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Mon, 18 May 2026 05:09:06 +0000 (GMT) Received: from aboo.ibm.com.com (unknown [9.124.214.53]) by smtpav06.fra02v.mail.ibm.com (Postfix) with ESMTP; Mon, 18 May 2026 05:09:06 +0000 (GMT) From: Aboorva Devarajan To: Madhavan Srinivasan , linuxppc-dev@lists.ozlabs.org Cc: Athira Rajeev , Aboorva Devarajan , Christophe Leroy , linux-kernel@vger.kernel.org, Sourabh Jain , Ritesh Harjani , Shrikanth Hegde Subject: [PATCH 2/3] powerpc/powernv: fix preempt count leak in pnv_kexec_wait_secondaries_down Date: Mon, 18 May 2026 10:38:54 +0530 Message-ID: <20260518050855.1147242-3-aboorvad@linux.ibm.com> X-Mailer: git-send-email 2.54.0 In-Reply-To: <20260518050855.1147242-1-aboorvad@linux.ibm.com> References: <20260518050855.1147242-1-aboorvad@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: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-Reinject: loops=2 maxloops=12 X-Proofpoint-ORIG-GUID: CiCmeEF6BZAC0CSoh_sFje-gfEyFPl3z X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNTE4MDA0NiBTYWx0ZWRfXyf8M8/yJRPjb KRnjrQibKNjBnRMM22NIZ+YojoOI0Sr56KDmLYOPJYRfpNP18W68N/8fkRXiMGsFFe8+zn/A6uH Z20MvQ6CKSpdHiAz7P2p19o3jCx4AX1B6b1o72FyPMdg12K08LrhnlVEw586tgTuRvRtrFbaHgZ nUoHT7eitfttxjIJ+VJyp2VKb+Bkme7OBbUtzTXJ08X1x2lPQ/rr6ItC+UF21QPDXMINJ2ak/3h qu2h8O7/5EsIyAm+zs2bHl3KJxggbcX7Ov4kWRxoW2ztdOAB5q6cTeODAsn0TRzPUKz0bSdeYKx 1Cmv15CukIldbIPX5WxiQY98KEiZQzFtLLe+8hWD2psPAKqB11eU2cZ1lOc6e74NXJpCT//vzob iymELWiFBQNJhfqbz8pBkB/R8RzgyjOYwgDvarBueRa4dDrJxQVgxfg7b5UDQU3FoLAgwRTR23G Z3kZzKPX/OXhPcsklcg== X-Proofpoint-GUID: VdaoM-S7813Xeq8EZmREkRSikfHjV2aL X-Authority-Analysis: v=2.4 cv=apyCzyZV c=1 sm=1 tr=0 ts=6a0a9ef9 cx=c_pps a=aDMHemPKRhS1OARIsFnwRA==:117 a=aDMHemPKRhS1OARIsFnwRA==:17 a=NGcC8JguVDcA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=V8glGbnc2Ofi9Qvn3v5h:22 a=VnNF1IyMAAAA:8 a=AoYj4kKG8rnORiwU5IoA:9 a=O8hF6Hzn-FEA:10 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.51,FMLib:17.12.100.49 definitions=2026-05-18_01,2026-05-15_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 malwarescore=0 lowpriorityscore=0 priorityscore=1501 impostorscore=0 bulkscore=0 suspectscore=0 adultscore=0 spamscore=0 phishscore=0 clxscore=1015 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2605130000 definitions=main-2605180046 pnv_kexec_wait_secondaries_down() calls get_cpu() to obtain the current CPU id but never calls the matching put_cpu(), leaking one preempt_disable() nesting level on every invocation. In practice the imbalance does not trigger a visible splat because the kexec teardown path is a one-way trip: IRQs are already disabled, no schedule() occurs after the leak, and default_machine_kexec() overwrites preempt_count with HARDIRQ_OFFSET before jumping into kexec_sequence() which never returns. However the bookkeeping is still wrong. In the kexec teardown path IRQs are already disabled and the CPU is pinned, so get_cpu()'s preempt_disable() side-effect is unnecessary. Replace get_cpu() with raw_smp_processor_id() which returns the CPU id without touching preempt_count. Fixes: 298b34d7d578 ("powerpc/powernv: Fix kexec races going back to OPAL") Signed-off-by: Aboorva Devarajan --- arch/powerpc/platforms/powernv/setup.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/powerpc/platforms/powernv/setup.c b/arch/powerpc/platforms/powernv/setup.c index 4dbb47ddbdcc4..177da0defcb36 100644 --- a/arch/powerpc/platforms/powernv/setup.c +++ b/arch/powerpc/platforms/powernv/setup.c @@ -396,7 +396,7 @@ static void pnv_kexec_wait_secondaries_down(void) { int my_cpu, i, notified = -1; - my_cpu = get_cpu(); + my_cpu = raw_smp_processor_id(); for_each_online_cpu(i) { uint8_t status; -- 2.54.0