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Peter Anvin" , Matthew Rosato , Farhan Ali , Eric Farman , Tony Krowiak , Halil Pasic , Jason Herne , Harald Freudenberger , Holger Dengler , Alex Williamson Cc: kvm@vger.kernel.org, linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org, Jason Gunthorpe References: <20260928-vfio-v4-0-e32e226d5932@linux.ibm.com> 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: <20260928-vfio-v4-0-e32e226d5932@linux.ibm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-Reinject: loops=2 maxloops=12 X-Proofpoint-ORIG-GUID: quLO0xM_1oMRqiXW3cFGDE3eQ7IMAgQE X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwOTI5MDA1MiBTYWx0ZWRfX1sjNKxg0FxFF dS2yCFbYRNn7u3CmLfE9wPqLAp4nRB6teBLYqXj3M9uV3Kw7ZFYHIdeXcEyA+G/oGKEH7xelwdq CHQH4Y62L+76pe2S7xx2UZr5gbrzeBHwAnc+IrjRmqpdR8XjMMuOmTKUFRKeO8+tKYPrTaTACrH 90ccSrioAtn7hH4LB024XnWFe38gzEBhHZwDxy72m2N4FP1Fzni7PtsGjVZwFcBsYthvP/UF7QH g7u1S/V+NCECVyGO4wxXCa+t+DKb/RX4qPif21d3Z98shrbR96B6c3g9XNPJxkZJ8zKYFDrnf+Y qoGJGvp62+plKvlFtq1hyy2c3GsEIQvv25gVuz21TtGX6hvwyJFt1VtxX8mr0MFUazGOvwmABMq 4fLPgfrMFHLcEcR/Lg35aihyUPxBE4KHCB4fOQ3yXpABfna7jh74fdnnpRpWjJeA6u8MxgoKJJR EfZjPca6t6wL2WpH8WA== X-Proofpoint-Spam-Info: AW1haW4tMjYwOTI5MDA1MiBTYWx0ZWRfXyLHiNOcW/jp4 BruZvu48upL1P/uDTY81fmSbSJgoZ6P+TmIt9rw/hzYijf9/M3lh8q92/B2aC9nZ82BH1hnI2ia Dj14UKniUwNN0WqFcOLAw+pVpvfNdIY= X-Authority-Analysis: v=2.4 cv=EY5d0/mC c=1 sm=1 tr=0 ts=6abbb7ab cx=c_pps a=bLidbwmWQ0KltjZqbj+ezA==:117 a=bLidbwmWQ0KltjZqbj+ezA==:17 a=IkcTkHD0fZMA:10 a=VdqzKS8jKosA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=RzCfie-kr_QcCd8fBx8p:22 a=VnNF1IyMAAAA:8 a=k4G1AkHzgUvhF1Ut7VEA:9 a=QEXdDO2ut3YA:10 X-Proofpoint-GUID: Hn9TX-Ez48Wm7k5Rrepn29YU2GLjTC5a 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=2026-09-29_04,2026-09-21_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=1011 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-2609290052 On 9/28/26 3:07 PM, Steffen Eiden wrote: > This series switches the KVM-VFIO interface and external consumers over to > standard file-based reference counting, eliminating all external KVM symbol > exports. > > This is a spin-off for the arm on s390 series (old version: [1]) to > address all the relevant persons w/o polluting their mailbox. The > arm-on-s390 series now dropped those patches and depends on this series > (for beeing able to link with KVM=y) > > Currently, VFIO integrates with KVM by looking up kvm_get_kvm_safe() and > kvm_put_kvm() dynamically using symbol_get(), manually tracking module > reference counts and storing a put_kvm function pointer in struct > vfio_device. > > In the ARM64-on-s390 architecture, a second concurrent KVM module > (kvm-arm64) is introduced alongside native KVM to host hardware-accelerated > ARM64 guests. Having exported global symbols (like kvm_get_kvm/kvm_put_kvm) > creates symbol conflicts and prevents clean coexistence of two KVM modules. > > Additionally, the file based counting simplifies the code and reuses > the existing fs refcounting. > > Instead of passing raw KVM pointers and managing module symbols manually, the > interface now passes the underlying VM file descriptor throughout VFIO and > associated architecture subsystems. To safely extract the KVM instance from a > file, an architecture-namespaced helper mechanism is introduced that verifies > the file belongs to the expected KVM implementation before accessing its > internal state. A back-pointer from the KVM instance to its associated file is > maintained across its lifecycle so subsystems can safely acquire file > references on demand. Finally, with VFIO, architecture page tracking, and > device hooks converted to use file references, the remaining KVM reference- > counting exports are restricted strictly to internal KVM modules. > > Steffen Series Acked-by: Janosch Frank