Re: Networking test runs run-vmm twice with the same VM ID

[Alyssa Ross <hi@alyssa.is>]

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Demi Marie Obenour <demiobenour@gmail.com> writes:

> On 7/16/26 04:29, Alyssa Ross wrote:
>> Demi Marie Obenour <demiobenour@gmail.com> writes:
>> 
>>> The networking test runs run-vmm twice with the same VM ID.
>>> If it waits for the previous cgroup to be empty, the second
>>> call waits forever.
>>>
>>> Is this expected?  I would expect that run-vmm is only called
>>> once.
>> 
>> Assuming you mean run twice in sequence, rather than run twice at the
>> same time, then yes, it is expected.
>> 
>> The way it works at the moment is that imported VMs have a VM ID
>> assigned when they're imported, and they can then be started any number
>> of times.  When the VM shuts down, the VMM exits, so if the VM is
>> started again after that, run-vmm will be run again with the same VM ID.
>> If this were not the case, VM IDs could not be assigned at import time,
>> and stay the same between successive boots of the same VM.
>> 
>> If your cgroup is not being emptied as expected, that is a bug,
>> regardless of whether it ends up being used again, because there
>> shouldn't be lingering processes or cgroups hanging around forever.
>> It sounds like we should have a test that confirms that this doesn't
>> happen, if it's hard to get right.
>> 
>> The networking test does do something slightly unusual, which is that it
>> restarts the VMM with s6-svc -Wr -r, rather than e.g. via the Cloud
>> Hypervisor API.  I would expect that this runs the finish script, but
>> might be worth confirming.
>
> What should happen if run-vmm is run more than once for the same VM?

At the same time?  That shouldn't happen.  That can either be ensured
outside of run-vmm or inside it — I don't think that every time we
factor out a common script it needs to add a new check that it's being
used correctly, or the codebase will end up all usage checks.

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