nvme-tcp bricks my computer

[Sagi Grimberg]

> Hi Sagi,
> 
> I was able to capture a bit more info. Again, because my computer 
> freezes (i.e. no keyboard or mouse response) I could only take a picture 
> of the screen (attached). This does say NULL pointer dereference.
> 
> To answer your questions:
> 
> Q) Does this happen if you directly connect to a normal nvme controller?
> A) I still need to try this. All I know is that it doesn't happen when 
> the controller returns OAES[31]=0.
> 
> Q) What is your target implementation? Is this the nvme target thatis 
> built into Linux?
> A) I work for Dell, and I'm on the same team as Douglas Farley and Erik 
> Smith, whom I believe you've had discussions with. Dell is currently 
> developing a Central Discovery Controller (CDC). That's the target I've 
> been testing with. I need to find different targets I can test with but 
> working from home makes it a bit difficult. I will check with my team 
> tomorrow to see if I can connect to a different target.
> 
> Q) Can you share your kernel config file?
> Q) Can you run gdb on vmlinux and share what this provides?
> A) I'll get that tomorrow (both questions).

For the record, I compiled Fedora 33 kernel and ran it on my VM
and it doesn't happen. I also modified Linux nvme target to
report the same limits as your target and still it doesn't happen.
--
[  162.006049] nvme nvme0: Failed to read smart log (error 24577)
[  162.006060] nvme nvme0: queue_size 128 > ctrl sqsize 32, clamping down
[  162.006063] nvme nvme0: sqsize 32 > ctrl maxcmd 31, clamping down
[  162.006778] nvme nvme0: new ctrl: NQN 
"nqn.2014-08.org.nvmexpress.discovery", addr 192.168.123.1:8009
[  162.008939] nvme nvme0: Removing ctrl: NQN 
"nqn.2014-08.org.nvmexpress.discovery"
--

So something here seems to be specific to your env.