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Mon, 21 Sep 2026 05:11:07 +0000 (GMT) Received: from [9.124.209.148] (unknown [9.124.209.148]) by smtpav02.fra02v.mail.ibm.com (Postfix) with ESMTP; Mon, 21 Sep 2026 05:11:07 +0000 (GMT) Message-ID: Date: Mon, 21 Sep 2026 10:42:10 +0530 Precedence: bulk X-Mailing-List: kvm-ppc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: 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> Content-Language: en-US From: Shrikanth Hegde In-Reply-To: <33342fbf-eb7b-bde6-2c8c-254fe8bfb993@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-Authority-Analysis: v=2.4 cv=G+OJgNk5 c=1 sm=1 tr=0 ts=6ab0bc75 cx=c_pps a=GFwsV6G8L6GxiO2Y/PsHdQ==:117 a=GFwsV6G8L6GxiO2Y/PsHdQ==:17 a=IkcTkHD0fZMA:10 a=VdqzKS8jKosA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=V8glGbnc2Ofi9Qvn3v5h:22 a=NEAV23lmAAAA:8 a=c3OQchQmIXNlVOc-g8QA:9 a=3ZKOabzyN94A:10 a=QEXdDO2ut3YA:10 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwOTIxMDA3MSBTYWx0ZWRfX0fui0lRP8wZE lX6oyJlf/Q04o+p3iCUd/JOxnZBNPitRRmn0pncVyiuezFWCdExten9e1WN1PhweR4i4rReqZom cCGFMdYkw4WA5wF3i06OC/JrVbpO/YYZfjCuq6T0QvuLlW2NR+bB5Lwaygr1nD0MMGqYUIvKxg2 VCIVcEUvp2pAS0mkK/Anj5W2IDcNoSCxsTQf/PZWUrdZLMz2NnB3qcDwIgxpvm4VHRkAVxmQy+k MXY7rXw14Z+TCaje9TJ/8NuXMQZGPw/VX9Genm6cMkmNrBjG6lIp/rCGKXwB90rkaRaCCQJur2t mNenzLjR+af/itgb7rold2CL3QgXSgafZk+E+WnGo0FzmTfPlKf4SFbG2eqFeTNx4YPCciXK1Su +/P1vAPUzuLz5KR8dlXnfo9zKC34hS+LrFVo9kl5/Amuhcg8PmZ1pNeIcS490CG50yM0/M4gx/8 9BNFOTXxup/UV+SKQLg== X-Proofpoint-ORIG-GUID: iDfdy2aqgn442U2Kx6zyvnoF2i5Q2YL7 X-Proofpoint-GUID: dZExppMaOjH1A6-mAmFv4AfcOwBmWjFu X-Proofpoint-Spam-Info: AW1haW4tMjYwOTIxMDA3MSBTYWx0ZWRfX7lwqXTqr3/iN IUHJTveXPn83iDXfXoa272PWee5oGr3FoRVa+KPaWNKJMunkUt6IZVhCuAE3ah1qJQx0jUtcqkD FEtbfMYfKfKVDzBDRN41i4xVklr842M= 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=2026-09-21_02,2026-09-16_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 suspectscore=0 adultscore=0 phishscore=0 lowpriorityscore=0 impostorscore=0 bulkscore=0 priorityscore=1501 clxscore=1015 spamscore=0 malwarescore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2609040000 definitions=main-2609210071 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(); } }