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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 14/14] KVM: s390: Move DAT table updates to kvm_arch_prepare_memory_region() Date: Thu, 30 Jul 2026 18:27:14 +0200 Message-ID: <20260730162714.133327-15-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-Spam-Info: AW1haW4tMjYwNzMwMDEyMyBTYWx0ZWRfXzcAT5C3K1alM j9uWyX/Aho4gyXrP1eF5svKY6l9JPTY0WR1rEv7VgL6tHpN2Yp4s7lRvhvL4gahbZkfEx3RneJq VuJe0Q4pPMtKrmJKAYY0FwRRptZ42NU= X-Proofpoint-GUID: DMVU7hwS49NWG7GSzFsv3aV6caDN6Tu4 X-Proofpoint-ORIG-GUID: DMVU7hwS49NWG7GSzFsv3aV6caDN6Tu4 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNzMwMDEyMyBTYWx0ZWRfXzsu05pGlePH1 yz43P6fPWG923gZc2qGyaRume8RZ3vM1rSSO0sdEV6jJFNbueo7rvIj5+G3NXND35L16omqmURq T0fHe+8ih1OtizCHehDLx96GNA5gu2XGKIzht2kAnB/eiAqVWAjb0ggkU3e+qx9DlcJZKy0Ddq5 tD8W6tA/wLnQW4xguozggTj62dWQGxb8ZuWUD9BwBdRxiobzZuY0Q7LMMxE9bhWmfiQ/LqQIi6E TGgmfiMlhQJ4X8yimLknK1zHi19d3yc6CbQ1IlGUF14OiYG90232IOZpLKPrnswjh8QfeVBgH4J DTyVnP/sjXGddIg0IlExkqzou+7A4WZp4+LPYhaxVvAvrJWv3pYwMUkG1isuwYjqG05v/Sfd2/f b7ecsifYPW79llegRFSjNDYRpTfQJRriZ77QKoWvHj+iPJyIKvOvo5G1GarsRXI9Xdyc0G/gIS+ OGwCRx8sX7D/Ppfpn1A== X-Authority-Analysis: v=2.4 cv=X5Vi7mTe c=1 sm=1 tr=0 ts=6a6b7b6c cx=c_pps a=AfN7/Ok6k8XGzOShvHwTGQ==:117 a=AfN7/Ok6k8XGzOShvHwTGQ==:17 a=RAioF0-LDSMA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=Y2IxJ9c9Rs8Kov3niI8_:22 a=VnNF1IyMAAAA:8 a=Ik9v8dO2Bu5cKhyEOHoA:9 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 clxscore=1015 impostorscore=0 lowpriorityscore=0 phishscore=0 priorityscore=1501 malwarescore=0 spamscore=0 suspectscore=0 bulkscore=0 adultscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2607300123 Currently, when a memslot is changed, the changes in the page tables are performed in kvm_arch_commit_memory_region(), which is assumed to never fail, as it cannot return an error code. If memory is tight, the allocation of page tables can fail, a warning is printed, and the system is left in an inconsistent state. Move the whole page table update into kvm_arch_prepare_memory_region() instead. This function can fail and return an appropriate error code, thus not leaving the system in an inconsistent state. Fixes: 598841ca9919 ("[S390] use gmap address spaces for kvm guest images") Fixes: e38c884df921 ("KVM: s390: Switch to new gmap") Signed-off-by: Claudio Imbrenda --- arch/s390/kvm/kvm-s390.c | 87 ++++++++++++++++++---------------------- 1 file changed, 40 insertions(+), 47 deletions(-) diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c index 035476ec7fbc..668272dffa18 100644 --- a/arch/s390/kvm/kvm-s390.c +++ b/arch/s390/kvm/kvm-s390.c @@ -5761,11 +5761,30 @@ bool kvm_arch_irqchip_in_kernel(struct kvm *kvm) } /* Section: memory related */ +static long cmma_d_count_pte(union pte *ptep, gfn_t gfn, gfn_t next, struct dat_walk *walk) +{ + union pgste pgste; + + pgste = pgste_get_lock(ptep); + if (pgste.cmma_d) { + pgste.cmma_d = 0; + atomic64_dec(walk->priv); + } + pgste_set_unlock(ptep, pgste); + return 0; +} + int kvm_arch_prepare_memory_region(struct kvm *kvm, const struct kvm_memory_slot *old, struct kvm_memory_slot *new, enum kvm_mr_change change) { + 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 = -ENOMEM; + + lockdep_assert_held(&kvm->slots_arch_lock); + if (kvm_is_ucontrol(kvm) && new && new->id < KVM_USER_MEM_SLOTS) return -EINVAL; @@ -5788,55 +5807,27 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm, return -EINVAL; } - if (!kvm->arch.migration_mode) - return 0; - - /* - * Turn off migration mode when: - * - userspace creates a new memslot with dirty logging off, - * - userspace modifies an existing memslot (MOVE or FLAGS_ONLY) and - * dirty logging is turned off. - * Migration mode expects dirty page logging being enabled to store - * its dirty bitmap. - */ - if (change != KVM_MR_DELETE && - !(new->flags & KVM_MEM_LOG_DIRTY_PAGES)) - WARN(kvm_s390_vm_stop_migration(kvm), - "Failed to stop migration mode"); - - return 0; -} - -static long cmma_d_count_pte(union pte *ptep, gfn_t gfn, gfn_t next, struct dat_walk *walk) -{ - union pgste pgste; - - pgste = pgste_get_lock(ptep); - if (pgste.cmma_d) { - pgste.cmma_d = 0; - atomic64_dec(walk->priv); + if (kvm->arch.migration_mode) { + /* + * Turn off migration mode when: + * - userspace creates a new memslot with dirty logging off, + * - userspace modifies an existing memslot (MOVE or FLAGS_ONLY) + * and dirty logging is turned off. + * Migration mode expects dirty page logging being enabled to + * store its dirty bitmap. + */ + if (change != KVM_MR_DELETE && + !(new->flags & KVM_MEM_LOG_DIRTY_PAGES)) + WARN(kvm_s390_vm_stop_migration(kvm), + "Failed to stop migration mode"); } - pgste_set_unlock(ptep, pgste); - return 0; -} - -void kvm_arch_commit_memory_region(struct kvm *kvm, - struct kvm_memory_slot *old, - const struct kvm_memory_slot *new, - enum kvm_mr_change change) -{ - 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 = -ENOMEM; - - guard(mutex)(&kvm->slots_arch_lock); if (change == KVM_MR_FLAGS_ONLY) - return; + return 0; mc = kvm_s390_new_mmu_cache(); if (!mc) - goto out; + return -ENOMEM; retry: scoped_guard(write_lock, &kvm->mmu_lock) { if (kvm->arch.migration_mode && kvm->arch.use_cmma && old) { @@ -5869,10 +5860,12 @@ void kvm_arch_commit_memory_region(struct kvm *kvm, if (!rc) goto retry; } -out: - if (KVM_BUG_ON(rc, kvm)) - pr_warn("failed to commit memory region\n"); - return; + return rc; +} + +void kvm_arch_commit_memory_region(struct kvm *kvm, struct kvm_memory_slot *old, + const struct kvm_memory_slot *new, enum kvm_mr_change change) +{ } /** -- 2.55.0