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Mon, 28 Sep 2026 12:36:49 +0000 (GMT) Received: from b46lp25.lnxne.boe (unknown [9.87.84.240]) by smtpav07.fra02v.mail.ibm.com (Postfix) with ESMTP; Mon, 28 Sep 2026 12:36:49 +0000 (GMT) From: Janosch Frank To: kvm@vger.kernel.org Cc: linux-s390@vger.kernel.org, borntraeger@linux.ibm.com, imbrenda@linux.ibm.com, pasic@linux.ibm.com Subject: [PATCH v5 3/3] KVM: s390: Add opportunistic floating IRQ delivery Date: Mon, 28 Sep 2026 12:30:57 +0000 Message-ID: <20260928123639.34226-4-frankja@linux.ibm.com> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260928123639.34226-1-frankja@linux.ibm.com> References: <20260928123639.34226-1-frankja@linux.ibm.com> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: rNZuWYxOZd_kWx85-FfHG0SK0vaErf-Q X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwOTI4MDA1MCBTYWx0ZWRfXyyx8tgdNKDWW Gjh2eXOhC4pNCcJcdD7ghCXPN4vplCd5Kk28oanEilFkUnoJ0PIFOUmt1I/3ztKD+Hnx9JO4pDU yyu0Uh7hC7RUYneSQZr/EEth2C7drPkSJtkD5x2u7dIE/QmzbHV6B3y4eHtEQv/3ldkmTuzsjXI 9q/bAE7gRbwrhMJa9S9S1z7aY3PRNXbjr3sQziQvBQz/yjYJP4SBFjrh30E2kGDeiZwC1vj6TgT 5EB6VEWJ/aGcDukj7VKaZmHdMVROuce8c9nF2NOCu9od9muQwdSBPrfyy/ehxt1I1QYiNG8PRAN 1ujd4ufXtvni2MGc1p7M4sT3t48EH9LSvvkh0Ewx9qPpoA4v3PO93ExAlMNRNfQ4FlRzntctXJv zZb12U6m7ZFAgFSpg8SHGqlb84/1tTsna0vUVYwMxXyrFFbpm+XG4AV1T4fD1XyUv/s/J3vUBNp DTPvfcOc35pJBCnb3YA== X-Proofpoint-Spam-Info: AW1haW4tMjYwOTI4MDA1MCBTYWx0ZWRfX7wpalZXEZJ6A RqSfz9NdTsIrnHFKHicSaPVTFpzlvXif5pKy34vbKXW4+vLdphzLxkzphArroU+aK/oRCsNeR6d 4pfpK+AWmOkMaNdNHLMSxjWHMgixv3E= X-Authority-Analysis: v=2.4 cv=EY5d0/mC c=1 sm=1 tr=0 ts=6aba5f65 cx=c_pps a=aDMHemPKRhS1OARIsFnwRA==:117 a=aDMHemPKRhS1OARIsFnwRA==:17 a=VdqzKS8jKosA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=RzCfie-kr_QcCd8fBx8p:22 a=VnNF1IyMAAAA:8 a=yyYbqD4tj2l4PXq5jccA:9 X-Proofpoint-GUID: rNZuWYxOZd_kWx85-FfHG0SK0vaErf-Q 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=2026-09-28_03,2026-09-21_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 phishscore=0 priorityscore=1501 suspectscore=0 adultscore=0 clxscore=1015 malwarescore=0 impostorscore=0 spamscore=0 lowpriorityscore=0 bulkscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2609040000 definitions=main-2609280050 Try to distribute floating IRQs which haven't been taken by a VCPU yet to sleeping VCPUs. This lowers the risk of floating IRQs not being delivered. Signed-off-by: Janosch Frank --- arch/s390/include/asm/kvm_host_s390.h | 1 + arch/s390/kvm/s390/interrupt.c | 34 +++++++++++++++++++++++++++ arch/s390/kvm/s390/s390.c | 1 + 3 files changed, 36 insertions(+) diff --git a/arch/s390/include/asm/kvm_host_s390.h b/arch/s390/include/asm/kvm_host_s390.h index cd692f8fb764..a86863e621b7 100644 --- a/arch/s390/include/asm/kvm_host_s390.h +++ b/arch/s390/include/asm/kvm_host_s390.h @@ -412,6 +412,7 @@ struct kvm_vm_stat { u64 gmap_shadow_r3_entry; u64 gmap_shadow_sg_entry; u64 gmap_shadow_pg_entry; + u64 inject_redist; }; struct kvm_arch_memory_slot { diff --git a/arch/s390/kvm/s390/interrupt.c b/arch/s390/kvm/s390/interrupt.c index 3c0e6216eee3..1b06775e581b 100644 --- a/arch/s390/kvm/s390/interrupt.c +++ b/arch/s390/kvm/s390/interrupt.c @@ -372,6 +372,38 @@ static unsigned long deliverable_irqs(struct kvm_vcpu *vcpu) return active_mask; } +static void distribute_float_irqs(struct kvm *kvm) +{ + struct kvm_vcpu *dst_vcpu; + int sigcpu, online_vcpus; + + if (!READ_ONCE(kvm->arch.float_int.pending_irqs)) + return; + + online_vcpus = atomic_read(&kvm->online_vcpus); + + /* + * Not too worried about synchronization for idle_mask. We + * might burn too many cycles but apart from that waking a + * vcpu is not harmful. + */ + sigcpu = find_first_bit(kvm->arch.idle_mask, online_vcpus); + + /* Well nobody's sleeping so someone will likely take the IRQ soon */ + if (sigcpu == online_vcpus) + return; + + do { + dst_vcpu = kvm_get_vcpu(kvm, sigcpu); + if (deliverable_irqs(dst_vcpu)) { + kvm->stat.inject_redist++; + kvm_s390_vcpu_wakeup(dst_vcpu); + break; + } + sigcpu = find_next_bit(kvm->arch.idle_mask, online_vcpus, ++sigcpu); + } while (sigcpu < online_vcpus); +} + static void __set_cpu_idle(struct kvm_vcpu *vcpu) { kvm_s390_set_cpuflags(vcpu, CPUSTAT_WAIT); @@ -1294,6 +1326,8 @@ int kvm_s390_handle_wait(struct kvm_vcpu *vcpu) if (!sltime) return 0; + distribute_float_irqs(vcpu->kvm); + __set_cpu_idle(vcpu); hrtimer_start(&vcpu->arch.ckc_timer, sltime, HRTIMER_MODE_REL); VCPU_EVENT(vcpu, 4, "enabled wait: %llu ns", sltime); diff --git a/arch/s390/kvm/s390/s390.c b/arch/s390/kvm/s390/s390.c index efd77b9cd36c..252fde3abc9c 100644 --- a/arch/s390/kvm/s390/s390.c +++ b/arch/s390/kvm/s390/s390.c @@ -87,6 +87,7 @@ const struct kvm_stats_desc kvm_vm_stats_desc[] = { STATS_DESC_COUNTER(VM, gmap_shadow_r3_entry), STATS_DESC_COUNTER(VM, gmap_shadow_sg_entry), STATS_DESC_COUNTER(VM, gmap_shadow_pg_entry), + STATS_DESC_COUNTER(VM, inject_redist), }; const struct kvm_stats_header kvm_vm_stats_header = { -- 2.53.0