[Bug 206579] KVM with passthrough generates "BUG: kernel NULL pointer dereference" and crashes

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https://bugzilla.kernel.org/show_bug.cgi?id=206579

--- Comment #54 from Anthony (anthonysanwo@googlemail.com) ---
Created attachment 288227
  --> https://bugzilla.kernel.org/attachment.cgi?id=288227&action=edit
Kvm-anthony-warnings

(In reply to muncrief from comment #53)
> (In reply to Anthony from comment #52)
> > ...
> > Good news I finally managed to reproduce the same errors both in a test VM
> > and my current config.
> > ...
> 
> Whew! I'm glad someone else is able to see it as well. I was beginning to
> wonder if I was just doing something wrong.
> 
> Just to be clear though, this error occurs every time I start my VM. It
> doesn't even matter if I login to the VM, the warnings have already appeared
> by the time the login screen appears.
> 
> Anyway, as you said, hopefully your discovery that CPU pinning and
> -overcommit cpu-pm get rid of the warnings will help guide the devs to a
> solution.
> 

In terms of getting the warnings early in the boot phase. I did some more
testing today and found some more things. In terms of the warnings happening
around early in the booting phase as you described I got warnings in 8 out of
10 cases when booting and shutting down my test VM.

I also found the reason changing things like the core count/topology and
kernel_irqchip=on/off can delay were the first warning appears.

I attached my test config qemu launch args/libvirt config. As well as dmesg
although the errors are basically the same as muncrief's.

> Also, I'm feeling a bit under the weather so if I don't respond to requests
> for more info for a few days it's because I need to get some rest and get
> well. But if anyone needs anything else just let me know and I'll get on it
> as soon as possible.

Take care and hope for a speedy recovery :)

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