Prompted by Sean’s comment on a different thread:
* nova has a policy of not allowign any use of raw qemu args
I’ve seen this come up a number of times, but I don’t recall seeing the justification for this policy.
On 27/11/2025 13:25, Nathan Harper wrote: there are 2 reasons for this First i marks the domain as tainted form the libvirt perspective so in some distros like rhel that woudl make the domain unsupproted form a rhel level. but the primary reason is because the qemu command line interface is not stable and we have selected libvirt to provider a stabel api over qemu and the other hypervisors it supports. this allows us to supprot a wide variaty of distos and qemu versoin by leverageing the sable api provided by libvirt.
We are looking at a scenario where we (as an operator) want to add some specific additional qemu flags to some VMs, but we’re now having to run a local Nova patch to achieve this (experiments with libvirt-hooks haven’t proven fruitful. we also do not supprot libvirt hooks
so while you coudl try to use them we woudl not consider any break of that as a nova bug so you are tacking a technical risk by using a feature of libvirt that we do not support operators using. we being upstream nova in this case.
I can see why we wouldn’t want users to add arbitrary flags, but an unsupported YMMV option in Nova would be helpful
did you test the flavor options i suggested to see fi that resovel the issue?
--
Regards,
Nathan Harper
Principal Engineer – Cloud Development
Platform Engineering
_nathanh@graphcore.ai_
_www.graphcore.ai → <http://www.graphcore.ai/>_
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