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Thu, 30 Jul 2026 16:27:17 +0000 (GMT) Received: from p-imbrenda.ehn-de.ibm.com (unknown [9.224.75.30]) by smtpav02.fra02v.mail.ibm.com (Postfix) with ESMTP; Thu, 30 Jul 2026 16:27:17 +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 v6 13/14] KVM: s390: Fix kvm_arch_commit_memory_region() when low on memory Date: Thu, 30 Jul 2026 18:27:13 +0200 Message-ID: <20260730162714.133327-14-imbrenda@linux.ibm.com> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260730162714.133327-1-imbrenda@linux.ibm.com> References: <20260730162714.133327-1-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: hUDrNWMSMdqt-8TQhDet8bE9ETev9MeO X-Proofpoint-ORIG-GUID: hUDrNWMSMdqt-8TQhDet8bE9ETev9MeO X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNzMwMDEyMyBTYWx0ZWRfX/YNGo4MFloLw O/bUweFnNlddsCstBH802ROgHkOk+9D+hoD15Tra5a/BW81KecXtlFfAlOA8wjAafKZdDeHZpVO VKTmBJzUWdu1xRV5I/kUOkoo4j9cdAVZTXFrr61s9Hq8yxinaySVfXyNYK9wMeobgkIkKVlWWxL /7/QtbZj5A59vT0vsfG+3kjLs3hHGKdJhyQvP6FVpJgAvGAZsIyB663n7W5z3iu7F8EGTh4kSKq G2KNIqJHVY0jkKyPasZ9IEVU7PRMh65rhi6h7P4ysP3niX7Q7GoQjv7gBu7c7IYDcq/7UxN9WDq 95yiB703Ohr7Y0obNNJx8i8a9ndg0thl6I2CZ032/l4NLpRhmtlElWFCztvs8gmLqoT5cyvkEU0 I7fE+TaQXUdcPX2ui/epkKrTbnUL7HUtocv4TfpeYEmoe38og/N8ebqcKLn657/ksm3mJFt9xX/ Fb4a1/vLMwekhyuz8+w== X-Authority-Analysis: v=2.4 cv=SKFykuvH c=1 sm=1 tr=0 ts=6a6b7b6c cx=c_pps a=bLidbwmWQ0KltjZqbj+ezA==:117 a=bLidbwmWQ0KltjZqbj+ezA==:17 a=RAioF0-LDSMA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=iQ6ETzBq9ecOQQE5vZCe:22 a=VnNF1IyMAAAA:8 a=UZJgiOjggnZcZ0CJR5AA:9 X-Proofpoint-Spam-Info: AW1haW4tMjYwNzMwMDEyMyBTYWx0ZWRfXz72FZgL8qDW7 f3znxj6qnbmNP1qr70ROzvJQ/a6g+oz+oS+tvq26WqQhgFCAzXqsrxTVf3olnCkD7yqhvfesnxt zeOZVcvz/QRuJ8Ic7lw6edvd4MN1D9o= 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=2026-07-30_04,2026-07-30_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 clxscore=1015 adultscore=0 lowpriorityscore=0 bulkscore=0 impostorscore=0 phishscore=0 spamscore=0 suspectscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2607300123 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 ba600c948887..035476ec7fbc 100644 --- a/arch/s390/kvm/kvm-s390.c +++ b/arch/s390/kvm/kvm-s390.c @@ -5827,7 +5827,7 @@ 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); @@ -5835,11 +5835,9 @@ 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, @@ -5862,11 +5860,17 @@ 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