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Wed, 19 Nov 2025 06:22:40 +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: [HELPER PATCH 2] helper: disable arch handling if paravirt file being written Date: Wed, 19 Nov 2025 11:51:00 +0530 Message-ID: <20251119062100.1112520-18-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: 566E-NdEMCyT0aZn6GFRw8QpsmanZnEV X-Authority-Analysis: v=2.4 cv=YqwChoYX c=1 sm=1 tr=0 ts=691d6239 cx=c_pps a=3Bg1Hr4SwmMryq2xdFQyZA==:117 a=3Bg1Hr4SwmMryq2xdFQyZA==:17 a=6UeiqGixMTsA:10 a=VkNPw1HP01LnGYTKEx00:22 a=VnNF1IyMAAAA:8 a=HHdVa3RH26sSkSPV0WkA:9 X-Proofpoint-ORIG-GUID: UG-YUdVlBcyyIrC5I96OYqAM-4YEvxoS X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUxMTE1MDAzMiBTYWx0ZWRfX01yexI9B0IqU YuSzdU0/YODhWmfAyQflLkG4GSN65CcDbH66ttQpUWu1uhOhTDOabk9cqMNRjLqRPwEpBUR6G32 MtfY2OdYy5ZtgRF/wcNqafp+4uPHts6Xpgd1fYC+GpwYBC2n5SC3GvATP/JBAtDgLfsV3b0lupd TuKZEQIFuHXaAIvkmjXoNbugwUL4ji4pqxm1cNag6DcCL7g8LMNyzd3Vw326DqpRkvgdh8G3/4/ xVtPP1j2wfRdh3wJByV72MP/9Had8uWUQdy865JMxvxiulzYnPtFm5kuSc5Xq5Vk0ELkLUGFUQz UUslSNlfSUY864r87auo5/r4JJXR1FAdvvzYWchQpe/iumXYaV4+Mpp046+1MnD7HYJpmlKuCOx nk/lY0vk4iYoWO/Ci6qHWxtzXde3jQ== 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 impostorscore=0 lowpriorityscore=0 malwarescore=0 clxscore=1015 adultscore=0 bulkscore=0 phishscore=0 spamscore=0 suspectscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.19.0-2510240000 definitions=main-2511150032 Arch specific code can update the mask based on the steal time. For debugging it is desired to overwrite the arch logic. Do that with this helper script. Signed-off-by: Shrikanth Hegde --- arch/powerpc/platforms/pseries/lpar.c | 3 +++ drivers/base/cpu.c | 2 ++ include/linux/sched.h | 4 ++++ kernel/sched/core.c | 1 + 4 files changed, 10 insertions(+) diff --git a/arch/powerpc/platforms/pseries/lpar.c b/arch/powerpc/platforms/pseries/lpar.c index 090e5c48243b..04bc75e22e7b 100644 --- a/arch/powerpc/platforms/pseries/lpar.c +++ b/arch/powerpc/platforms/pseries/lpar.c @@ -681,6 +681,9 @@ static void process_steal(int cpu) unsigned long steal = 0; unsigned int i; + if (static_branch_unlikely(&disable_arch_paravirt_handling)) + return; + if (!should_cpu_process_steal(cpu)) return; diff --git a/drivers/base/cpu.c b/drivers/base/cpu.c index 043e4f4ce1a9..fbaddbfe0b01 100644 --- a/drivers/base/cpu.c +++ b/drivers/base/cpu.c @@ -402,7 +402,9 @@ static ssize_t store_paravirt_cpus(struct device *dev, /* No more paravirt cpus */ if (cpumask_empty(temp_mask)) { cpumask_copy((struct cpumask *)&__cpu_paravirt_mask, temp_mask); + static_branch_disable(&disable_arch_paravirt_handling); } else { + static_branch_enable(&disable_arch_paravirt_handling); cpumask_copy((struct cpumask *)&__cpu_paravirt_mask, temp_mask); /* Enable tick on nohz_full cpu */ diff --git a/include/linux/sched.h b/include/linux/sched.h index 3628edd1468b..1afa5dd5b0ae 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -2427,4 +2427,8 @@ extern void migrate_enable(void); DEFINE_LOCK_GUARD_0(migrate, migrate_disable(), migrate_enable()) +#ifdef CONFIG_PARAVIRT +DECLARE_STATIC_KEY_FALSE(disable_arch_paravirt_handling); +#endif + #endif diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 65c247c24191..b65a9898c694 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -10873,6 +10873,7 @@ void sched_change_end(struct sched_change_ctx *ctx) #ifdef CONFIG_PARAVIRT struct cpumask __cpu_paravirt_mask __read_mostly; EXPORT_SYMBOL(__cpu_paravirt_mask); +DEFINE_STATIC_KEY_FALSE(disable_arch_paravirt_handling); static DEFINE_PER_CPU(struct cpu_stop_work, pv_push_task_work); -- 2.47.3