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Wed, 10 Sep 2025 17:43:54 +0000 (GMT) From: Shrikanth Hegde To: 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, linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, gregkh@linuxfoundation.org Cc: sshegde@linux.ibm.com, vschneid@redhat.com, iii@linux.ibm.com, huschle@linux.ibm.com, rostedt@goodmis.org, dietmar.eggemann@arm.com, vineeth@bitbyteword.org, jgross@suse.com, pbonzini@redhat.com, seanjc@google.com Subject: [RFC PATCH v3 04/10] sched/core: Dont allow to use CPU marked as paravirt Date: Wed, 10 Sep 2025 23:12:04 +0530 Message-ID: <20250910174210.1969750-5-sshegde@linux.ibm.com> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20250910174210.1969750-1-sshegde@linux.ibm.com> References: <20250910174210.1969750-1-sshegde@linux.ibm.com> X-Mailing-List: linuxppc-dev@lists.ozlabs.org List-Id: List-Help: List-Owner: List-Post: List-Archive: , List-Subscribe: , , List-Unsubscribe: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-GUID: OBLXkql8hx1WhZzBKbV5CV2vi8mOdkie X-Authority-Analysis: v=2.4 cv=Mp1S63ae c=1 sm=1 tr=0 ts=68c1b8e6 cx=c_pps a=bLidbwmWQ0KltjZqbj+ezA==:117 a=bLidbwmWQ0KltjZqbj+ezA==:17 a=uXBPIk7YWzXHA4pK:21 a=yJojWOMRYYMA:10 a=VnNF1IyMAAAA:8 a=P8M16rivtmrVeddd8boA:9 X-Proofpoint-ORIG-GUID: v1625mvTieLv0K7jrC5ulkCE9e2nrFd_ X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUwOTA2MDAwMCBTYWx0ZWRfX4tA+a7oT5KZT A/mrIFeUY6v8Wd8HBOCxxRktr2qgNDKTFJfaIzYseNbf834EiCUCMDHDeNsqeMXUMRgnZfa7qiE SOFHOZsI3OtvGqSuLUzBlxswNjO3JxhlAeGiylLTrCtK5R5T0hrNuQlvBiwaZePDNPCvBaRydQH bRPz/jFuO2GVOSeJHJUSfam/T4kC6DxCA/P4X1I0A09lxgopOHKHIjZ/StxmISY1FiHezmitA0K lEyK3H3a/QqtcZLBhRUCeQ7tOzHccV2ucMPiLM2Nxm6v+I2WN+ktDVHymbJovCIJLPm3zP58L+k EooVQmnB2U3KTKYs5maUTfGAJPxyKN1FwHgXz5Q0G/6MmxnTmfVh9YeGfDC6xZjltY5tZOBgPet FOqPne/s X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1117,Hydra:6.1.9,FMLib:17.12.80.40 definitions=2025-09-10_03,2025-09-10_01,2025-03-28_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 impostorscore=0 malwarescore=0 clxscore=1015 phishscore=0 spamscore=0 adultscore=0 priorityscore=1501 bulkscore=0 suspectscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.19.0-2507300000 definitions=main-2509060000 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 b8a84e4691c8..279b0dd72b5e 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -2462,8 +2462,13 @@ static inline bool is_cpu_allowed(struct task_struct *p, int cpu) return cpu_online(cpu); /* 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 (is_cpu_paravirt(cpu)) + return false; + else + return cpu_active(cpu); + } /* KTHREAD_IS_PER_CPU is always allowed. */ if (kthread_is_per_cpu(p)) @@ -2473,6 +2478,10 @@ static inline bool is_cpu_allowed(struct task_struct *p, int cpu) if (cpu_dying(cpu)) return false; + /* Non percpu kthreads should stay away from paravirt cpu*/ + if (is_cpu_paravirt(cpu)) + return false; + /* But are allowed during online. */ return cpu_online(cpu); } -- 2.47.3