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Wed, 19 Nov 2025 06:21:39 +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: [RFC PATCH v4 03/17] sched/core: Dont allow to use CPU marked as paravirt Date: Wed, 19 Nov 2025 11:50:46 +0530 Message-ID: <20251119062100.1112520-4-sshegde@linux.ibm.com> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20251119062100.1112520-1-sshegde@linux.ibm.com> References: <20251119062100.1112520-1-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: RmD7JrXzjaEmULP8Wb7yKpvJTEVFNXuP X-Proofpoint-ORIG-GUID: Yi_8-_bdtM2cdPdRlxASLrxMuM8z5HHX X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUxMTE1MDAzMiBTYWx0ZWRfX7sLczRLJaOz7 eG75Ua8tzMMTeWsg4lhNEBo6CYOBm3E3p1vQ8P6AbSSRBf+JX9xDozJGzrpl7ynBUaOl8zgGp8h xSwzaFPp/KlBLKBd4VYSRyJHd49hjfd+3XLDt8aN7m9proYeIGhkmPHBP+I5w+r1rmk5ufVJaw8 kZI8v/cFTT/cN3royXzhQH4W6fFB60XzCreKeadRfEUNbNe/do3DAvkVNSydtSFz+YOls37xQ6b m3nvX8DtOjqma62cCMQWrGBX2wWE9lI6LJfFiPu8Dt5uG3sCtd9Tew6+1gjPfl8PS+qv+Ft94fv K39JG4GPkYTEohQ9Hcv7kahjIutlr0gbDFw8C4O/L6R3k2dqN1B8SwqAXTV7V8EyiVg7wIX5OqZ QvkFWU0y+5gf6Y3oYMUJ5RyKibgUAw== X-Authority-Analysis: v=2.4 cv=SvOdKfO0 c=1 sm=1 tr=0 ts=691d61fc cx=c_pps a=GFwsV6G8L6GxiO2Y/PsHdQ==:117 a=GFwsV6G8L6GxiO2Y/PsHdQ==:17 a=uXBPIk7YWzXHA4pK:21 a=6UeiqGixMTsA:10 a=VkNPw1HP01LnGYTKEx00:22 a=VnNF1IyMAAAA:8 a=P8M16rivtmrVeddd8boA:9 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_01,2025-11-18_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 lowpriorityscore=0 spamscore=0 clxscore=1015 suspectscore=0 phishscore=0 adultscore=0 bulkscore=0 impostorscore=0 malwarescore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.19.0-2510240000 definitions=main-2511150032 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); /* 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); + } /* 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; + /* Non percpu kthreads should stay away from paravirt cpu*/ + if (cpu_paravirt(cpu)) + return false; + /* But are allowed during online. */ return cpu_online(cpu); } -- 2.47.3