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Mon, 27 Oct 2025 16:47:29 GMT Received: from smtpav04.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 87CB220043; Mon, 27 Oct 2025 16:47:29 +0000 (GMT) Received: from smtpav04.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id C59A320040; Mon, 27 Oct 2025 16:47:28 +0000 (GMT) Received: from p-imbrenda (unknown [9.155.209.42]) by smtpav04.fra02v.mail.ibm.com (Postfix) with ESMTP; Mon, 27 Oct 2025 16:47:28 +0000 (GMT) Date: Mon, 27 Oct 2025 17:47:26 +0100 From: Claudio Imbrenda To: David Hildenbrand Cc: Christian Borntraeger , Balbir Singh , 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 Subject: Re: linux-next: KVM/s390x regression Message-ID: <20251027174726.5d8fcce7@p-imbrenda> In-Reply-To: <748cdc18-e32d-41bd-90d1-a102b1c51e06@redhat.com> 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> <74272098-cfb7-424b-a55e-55e94f04524e@linux.ibm.com> <84349344-b127-41f6-99f1-10f907c2bd07@redhat.com> <748cdc18-e32d-41bd-90d1-a102b1c51e06@redhat.com> Organization: IBM X-Mailer: Claws Mail 4.3.1 (GTK 3.24.49; x86_64-redhat-linux-gnu) Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: ubob-5LekCHHco6DkR2SSF7gBcYPozRH X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUxMDI1MDAwMSBTYWx0ZWRfX76PA6OE8xQR1 w6FqXRJhMr8hQX2vlEjfyQrEeLlINNckKrCpHqV9x3C8T+/0MOhO77PRRlZuHvtxhrvJ14q4LDO gy6rQVqHOBPRsjm8rzQ8UM+K3vmNugEiNmmNaWYNYuyqgAXHCYVezSpfCtook6eZfohpVsMTAMS 5pCfRkzynTMtXsJm4Shk77fu6hXApSLdiPXkdeRzPU6K1xQ04NwgFg0yewqrHjtiOSFUCftOrCi omXYZd64bQs5akgGifdp5LPzr8OIZUb23x6uhz2nt728Y1Oj8Cm8sHG2RjBZ5hjnfHNj9VV9gYq BwYfWdkAHiGeFDchPidmxmgC7VQQkseyNKh6QrnlvNqYyhG7dK2opBh9/BoJMwi2G/meyseDjdq GWSKir29IsZ3GOZL1FJz7G8+NgayeA== X-Proofpoint-GUID: 6rmIiatZmSL_xPvg8AlM1iNfS4Hou4ZO X-Authority-Analysis: v=2.4 cv=FaE6BZ+6 c=1 sm=1 tr=0 ts=68ffa225 cx=c_pps a=GFwsV6G8L6GxiO2Y/PsHdQ==:117 a=GFwsV6G8L6GxiO2Y/PsHdQ==:17 a=kj9zAlcOel0A:10 a=x6icFKpwvdMA:10 a=VkNPw1HP01LnGYTKEx00:22 a=20KFwNOVAAAA:8 a=ph-KnSEqExXM2Mgme_gA:9 a=CjuIK1q_8ugA:10 a=nl4s5V0KI7Kw-pW0DWrs:22 a=pHzHmUro8NiASowvMSCR:22 a=xoEH_sTeL_Rfw54TyV31:22 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=2025-10-27_06,2025-10-22_01,2025-03-28_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 phishscore=0 malwarescore=0 suspectscore=0 lowpriorityscore=0 adultscore=0 impostorscore=0 priorityscore=1501 clxscore=1015 bulkscore=0 spamscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.19.0-2510020000 definitions=main-2510250001 On Mon, 20 Oct 2025 10:41:28 +0200 David Hildenbrand wrote: > On 20.10.25 09:00, Christian Borntraeger wrote: > > Am 17.10.25 um 23:56 schrieb Balbir Singh: > > > >> In the meanwhile, does this fix/workaround work? > >> > >> diff --git a/mm/pgtable-generic.c b/mm/pgtable-generic.c > >> index 0c847cdf4fd3..31c1754d5bd4 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_non_present_folio_entry(pmdval))) > >> goto nomap; > >> if (unlikely(pmd_trans_huge(pmdval))) > >> goto nomap; > >> > > > > Yes, this seems to work. > > Right, but that's not what we will want here. We'll have to adjust s390x > gmap code (which is getting redesigned either way) to only take the page > lock. > > In the end, we'll want here later a single > > if (!pmd_present(pmdval)) > goto nomap; > this seems to do the trick: diff --git a/arch/s390/mm/gmap.c b/arch/s390/mm/gmap.c index 8ff6bba107e8..22c448b32340 100644 --- a/arch/s390/mm/gmap.c +++ b/arch/s390/mm/gmap.c @@ -599,8 +599,9 @@ int __gmap_link(struct gmap *gmap, unsigned long gaddr, unsigned long vmaddr) | _SEGMENT_ENTRY_GMAP_UC | _SEGMENT_ENTRY; } else - *table = pmd_val(*pmd) & - _SEGMENT_ENTRY_HARDWARE_BITS; + *table = (pmd_val(*pmd) & + _SEGMENT_ENTRY_HARDWARE_BITS) + | _SEGMENT_ENTRY; } } else if (*table & _SEGMENT_ENTRY_PROTECT && !(pmd_val(*pmd) & _SEGMENT_ENTRY_PROTECT)) { it marks non-leaf gmap segment (pmd) entries as present, just as normal pmds would be. I think it's a good enough fix for now, pending the rewrite, which I hope to get in the next merge window