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Thu, 20 Aug 2026 07:24:59 +0000 (GMT) Received: from [9.87.135.213] (unknown [9.87.135.213]) by smtpav03.fra02v.mail.ibm.com (Postfix) with ESMTP; Thu, 20 Aug 2026 07:24:59 +0000 (GMT) Message-ID: <43f7856a-dd03-407e-b8d8-a5534a9f10ca@linux.ibm.com> Date: Thu, 20 Aug 2026 09:24:58 +0200 Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 1/3] KVM: s390: Improve floating IRQ injection behavior To: sashiko-reviews@lists.linux.dev Cc: Heiko Carstens , Alexander Gordeev , linux-s390@vger.kernel.org, kvm@vger.kernel.org, Vasily Gorbik , Christian Borntraeger References: <20260819190408.247843-1-frankja@linux.ibm.com> <20260819190408.247843-2-frankja@linux.ibm.com> <20260819191317.2C7961F00A3A@smtp.kernel.org> Content-Language: en-US From: Janosch Frank Autocrypt: addr=frankja@linux.ibm.com; keydata= xsFNBFubpD4BEADX0uhkRhkj2AVn7kI4IuPY3A8xKat0ihuPDXbynUC77mNox7yvK3X5QBO6 qLqYr+qrG3buymJJRD9xkp4mqgasHdB5WR9MhXWKH08EvtvAMkEJLnqxgbqf8td3pCQ2cEpv 15mH49iKSmlTcJ+PvJpGZcq/jE42u9/0YFHhozm8GfQdb9SOI/wBSsOqcXcLTUeAvbdqSBZe zuMRBivJQQI1esD9HuADmxdE7c4AeMlap9MvxvUtWk4ZJ/1Z3swMVCGzZb2Xg/9jZpLsyQzb lDbbTlEeyBACeED7DYLZI3d0SFKeJZ1SUyMmSOcr9zeSh4S4h4w8xgDDGmeDVygBQZa1HaoL Esb8Y4avOYIgYDhgkCh0nol7XQ5i/yKLtnNThubAcxNyryw1xSstnKlxPRoxtqTsxMAiSekk 0m3WJwvwd1s878HrQNK0orWd8BzzlSswzjNfQYLF466JOjHPWFOok9pzRs+ucrs6MUwDJj0S cITWU9Rxb04XyigY4XmZ8dywaxwi2ZVTEg+MD+sPmRrTw+5F+sU83cUstuymF3w1GmyofgsU Z+/ldjToHnq21MNa1wx0lCEipCCyE/8K9B9bg9pUwy5lfx7yORP3JuAUfCYb8DVSHWBPHKNj HTOLb2g2UT65AjZEQE95U2AY9iYm5usMqaWD39pAHfhC09/7NQARAQABzSVKYW5vc2NoIEZy YW5rIDxmcmFua2phQGxpbnV4LmlibS5jb20+wsF3BBMBCAAhBQJbm6Q+AhsjBQsJCAcCBhUI CQoLAgQWAgMBAh4BAheAAAoJEONU5rjiOLn4p9gQALjkdj5euJVI2nNT3/IAxAhQSmRhPEt0 AmnCYnuTcHRWPujNr5kqgtyER9+EMQ0ZkX44JU2q7OWxTdSNSAN/5Z7qmOR9JySvDOf4d3mS bMB5zxL9d8SbnSs1uW96H9ZBTlTQnmLfsiM9TetAjSrR8nUmjGhe2YUhJLR1v1LguME+YseT eXnLzIzqqpu311/eYiiIGcmaOjPCE+vFjcXL5oLnGUE73qSYiujwhfPCCUK0850o1fUAYq5p CNBCoKT4OddZR+0itKc/cT6NwEDwdokeg0+rAhxb4Rv5oFO70lziBplEjOxu3dqgIKbHbjza EXTb+mr7VI9O4tTdqrwJo2q9zLqqOfDBi7NDvZFLzaCewhbdEpDYVu6/WxprAY94hY3F4trT rQMHJKQENtF6ZTQc9fcT5I3gAmP+OEvDE5hcTALpWm6Z6SzxO7gEYCnF+qGXqp8sJVrweMub UscyLqHoqdZC2UG4LQ1OJ97nzDpIRe0g6oJ9ZIYHKmfw5jjwH6rASTld5MFWajWdNsqK15k/ RZnHAGICKVIBOBsq26m4EsBlfCdt3b/6emuBjUXR1pyjHMz2awWzCq6/6OWs5eANZ0sdosNq