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Mon, 17 Aug 2026 10:59:21 +0000 (GMT) Received: from tuxmaker.boeblingen.de.ibm.com (unknown [9.87.85.9]) by smtpav03.fra02v.mail.ibm.com (Postfix) with ESMTP; Mon, 17 Aug 2026 10:59:21 +0000 (GMT) From: Thomas Richter To: linux-s390@vger.kernel.org Cc: Thomas Richter , Sumanth Korikkar , Heiko Carstens Subject: [PATCH v3] s390/pai: Handle multiple PMU stop callback invocations Date: Mon, 17 Aug 2026 12:59:04 +0200 Message-ID: <20260817105904.3933179-1-tmricht@linux.ibm.com> X-Mailer: git-send-email 2.53.0 Precedence: bulk X-Mailing-List: linux-s390@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwODE3MDA3OCBTYWx0ZWRfXw6t6CsCkDn5M fiE+xChiHgF0JX3J64RHTyOh5ya9PslGF7R1hexdDWH/GYFt9CqNj5ly1Zce5Q9ASj13rRd5ts9 YZcW+HlxUX7mll4qxTNlL8Bml+xvmRk9sZBqkPTUgd+hImwOTed2lqcgSI6d0YVUqQP+ARYPEoo A2u6zSGWJtD2Bn6dTNjczKIMueiXmLeZMBMjRIjqHA6isztcCnfQhyqNS+53iDKFij36l9UeDXC kEpRcrO48iDYMjFtDZxfy7W+BnMiNOMWpgkHak+se5zDrq00Y69MtMgr4Y5M8w+FEPDbnH2fnzJ pyX+vsCCP+MMkvi3HwAAr434fyc6KwDuR8XUrMgTjO/b4dTM7trwmesepc1uURi8nhmJVabyWuy MKn16C24IGIa+diZVupmOWWPTiUmtxHv6dPTHuem4wmmqjGD2+tTmHnEu2d9a2vURq89574bM6M R2Bz2vfP4n8Xps8R7/g== X-Proofpoint-Spam-Info: AW1haW4tMjYwODE3MDA3OCBTYWx0ZWRfXxRARJ7AxVMqc FnV/qSjuTJ8yyVTb/oj3xRIfmEwdAWeNVgjYgFSi8aWSPmbewvK1aOGz0NMESLYX8VW+DFLV7ur Kg/9gBb/aQDqFxMn/XFoTQWmUGhiOY4= X-Authority-Analysis: v=2.4 cv=JKkLdcKb c=1 sm=1 tr=0 ts=6a82e98e cx=c_pps a=aDMHemPKRhS1OARIsFnwRA==:117 a=aDMHemPKRhS1OARIsFnwRA==:17 a=Sv0fKeRqtYgA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=Y2IxJ9c9Rs8Kov3niI8_:22 a=VwQbUJbxAAAA:8 a=VnNF1IyMAAAA:8 a=OIqSdt047_wi2S7goKUA:9 X-Proofpoint-ORIG-GUID: UpAz5Pf1PQkCcsb01FFs68IfhsibeOR_ X-Proofpoint-GUID: UpAz5Pf1PQkCcsb01FFs68IfhsibeOR_ X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1176,Hydra:6.1.134,FMLib:17.12.100.49 definitions=2026-08-16_06,2026-08-12_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 suspectscore=0 bulkscore=0 malwarescore=0 priorityscore=1501 lowpriorityscore=0 clxscore=1015 adultscore=0 impostorscore=0 spamscore=0 phishscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2608170078 Handle the following scenario: The kernel protects itself against a very high sampling load and throttles the sampling using: perf_event_throttle() --> PMU->stop() Shortly later the scheduler may terminate the task and removes it from the CPU. It again calls PMU->stop() which results in two invocations of PMU->stop() called back to back. Protect against this and check the PERF_HES_STOPPED bit on function entry. If it is already set return. Clear bit PERF_HES_STOPPED in PMU->start(). Also fix unsafe iteration over syswide_list in pai_have_samples() which might lead to a kernel crash (LIST_POISON dereference) if an event overflows and is synchronously throttled during the loop. Move calls to perf_sched_cb_inc() and perf_sched_cb_dec() to functions pai_add() and pai_del() to avoid list corruption during event throttling processing. #Cc: