Hi, I had the same issue a few days ago a server hardware of mine. I just ran 'cvs up'. So, it looks like a generic bug in FFS and not related to vmm.
OpenBSD 6.9-beta (GENERIC.MP) #396: Thu Mar 11 19:15:56 MST 2021 dera...@amd64.openbsd.org:/usr/src/sys/arch/amd64/compile/GENERIC.MP ciao, Jan ddb{2}> show panic ffs_valloc: dup alloc ddb{2}> trace db_enter() at db_enter+0x10 panic(ffffffff81dda170) at panic+0x12a ffs_inode_alloc(fffffd8a1acb50f0,81a4,fffffd8c3f7ba120,ffff8000229d3088) at ffs _inode_alloc+0x442 ufs_makeinode(81a4,fffffd8a8a498940,ffff8000229d3380,ffff8000229d33d0) at ufs_m akeinode+0x7f ufs_create(ffff8000229d3130) at ufs_create+0x3c VOP_CREATE(fffffd8a8a498940,ffff8000229d3380,ffff8000229d33d0,ffff8000229d3190) at VOP_CREATE+0x4a vn_open(ffff8000229d3350,602,1a4) at vn_open+0x182 doopenat(ffff800022915500,ffffff9c,cc7a0280ad0,601,1b6,ffff8000229d3550) at doo penat+0x1cd syscall(ffff8000229d35c0) at syscall+0x389 Xsyscall() at Xsyscall+0x128 end of kernel end trace frame: 0x7f7ffffc5520, count: -10 ddb{2}> ps PID TID PPID UID S FLAGS WAIT COMMAND *56226 366608 70629 0 7 0x100003 cvs