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Tue, 11 Aug 2026 15:56:43 +0000 (GMT) Received: from p-imbrenda.ehn-de.ibm.com (unknown [9.224.75.30]) by smtpav01.fra02v.mail.ibm.com (Postfix) with ESMTP; Tue, 11 Aug 2026 15:56:43 +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 v1 07/11] KVM: s390: Move all code into kvm_arch_prepare_memory_region() Date: Tue, 11 Aug 2026 17:56:37 +0200 Message-ID: <20260811155641.219777-8-imbrenda@linux.ibm.com> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260811155641.219777-1-imbrenda@linux.ibm.com> References: <20260811155641.219777-1-imbrenda@linux.ibm.com> Precedence: bulk X-Mailing-List: linux-s390@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Authority-Analysis: v=2.4 cv=RsP16imK c=1 sm=1 tr=0 ts=6a7b4642 cx=c_pps a=3Bg1Hr4SwmMryq2xdFQyZA==:117 a=3Bg1Hr4SwmMryq2xdFQyZA==:17 a=Sv0fKeRqtYgA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=RzCfie-kr_QcCd8fBx8p:22 a=VnNF1IyMAAAA:8 a=XQGuvBUbV6v71_fLNr4A:9 X-Proofpoint-GUID: EuSe__kzKG7bJo_LBVr4_fBqczS4ynF6 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwODExMDEzMCBTYWx0ZWRfX4ouYUjMuFLYN Kl1rK4+pNZYb4D5FTwyNciVrthtqsdWMwmPBymynezrFMeYEazc0V5XdOiittt306ILVxAq9HVI Z9dyb+i+QtMTztWxuFgO05wsYZlcHy3D+E0C22rXo7ljFkktiIzrpalpDmewFCBwLQvDwo5mtNo bYW9oz4oXU5uG50BkJ6mtId2r0qcetm6QLuc0WMxGd435L7pGaid+ulVuqSsgPPwZkR51VhuKki YuDNr4lWFpLB5+wo3ygcrRqtPOnDR7sYxzetdCFA0mrdaAXHKF8OKEBacuyRlFX7CcBG5nj+r5c oEmcsRaFjTLv2QdLlufZ3lRJksGxvTeveLBYqWgSdbQgKb9ydoH8QY/lqp+bJUAUgGZr4MzhEAw w069wXEWOLlInkMWhwDf7TMU6snVbDp/LnN1MXVn9rRVny7zte9XQeFs87Zcrz4jq/0X891+Y/P ovhOSceIxL3NvNHB5bg== X-Proofpoint-ORIG-GUID: EuSe__kzKG7bJo_LBVr4_fBqczS4ynF6 X-Proofpoint-Spam-Info: AW1haW4tMjYwODExMDEzMCBTYWx0ZWRfX5TAV0xGvqyFa pqm9FfthvwKz4+gK4JuaBv8WDTZ8oDdc9kf0UCpLdqrLXp8xAb2g5nqFvCUgX9fKhi8Bv6iTgjF BfTq0z3acEioTyowC14mgUa1hsCQjiU= X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1176,Hydra:6.1.134,FMLib:17.12.100.49 definitions=2026-08-11_03,2026-08-10_03,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 impostorscore=0 suspectscore=0 clxscore=1015 malwarescore=0 phishscore=0 adultscore=0 lowpriorityscore=0 priorityscore=1501 bulkscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2608110130 Move all code from kvm_arch_commit_memory_region() into kvm_arch_prepare_memory_region(). This allows the function to fail gracefully if needed. The previous behaviour was to print a warning and continue execution with page tables incosistent with the memslots. The new kvm_s390_mmu_cache_extended_topup() function is used to guarantee that the necessary DAT table updates can be performed successfully. Signed-off-by: Claudio Imbrenda Fixes: e38c884df921 ("KVM: s390: Switch to new gmap") --- arch/s390/kvm/kvm-s390.c | 124 +++++++++++++++++++-------------------- 1 file changed, 59 insertions(+), 65 deletions(-) diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c index 02c5428ba239..c4196f9af05d 100644 --- a/arch/s390/kvm/kvm-s390.c +++ b/arch/s390/kvm/kvm-s390.c @@ -5766,11 +5766,28 @@ 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 = 0; + if (kvm_is_ucontrol(kvm) && new && new->id < KVM_USER_MEM_SLOTS) return -EINVAL; @@ -5785,6 +5802,10 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm, * and munmap() stuff in this slot after doing this call at any * time. */ + if (change != KVM_MR_MOVE && change != KVM_MR_CREATE) { + WARN(1, "Unknown KVM MR CHANGE: %d\n", change); + return -EINVAL; + } if (new->userspace_addr & ~PAGE_MASK) return -EINVAL; if ((new->base_gfn + new->npages) * PAGE_SIZE > kvm->arch.mem_limit) @@ -5793,57 +5814,27 @@ 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 = 0; - - guard(mutex)(&kvm->slots_arch_lock); if (change == KVM_MR_FLAGS_ONLY) - return; + return 0; mc = kvm_s390_new_mmu_cache(); - if (!mc) { - rc = -ENOMEM; - goto out; - } + if (!mc || kvm_s390_mmu_cache_extended_topup(mc)) + return -ENOMEM; scoped_guard(write_lock, &kvm->mmu_lock) { if (kvm->arch.migration_mode && kvm->arch.use_cmma && old) { @@ -5852,28 +5843,31 @@ void kvm_arch_commit_memory_region(struct kvm *kvm, &kvm->arch.cmma_dirty_pages); } - switch (change) { - case KVM_MR_DELETE: + if (change == KVM_MR_DELETE || change == KVM_MR_MOVE) rc = dat_delete_slot(mc, kvm->arch.gmap->asce, old->base_gfn, old->npages); - break; - case KVM_MR_MOVE: - rc = dat_delete_slot(mc, kvm->arch.gmap->asce, old->base_gfn, old->npages); - if (rc) - break; - fallthrough; - case KVM_MR_CREATE: + if (!rc && (change == KVM_MR_MOVE || change == KVM_MR_CREATE)) rc = dat_create_slot(mc, kvm->arch.gmap->asce, new->base_gfn, new->npages); - break; - case KVM_MR_FLAGS_ONLY: - break; - default: - WARN(1, "Unknown KVM MR CHANGE: %d\n", change); - } } -out: - if (rc) - pr_warn("failed to commit memory region\n"); - return; + + /* + * dat_{create,delete}_slot() can only fail in two cases: + * - Internal consistency error in the gmap DAT tables + * - Out of memory while allocating DAT tables + * The first case should not be possible in general, and is a symptom of + * a serious KVM bug; the second should also be impossible because the + * mmu cache has been filled to the brim, and has more than enough + * capacity to handle the worst cases. Hence it is safe to put this + * KVM_BUG_ON() here, as it should not be triggerable unless some + * serious bug has occurred somewhere else. + */ + return KVM_BUG_ON(rc, kvm); +} + +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