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Wed, 19 Nov 2025 12:45:12 GMT Received: from smtpav05.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id D64AB20043; Wed, 19 Nov 2025 12:45:11 +0000 (GMT) Received: from smtpav05.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id CAEDA20040; Wed, 19 Nov 2025 12:45:07 +0000 (GMT) Received: from li-7bb28a4c-2dab-11b2-a85c-887b5c60d769.ibm.com.com (unknown [9.39.25.220]) by smtpav05.fra02v.mail.ibm.com (Postfix) with ESMTP; Wed, 19 Nov 2025 12:45:07 +0000 (GMT) From: Shrikanth Hegde To: linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org Cc: sshegde@linux.ibm.com, mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com, vincent.guittot@linaro.org, tglx@linutronix.de, yury.norov@gmail.com, maddy@linux.ibm.com, srikar@linux.ibm.com, gregkh@linuxfoundation.org, pbonzini@redhat.com, seanjc@google.com, kprateek.nayak@amd.com, vschneid@redhat.com, iii@linux.ibm.com, huschle@linux.ibm.com, rostedt@goodmis.org, dietmar.eggemann@arm.com, christophe.leroy@csgroup.eu Subject: [PATCH 03/17] sched/core: Dont allow to use CPU marked as paravirt Date: Wed, 19 Nov 2025 18:14:35 +0530 Message-ID: <20251119124449.1149616-4-sshegde@linux.ibm.com> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20251119124449.1149616-1-sshegde@linux.ibm.com> References: <20251119124449.1149616-1-sshegde@linux.ibm.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-TM-AS-GCONF: 00 X-Authority-Analysis: v=2.4 cv=BanVE7t2 c=1 sm=1 tr=0 ts=691dbbdd cx=c_pps a=aDMHemPKRhS1OARIsFnwRA==:117 a=aDMHemPKRhS1OARIsFnwRA==:17 a=uXBPIk7YWzXHA4pK:21 a=6UeiqGixMTsA:10 a=VkNPw1HP01LnGYTKEx00:22 a=VnNF1IyMAAAA:8 a=P8M16rivtmrVeddd8boA:9 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUxMTE1MDAzMiBTYWx0ZWRfX+88NmJCzFF+z p2JgKeRuT2UBw1Xc1tb7C/0+13+AvFKoOXdKQJcMtGx8PykUFeiLR5/GEbuLNvZSgHLrs4cXjj4 NaUS7Vno6/S40RlHA1nCO7OsHWcWRUYL4uHw+/OyCSqpoIagkNgNQfIJpoEMISkSrPMKLnlJYa7 SZuFwv+ikdXm6dlH7jIhfYnExkSWlWasxjjgnCXgYFN4kFGrHxmR8yg3gO4DOko929tQi2VbhBb tpoF57Q3t2QVHqs4xn+EKHtzlCVKmOXQy9irjxc7XvC1r/ITFTAnIi/qADwUpDXl9Awrge2bgEY go8m/882ZsOzy7+bmFvfNZQvA+xlEYbhjfGAhW7WcAbP5d5h5RnBXMODOYmyXJ3/z713s1P+JdZ u4wjDfwEhEVoXViVrYUEN2R/P+05bg== X-Proofpoint-GUID: vw7_NsIAk2cZqNBvjGxQNDHy46UTcYUr X-Proofpoint-ORIG-GUID: qdSjYMpwCHZoj85jCh5fosZgVY_O6JZp X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1121,Hydra:6.1.9,FMLib:17.12.100.49 definitions=2025-11-19_03,2025-11-18_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 malwarescore=0 lowpriorityscore=0 suspectscore=0 spamscore=0 impostorscore=0 priorityscore=1501 clxscore=1015 phishscore=0 bulkscore=0 adultscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.19.0-2510240000 definitions=main-2511150032 Content-Type: text/plain; charset="utf-8" Don't allow a paravirt CPU to be used while looking for a CPU to use. Push task mechanism uses stopper thread which going to call select_fallback_rq and use this mechanism to avoid picking a paravirt CPU. Signed-off-by: Shrikanth Hegde --- kernel/sched/core.c | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 40db5e659994..90fc04d84b74 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -2397,8 +2397,13 @@ static inline bool is_cpu_allowed(struct task_struct= *p, int cpu) return cpu_online(cpu); =20 /* Non kernel threads are not allowed during either online or offline. */ - if (!(p->flags & PF_KTHREAD)) - return cpu_active(cpu); + if (!(p->flags & PF_KTHREAD)) { + /* A user thread shouldn't be allowed on a paravirt cpu */ + if (cpu_paravirt(cpu)) + return false; + else + return cpu_active(cpu); + } =20 /* KTHREAD_IS_PER_CPU is always allowed. */ if (kthread_is_per_cpu(p)) @@ -2408,6 +2413,10 @@ static inline bool is_cpu_allowed(struct task_struct= *p, int cpu) if (cpu_dying(cpu)) return false; =20 + /* Non percpu kthreads should stay away from paravirt cpu*/ + if (cpu_paravirt(cpu)) + return false; + /* But are allowed during online. */ return cpu_online(cpu); } --=20 2.47.3