26.7.3 boot loop on Hyper-V guest -- anyone else?

[iorx]

Upgraded a Hyper-V VM (gen 2, synthetic NIC) from 26.7.2 to 26.7.3 and hit a restart loop. No panic output captured -- reverted to snapshot before I could gather logs.

Running: Windows Server Hyper-V, OPNsense amd64, VLANs on synthetic adapters (hn0--hn5).

Has anyone else on Hyper-V seen this with 26.7.3?

Was able to get this, it just flashes by... and then restart. Reverted back a snapshot of .2 to get it running again.

[Monviech (Cedrik)]

Whats your processor architecture? Intel, AMD, which generation?

This could be related or not, cannot see the backtrace.
https://github.com/opnsense/src/issues/297

[iorx]

Host:
Windows Server 2025 Standard (Build 26100), Hyper-V Generation 2 guest.

Host CPU:
AMD64 Family 23 Model 113 Stepping 0 (Zen 2 / Ryzen 7 3700X, ~3573 MHz). BIOS AMI P4.10 (2021-05-18).

Guest config:
8 vCPU, 5 GB static RAM, 6 synthetic NICs (vmbus/hn), VLANs handled via Hyper-V Access mode per adapter. No SR-IOV assigned to guest.

Relevant tunables active at time of upgrade:

debug.kassert.warn_only = 1
net.inet.rss.enabled = 1
net.inet.rss.bits = 3 (8 RSS queues matching 8 vCPUs)
net.isr.maxthreads = -1

I'm going to check your link, looks interesting. Trying to get a chance to turn it of and change vCPU to one.

[iorx]

Some more info.

Tried 26.7.3_8, showed the same problem.

Updated another system which went well:
Intel i7-8559U, 3 vCPU, I219-LM, Windows Server 2025

Claudes take on the information provided on the troublesome upgrade:
Both are Hyper-V Gen 2, Windows Server 2025, synthetic NICs (vmbus/hn), static RAM.

Worth noting: the AMD guest ran 26.7.2 (FreeBSD 15.1-p2) stably for weeks with the same 8-vCPU and RSS configuration. The boot loop only appeared with 26.7.3 (p3), which suggests a regression introduced in p2 → p3 rather than a pre-existing Hyper-V SMP issue. This also makes the Issue #297 link less likely to be the root cause, since that was reported against RC1 (p1) and should have manifested earlier.

Next planned test: disable RSS (net.inet.rss.enabled=0) before retrying the upgrade, to isolate whether RSS or vCPU count is the deciding factor.

Can't test this right now, but can give it a shoot on Sunday. That and the vCPU=1, but that should have shown for 26.7 already as I understand it.