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Tue, 4 Aug 2026 14:53:23 +0000 (GMT) Message-ID: Date: Tue, 4 Aug 2026 20:23:22 +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 To: Venkat Rao Bagalkote 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: Shrikanth Hegde Content-Language: en-US In-Reply-To: <96dae110-f79b-4e54-8a9b-514369019b5d@linux.ibm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-Reinject: loops=2 maxloops=12 X-Proofpoint-Spam-Info: AW1haW4tMjYwODA0MDEyMCBTYWx0ZWRfX2IGB3MsfLEmt 0oEg6bQXZkWv5SqcaG62riK1GmbsxZHcIPiuQ+nLYcjLM3rpwh6nqsfQwPrYruhO/Bp/erf2HeC Yt716sOjXPL4+xOwC44lzqu2yoLu/B4= X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwODA0MDEyMCBTYWx0ZWRfX4/IwkIhUj01R er4NpNTbbqEs8zr/WUg5oysaWcFMQd80Phq9kWVrHmTPZangtT4BRutvsVaKr+FSOHXCAGa7UtT E19+eo2Yo5jH/ihPYHEGNVNECpSGNvlqxfe7LlA18Nqdsb5Q4OUWPhMTQ3iWUqMhhERI0CIq+YY xPZ2W0Dc8Xkaxjl8t2Re+EemW9awg4qgVYtsN7CAeOjHXkV/p63ZbINesv/Cf2b5ZDrBJXqvTn7 UuW9KWONlYEquaPoFsQTnpQ2aXXQST8zNy28lScBmiDxwCeztcBAKshimZcGjsCxE0OWbrPULNg jedlwr+TC+1t0M6XL0M1Yh9v4EXFYZJ1VkL+ClDwP4qoP8MGDBOMnHBdo2fdS7dhNG2hcZWUK5Y uOckcCf7Fo2K80l2Q4obg8KgAVY0W3wFDJLbv/BMoiAptfei5G7E4dU5ZNWF1pwSIvNz/qbRURH noRh80RYNIwTuzs4hIA== X-Authority-Analysis: v=2.4 cv=SI1ykuvH c=1 sm=1 tr=0 ts=6a71fcec cx=c_pps a=GFwsV6G8L6GxiO2Y/PsHdQ==:117 a=GFwsV6G8L6GxiO2Y/PsHdQ==:17 a=IkcTkHD0fZMA:10 a=Sv0fKeRqtYgA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=U7nrCbtTmkRpXpFmAIza:22 a=dHNt9147D3xgIyPlxCMA:9 a=QEXdDO2ut3YA:10 X-Proofpoint-ORIG-GUID: tFHu5O9I3pqZTjqJH_KcgWltEx4u8evU X-Proofpoint-GUID: RmOa5D-wxCTEuaPXTzfaAD3WPZ_WWWbU 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=2026-08-04_03,2026-08-03_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 clxscore=1015 bulkscore=0 suspectscore=0 impostorscore=0 spamscore=0 phishscore=0 priorityscore=1501 lowpriorityscore=0 adultscore=0 malwarescore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2608040120 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? > 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" > 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.