On 04/03/2024 18:12, John Ogness wrote: > [...] >> The second question is how to simulate a panic context in a >> non-destructive way, so we can test the panic notifiers in CI, without >> crashing the machine. > > I'm wondering if a "fake panic" can be implemented that quiesces all the > other CPUs via NMI (similar to kdb) and then calls the panic > notifiers. And finally releases everything back to normal. That might > produce a fairly realistic panic situation and should be fairly > non-destructive (depending on what the notifiers do and how long they > take). > Hi Jocelyn / John, one concern here is that the panic notifiers are kind of a no man's land, so we can have very simple / safe ones, while others are destructive in nature. An example of a good behaving notifier that is destructive is the Hyper-V one, that destroys an essential host-guest interface (called "vmbus connection"). What happens if we trigger this one just for testing purposes in a debugfs interface? Likely the guest would die... [+CCing Michael Kelley here since he seems interested in panic and is also expert in Hyper-V, just in case my example is bogus.] So, maybe the problem could be split in 2: the non-notifiers portion of the panic path, and the the notifiers; maybe restricting the notifiers you'd run is a way to circumvent the risks, like if you could pass a list of the specific notifiers you aim to test, this could be interesting. Let's see what the others think and thanks for your work in the DRM panic notifier =) Cheers, Guilherme
