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Tue, 9 Jun 2026 15:09:34 +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 v2 2/4] KVM: s390: Add capability to support 2G hugepages Date: Tue, 9 Jun 2026 17:09:28 +0200 Message-ID: <20260609150930.665370-3-imbrenda@linux.ibm.com> X-Mailer: git-send-email 2.54.0 In-Reply-To: <20260609150930.665370-1-imbrenda@linux.ibm.com> References: <20260609150930.665370-1-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-Authority-Analysis: v=2.4 cv=HppG3UTS c=1 sm=1 tr=0 ts=6a282cb6 cx=c_pps a=3Bg1Hr4SwmMryq2xdFQyZA==:117 a=3Bg1Hr4SwmMryq2xdFQyZA==:17 a=FelO9ux0wxsA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=uAbxVGIbfxUO_5tXvNgY:22 a=VnNF1IyMAAAA:8 a=QhT8cEMGEDdk696zIO8A:9 X-Proofpoint-GUID: i8b4eY45QXe_iLfcjRjZE4VOYpxkK1i8 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNjA5MDE0NCBTYWx0ZWRfXxEhccUw31e7x LE8HHDuro8Vy2QvbHPO4MjZPk7hIs0KUpeEo9gwUXoQFS8JGowHuHDnCnoI1uLEyQASsrm6M8W8 MSQOpADaZqpwPtctiZ89tGyuMcHZm/+nJgB/+am/O0yDdSndfPhK6vg7F4XeB7b6s2+v79bqrJF V52G2JwqnSn7kRVZvwrjl1s0uZ+7cWAgUWVsh4Nbba+18cHUbjzQMZbtqiNL1HWWUhZvOEu6QKo 44Kl73ETK4VLuBFrFXdPSB4rCV+lq8FxYWaHRyJOhIWQerJ0GHPCH3ZI0AEhqFWT1a4p1+lxkZZ qVTlY+2DGducjbbw9a2jPJsyisHrKMxgIG3LHocofgD8Xw58yf+xBYaZEcHFgdTHiGLkRwS81QG zVx+6JZ08ds/4kc2vobhTjS66G6tf8z834bXLxGhtKF2ZKNm007y3FGLaiWo5B43qsqgWWbWdB5 yj4xUh/nUk/9ZArH96w== X-Proofpoint-ORIG-GUID: i8b4eY45QXe_iLfcjRjZE4VOYpxkK1i8 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.125,FMLib:17.12.100.49 definitions=2026-06-09_03,2026-06-09_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 lowpriorityscore=0 adultscore=0 phishscore=0 malwarescore=0 impostorscore=0 priorityscore=1501 clxscore=1015 bulkscore=0 spamscore=0 suspectscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2605210000 definitions=main-2606090144 Add KVM_CAP_S390_HPAGE_2G to signal to userspace that 2G hugepages may be used to back the guest; restrictions apply similar to 1M hugepages. Enable the (for now still ignored) GMAP_FLAG_ALLOW_HPAGE_2G flag for the guest gmap, and propagate / disable it as necessary. Reviewed-by: Steffen Eiden Signed-off-by: Claudio Imbrenda --- arch/s390/kvm/gmap.c | 5 +++++ arch/s390/kvm/kvm-s390.c | 26 ++++++++++++++++++++++++++ arch/s390/kvm/pv.c | 5 ++++- include/uapi/linux/kvm.h | 1 + 4 files changed, 36 insertions(+), 1 deletion(-) diff --git a/arch/s390/kvm/gmap.c b/arch/s390/kvm/gmap.c index 52d55ddea8d4..c9e348149ba1 100644 --- a/arch/s390/kvm/gmap.c +++ b/arch/s390/kvm/gmap.c @@ -105,6 +105,11 @@ static void gmap_add_child(struct gmap *parent, struct gmap *child) else clear_bit(GMAP_FLAG_ALLOW_HPAGE_1M, &child->flags); + if (test_bit(GMAP_FLAG_ALLOW_HPAGE_2G, &parent->flags)) + set_bit(GMAP_FLAG_ALLOW_HPAGE_2G, &child->flags); + else + clear_bit(GMAP_FLAG_ALLOW_HPAGE_2G, &child->flags); + if (kvm_is_ucontrol(parent->kvm)) clear_bit(GMAP_FLAG_OWNS_PAGETABLES, &child->flags); list_add(&child->list, &parent->children); diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c index 801a622691b6..616d1db7c0d9 100644 --- a/arch/s390/kvm/kvm-s390.c +++ b/arch/s390/kvm/kvm-s390.c @@ -645,6 +645,11 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext) if (hpage && !(kvm && kvm_is_ucontrol(kvm))) r = 1; break; + case KVM_CAP_S390_HPAGE_2G: + r = 0; + if (hpage_2g && !(kvm && kvm_is_ucontrol(kvm))) + r = 1; + break; case KVM_CAP_S390_MEM_OP: r = MEM_OP_MAX_SIZE; break; @@ -901,6 +906,27 @@ int kvm_vm_ioctl_enable_cap(struct kvm *kvm, struct kvm_enable_cap *cap) VM_EVENT(kvm, 3, "ENABLE: CAP_S390_HPAGE %s", r ? "(not available)" : "(success)"); break; + case KVM_CAP_S390_HPAGE_2G: + mutex_lock(&kvm->lock); + if (kvm->created_vcpus) { + r = -EBUSY; + } else if (!hpage_2g || kvm->arch.use_cmma || kvm_is_ucontrol(kvm)) { + r = -EINVAL; + } else { + r = 0; + set_bit(GMAP_FLAG_ALLOW_HPAGE_2G, &kvm->arch.gmap->flags); + /* + * We might have to create fake 4k page + * tables. To avoid that the hardware works on + * stale PGSTEs, we emulate these instructions. + */ + kvm->arch.use_skf = 0; + kvm->arch.use_pfmfi = 0; + } + mutex_unlock(&kvm->lock); + VM_EVENT(kvm, 3, "ENABLE: CAP_S390_HPAGE_2G %s", + r ? "(not available)" : "(success)"); + break; case KVM_CAP_S390_USER_STSI: VM_EVENT(kvm, 3, "%s", "ENABLE: CAP_S390_USER_STSI"); kvm->arch.user_stsi = 1; diff --git a/arch/s390/kvm/pv.c b/arch/s390/kvm/pv.c index 4b865e75351c..1beacc841ca8 100644 --- a/arch/s390/kvm/pv.c +++ b/arch/s390/kvm/pv.c @@ -740,7 +740,10 @@ int kvm_s390_pv_init_vm(struct kvm *kvm, u16 *rc, u16 *rrc) uvcb.flags.ap_allow_instr = kvm->arch.model.uv_feat_guest.ap; uvcb.flags.ap_instr_intr = kvm->arch.model.uv_feat_guest.ap_intr; - clear_bit(GMAP_FLAG_ALLOW_HPAGE_1M, &kvm->arch.gmap->flags); + scoped_guard(write_lock, &kvm->mmu_lock) { + clear_bit(GMAP_FLAG_ALLOW_HPAGE_1M, &kvm->arch.gmap->flags); + clear_bit(GMAP_FLAG_ALLOW_HPAGE_2G, &kvm->arch.gmap->flags); + } gmap_split_huge_pages(kvm->arch.gmap); cc = uv_call_sched(0, (u64)&uvcb); diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h index 6c8afa2047bf..419011097fa8 100644 --- a/include/uapi/linux/kvm.h +++ b/include/uapi/linux/kvm.h @@ -996,6 +996,7 @@ struct kvm_enable_cap { #define KVM_CAP_S390_USER_OPEREXEC 246 #define KVM_CAP_S390_KEYOP 247 #define KVM_CAP_S390_VSIE_ESAMODE 248 +#define KVM_CAP_S390_HPAGE_2G 249 struct kvm_irq_routing_irqchip { __u32 irqchip; -- 2.54.0