On Thu, Jan 07, 2021 at 06:55:45PM -0500, Matt Coleman wrote:
> > On Nov 26, 2020, at 9:26 AM, Daniel P. Berrangé <berrange@xxxxxxxxxx> wrote:
> >
> > On Tue, Nov 24, 2020 at 02:48:31PM -0500, Matt Coleman wrote:
> >> + /* try to shut down the VM if it's not disabled, just to be safe */
> >> + if (computerSystem->data->EnabledState != MSVM_COMPUTERSYSTEM_ENABLEDSTATE_DISABLED &&
> >> + hypervDomainShutdown(domain) < 0) {
> >> + goto cleanup;
> >> + }
> >
> > Many, but not all, drivers in libvirt allow undefining the cofig for a running
> > VM. ie we can delete the config on disk, without affecting the running VM.
> > This results in a so called "transient" VM - basically a VM which only exists
> > as long as it is running - virDomainCreateXML creates such a beast, while
> > virDomainDefineXML+virDomainCreate creates a "persistent" VM and starts it.
> >
> > If hyperv doesn't allow that, then shutting down the VM is likely to be
> > surprising.
> >
> > I'd suggest we report an error indicating undefine is not permitted for a
> > running VM in such a case.
>
> Hyper-V does not allow a VM's definition to be deleted if it's active,
> paused, or in state transition.
>
> If I remove the check entirely, it displays an error including
> Hyper-V's method name, the error code from Hyper-V, and a string that's
> generated by hypervReturnCodeToString() from hyperv_wmi.c.
>
> For example, `virsh undefine runningvm` would throw the error:
>
> error: Failed to undefine domain runningvm
> error: internal error: Invocation of DestroySystem returned an error: Invalid state for this operation (32775)
>
> That simplifies the code significantly and provides details (the method
> name and error code) that users could look up in Microsoft's
> documentation. However, I don't think it's very clearly phrased.
> "Domain must not be active or in state transition" with the error code
> set to VIR_ERR_OPERATION_INVALID produces the following error output:
>
> error: Failed to undefine domain testvm
> error: Requested operation is not valid: Domain must not be active or in state transition
>
> It's a difference of 18 lines (51 vs 33). The shorter version
> eliminates the result and computerSystem variables, does not use goto,
> and only sends a single WMI request to Hyper-V since it does not have
> to query the VM state before attempting to undefine it.
Querying state ahead of time leaves a race condition, so either just
let hyperv fail, or catch the error when it fails and report a different
error mesage.
> Would you prefer to have simpler code or a custom error message?
I don't mind on that front.
Regards,
Daniel
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