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Wed, 29 Jul 2026 15:29:40 +0000 (GMT) Received: from p-imbrenda.ehn-de.ibm.com (unknown [9.224.75.30]) by smtpav01.fra02v.mail.ibm.com (Postfix) with ESMTP; Wed, 29 Jul 2026 15:29:40 +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 v5 13/13] KVM: s390: Fix kvm_arch_commit_memory_region() when low on memory Date: Wed, 29 Jul 2026 17:29:38 +0200 Message-ID: <20260729152938.782383-14-imbrenda@linux.ibm.com> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260729152938.782383-1-imbrenda@linux.ibm.com> References: <20260729152938.782383-1-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-GUID: Ll2t0jPL46u0Wydjm_D5XG-oIo7lmFUr X-Proofpoint-ORIG-GUID: Ll2t0jPL46u0Wydjm_D5XG-oIo7lmFUr X-Proofpoint-Spam-Info: AW1haW4tMjYwNzI5MDEyMyBTYWx0ZWRfX+JgBFiAaYAuK hGuEr9R2dg+Dfi4fTj2e+RFV906Bp4EQM+b5m8aR1LNogAypwaVa14jdODRlmb2HOUr4JQQToJM q2US4ZIO1lVQiz2siSg+GOQlJre2oKE= X-Authority-Analysis: v=2.4 cv=dYuwG3Xe c=1 sm=1 tr=0 ts=6a6a1c6c cx=c_pps a=3Bg1Hr4SwmMryq2xdFQyZA==:117 a=3Bg1Hr4SwmMryq2xdFQyZA==:17 a=RAioF0-LDSMA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=U7nrCbtTmkRpXpFmAIza:22 a=VnNF1IyMAAAA:8 a=UZJgiOjggnZcZ0CJR5AA:9 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNzI5MDEyMyBTYWx0ZWRfXw0NEquilzZae 5XHX4ez9zwxerc/U2WGger11IXGhfAeow+BBVqI9Bg89hibhKt1EGJuXA7n7mnWahiKSF17xkzy 6LARvD2RNVjMFmBLyrxbjLHc3Vgoq4skJgmwuzzwg4LbQ8yezpbfyuv9E/xn6NeOK80REYNQLQY Fchhl2SyVB7XgOMVbE2Y05NQaJY6c+l/6Q+CUI1oWME6kFioVYcTX9rKaFdrYRavxBBxqDln8Oo kC/Ll8FdmwaSjMU3Quhe+YfydeMAqGXCdTGAmLPagOJrjWdCuQ5vtwtDx7d/wvWiRpwd0zLacX2 FSiiO62I/KYmFDf7BQ+8nvizfqkqqr4cDOG2ewAor6wc6Wyd+lZ8lMrNSHfGDpeERVH8DaLWOyd pvY8c0BEq+GbJ3piVQPy9O6BDVBnFTYwbdP7ufHezC9fKoq/XnzrwCikNBOIIF2QwtvoHedXpVa 4zAzd5R3kcDL+5t9C+w== 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=2026-07-29_06,2026-07-29_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 impostorscore=0 clxscore=1015 phishscore=0 malwarescore=0 spamscore=0 lowpriorityscore=0 bulkscore=0 suspectscore=0 adultscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2607290123 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 | 16 ++++++++++------ 1 file changed, 10 insertions(+), 6 deletions(-) diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c index cdda7a00a0ff..b29e5460f5ef 100644 --- a/arch/s390/kvm/kvm-s390.c +++ b/arch/s390/kvm/kvm-s390.c @@ -5824,7 +5824,7 @@ 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); @@ -5832,11 +5832,9 @@ 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, @@ -5859,11 +5857,17 @@ 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) + if (KVM_BUG_ON(rc, kvm)) pr_warn("failed to commit memory region\n"); return; } -- 2.55.0