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([2a05:6e02:1041:c10:b0eb:75fa:2a81:cf30]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-492203d2449sm234107825e9.14.2026.06.15.05.13.38 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 15 Jun 2026 05:13:38 -0700 (PDT) Message-ID: <6a7db21f-a0d8-45e0-b71a-cad63fb043d0@oss.qualcomm.com> Date: Mon, 15 Jun 2026 14:13:38 +0200 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: [PATCH] kernel/cpu: Disallow offlining boot CPU based on config To: Thomas Gleixner , Peter Zijlstra , Sneh Mankad Cc: "Rafael J. Wysocki" , Pavel Machek , Len Brown , linux-arm-msm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org References: <20260605-disable_boot_cpu_offline-v1-1-4c68fe1a6cf8@oss.qualcomm.com> <20260605104330.GX3102624@noisy.programming.kicks-ass.net> <87ik7x5gba.ffs@fw13> Content-Language: en-US From: Daniel Lezcano In-Reply-To: <87ik7x5gba.ffs@fw13> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Authority-Analysis: v=2.4 cv=V5tNF+ni c=1 sm=1 tr=0 ts=6a2fec75 cx=c_pps a=+D9SDfe9YZWTjADjLiQY5g==:117 a=xqWC_Br6kY4A:10 a=IkcTkHD0fZMA:10 a=FelO9ux0wxsA:10 a=s4-Qcg_JpJYA:10 a=VkNPw1HP01LnGYTKEx00:22 a=u7WPNUs3qKkmUXheDGA7:22 a=Um2Pa8k9VHT-vaBCBUpS:22 a=58ofpu1a7HmJm70nKAsA:9 a=3ZKOabzyN94A:10 a=QEXdDO2ut3YA:10 a=vmgOmaN-Xu0dpDh8OwbV:22 X-Proofpoint-GUID: H5KcXKFP34AylBbYxD0M2j725YbnBNkR X-Proofpoint-Spam-Info: AW1haW4tMjYwNjE1MDEyOSBTYWx0ZWRfXy+jkdrnbDRxQ Cw0pV17IcYVf7qrqnUlJ+QHkhLvt4iI5hdeFz13PIeyVw5pBl9RoyjTfcM8FR2ys1cdteIJqFBt zxAuWYZMvnv3T5uTYY/E4Nt5d/P/ITg= X-Proofpoint-ORIG-GUID: H5KcXKFP34AylBbYxD0M2j725YbnBNkR X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNjE1MDEyOSBTYWx0ZWRfX6Y5CjWk3pOyB /I2FRryJGyshTPAEU50zcikapZrX+zsCFpMB5rLd11gsSmhccCAOGep4H9DbXdW6emPmRlCbw5x Uxcm3YXyChWPyoN2+zZ+GSue/zYZMj66sbKtDP4rF+9Sgr9EDOAS5LYWEKqJCW+eUtdSNTQZqvG zLScQa7mUvHv/s4VRrSmGd2rpe/O41No/hF2EIGv+5RB3DpKG0nVZJhQBLeRBMDZV5L85w9pZjE cIjlcXk/qnZL24SOXGuHxyQK7vZtCWgw1YeQszRwV0xalIExN3fD62jZZHjOF0Omg0lAtQ/I1jc aywJW6yrigp1S+MBdVUK0HewOjEcRwTcVa26SDpGJJILlOhjyKsQkBUfSimmhWm8K0dpQ9U33ab jnYvvBSKfK2TcX46JROF+THoNfWnYveBfc52f+po1n/ZhUoTgo2AIFmzRhcs3cApiy252/1HWLO +UCqg/R/Q9j4fIfmbLg== X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.125,FMLib:17.12.100.49 definitions=2026-06-15_03,2026-06-15_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 suspectscore=0 impostorscore=0 phishscore=0 malwarescore=0 priorityscore=1501 adultscore=0 lowpriorityscore=0 clxscore=1015 bulkscore=0 spamscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606040000 definitions=main-2606150129 Hi Thomas, Le 05/06/2026 à 14:20, Thomas Gleixner a écrit : > On Fri, Jun 05 2026 at 12:43, Peter Zijlstra wrote: > >> On Fri, Jun 05, 2026 at 04:00:46PM +0530, Sneh Mankad wrote: >>> The Qualcomm SoCs like LeMans, Monaco support suspend to ram which leads >>> the SoC to ACPI S3 similar state where SoC is turned off and DDR is >>> retained. >>> The hardware design on these SoCs forces a constraint to suspend and >>> resume the system on boot CPU / CPU0. >>> >>> If CPU0 is already offline before starting suspend to ram the >>> freeze_secondary_cpus() picks alternate CPU as primary / last CPU and >>> proceed further to invoke PSCI SYSTEM_SUSPEND. >>> This leads to a system crash. >>> >>> In order to prevent such an issue introduce PM_SLEEP_SMP_CPU_ZERO_STRICT >>> config and when enabled prohibit the CPU0 to be offline. >> >> Why do this in generic code? Why can't this live in arch code. >> Specifically, x86 can't typically unplug CPU0 at all either. > > arch_cpu_is_hotpluggable(cpu) provides that info to the cpu device core. > > No hackery in cpu.c required at all. Ah, thanks for pointing this out !