On 04.02.26 08:00, Wei Liu wrote: > On Tue, Feb 03, 2026 at 05:01:30PM +0100, Jan Kiszka wrote: >> From: Jan Kiszka <[email protected]> >> >> Resolves the following lockdep report when booting PREEMPT_RT on Hyper-V >> with related guest support enabled: > > So all it takes to reproduce this is to enabled PREEMPT_RT? >
...and enable CONFIG_PROVE_LOCKING so that you do not have to wait for your system to actually run into the bug. Lockdep already triggers during bootup. > Asking because ... > >> struct pt_regs *old_regs = set_irq_regs(regs); >> @@ -158,8 +196,12 @@ DEFINE_IDTENTRY_SYSVEC(sysvec_hyperv_callback) >> if (mshv_handler) >> mshv_handler(); > > ... to err on the safe side we should probably do the same for > mshv_handler as well. > Valid question. We so far worked based on lockdep reports, and the mshv_handler didn't trigger yet. Either it is not run in our setup, or it is actually already fine. But I have a code review on my agenda regarding potential remaining issues in mshv. Is there something needed to trigger the mshv_handler so that we can test it? > Note we don't support RT yet, but if issues are found we might as well > just fix them up. This is actually not about RT itself but about supporting all configurable locking semantics of the. And the mshv drivers fail here. > > How urgent do you want this patch to get applied? If I asked my folks: yesterday (we shipped it...). We would also need in upstream stable and stable-rt, though it may not reach the current production kernel anymore (6.1-rt from bookworm) because it reaching EOL in a few months. Jan -- Siemens AG, Foundational Technologies Linux Expert Center
