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Mon, 28 Sep 2026 12:36:48 +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 12:36:48 +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 1/3] KVM: s390: Improve floating IRQ injection behavior Date: Mon, 28 Sep 2026 12:30:55 +0000 Message-ID: <20260928123639.34226-2-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: 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-Proofpoint-Spam-Info: AW1haW4tMjYwOTI4MDA1MCBTYWx0ZWRfX9UzSGI9imE7t Z1xtsGx2bLRfqZHK3p7q3jdBBIX/KHGLGnAsXMefu/KTlQfL0VaraiYSTQDRI4spqkzQNkF6zNb 0mwX77QABeGRFk/uM0O62gfdfxzmXyo= X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwOTI4MDA1MCBTYWx0ZWRfXyfv1cfBTdhNj MT3bVgay9Xl3yB3KEcjmEnoXowclxMXW4tYgcTRfkE4SJpyo3FlYiAJPX0NytXaeuojbnXi+HsJ nVC1ij/IRekROhzUbZzzO13wTgoQMUyhp78xdSZNIrGfsZhAOd78kps1erH5WyoT4h6N5VeAfaf c7PCGUXitqC3j+jEEpxgWDaAbrDPDNzCRbjXZpKywx8i91luhICp/per2kh25fgb4Mmy5S8NLsH noclvs76RYAdHubNN+D67vgDjZPuvRib6SdaLuQtNqqRKf818IXpWErfCQnudv/Orz/XZWOxbOA ZLD4KXp5UctypCp66AEsEWKrTCKSYhTaX5GEGkdC4KXtuS/hKZN/kdJ4KYDa1AFo9bb8W3Qgfrh E6uRmlsQSg0AxzH3u/hoA9I4Rkp+6Fhub9LjwLaBDDv1A3dxuFvn62MLOdpXweiwe0BaFv6DefV JrHIqIKIvhefM9Q6wiA== X-Proofpoint-GUID: 8m4f8o0XjS4z7sO13eWwOLMS6TYQZU0r X-Authority-Analysis: v=2.4 cv=RKcmjIi+ c=1 sm=1 tr=0 ts=6aba5f66 cx=c_pps a=5BHTudwdYE3Te8bg5FgnPg==:117 a=5BHTudwdYE3Te8bg5FgnPg==:17 a=VdqzKS8jKosA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=iQ6ETzBq9ecOQQE5vZCe:22 a=VnNF1IyMAAAA:8 a=mNrvo4Ka_OWIiVjgUZwA:9 X-Proofpoint-ORIG-GUID: 8m4f8o0XjS4z7sO13eWwOLMS6TYQZU0r 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 clxscore=1015 priorityscore=1501 spamscore=0 bulkscore=0 impostorscore=0 adultscore=0 lowpriorityscore=0 suspectscore=0 malwarescore=0 phishscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2609040000 definitions=main-2609280050 Floating IRQs can be handled by any VCPU that opened its masks. The current design does not check if the mask is open when a floating IRQ is injected via the FLIC. It will wakeup the last VCPU that went sleeping hoping it's the correct one. Improve this by checking if the VCPU can deliver that partiqular IRQ and if not try to find another VCPU which can take the IRQ. This is not the final fix around this topic but we'll eventually inject a pending IRQ. The current code can easily deadlock a VM and with this fix we work around that. Signed-off-by: Janosch Frank Acked-by: Christian Borntraeger --- arch/s390/kvm/s390/interrupt.c | 86 ++++++++++++++++++++++++++-------- 1 file changed, 66 insertions(+), 20 deletions(-) diff --git a/arch/s390/kvm/s390/interrupt.c b/arch/s390/kvm/s390/interrupt.c index f892f4307883..1e013058f558 100644 --- a/arch/s390/kvm/s390/interrupt.c +++ b/arch/s390/kvm/s390/interrupt.c @@ -1918,49 +1918,93 @@ static int __inject_io(struct kvm *kvm, struct kvm_s390_interrupt_info *inti) return 0; } +static u64 inti_to_irq_pend_mask(u64 type, int isc) +{ + switch (type) { + case KVM_S390_MCHK: + /* Only repressible machine checks are floating */ + return BIT(IRQ_PEND_MCHK_REP); + case KVM_S390_INT_VIRTIO: + return BIT(IRQ_PEND_VIRTIO); + case KVM_S390_INT_SERVICE: + return BIT(IRQ_PEND_EXT_SERVICE) | + BIT(IRQ_PEND_EXT_SERVICE_EV); + case