `target` and `fast_switch`
functions if `adjust_perf` function pointer is set for the driver. But in
some rare cases, schedutil tries to call `fast_switch` function even the
function pointer is not set. This happens when frequency invariance is
turned off.  When frequency invariance is turned off schedutil falls
back to `sugov_update_single_freq` which currently relies on the
`fast_switch` callback.

Currently, frequency invariance is turned off when any anomaly is
detected with aperf/mperf readings. Which triggers this problem.

Fix this by adding a NULL check before calling `fast_switch` in
`sugov_update_single_freq`.  But this will force schedutil to take a
slower path to update frequency.  Therefore to fix this add fast_switch
function on amd_pstate to take advantage of fast frequency update.

Gautham R. Shenoy (1):
  amd_pstate: Add ->fast_switch() callback

Wyes Karny (1):
  cpufreq/schedutil: Add fast_switch callback check

 drivers/cpufreq/amd-pstate.c     | 33 ++++++++++++++++++++++++++------
 drivers/cpufreq/cpufreq.c        | 11 +++++++++++
 include/linux/cpufreq.h          |  1 +
 kernel/sched/cpufreq_schedutil.c |  2 +-
 4 files changed, 40 insertions(+), 7 deletions(-)

-- 
2.34.1