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Wed, 23 Sep 2026 05:14:10 +0000 (GMT) Received: from smtpav02.fra02v.mail.ibm.com (smtpav02.fra02v.mail.ibm.com [10.20.54.101]) by smtprelay04.fra02v.mail.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 68N5E6FC25428626 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Wed, 23 Sep 2026 05:14:06 GMT Received: from smtpav02.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 0AC7620043; Wed, 23 Sep 2026 05:14:06 +0000 (GMT) Received: from smtpav02.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 5698F20040; Wed, 23 Sep 2026 05:14:00 +0000 (GMT) Received: from [9.124.209.29] (unknown [9.124.209.29]) by smtpav02.fra02v.mail.ibm.com (Postfix) with ESMTP; Wed, 23 Sep 2026 05:14:00 +0000 (GMT) Message-ID: <9c1d7cf0-40f5-4a93-81ee-f5a4c5adcb9d@linux.ibm.com> Date: Wed, 23 Sep 2026 10:43:59 +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: Christian Zigotzky , =?UTF-8?Q?Michal_Such=C3=A1nek?= Cc: "Christophe Leroy (CS GROUP)" , Michael Ellerman , harshpb@linux.ibm.com, Gautam Menghani , amachhiw@linux.ibm.com, linuxppc-dev , "kvm-ppc@vger.kernel.org" , Madhavan Srinivasan , Peter Zijlstra , "R.T.Dickinson" , hypexed@yahoo.com.au, mad skateman , Christian Zigotzky , Samir M , Venkat Rao Bagalkote , Narayana Murty N , Hari Bathini References: <25cf64ab-2a32-4d4c-a0c7-2e9007c276d4@linux.ibm.com> <9b58bd58-d0e4-463e-bff9-e33b153b2987@linux.ibm.com> <7ad57b61-4567-42c8-a9f6-faaabe7766a7@linux.ibm.com> <7e06fb84-ca2e-dbb4-47bd-e95ee11113c9@xenosoft.de> <79f9d4e3-ce55-d238-e4a9-b11e9ce27c5f@xenosoft.de> <33342fbf-eb7b-bde6-2c8c-254fe8bfb993@xenosoft.de> <7fb5baa6-9d06-2c61-2b43-6835e8fb0d1a@xenosoft.de> Content-Language: en-US From: Shrikanth Hegde In-Reply-To: <7fb5baa6-9d06-2c61-2b43-6835e8fb0d1a@xenosoft.de> 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-Proofpoint-ORIG-GUID: JCSBF24Yn6g5t4Dqmp2iVTDyyAVAtH3I X-Authority-Analysis: v=2.4 cv=EOCTQFZC c=1 sm=1 tr=0 ts=6ab36023 cx=c_pps a=AfN7/Ok6k8XGzOShvHwTGQ==:117 a=AfN7/Ok6k8XGzOShvHwTGQ==:17 a=IkcTkHD0fZMA:10 a=VdqzKS8jKosA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=uAbxVGIbfxUO_5tXvNgY:22 a=NEAV23lmAAAA:8 a=oxC9TbpiAAAA:20 a=TyhM5VrcfDcAQIkWa9IA:9 a=3ZKOabzyN94A:10 a=QEXdDO2ut3YA:10 a=bA3UWDv6hWIuX7UZL3qL:22 X-Proofpoint-Spam-Info: AW1haW4tMjYwOTIzMDAyMCBTYWx0ZWRfX5cWjgvWu8hKX nnYaKVZ40kkKw3wJS9m8kKTZSLKHqMZtn7Lfxuw6NAhlI9LRHXgLSKbCfp4+TELg+p7UsunGz9f ECbImzimkjtIUGfYcHn8hVnwvd3phxY= X-Proofpoint-GUID: A4doiWS49zoeNluiBCfPV4hccmLA9dLx X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwOTIzMDAyMCBTYWx0ZWRfX8pEnAifyIA0b WPumZpdDoVxwTDQihilDpYBkmFI6f4VD9Twj9DyRlU0QV9H6+M9yBdjGVbmrUTMNbZURUuoGxTB WNaK7tD6wz4a2AL115vU4WKAdbb9QJSu8DssyIPUJe7LQ7PcRJAUnytBJR8nS8G+opFLnQjlHyI HBybdyd+P5tlc1fkGhAF0PWc0liGbdSaBwDfbwWhvEW39muASeASamtlhJ9kQkXW5yx7/+4EAx1 ZCLiCywhIpOGLEHaGCVlWRHMGsMUmEq0uThDY8czOhOkVNFSPeBsXmM4GIFNTkqiY4+p2TzzdE3 r4vOD3gtbDAY8PLEyZpg+WzpoHJDo6UfWdZsZlhjNLtycYPDMdbSCkfcF+CqqlVCNH8uiWfbfxt H9hfsuqjNo6LcfYkcdNdYlKpbWyDELLHFozA48xeKrk2Xe0q1NFoFfA57Ehsv7uNt1jIItal0aC b5Mzzlt+uXv5fRdaKXQ== 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=2026-09-23_02,2026-09-21_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 bulkscore=0 phishscore=0 priorityscore=1501 clxscore=1015 spamscore=0 adultscore=0 impostorscore=0 lowpriorityscore=0 suspectscore=0 malwarescore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2609040000 definitions=main-2609230020 On 9/23/26 10:39 AM, Christian Zigotzky wrote: > On 21/09/26 07:12, Shrikanth Hegde wrote: >> Hi Christian. >> >> On 9/20/26 6:34 PM, Christian Zigotzky wrote: >>> On 09/20/2026 01:49 PM, Christian Zigotzky wrote: >>>> On 