KVM_S390_INT_PFAULT_DONE: + return BIT(IRQ_PEND_PFAULT_DONE); + case KVM_S390_INT_IO_MIN...KVM_S390_INT_IO_MAX: + return BIT(isc_to_irq_type(isc)); + default: + return 0; + } +} + +/* + * Setup intervention masks to catch running vcpus that hopefully open + * their masks soonish and kick sleeping vcpus to motivate them to + * take IRQs. + */ +static void vcpu_intervention_kick(struct kvm_vcpu *vcpu, u64 type) +{ + /* make the VCPU drop out of the SIE, or wake it up if sleeping */ + switch (type) { + case KVM_S390_MCHK: + kvm_s390_set_cpuflags(vcpu, CPUSTAT_STOP_INT); + break; + case KVM_S390_INT_IO_MIN...KVM_S390_INT_IO_MAX: + if (!(type & KVM_S390_INT_IO_AI_MASK && + vcpu->kvm->arch.gisa_int.origin) || + kvm_s390_pv_cpu_get_handle(vcpu)) + kvm_s390_set_cpuflags(vcpu, CPUSTAT_IO_INT); + break; + default: + kvm_s390_set_cpuflags(vcpu, CPUSTAT_EXT_INT); + break; + } + kvm_s390_vcpu_wakeup(vcpu); +} + /* * Find a destination VCPU for a floating irq and kick it. */ -static void __floating_irq_kick(struct kvm *kvm, u64 type) +static void __floating_irq_kick(struct kvm *kvm, u64 type, int isc) { struct kvm_vcpu *dst_vcpu; int sigcpu, online_vcpus, nr_tries = 0; + u64 irq_pend_mask; + unsigned long i; online_vcpus = atomic_read(&kvm->online_vcpus); if (!online_vcpus) return; + irq_pend_mask = inti_to_irq_pend_mask(type, isc); for (sigcpu = kvm->arch.float_int.last_sleep_cpu; ; sigcpu++) { sigcpu %= online_vcpus; dst_vcpu = kvm_get_vcpu(kvm, sigcpu); - if (!is_vcpu_stopped(dst_vcpu)) + if (!is_vcpu_stopped(dst_vcpu) && + deliverable_irqs(dst_vcpu) & irq_pend_mask) break; /* avoid endless loops if all vcpus are stopped */ - if (nr_tries++ >= online_vcpus) - return; + if (nr_tries++ >= online_vcpus) { + dst_vcpu = NULL; + break; + } } - /* make the VCPU drop out of the SIE, or wake it up if sleeping */ - switch (type) { - case KVM_S390_MCHK: - kvm_s390_set_cpuflags(dst_vcpu, CPUSTAT_STOP_INT); - break; - case KVM_S390_INT_IO_MIN...KVM_S390_INT_IO_MAX: - if (!(type & KVM_S390_INT_IO_AI_MASK && - kvm->arch.gisa_int.origin) || - kvm_s390_pv_cpu_get_handle(dst_vcpu)) - kvm_s390_set_cpuflags(dst_vcpu, CPUSTAT_IO_INT); - break; - default: - kvm_s390_set_cpuflags(dst_vcpu, CPUSTAT_EXT_INT); - break; + /* Nobody was enabled, time to wake all of them */ + if (!dst_vcpu) { + kvm_for_each_vcpu(i, dst_vcpu, kvm) + vcpu_intervention_kick(dst_vcpu, type); + return; } - kvm_s390_vcpu_wakeup(dst_vcpu); + + vcpu_intervention_kick(dst_vcpu, type); } static int __inject_vm(struct kvm *kvm, struct kvm_s390_interrupt_info *inti) { u64 type = READ_ONCE(inti->type); + int isc = -1; int rc; switch (type) { @@ -1977,6 +2021,8 @@ static int __inject_vm(struct kvm *kvm, struct kvm_s390_interrupt_info *inti) rc = __inject_pfault_done(kvm, inti); break; case KVM_S390_INT_IO_MIN...KVM_S390_INT_IO_MAX: + /* Grab isc here since __inject_io() might free inti */ + isc = int_word_to_isc(inti->io.io_int_word); rc = __inject_io(kvm, inti); break; default: @@ -1985,7 +2031,7 @@ static int __inject_vm(struct kvm *kvm, struct kvm_s390_interrupt_info *inti) if (rc) return rc; - __floating_irq_kick(kvm, type); + __floating_irq_kick(kvm, type, isc); return 0; } -- 2.53.0