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Mon, 10 Aug 2026 11:49:29 +0000 (GMT) Received: from [9.61.242.9] (unknown [9.61.242.9]) by smtpav03.dal12v.mail.ibm.com (Postfix) with ESMTP; Mon, 10 Aug 2026 11:49:29 +0000 (GMT) Message-ID: <6d1b5f38-f4e4-46ca-88b4-7c18dd6c6280@linux.ibm.com> Date: Mon, 10 Aug 2026 17:19:27 +0530 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [REGRESSION] Power9 pseries boot hang in v7.2-rc6, narrowed to PowerPC GENERIC_ENTRY conversion window Content-Language: en-GB To: Shrikanth Hegde Cc: LKML , linuxppc-dev , "Mukesh Kumar Chaurasiya (IBM)" , Madhavan Srinivasan , "Christophe Leroy (CS GROUP)" , Peter Zijlstra References: <96dae110-f79b-4e54-8a9b-514369019b5d@linux.ibm.com> From: Venkat Rao Bagalkote In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-Reinject: loops=2 maxloops=12 X-Authority-Analysis: v=2.4 cv=RsP16imK c=1 sm=1 tr=0 ts=6a79bacd cx=c_pps a=bLidbwmWQ0KltjZqbj+ezA==:117 a=bLidbwmWQ0KltjZqbj+ezA==:17 a=IkcTkHD0fZMA:10 a=Sv0fKeRqtYgA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=RzCfie-kr_QcCd8fBx8p:22 a=plJz23ppZ1qP7UB_1pIA:9 a=3ZKOabzyN94A:10 a=QEXdDO2ut3YA:10 X-Proofpoint-GUID: guFQ0oo0TQiDzo-BRrZ3lXsakR4jRL_b X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwODEwMDEwMSBTYWx0ZWRfX/pPYAa61JxhC r5WIauspdhFFEKqj5NNhOSYswrG7tzycevfWBFcA3MCzS0Atb8txcZPexEgLFwcOWsZk4kF2rwD pqHP+BkWe3A2sN4D+xZsOztWbKw3NvZ9zOIo7nZazfjqXrET9R1Kj0KWZDK6bZcTnzuFNJud1Zu HCIqdD6s7HevDKIuNb5bDBrBM8FwuNau4yMBTlObetPpUEQ0sfQ2brxGN/ApTJnrNiCcS5bWrgp 29boigD1SLsPjpZNIEH7wyM09PJkUSnlT0w0tI/1VTmgzAYMD1Zj8tkmKHwuZITQlEPfsqNUlh/ 5OFmeLvMVmOjzRgrnWr9dgVRnxrPYTMimq9h8XQjs3YCjSc4NzD84HdhMUCHjh5hCfEQSYQCDxY DK1vnNcUH0zoktZyB1JO/fzfWWcYrG1ycdziYHUdJyR8VgCPZQDuLohxmX9jQT+3QgfoTeoLd4n cjHBHEVhLAkW1CNFAVQ== X-Proofpoint-ORIG-GUID: le5p0A4EKy4c2iPKSvJ3aiF91qf6kc5P X-Proofpoint-Spam-Info: AW1haW4tMjYwODEwMDEwMSBTYWx0ZWRfX4NFCztzwfxt4 kYUn7yD9+mfM/jxgPIoftGkE/RuiQV8zs7u9Oqy7BjJ8jG+KwWsbH7iscPHEtQO73rc4grNN1a4 z9XaQypoaMp/TAKk4xES0Hu2nGI5IuQ= X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1176,Hydra:6.1.134,FMLib:17.12.100.49 definitions=2026-08-10_02,2026-08-07_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 impostorscore=0 suspectscore=0 clxscore=1015 malwarescore=0 phishscore=0 adultscore=0 lowpriorityscore=0 priorityscore=1501 bulkscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2608100101 Hi Shrikanth, On 04/08/26 8:23 pm, Shrikanth Hegde wrote: > Hi Venkat. > > On 8/4/26 2:04 PM, Venkat Rao Bagalkote wrote: >> Hi, >> >> I'm seeing a boot regression on a Power9 pseries LPAR. The system >> hangs very early during boot after: >> >> Quiescing Open Firmware ... >> Booting Linux via __start() ... >> > > That is strange. not sure where to look at without any logs. > Is it a specific config that fails or this specific LPAR that fails? > >> No further kernel output is produced. >> >> Known good:8cd9520d35a6 ("Linux 7.1") >> Known bad: 075b74841bd0 ("Linux 7.2-rc6") >> > > Is the kernel built correct at 075b74841bd0 without any errors? The known bad revision 075b74841bd0 ("Linux 7.2-rc6") builds successfully with my configuration and the issue is observed at boot time only. > >> Initial bisect: >> >> A full bisect from v7.1 to v7.2-rc6 converged to: >> >> c5e8e224eb7a >> MIPS: RB532: attach the software node to its target GPIO controller >> >> >> However this commit only modifies: >> >> arch/mips/rb532/devices.c >> arch/mips/rb532/gpio.c >> >> and appears unrelated to a Power9/pseries boot hang. >> >> I then narrowed the investigation to the PowerPC pull. >> >> The following commits were tested and boot successfully: >> >> baa590018fbf powerpc: rename arch_irq_disabled_regs >> dec63ea6faff powerpc: Prepare to build with generic entry/exit framework >> 09a9d3a8499d powerpc: introduce arch_enter_from_user_mode >> 893082ac769b powerpc: Prepare for IRQ entry exit >> >> The following commit reproduces the hang: >> >> 334f3f6d7a16 powerpc/entry: Disable interrupts before irqentry_exit >> >> >> >> Between the last known good and first known bad points: >> >> >> 893082ac769b powerpc: Prepare for IRQ entry exit >> ... >> bee25f97ad24 powerpc: Enable GENERIC_ENTRY feature >> ... >> 334f3f6d7a16 powerpc/entry: Disable interrupts before irqentry_exit >> >> >> The only substantial architectural/runtime change in this window >> appears to be: >> >> bee25f97ad24 powerpc: Enable GENERIC_ENTRY feature >> >> >> >> I attempted to test: >> >> bee25f97ad24 powerpc: Enable GENERIC_ENTRY feature >> >> directly, however that commit does not build with my configuration >> due to: >> >> arch/powerpc/kernel/ptrace/ptrace.c >> >> error: implicit declaration of function 'trace_sys_enter' >> error: implicit declaration of function 'trace_sys_exit' >> >> Therefore I could not directly classify bee25f97ad24 as good or bad. >> >> > > Can you try one commit after this and see if it builds? > i.e  "powerpc: Remove unused functions" > I tested: 6ed60999d33d ("powerpc: Remove unused functions") The kernel builds successfully with my configuration, but the system still hangs during boot on the Power9 pseries LPAR after:   Quiescing Open Firmware ...   Booting Linux via __start() ... with no further output. So currently I have:   893082ac769b ("powerpc: Prepare for IRQ entry exit")  GOOD   bee25f97ad24 ("powerpc: Enable GENERIC_ENTRY feature") UNTESTABLE   6ed60999d33d ("powerpc: Remove unused functions")      BAD Given that 6ed60999d33d builds and reproduces the hang, the regression appears to be present immediately after the introduction of GENERIC_ENTRY. Regards, Venkat. >> Please let me know if there are specific debug patches or boot >> parameters you'd like me to test. >> >> >> Attached is the config file I used. >> >> >> Regards, >> >> Venkat. > >