09/18/2026 09:10 AM, Michal Suchánek wrote: >>>>> On Fri, Sep 18, 2026 at 04:39:57AM +0200, Christian Zigotzky wrote: >>>>>> On 17/09/26 16:15, Shrikanth Hegde wrote: >>>>>>> Hi Michal, >>>>>>> >>>>>>>>> Give it a try. >>>>>>>>> >>>>>>>>> I am suspecting both lockup, stack corruptions are secondary >>>>>>>>> symptoms here. >>>>>>>>> While recreate, I have different type of traces. >>>>>>>> Yes, it does work for the crash I see. >>>>>>> Thanks. Give me sometime to see further on that. Didn't get any time >>>>>>> today. >>>>>>> >>>>>>>> However, we hijacked the report >>>>>>>> of KVM locking up on FSL Cyrus+, and that is likely a different problem >>>>>>>> still not addressed. >>>>>>>> >>>>>>> Ah, that's what you meant. Yes, i still don't know where FSL Cyrus+ is >>>>>>> stuck. >>>>>>> >>>>>>> I would need help from FSL Cyrus+ to get some logs or is there a way we >>>>>>> can spin of >>>>>>> a QEMU guest of it? We should have the log to start somewhere. >>>>>>> >>>>>>> >>>>>> It's difficult to get a log because it freezes and can't write any error >>>>>> messages to the log files. This bug is very old. We had this issue some >>>>>> years ago but we was able to disable PREEMPT because we don't need it. >>>>> I would expect serial console and sysrq could give something, depending >>>>> on how much of the kernel is frozen. >>>>> >>>>> Thanks >>>>> >>>>> Michal >>>> Here is a serial log: https://github.com/user-attachments/files/32433586/e5500_preempt_putty.log >>>> >> >> Thanks Michal for helping to get the traces. >> >>> Another serial log with pcie_ports=compat: https://github.com/user-attachments/files/32434487/e5500_preempt_pcie_ports_compat_putty.log >>> >> >> I see it is mostly busy with printing >> WARNING: at .enable_kernel_fp+0x30/0x78, CPU#3: qemu-system-ppc/4884 >> >> The path seems to be same also. >> >> [c000000085ca7700] [c00000000005de84] .kvmppc_load_guest_fp+0x30/0x80 >> [c000000085ca7780] [c00000000005f2a0] .kvmppc_handle_exit+0x5bc/0x5cc >> [c000000085ca7830] [c00000000006204c] .kvmppc_resume_host+0xb8/0x10c >> >> >> Does below help to boot or make it stable? >> --- >>  arch/powerpc/kvm/booke.c | 9 ++++++++- >>  1 file changed, 8 insertions(+), 1 deletion(-) >> >> diff --git a/arch/powerpc/kvm/booke.c b/arch/powerpc/kvm/booke.c >> index 13ad4cf5fa71..d4be7a306bfc 100644 >> --- a/arch/powerpc/kvm/booke.c >> +++ b/arch/powerpc/kvm/booke.c >> @@ -1404,10 +1404,17 @@ int kvmppc_handle_exit(struct kvm_vcpu *vcpu, unsigned int exit_nr) >>          if (s <= 0) >>              r = (s << 2) | RESUME_HOST | (r & RESUME_FLAG_NV); >>          else { >> -            /* interrupts now hard-disabled */ >> +            /* >> +             * interrupts now hard-disabled. i.e EE=0 >> +             * But irqs_disabled relies on PACA entries >> +             * and fixup below enables it. >> +             * So irqs_disabled == false >> +             */ >>              kvmppc_fix_ee_before_entry(); >> +            preempt_disable(); >>              kvmppc_load_guest_fp(vcpu); >>              kvmppc_load_guest_altivec(vcpu); >> +            preempt_enable_no_resched(); >>          } >>      } >> >> > Hi, > > Thanks a lot for your patch! > > I patched the 7.3-rc4 kernel sources with your new patch and compiled the kernel again yesterday. [1] > Thanks for trying. > Unfortunately, the issue still exists. > Can you share the console log of the kernel with the patch applied? We need to see where it is stuck now. Has it made forward progress? > I tested it with a guest kernel with and without preempt support. > > Cheers, > Christian > > [1] https://github.com/chzigotzky/kernels/releases/tag/v7.3.0-rc4-2-preempt >