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Mon, 23 Feb 2026 03:45:13 +0000 (GMT) Message-ID: Date: Mon, 23 Feb 2026 09:15:12 +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] KVM PR and KVM HV do not work if the kernel was compiled with PREEMPT To: Christian Zigotzky , linuxppc-dev , "kvm-ppc@vger.kernel.org" , Madhavan Srinivasan Cc: "R.T.Dickinson" , hypexed@yahoo.com.au, mad skateman , Christian Zigotzky References: <185d7a42-f7b4-44e1-a129-f5989d211c74@linux.ibm.com> <40154f6a-39da-959d-e039-5ab9ff62db3c@xenosoft.de> <709b864f-9daa-4a48-b3d6-39baedce63b2@linux.ibm.com> <843b7c60-23f1-47d0-b4e8-2147c3e40c23@linux.ibm.com> <2a27e6fc-7eb4-41a5-ba88-58f6a22625b5@xenosoft.de> <1d79ec6f-ce7f-4432-80e0-a54fa1668642@linux.ibm.com> Content-Language: en-US From: Shrikanth Hegde In-Reply-To: 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: 3F2JuIXyLO7ZJjv4yYD4iiIXOi8YIsaV X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwMjIzMDAyOSBTYWx0ZWRfXzrNJq3YQZKnY 2hgb6pYpRSorP6VnZIiFzkrj0I1SJa6BXbe8AGOI5Eh3wc+kOv2kQ9XVDk7u8iFhSIC35EEcawj qUFeyDiv6vpk312XP2ZJIWtj+pIOHFCB7cT63zexMVGn6ihD4ZfXgM6ss+OnZLfRZX0trHlgwMp C3TcvZhgfyA0nRBKizJwTZpa17kgqXFLsH2oF3iQXGAqw4oRP/D438HUjHfdkxM1bpF7n7HTjIg sDm6JSIe/b0AK9PaawhiWXvD9DEL6Bd0JE9/CZhZ+weP7PpcpshJysGVQJKNFXq0NFX2Jp5mEvj pJQQvMWY4+kokNXelB3BBE/zhP9ftb30f0JGNT0jkEFuSXOzOdVODzD5kmLenDXVStQR8UpJNFm QQkuGdnURdANi36QkTYtuXzfhzkk/9eZXtUr2EhpR29FspK8VtP04RO2SLOa11gxPtyoW8l0FkD UrI74xpktUSvF6hYOpQ== X-Authority-Analysis: v=2.4 cv=R7wO2NRX c=1 sm=1 tr=0 ts=699bcd51 cx=c_pps a=3Bg1Hr4SwmMryq2xdFQyZA==:117 a=3Bg1Hr4SwmMryq2xdFQyZA==:17 a=IkcTkHD0fZMA:10 a=HzLeVaNsDn8A:10 a=VkNPw1HP01LnGYTKEx00:22 a=Mpw57Om8IfrbqaoTuvik:22 a=GgsMoib0sEa3-_RKJdDe:22 a=LpcYUoi4WhtTY--kXmYA:9 a=3ZKOabzyN94A:10 a=QEXdDO2ut3YA:10 X-Proofpoint-GUID: AwVlqX4TNhBbZR4cJm0A8rsBXpk1O0Z2 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1121,Hydra:6.1.51,FMLib:17.12.100.49 definitions=2026-02-23_01,2026-02-20_04,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 clxscore=1015 impostorscore=0 phishscore=0 spamscore=0 suspectscore=0 malwarescore=0 bulkscore=0 adultscore=0 lowpriorityscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2601150000 definitions=main-2602230029 Hi Christian. >> If possible give the below try. >> (Note: Didn;t replicate your issue) >> >> --- >> >> diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c >> index 7667563fb9ff..bf0ca49c9915 100644 >> --- a/arch/powerpc/kvm/book3s_hv.c >> +++ b/arch/powerpc/kvm/book3s_hv.c >> @@ -4825,10 +4825,13 @@ static int kvmppc_run_vcpu(struct kvm_vcpu *vcpu) >>          vc->runner = vcpu; >>          if (n_ceded == vc->n_runnable) { >>              kvmppc_vcore_blocked(vc); >> -        } else if (need_resched()) { >> +        } else if (need_resched() || spin_needbreak(&vc->lock)) { >>              kvmppc_vcore_preempt(vc); >>              /* Let something else run */ >> -            cond_resched_lock(&vc->lock); >> +            spin_unlock(&vc->lock); >> +            schedule(); >> +            //cond_resched_lock(&vc->lock); >> +            spin_lock(&vc->lock); >>              if (vc->vcore_state == VCORE_PREEMPT) >>                  kvmppc_vcore_end_preempt(vc); >>          } else { >> @@ -4901,7 +4904,7 @@ int kvmhv_run_single_vcpu(struct kvm_vcpu *vcpu, >> u64 time_limit, >>      } >> >>      if (need_resched()) >> -        cond_resched(); >> +        schedule(); >> >>      kvmppc_update_vpas(vcpu); >> >> diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c >> index 9a89a6d98f97..54963c1d8b58 100644 >> --- a/arch/powerpc/kvm/powerpc.c >> +++ b/arch/powerpc/kvm/powerpc.c >> @@ -86,7 +86,7 @@ int kvmppc_prepare_to_enter(struct kvm_vcpu *vcpu) >>      while (true) { >>          if (need_resched()) { >>              local_irq_enable(); >> -            cond_resched(); >> +            schedule(); >>              hard_irq_disable(); >>              continue; >>          } >> > Hello Shrikanth, > t > I tested your patch today. The patched preempt kernel boots on my e5500 > host and in an e5500 VM. Unfortunately my guest and host freeze after > loading the VirtIO-GPU. > > Thanks for your help, > > Christian Glad it helps you to boot into. Since you said even host freezes, host maybe crashing. Do you have the console log when you load the VirtIO-GPU?