dq2v0ULYTazJz2rlCXV89qRa7ukkNwdBSZNEwsD4eEMicj1LSrqWDZMAALw50L4jxaMD7lPL jJbazsFNBFubpD4BEADAcUTRqXF/aY53OSH7IwIK9lFKxIm0IoFkOEh7LMfp7FGzaP7ANrZd cIzhZi38xyOkcaFY+npGEWvko7rlIAn0JpBO4x3hfhmhBD/WSY8LQIFQNNjEm3vzrMo7b9Jb JAqQxfbURY3Dql3GUzeWTG9uaJ00u+EEPlY8zcVShDltIl5PLih20e8xgTnNzx5c110lQSu0 iZv2lAE6DM+2bJQTsMSYiwKlwTuv9LI9Chnoo6+tsN55NqyMxYqJgElk3VzlTXSr3+rtSCwf tq2cinETbzxc1XuhIX6pu/aCGnNfuEkM34b7G1D6CPzDMqokNFbyoO6DQ1+fW6c5gctXg/lZ 602iEl4C4rgcr3+EpfoPUWzKeM8JXv5Kpq4YDxhvbitr8Dm8gr38+UKFZKlWLlwhQ56r/zAU v6LIsm11GmFs2/cmgD1bqBTNHHcTWwWtRTLgmnqJbVisMJuYJt4KNPqphTWsPY8SEtbufIlY HXOJ2lqUzOReTrie2u0qcSvGAbSfec9apTFl2Xko/ddqPcZMpKhBiXmY8tJzSPk3+G4tqur4 6TYAm5ouitJsgAR61Cu7s+PNuq/pTLDhK+6/Njmc94NGBcRA4qTuysEGE79vYWP2oIAU4Fv6 gqaWHZ4MEI2XTqH8wiwzPdCQPYsSE0fXWiYu7ObeErT6iLSTZGx4rQARAQABwsFfBBgBCAAJ BQJbm6Q+AhsMAAoJEONU5rjiOLn4DDEP/RuyckW65SZcPG4cMfNgWxZF8rVjeVl/9PBfy01K 8R0hajU40bWtXSMiby7j0/dMjz99jN6L+AJHJvrLz4qYRzn2Ys843W+RfXj62Zde4YNBE5SL jJweRCbMWKaJLj6499fctxTyeb9+AMLQS4yRSwHuAZLmAb5AyCW1gBcTWZb8ON5BmWnRqeGm IgC1EvCnHy++aBnHTn0m+zV89BhTLTUal35tcjUFwluBY39R2ux/HNlBO1GY3Z+WYXhBvq7q katThLjaQSmnOrMhzqYmdShP1leFTVbzXUUIYv/GbynO/YrL2gaQpaP1bEUEi8lUAfXJbEWG dnHFkciryi092E8/9j89DJg4mmZqOau7TtUxjRMlBcIliXkzSLUk+QvD4LK1kWievJse4mte FBdkWHfP4BH/+8DxapRcG1UAheSnSRQ5LiO50annOB7oXF+vgKIaie2TBfZxQNGAs3RQ+bga DchCqFm5adiSP5+OT4NjkKUeGpBe/aRyQSle/RropTgCi85pje/juYEn2P9UAgkfBJrOHvQ9 Z+2Sva8FRd61NJLkCJ4LFumRn9wQlX2icFbi8UDV3do0hXJRRYTWCxrHscMhkrFWLhYiPF4i phX7UNdOWBQ90qpHyAxHmDazdo27gEjfvsgYMdveKknEOTEb5phwxWgg7BcIDoJf9UMC In-Reply-To: <20260819191317.2C7961F00A3A@smtp.kernel.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Authority-Analysis: v=2.4 cv=MthiLWae c=1 sm=1 tr=0 ts=6a86abd0 cx=c_pps a=bLidbwmWQ0KltjZqbj+ezA==:117 a=bLidbwmWQ0KltjZqbj+ezA==:17 a=IkcTkHD0fZMA:10 a=Sv0fKeRqtYgA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=U7nrCbtTmkRpXpFmAIza:22 a=VwQbUJbxAAAA:8 a=VnNF1IyMAAAA:8 a=xrtE07GcD8d4jnkWsSQA:9 a=QEXdDO2ut3YA:10 X-Proofpoint-ORIG-GUID: HLgb8-yv2yQxduJGd74Ce5fqTyoivbL7 X-Proofpoint-GUID: HLgb8-yv2yQxduJGd74Ce5fqTyoivbL7 X-Proofpoint-Spam-Info: AW1haW4tMjYwODIwMDA0OSBTYWx0ZWRfX3u2MdKsolsBe bje6O/uvOhtUgcAMbLxAABLt9QZujzRD9ayj+7/OpxPZlDgOJC1CVcP8zuuRKx16Be+wV0p8K0B