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Thu, 03 Sep 2026 11:31:18 +0000 (GMT) Received: from smtpav02.fra02v.mail.ibm.com (smtpav02.fra02v.mail.ibm.com [10.20.54.101]) by smtprelay05.fra02v.mail.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 683BVGfB39190958 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 3 Sep 2026 11:31:16 GMT Received: from smtpav02.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 45A822004B; Thu, 3 Sep 2026 11:31:16 +0000 (GMT) Received: from smtpav02.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id ECF982004E; Thu, 3 Sep 2026 11:31:13 +0000 (GMT) Received: from [9.123.5.233] (unknown [9.123.5.233]) by smtpav02.fra02v.mail.ibm.com (Postfix) with ESMTP; Thu, 3 Sep 2026 11:31:13 +0000 (GMT) Message-ID: Date: Thu, 3 Sep 2026 17:01:13 +0530 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 User-Agent: Mozilla Thunderbird Subject: Re: [Linux PPC] Disable PREEMPT To: =?UTF-8?Q?Michal_Such=C3=A1nek?= Cc: "Christophe Leroy (CS GROUP)" , Christian Zigotzky , linuxppc-dev , "kvm-ppc@vger.kernel.org" , Madhavan Srinivasan , Peter Zijlstra , "R.T.Dickinson" , hypexed@yahoo.com.au, mad skateman , Christian Zigotzky References: <843b7c60-23f1-47d0-b4e8-2147c3e40c23@linux.ibm.com> <2a27e6fc-7eb4-41a5-ba88-58f6a22625b5@xenosoft.de> <1d79ec6f-ce7f-4432-80e0-a54fa1668642@linux.ibm.com> <1c9b879a-7907-4849-a416-5df3db5617d6@kernel.org> <34112e67-85a5-a380-a42b-24c6562d65be@xenosoft.de> <8c6f2510-1dc5-4c45-9288-6b9c8f9b6b24@kernel.org> <9a58d944-405c-4519-852e-8fa04c22c2db@linux.ibm.com> Content-Language: en-US From: Shrikanth Hegde In-Reply-To: Content-Type: text/plain; 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Will need to check that. >>> >> >> If possible run against current upstream and share the results. > > https://github.com/openSUSE/kernel-source/blob/6824496d1801f73def615dca8794202eeb7b0d86/config/ppc64le/default > > [ 472.091531][ T6181] Kernel panic - not syncing: stack-protector: Kernel stack is corrupted in: kvmhv_run_single_vcpu+0x19d4/0x1b50 [kvm_hv] > [ 472.091598][ T6181] CPU: 29 UID: 107 PID: 6181 Comm: CPU 112/KVM Not tainted 7.2.2-5.g6824496-default #1 PREEMPT(full) openSUSE Tumbleweed (unreleased) 61871a5f06863b4006f5ef27cd9f18e8a7a2edad > [ 472.091612][ T6181] Hardware name: IBM,9824-42A Power11 (architected) 0x820200 0xf000007 of:IBM,FW1110.20 (OB1110_130) hv:phyp pSeries > [ 472.091624][ T6181] Call Trace: > [ 472.091630][ T6181] [c00000000fdfb680] [c00000000134ce90] dump_stack_lvl+0x84/0xc0 (unreliable) > [ 472.091653][ T6181] [c00000000fdfb6b0] [c00000000022e7c8] vpanic+0x324/0x5e4 > [ 472.091666][ T6181] [c00000000fdfb760] [c00000000022eac4] do_panic_on_target_cpu+0x0/0x2c > [ 472.091677][ T6181] [c00000000fdfb780] [c0000000013c1ff8] __stack_chk_fail+0x48/0x60 > [ 472.091689][ T6181] [c00000000fdfb7f0] [c00800001aae219c] kvmhv_run_single_vcpu+0x19d4/0x1b50 [kvm_hv] > [ 472.091712][ T6181] [c00000000fdfb940] [c00800001aae24b4] kvmppc_vcpu_run_hv+0x19c/0x12f0 [kvm_hv] > [ 472.091732][ T6181] [c00000000fdfba10] [c00800001aeeed18] kvmppc_vcpu_run+0x30/0x48 [kvm] > [ 472.091779][ T6181] [c00000000fdfba30] [c00800001aee9ef4] kvm_arch_vcpu_ioctl_run+0x35c/0x4a0 [kvm] > [ 472.091813][ T6181] [c00000000fdfbac0] [c00800001aedaac4] kvm_vcpu_ioctl+0x1ac/0xad8 [kvm] > [ 472.091844][ T6181] [c00000000fdfbca0] [c0000000007f1244] sys_ioctl+0x374/0x1060 > [ 472.091857][ T6181] [c00000000fdfbdb0] [c00000000002f7f8] system_call_exception+0x188/0x430 > [ 472.091871][ T6181] [c00000000fdfbe50] [c00000000000cfdc] system_call_vectored_common+0x15c/0x2ec > [ 472.091886][ T6181] ---- interrupt: 3000 at 0x7fffb5565fac > [ 472.091896][ T6181] NIP: 00007fffb5565fac LR: 00007fffb5565fac CTR: 0000000000000000 > [ 472.091904][ T6181] REGS: c00000000fdfbe80 TRAP: 3000 Not tainted (7.2.2-5.g6824496-default) > [ 472.091911][ T6181] MSR: 800000000280f033 CR: 42044402 XER: 00000000 > [ 472.091938][ T6181] IRQMASK: 0 > [ 472.091938][ T6181] GPR00: 0000000000000036 00007fbfa77ed7a0 00007fffb5677100 00000000000000fa > [ 472.091938][ T6181] GPR04: 000000002000ae80 0000000000000000 0000000000000000 0000000000000000 > [ 472.091938][ T6181] GPR08: 00000000000000fa 0000000000000000 0000000000000000 0000000000000000 > [ 472.091938][ T6181] GPR12: 0000000000000000 00007fbfa77f5ec0 000000014676f000 00007fbfa77ee7c0 > [ 472.091938][ T6181] GPR16: 000000014674e8d0 00007fbfa77eeec0 00007fbfa77eeec0 fffffffffffffff7 > [ 472.091938][ T6181] GPR20: 00007fffb71210d0 0000000000000001 00007fbfa77eeec0 0000000000000000 > [ 472.091938][ T6181] GPR24: 00007fbfa77ed8e8 0000000105971428 000000002000ae80 0000000105f77a70 > [ 472.091938][ T6181] GPR28: 0000000000000000 0000000000000000 000000002000ae80 000000014674f000 > [ 472.092020][ T6181] NIP [00007fffb5565fac] 0x7fffb5565fac > [ 472.092027][ T6181] LR [00007fffb5565fac] 0x7fffb5565fac > [ 472.092033][ T6181] ---- interrupt: 3000 > [ 472.098256][ T6181] pstore: backend (nvram) writing error (-1) > > This is the host, cannot run the kernel as guest because it fails to boot most > of the time inside KVM. > Will look into. btw the patch shared i.e below patch fixes the boot hanf issue? https://lore.kernel.org/all/1d79ec6f-ce7f-4432-80e0-a54fa1668642@linux.ibm.com/ >> >>> Nonethless, there are quite a few platforms. Originally no preemption >>> was the only option, and that's the reason why many people run that. >>> It's the conservative, known working option. And that's the reason a lot >>> of platfrom code does not get tested with more aggressive preemtion >>> models, and never gets fixed to work with them. >>> >> >> Full preemption has been there for many years!. > > Possible for years, forced only recently. > >> Lazy is not that aggressive compared to that. >> >>> Simply disabling the no preemtion option does not make the platform code >>> ready. >>> >> >> Let's understand your crash case. Let's see where it is going wrong. I am suspecting >> it is some wrong usage of preemption api rather than arch can't support preemption. > > Very likely some wrong use of the preemption API by the arch code, or no > use where it should have been used. It did not matter so long as people > could run their no preempt configs and ignore the problem. > > Thanks > > Michal