stable@vger.kernel.org # v6.19+ Fixes: 9f66572f2889 ("s390/pai_crypto: Enable per-task and system-wide sampling event") Fixes: 582cc1b28e8c ("s390/pai_ext: Enable per-task and system-wide sampling event") Signed-off-by: Thomas Richter Reviewed-by: Sumanth Korikkar Suggested-by: Heiko Carstens --- arch/s390/kernel/perf_pai.c | 21 ++++++++++++++++----- 1 file changed, 16 insertions(+), 5 deletions(-) diff --git a/arch/s390/kernel/perf_pai.c b/arch/s390/kernel/perf_pai.c index cdb8006220ca..388941d9aec1 100644 --- a/arch/s390/kernel/perf_pai.c +++ b/arch/s390/kernel/perf_pai.c @@ -456,14 +456,13 @@ static void pai_start(struct perf_event *event, int flags, local64_set(&event->hw.prev_count, sum); } else { /* Sampling */ memcpy((void *)PAI_SAVE_AREA(event), cpump->area, pp->area_size); - /* Enable context switch callback for system-wide sampling */ if (!(event->attach_state & PERF_ATTACH_TASK)) { list_add_tail(PAI_SWLIST(event), &cpump->syswide_list); - perf_sched_cb_inc(event->pmu); } else { cpump->event = event; } } + event->hw.state &= ~PERF_HES_STOPPED; } static void paicrypt_start(struct perf_event *event, int flags) @@ -492,6 +491,9 @@ static int pai_add(struct perf_event *event, int flags) local_ctl_set_bit(0, CR0_PAI_EXTENSION_BIT); } } + /* Enable context switch callback for system-wide sampling */ + if (!(event->attach_state & PERF_ATTACH_TASK)) + perf_sched_cb_inc(event->pmu); if (flags & PERF_EF_START) pai_pmu[idx].pmu->start(event, PERF_EF_RELOAD); event->hw.state = 0; @@ -510,11 +512,17 @@ static void pai_stop(struct perf_event *event, int flags) struct pai_mapptr *mp = this_cpu_ptr(pai_root[idx].mapptr); struct pai_map *cpump = mp->mapptr; + /* Cope with multiple invocations: + * 1. perf_event_throttle() --> PMU->stop() + * 2. task schedules out --> PMU->stop() + * Check for event already stopped. + */ + if (event->hw.state & PERF_HES_STOPPED) + return; if (!event->attr.sample_period) { /* Counting */ pai_pmu[idx].pmu->read(event); } else { /* Sampling */ if (!(event->attach_state & PERF_ATTACH_TASK)) { - perf_sched_cb_dec(event->pmu); list_del(PAI_SWLIST(event)); } else { pai_have_sample(event, cpump); @@ -537,6 +545,9 @@ static void pai_del(struct perf_event *event, int flags) struct paiext_cb *pcb = cpump->paiext_cb; pai_pmu[idx].pmu->stop(event, PERF_EF_UPDATE); + /* Disable context switch callback for system-wide sampling */ + if (!(event->attach_state & PERF_ATTACH_TASK)) + perf_sched_cb_dec(event->pmu); if (--cpump->active_events == 0) { if (!pcb) { /* PAI crypto */ local_ctl_clear_bit(0, CR0_CRYPTOGRAPHY_COUNTER_BIT); @@ -672,9 +683,9 @@ static void pai_have_samples(int idx) { struct pai_mapptr *mp = this_cpu_ptr(pai_root[idx].mapptr); struct pai_map *cpump = mp->mapptr; - struct perf_event *event; + struct perf_event *event, *e2; - list_for_each_entry(event, &cpump->syswide_list, hw.tp_list) + list_for_each_entry_safe(event, e2, &cpump->syswide_list, hw.tp_list) pai_have_sample(event, cpump); } -- 2.55.0