rbvwS66wk9DGbM7M3vJ2H8gFXCoZly0= X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwODIwMDA0OSBTYWx0ZWRfX+5Dsvgna6CgF gCUZHyq+EcTi8E9WYh/UrsLbX0NlU3ubA7f4TUE3YgBTbpXFCoB6GhFckItGRJLI8Z/cSQ/H03Q zD3eAUP3CWbYH0KEl7Cr3rJQclOLfbVJkDMG14xUzFkpStev18kMX2grPUDGiAvrY77yn4dSlrk SOrFCEBrg0T6Wek+JED4mpf6SgZqyjMWq8iTFCXizxDsjtF7Tf8BkUSTm346PvGNii3USVRPn5F X14Fa45sUnv+rBkRWYvAetEP8dPs+OUUOeI1q96JgH6hbOyZ8U4KfjNTslxmqAgqqFuArdIErb+ sO8ERgNAg6hbpOJNSL2DcN98DtizbfNezWzmCJ//z3r4iUMA9IQOygY23WAGQuEOYS0rakNRpM7 U/XlZZDCUweHotFo5uKxkGI3FYZToV6ebIAWRGcawQH3OVm/wUst8TW6vEmB4P1ZDr/pa7t184x aZklDYzZvhaRjhGtA2Q== 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-2608200049 On 8/19/26 9:13 PM, sashiko-bot@kernel.org wrote: > Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider: > - [High] Incorrect bitmask computation for floating I/O interrupts causes thundering herd performance regressions or lost wakeups. > -- > > --- Patch [1]: [PATCH v3 1/3] KVM: s390: Improve floating IRQ injection behavior --- > commit 8a0b82ce7a926dc2db73a2448ac2bcc105213707 > Author: Janosch Frank > > KVM: s390: Improve floating IRQ injection behavior > > This commit improves floating IRQ injection by checking if a VCPU has pending > IRQs instead of blindly waking up the last VCPU that went to sleep. This aims > to prevent deadlocks when a VCPU is sleeping without an open mask. > >> diff --git a/arch/s390/kvm/interrupt.c b/arch/s390/kvm/interrupt.c >> index 8f24bcd1a6d36..3af060ec5be8e 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 isc_to_irq_type(isc); > > [Severity: High] > Does this correctly return a bitmask? The other cases return BIT() masks, but > this returns a raw integer resulting from isc_to_irq_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 = isc_to_irq_type(int_word_to_isc(inti->io.io_int_word)); > > [Severity: High] > Are we applying isc_to_irq_type() twice for I/O interrupts? > > This converts the ISC to an IRQ bit index before assigning it to `isc`. Later, > __floating_irq_kick() passes it to inti_to_irq_pend_mask(), which calls > isc_to_irq_type() a second time on the same value. > > Since isc_to_irq_type() is implemented as `IRQ_PEND_IO_ISC_0 - isc`, calling it > twice will reverse the calculation and yield the original ISC value instead > of the expected IRQ bit index. Rebase damage, will fix both.