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Thu, 20 Aug 2026 12:15:54 +0000 (GMT) Received: from b46lp25.lnxne.boe (unknown [9.87.84.240]) by smtpav01.fra02v.mail.ibm.com (Postfix) with ESMTP; Thu, 20 Aug 2026 12:15:54 +0000 (GMT) From: Janosch Frank To: kvm@vger.kernel.org Cc: imbrenda@linux.ibm.com, linux-s390@vger.kernel.org, borntraeger@linux.ibm.com, pasic@linux.ibm.com Subject: [PATCH v4 3/3] KVM: s390: Add opportunistic floating IRQ injection Date: Thu, 20 Aug 2026 12:12:18 +0000 Message-ID: <20260820121546.24694-4-frankja@linux.ibm.com> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260820121546.24694-1-frankja@linux.ibm.com> References: <20260820121546.24694-1-frankja@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=MthiLWae c=1 sm=1 tr=0 ts=6a86efff cx=c_pps a=bLidbwmWQ0KltjZqbj+ezA==:117 a=bLidbwmWQ0KltjZqbj+ezA==:17 a=Sv0fKeRqtYgA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=U7nrCbtTmkRpXpFmAIza:22 a=VnNF1IyMAAAA:8 a=ceVPMvoHt_UTMoFkilYA:9 X-Proofpoint-ORIG-GUID: fvO7uhiM1p0Y_xkw8MfesxvVdeCNyOYz X-Proofpoint-GUID: fvO7uhiM1p0Y_xkw8MfesxvVdeCNyOYz X-Proofpoint-Spam-Info: AW1haW4tMjYwODIwMDA4OSBTYWx0ZWRfX2SrxhDHK/1ZD ojBY2DeSYdbjOpK6CjmOy714piq0hbdnTTXkZiPS9gF3iKVPvuCEwbzaE5yi5qAS/EEmC30cv/F Do64I+dxscmLpvy135tCrk7Wq25P0jk= X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwODIwMDA4OSBTYWx0ZWRfX8Nfp/PbEZqbD /A11xd3HIFfjxEXGA4+O1TPgcLxV3RrS27iguUdZHJFEyMPz+PpJBC3IMlo58rUPnki1WYLVflw gk1WKmX4bkvqZ11ifHmq5/IMbKjinpIMO/JMZStr1+b2MPXALFojrdMabRywLGcfEbZP09RHu5W 1QTHI6GxOMGPr3JbG8bKHC66uFTzPhAKKmKvnqEb4Zpop6lGjmjuBurWdzyV84nmAAJH6T96zFb VV9PTQeq3pHK6E8AWE0eCqCJyheH0AueKFg/f9eWG7fGMt4F5JbQO8zHFRprLs/L4x0WPPwGAzU GD1syudOgUQp79QVDiz5sJd1qBtT/gYQ4dkUMVW9bdVyaizToEQdFGq1Mbx4M3Y6JMgG8zCKZMS vKTFH7m1tgz8cdILHqhPb10a/HsaVyaKpkhy/6i3tSsXMP41zITrnt++Tb6rNUOS3q9w0SvPORw tTD+mGXBgLotC7gNccA== 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=2026-08-19_06,2026-08-19_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 malwarescore=0 impostorscore=0 bulkscore=0 phishscore=0 clxscore=1015 spamscore=0 adultscore=0 lowpriorityscore=0 priorityscore=1501 suspectscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2608200089 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.h | 1 + arch/s390/kvm/interrupt.c | 31 +++++++++++++++++++++++++++++++ arch/s390/kvm/kvm-s390.c | 3 +++ arch/s390/kvm/kvm-s390.h | 1 + 4 files changed, 36 insertions(+) diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h index b4182ca4435f..1d62bdd7aca5 100644 --- a/arch/s390/include/asm/kvm_host.h +++ b/arch/s390/include/asm/kvm_host.h @@ -467,6 +467,7 @@ 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/interrupt.c b/arch/s390/kvm/interrupt.c index b3e4bfeacff2..54f20347f553 100644 --- a/arch/s390/kvm/interrupt.c +++ b/arch/s390/kvm/interrupt.c @@ -367,6 +367,37 @@ static unsigned long deliverable_irqs(struct kvm_vcpu *vcpu) return active_mask; } +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); diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c index 518a69c55e85..d6d46688d980 100644 --- a/arch/s390/kvm/kvm-s390.c +++ b/arch/s390/kvm/kvm-s390.c @@ -86,6 +86,7 @@ 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 = { @@ -4572,6 +4573,8 @@ static int vcpu_pre_run(struct kvm_vcpu *vcpu) rc = kvm_s390_deliver_pending_interrupts(vcpu); if (rc || guestdbg_exit_pending(vcpu)) return rc; + + distribute_float_irqs(vcpu->kvm); } rc = kvm_s390_handle_requests(vcpu); diff --git a/arch/s390/kvm/kvm-s390.h b/arch/s390/kvm/kvm-s390.h index 8e886bcef4a0..7115a8f5b188 100644 --- a/arch/s390/kvm/kvm-s390.h +++ b/arch/s390/kvm/kvm-s390.h @@ -376,6 +376,7 @@ int __must_check kvm_s390_deliver_pending_interrupts(struct kvm_vcpu *vcpu); void kvm_s390_clear_local_irqs(struct kvm_vcpu *vcpu); void kvm_s390_clear_float_irqs(struct kvm *kvm); void kvm_s390_pv_sclp_kick(struct kvm_vcpu *vcpu); +void distribute_float_irqs(struct kvm *kvm); int __must_check kvm_s390_inject_vm(struct kvm *kvm, struct kvm_s390_interrupt *s390int, struct kvm_s390_interrupt_info *inti); -- 2.53.0