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Fri, 31 Jul 2026 13:01:52 +0000 (GMT) Received: from p-imbrenda.ibmuc.com (unknown [9.111.4.62]) by smtpav04.fra02v.mail.ibm.com (Postfix) with ESMTP; Fri, 31 Jul 2026 13:01:52 +0000 (GMT) From: Claudio Imbrenda To: linux-kernel@vger.kernel.org Cc: kvm@vger.kernel.org, linux-s390@vger.kernel.org, borntraeger@de.ibm.com, frankja@linux.ibm.com, david@kernel.org, seiden@linux.ibm.com, nrb@linux.ibm.com, schlameuss@linux.ibm.com, gra@linux.ibm.com Subject: [PATCH v7 14/14] KVM: s390: Fix kvm_arch_commit_memory_region() when low on memory Date: Fri, 31 Jul 2026 15:01:38 +0200 Message-ID: <20260731130138.173983-15-imbrenda@linux.ibm.com> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260731130138.173983-1-imbrenda@linux.ibm.com> References: <20260731130138.173983-1-imbrenda@linux.ibm.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-Spam-Info: AW1haW4tMjYwNzMxMDA5NiBTYWx0ZWRfX3vHTqdDiCkri ifXg3Dkyr/Y0O7f6G55kOzoeXSBXO2KuJPBewuUrPJLjy5eNCtR57eXWjHvJfixLjQ08rewdu0f 5UGOYYraApYx4BlyDVIRCoHaCXjpE/A= X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNzMxMDA5NiBTYWx0ZWRfXwmdoRzAl4n+s wESxoNTVS+pqiBgNTIUfmuSLTjoxmZeNylf+Fy+UiwxXh/3tKsYQS82TgU4BWnB5TVLELRKt6ai ZpTze1xFBvdafkdRowVKPoyaEkgWs6WEf1NzE+vk4pG6EInrh7dArGQXDG/x0sbj6orpF/zxnK/ BpJwp+YgGaiebEuF45onLei5khMyHPCquSH5A8wpiAvIXVbtNPOhh3B106WnC5wQ8INsS/Pclb5 HuvStyn6u1AxhFZkalQaoKWI2mPyew12t2yenUBVwKju1mNNTMxwCFPZ2u7d4S46FEVtynT1ytS LIH/pNLctRp2/2kWSlSH2Xdz51JxF06tJX875V0F8bhZxz1OxByF/dCezco8B6V6CNeBsjQXRlG dnadg0mit/GPocduRA+i9vYwJj1vYv37zkSavO1UnNFE4gxL+81CGOLvN10zpmyK6M5myylgGQ4 YIe0l2URxDVnoVolRew== X-Authority-Analysis: v=2.4 cv=b5WCJNGx c=1 sm=1 tr=0 ts=6a6c9cc9 cx=c_pps a=bLidbwmWQ0KltjZqbj+ezA==:117 a=bLidbwmWQ0KltjZqbj+ezA==:17 a=RAioF0-LDSMA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=V8glGbnc2Ofi9Qvn3v5h:22 a=VnNF1IyMAAAA:8 a=UZJgiOjggnZcZ0CJR5AA:9 X-Proofpoint-GUID: lGkeF6Uwoupbth2r2MTLuJL4rZ2ps_Vl X-Proofpoint-ORIG-GUID: lGkeF6Uwoupbth2r2MTLuJL4rZ2ps_Vl X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.134,FMLib:17.12.100.49 definitions=2026-07-31_04,2026-07-30_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 spamscore=0 adultscore=0 malwarescore=0 impostorscore=0 bulkscore=0 phishscore=0 suspectscore=0 clxscore=1015 lowpriorityscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2607310096 When low on memory, kvm_arch_commit_memory_region() might not perform the required action completely, and instead just print a warning and return. This allows the VM to continue running with an inconsistent state. Fix by refilling the struct kvm_s390_mmu_cache and trying again. A true failure only happens if the refill fails, or if the cache cannot be allocated at all; in such case print a warning and kill the VM. Such a failure cannot currently happen. Signed-off-by: Claudio Imbrenda Fixes: e38c884df921 ("KVM: s390: Switch to new gmap") --- arch/s390/kvm/kvm-s390.c | 14 +++++++++----- 1 file changed, 9 insertions(+), 5 deletions(-) diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c index 518a69c55e85..fd8badb0d571 100644 --- a/arch/s390/kvm/kvm-s390.c +++ b/arch/s390/kvm/kvm-s390.c @@ -5830,7 +5830,7 @@ void kvm_arch_commit_memory_region(struct kvm *kvm, { const struct dat_walk_ops ops = { .pte_entry = cmma_d_count_pte, }; struct kvm_s390_mmu_cache *mc __free(kvm_s390_mmu_cache) = NULL; - int rc = 0; + int rc = -ENOMEM; guard(mutex)(&kvm->slots_arch_lock); @@ -5838,11 +5838,9 @@ void kvm_arch_commit_memory_region(struct kvm *kvm, return; mc = kvm_s390_new_mmu_cache(); - if (!mc) { - rc = -ENOMEM; + if (!mc) goto out; - } - +retry: scoped_guard(write_lock, &kvm->mmu_lock) { if (kvm->arch.migration_mode && kvm->arch.use_cmma && old) { _dat_walk_gfn_range(old->base_gfn, old->base_gfn + old->npages, @@ -5865,9 +5863,15 @@ void kvm_arch_commit_memory_region(struct kvm *kvm, case KVM_MR_FLAGS_ONLY: break; default: + rc = 0; WARN(1, "Unknown KVM MR CHANGE: %d\n", change); } } + if (rc == -ENOMEM) { + rc = kvm_s390_mmu_cache_topup(mc); + if (!rc) + goto retry; + } out: if (rc) pr_warn("failed to commit memory region\n"); -- 2.55.0