Re: [PATCH v3] wifi: mac80211: fix monitor mode frame capture for real chanctx drivers

[Devin Wittmayer]

Hi Johannes,

Apologies for the nesting -- I'll keep replies top-level from here.

On 19 May 2026 00:02 (CEST), Johannes Berg wrote:
> I'm sure we can basically get rid of the "emulate" check now

Agreed. v4 will drop it.

> So what changed? Could you do some investigation if mt76 got bugfixes
> in this area perhaps? Or are you just using slightly different devices
> than Oscar?

Same chip family. Oscar's MT7921U/MT7921AUN (0e8d:7961) matches my v3
rigs (mt7921e PCIe, mt7921u USB, Kali VM with MT7921U passthrough).

mt76 has had three chanctx-touching commits since 2025-12-16 (de62b24224ac
"abort ROC on chanctx changes", f0fb9afb74ec "check chanctx before
restoring channel after ROC", 381733b3a14a "nullfunc PS on offchannel
transitions"). None touches ieee80211_monitor_start_xmit or the
chanctx_list lookup v3 does.

I think it's the reproducer environment. Back in March I matched Oscar's
stack -- Kali 6.18.12, fjh1997 v2 applied, MT7921U passthrough, airgeddon
evil twin, aireplay-ng deauth into the monitor VIF. No crash. The one
variable I couldn't match was the hypervisor: I used QEMU/KVM, Oscar
hasn't said. The symptoms (instant VM freeze on deauth start) read more
like a hypervisor USB-proxy stall than a kernel hang.

I'll send v4 with the collapse.

Devin