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Thu, 20 Aug 2026 12:15:53 +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 12:15:53 +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 1/3] KVM: s390: Improve floating IRQ injection behavior Date: Thu, 20 Aug 2026 12:12:16 +0000 Message-ID: <20260820121546.24694-2-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=CpuPtH4D c=1 sm=1 tr=0 ts=6a86effe cx=c_pps a=AfN7/Ok6k8XGzOShvHwTGQ==:117 a=AfN7/Ok6k8XGzOShvHwTGQ==:17 a=Sv0fKeRqtYgA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=RzCfie-kr_QcCd8fBx8p:22 a=VnNF1IyMAAAA:8 a=mNrvo4Ka_OWIiVjgUZwA:9 X-Proofpoint-ORIG-GUID: sV23ySkh-HNGoJ9AM3LKavM0mzUoEpm1 X-Proofpoint-GUID: sV23ySkh-HNGoJ9AM3LKavM0mzUoEpm1 X-Proofpoint-Spam-Info: AW1haW4tMjYwODIwMDA4OSBTYWx0ZWRfX2JBB6OkGYDix 3XddHjB/KAlG7ogagsEZhNG9TiqENGnEqJjhpZhHOls68xTOilmRibcy0XBK8nJbPCFAIpb6qg5 LXlpLLkrS6kkHXm5wCMxp03OwTA2kB4= X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwODIwMDA4OSBTYWx0ZWRfX1hCJfG4olpjr s3WWqhtFznaNhR4ghjSafruD8eSInTVD4wIFo1NJYQIZpH0NXuMNVVyW4IRwgfi6dbcdDng4BLV I8JCyU7M8rubeW99SXhuk75Kboh0bBOM3Q4lM8A4Lw2o6Se9nCZpzsUBzUdyUWKbj5ta58JAcu8 S46PSY1Gnrq8Mz5PuWPA6uyMcj51zPyOYXB/eaX2viywVq/RWk8O0+1dwI2Nr2wzWI7/ZPBc4RX L5KCCPnimvqHQ2XpyZiD9cH5xbtvdG6Mro3HZNwQdJUpY2u1x1c+Z2/CtdEohdgfBRFCCDaJqud p78dkzgoyPdsy7NXB+6nsvdf3sx+Wm2pMiEKA2ycFguczRdykY2QEqObYhw6qqHpSwCu/vQi7Zo 7tqp5tZAQemmytyFXz8MfeYimtmyMWeq/HIr+co/hlAvzTEBOeDLGdclTKVHRzrOAm+FYRP2ieO 3pGNKfze71PKIfAcybA== 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 impostorscore=0 adultscore=0 bulkscore=0 malwarescore=0 phishscore=0 lowpriorityscore=0 spamscore=0 clxscore=1015 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 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 has pending IRQs 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 --- arch/s390/kvm/interrupt.c | 86 ++++++++++++++++++++++++++++++--------- 1 file changed, 66 insertions(+), 20 deletions(-) diff --git a/arch/s390/kvm/interrupt.c b/arch/s390/kvm/interrupt.c index 8f24bcd1a6d3..87caad037765 100644 --- a/arch/s390/kvm/interrupt.c +++ b/arch/s390/kvm/interrupt.c @@ -1915,49 +1915,93 @@ 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 * 2) { + 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) { @@ -1974,6 +2018,8 @@ 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: @@ -1982,7 +2028,7 @@ 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