kern/57358: panic: kernel diagnostic assertion "ret == 0" failed: file "/home/riastradh/netbsd/current/src/sys/dev/virtio/viocon.c", line 458

[campbell+netbsd%mumble.net@localhost]

>Number:         57358
>Category:       kern
>Synopsis:       panic: kernel diagnostic assertion "ret == 0" failed: file "/home/riastradh/netbsd/current/src/sys/dev/virtio/viocon.c", line 458
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sun Apr 16 18:15:01 +0000 2023
>Originator:     Taylor R Campbell
>Release:        current
>Organization:
The NetBSD Condation
>Environment:
>Description:
# cu -l /dev/ttyVI00
Connected
[  47.4172685] panic: kernel diagnostic assertion "ret == 0" failed: file "/home/riastradh/netbsd/current/src/sys/dev/virtio/viocon.c", line 458
[  47.4172685] cpu0: Begin traceback...
[  47.4172685] trace fp ffffc000bf0279a0
[  47.4172685] fp ffffc000bf0279d0 vpanic() at ffffc000005d23a8 netbsd:vpanic+0x178
[  47.4172685] fp ffffc000bf027a30 kern_assert() at ffffc0000086dc28 netbsd:kern_assert+0x58
[  47.4172685] fp ffffc000bf027ac0 vioconstart() at ffffc000003e5050 netbsd:vioconstart+0x200
[  47.4172685] fp ffffc000bf027b30 ttwrite() at ffffc000005fb7d8 netbsd:ttwrite+0x284
[  47.4172685] fp ffffc000bf027c00 cdev_write() at ffffc000005b9698 netbsd:cdev_write+0x88
[  47.4172685] fp ffffc000bf027c50 spec_write() at ffffc0000065d724 netbsd:spec_write+0xe4
[  47.4172685] fp ffffc000bf027ce0 VOP_WRITE() at ffffc0000064de24 netbsd:VOP_WRITE+0x130
[  47.4172685] fp ffffc000bf027d50 vn_write() at ffffc00000644ea8 netbsd:vn_write+0x108
[  47.4172685] fp ffffc000bf027da0 dofilewrite() at ffffc000005e4bc0 netbsd:dofilewrite+0x70
[  47.4172685] fp ffffc000bf027e20 syscall() at ffffc000000b424c netbsd:syscall+0x19c
[  47.4172685] tf ffffc000bf027ed0 el0_trap() at ffffc000000b77f0 netbsd:el1_trap_exit+0x68
[  47.4172685] ---- SVC Instruction Execution: trapframe 0xffffc000bf027ed0 (304 bytes) ----

>How-To-Repeat:
# add to GENERIC
viocon* at virtio?

# run on host
qemu-system-* ... -device virtio-serial -chardev socket,path=/tmp/ttyVI00,server=on,wait=off,id=ttyVI00 -device virtconsole,chardev=ttyVI00,name=org.NetBSD.dev.ttyVI00 ...

# run in guest
cu -l /dev/ttyVI00
>Fix:
Yes, please!