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Tue, 26 May 2026 01:53:23 +0000 (GMT) Received: from 9.60.13.83 (unknown [9.60.13.83]) by smtpav05.dal12v.mail.ibm.com (Postfix) with ESMTP; Tue, 26 May 2026 01:53:23 +0000 (GMT) From: Douglas Freimuth To: borntraeger@linux.ibm.com, imbrenda@linux.ibm.com, frankja@linux.ibm.com, david@kernel.org, hca@linux.ibm.com, gor@linux.ibm.com, agordeev@linux.ibm.com, svens@linux.ibm.com, kvm@vger.kernel.org, linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org Cc: mjrosato@linux.ibm.com, freimuth@linux.ibm.com Subject: [PATCH v8 0/3] KVM: s390: Introducing kvm_arch_set_irq_inatomic Fast Inject Date: Tue, 26 May 2026 03:53:17 +0200 Message-ID: <20260526015323.207343-1-freimuth@linux.ibm.com> X-Mailer: git-send-email 2.54.0 Precedence: bulk X-Mailing-List: linux-s390@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNTI2MDAwOCBTYWx0ZWRfX308E79GmhOEE MXcMdEzvq6bQYFa1f0JBqW0S6/RfvHr4CI6GjyV/CNu/W00A66U/kkk1XVouVym2He62sydO5Fq Ht48Zzl10AhsTUb4v6oHIjBmtWrRuhNY7nCRNxuUO4YlDRNkBLkEoXqZ94hxkdWgYMxRjiRfC2D YnS49jpzvg5TEWbJi7+5BD7yVIsVA2yzOjmNW2W9jOE5YQfHuvnDU+UYunsfRFAz7f3qhq3d/Cf Ati4eiQFkemcMGyVE4GnpcMKMf36eWy+M987S+VmPtBDlqUPkoDFXbky2VEMS7PMUERDVP4m7lZ QwKg5TLAEFex4ULelDepuGOgabccpPtBjJ5L0h3iu0MJo5agpGxcnq4kRw2LYLK3re2kI3ctX4u 2lDmGtIdHKUVKuwv+9Nq/u9YfgV8qNR19juDTc4P3Sej7B5P0UV32/N5GxWtm/JlYhCiiu0hDvC DQvFO9A9M9HzHYaKeYA== X-Authority-Analysis: v=2.4 cv=UtJT8ewB c=1 sm=1 tr=0 ts=6a14fd16 cx=c_pps a=3Bg1Hr4SwmMryq2xdFQyZA==:117 a=3Bg1Hr4SwmMryq2xdFQyZA==:17 a=IkcTkHD0fZMA:10 a=NGcC8JguVDcA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=iQ6ETzBq9ecOQQE5vZCe:22 a=NCD-c_4OtPvmz__zez8A:9 a=3ZKOabzyN94A:10 a=QEXdDO2ut3YA:10 X-Proofpoint-ORIG-GUID: aILvAhV6VEuOKxtXP0-8fK-cXt-xkWVL X-Proofpoint-GUID: aILvAhV6VEuOKxtXP0-8fK-cXt-xkWVL X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.51,FMLib:17.12.100.49 definitions=2026-05-25_07,2026-05-18_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 suspectscore=0 adultscore=0 clxscore=1015 bulkscore=0 phishscore=0 impostorscore=0 malwarescore=0 lowpriorityscore=0 priorityscore=1501 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2605130000 definitions=main-2605260008 s390 needs this series of three patches in order to enable a non-blocking path for irqfd injection on s390 via kvm_arch_set_irq_inatomic(). Before these changes, kvm_arch_set_irq_inatomic() would just return -EWOULDBLOCK and place all interrupts on the global work queue, which must subsequently be processed by a different thread. This series of patches implements an s390 version of inatomic and is relevant to virtio-blk and virtio-net and was tested against virtio-pci and virtio-ccw. The inatomic fast path cannot lose control since it is running with interrupts disabled. This meant making the following changes that exist on the slow path today. First, the adapter_indicators page needs to be mapped since it is accessed with interrupts disabled, so we added map/unmap functions. Second, access to shared resources between the fast and slow paths needed to be changed from mutex and semaphores to spin_lock's. Finally, the memory allocation on the slow path utilizes GFP_KERNEL_ACCOUNT but we had to implement the fast path with GFP_ATOMIC allocation. Each of these enhancements were required to prevent blocking on the fast inject path. s390 doesn't support a PREEMPT_RT kernel and this patch doesn't either. Given this fact, we are not using raw_spin_lock instead we are using regular spin_lock. Statistical counters have been added to enable analysis of irq injection on the fast path and slow path including io_390_inatomic, io_flic_inject_airq, io_set_adapter_int and io_390_inatomic_adapter_masked_or_coalesced. And counters have been added to analyze map/unmap of the adapter_indicator pages in non-Secure Execution environments and to track fencing of Fast Inject in Secure Execution environments. In order to take advantage of this kernel series with virtio-pci, a QEMU that includes the 's390x/pci: set kvm_msi_via_irqfd_allowed' fix is needed. Additionally, the guest xml needs a thread pool and threads explicitly assigned per disk device using the common way of defining threads for disks. Patch 1 enables map/unmap of adapter indicator pages but for Secure Execution environments it avoids the long term mapping. v7->v8: Move acquisition of kvm->lock to top of register_io_adapter() v7->v8: If !summary_page WARN_ON_ONCE if set indicator but not summary v7->v8: Remove kfree(init) from kvm_s390_inject_vm() default case v7->v8: return 0 if !level in kvm_arch_set_irq_inatomic() v7->v8: Use irqsave/irqrestore for spin_lock/unlock on fi->lock v7->v8: Modify statistic name io_390_inatomic_adapter_masked_or_coalesced Douglas Freimuth (3): KVM: s390: Add map/unmap ioctl and clean mappings post-guest KVM: s390: Enable adapter_indicators_set to use mapped pages KVM: s390: Introducing kvm_arch_set_irq_inatomic fast inject arch/s390/include/asm/kvm_host.h | 11 +- arch/s390/kvm/intercept.c | 5 +- arch/s390/kvm/interrupt.c | 525 +++++++++++++++++++++++++------ arch/s390/kvm/kvm-s390.c | 30 +- arch/s390/kvm/kvm-s390.h | 5 +- 5 files changed, 467 insertions(+), 109 deletions(-) -- 2.54.0