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Fri, 17 Oct 2025 15:20:57 GMT Received: from smtpav07.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id EA2012004B; Fri, 17 Oct 2025 15:20:56 +0000 (GMT) Received: from smtpav07.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id B922020040; Fri, 17 Oct 2025 15:20:55 +0000 (GMT) Received: from [9.111.36.47] (unknown [9.111.36.47]) by smtpav07.fra02v.mail.ibm.com (Postfix) with ESMTP; Fri, 17 Oct 2025 15:20:55 +0000 (GMT) Message-ID: <74272098-cfb7-424b-a55e-55e94f04524e@linux.ibm.com> Date: Fri, 17 Oct 2025 17:20:55 +0200 Precedence: bulk X-Mailing-List: linux-s390@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: linux-next: KVM/s390x regression To: David Hildenbrand , balbirs@nvidia.com Cc: Liam.Howlett@oracle.com, airlied@gmail.com, akpm@linux-foundation.org, apopple@nvidia.com, baohua@kernel.org, baolin.wang@linux.alibaba.com, byungchul@sk.com, dakr@kernel.org, dev.jain@arm.com, dri-devel@lists.freedesktop.org, francois.dugast@intel.com, gourry@gourry.net, joshua.hahnjy@gmail.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, lorenzo.stoakes@oracle.com, lyude@redhat.com, matthew.brost@intel.com, mpenttil@redhat.com, npache@redhat.com, osalvador@suse.de, rakie.kim@sk.com, rcampbell@nvidia.com, ryan.roberts@arm.com, simona@ffwll.ch, ying.huang@linux.alibaba.com, ziy@nvidia.com, kvm@vger.kernel.org, linux-s390@vger.kernel.org, linux-next@vger.kernel.org References: <20251001065707.920170-4-balbirs@nvidia.com> <20251017144924.10034-1-borntraeger@linux.ibm.com> <9beff9d6-47c7-4a65-b320-43efd1e12687@redhat.com> <8c778cd0-5608-4852-9840-4d98828d7b33@redhat.com> Content-Language: en-US From: Christian Borntraeger In-Reply-To: <8c778cd0-5608-4852-9840-4d98828d7b33@redhat.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-GUID: DcfLWxOGbv9bYKiDoMpZ6va0xN-YJXnG X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUxMDE1MDEyNSBTYWx0ZWRfXxU8GH3q1YuZ0 c8BgXMsDBFk4hHBo0vPh+QUbB0ubWIN3+kWBj/+COUXkJBKtLbfQoiwRBWeXdw/GkNP3E7O3mnG MjRp5R24at9SzmEtPfe8IaV0KYWgCseqOjVH3PD7I13IA4rLOMlm3dx8nFFSgJpwHIkLZUs4nKz UfkyFGF4BnRXztDDU3rymsyOUnTHW6xNzyK0jzzDgSQ7kgEy3/tJTx8mSdDPl/rACGztbSsGGg9 7UVhoK3OxQzkhpE3LFEex92y4kPkzFXVMcS2uw1HRLIkPJExq2bgk65n9hXFGTvym2/wGd/VPyf SS/JwNJAYEl0F7B/ztPHDmw4XKNN05Ngz/7j+W8s0WveeTQn+7Oh19xOyvxl7gnbRpbkiGIRStK u8sdlROg1EfmKkjNfCANEDX13yoRYw== X-Authority-Analysis: v=2.4 cv=R+wO2NRX c=1 sm=1 tr=0 ts=68f25edc cx=c_pps a=5BHTudwdYE3Te8bg5FgnPg==:117 a=5BHTudwdYE3Te8bg5FgnPg==:17 a=IkcTkHD0fZMA:10 a=x6icFKpwvdMA:10 a=VkNPw1HP01LnGYTKEx00:22 a=czJfVngKFEUMndguRe4A:9 a=QEXdDO2ut3YA:10 a=nl4s5V0KI7Kw-pW0DWrs:22 a=pHzHmUro8NiASowvMSCR:22 a=xoEH_sTeL_Rfw54TyV31:22 X-Proofpoint-ORIG-GUID: HxlDaZqVRm6WsCaN2EWRamDscKrmDVZz X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1121,Hydra:6.1.9,FMLib:17.12.80.40 definitions=2025-10-17_05,2025-10-13_01,2025-03-28_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 phishscore=0 lowpriorityscore=0 suspectscore=0 bulkscore=0 clxscore=1015 priorityscore=1501 adultscore=0 spamscore=0 impostorscore=0 malwarescore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.19.0-2510020000 definitions=main-2510150125 Am 17.10.25 um 17:07 schrieb David Hildenbrand: > On 17.10.25 17:01, Christian Borntraeger wrote: >> Am 17.10.25 um 16:54 schrieb David Hildenbrand: >>> On 17.10.25 16:49, Christian Borntraeger wrote: >>>> This patch triggers a regression for s390x kvm as qemu guests can no longer start >>>> >>>> error: kvm run failed Cannot allocate memory >>>> PSW=mask 0000000180000000 addr 000000007fd00600 >>>> R00=0000000000000000 R01=0000000000000000 R02=0000000000000000 R03=0000000000000000 >>>> R04=0000000000000000 R05=0000000000000000 R06=0000000000000000 R07=0000000000000000 >>>> R08=0000000000000000 R09=0000000000000000 R10=0000000000000000 R11=0000000000000000 >>>> R12=0000000000000000 R13=0000000000000000 R14=0000000000000000 R15=0000000000000000 >>>> C00=00000000000000e0 C01=0000000000000000 C02=0000000000000000 C03=0000000000000000 >>>> C04=0000000000000000 C05=0000000000000000 C06=0000000000000000 C07=0000000000000000 >>>> C08=0000000000000000 C09=0000000000000000 C10=0000000000000000 C11=0000000000000000 >>>> C12=0000000000000000 C13=0000000000000000 C14=00000000c2000000 C15=0000000000000000 >>>> >>>> KVM on s390x does not use THP so far, will investigate. Does anyone have a quick idea? >>> >>> Only when running KVM guests and apart from that everything else seems to be fine? >> >> We have other weirdness in linux-next but in different areas. Could that somehow be >> related to use disabling THP for the kvm address space? > > Not sure ... it's a bit weird. I mean, when KVM disables THPs we essentially just remap everything to be mapped by PTEs. So there shouldn't be any PMDs in that whole process. > > Remapping a file THP (shmem) implies zapping the THP completely. > > > I assume in your kernel config has CONFIG_ZONE_DEVICE and CONFIG_ARCH_ENABLE_THP_MIGRATION set, right? yes. > > I'd rule out copy_huge_pmd(), zap_huge_pmd() a well. > > > What happens if you revert the change in mm/pgtable-generic.c? That partial revert seems to fix the issue diff --git a/mm/pgtable-generic.c b/mm/pgtable-generic.c index 0c847cdf4fd3..567e2d084071 100644 --- a/mm/pgtable-generic.c +++ b/mm/pgtable-generic.c @@ -290,7 +290,7 @@ pte_t *___pte_offset_map(pmd_t *pmd, unsigned long addr, pmd_t *pmdvalp) if (pmdvalp) *pmdvalp = pmdval; - if (unlikely(pmd_none(pmdval) || !pmd_present(pmdval))) + if (unlikely(pmd_none(pmdval) || is_pmd_migration_entry(pmdval))) goto nomap; if (unlikely(pmd_trans_huge(pmdval))) goto nomap;