RE: [ndctl PATCH v2 4/4] ndctl, monitor: support NVDIMM_FAMILY_HYPERV

["qi.fuli@fujitsu.com" <qi.fuli@fujitsu.com>]

> 
> Hi Qi,
> Generally speaking, I agree with you, but here the fact is that we can only monitor this
> one single event "dimm-health-state" for Hyper-V Virtual NVDIMM, and the other
> events are meaningless for Hyper-V Virtual NVDIMM, as they're not supported by
> Hyper-V Virtual NVDIMM.
> 
> So, if the user specifies more events than just "dimm-health-state", or the user doesn't
> specify "dimm-health-state", it's reasonable to force monitor.event_flags to equal to
> ND_EVENT_HEALTH_STATE, and I explicitly print a warning.
> 
> The line "monitor.event_flags = ND_EVENT_HEALTH_STATE" only runs in a Linux VM
> running on Hyper-V. It can't adversely affect bare metal cases. In a Linux VM on
> Hyper-V, all the NVDIMMs appearing in the VM are Hyper-V Virtual NVDIMMs.
> 
> A physical NVDIMM can't be directly passed through to a VM and the hypervisors (e.g.,
> Xen, KVM, Hyper-V, Qemu, etc.) have to virtualize it to make it available to a VM. In a
> VM, the NVDIMM_FAMILY is NVDIMM_FAMILY_HYPERV only when the VM runs on
> Hyper-V.
> 
> So I think we should be good. :-)
> 
> Thanks,
> -- Dexuan

Hi Dexuan,

Thanks for your explanation.
I think at least we should document it into man page, so that the users could know that their options may be modified by monitor.
Though I have a little concern about that there may be other events for Hyper-V Virtual NVDIMM can be monitored in future...

Thanks
 Qi
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