Re: [libvirt] [RFC PATCH v2 3/3] qemu: memory pre-pinning support for RDMA migration

On 04/04/2014 12:29 AM, Michael R. Hines wrote: > Yes, it's present, but it still does not guarantee that QEMU supports > it if RDMA was compiled out - only the version number is a > (minimal) guarantee, and even then the hardware can still throw > an error if RDMA itself is not supported. Which sounds like you want a feature test (is it supported in the build you are talking to, answer is always correct) and not a version test (is the build you are talking to new enough to possibly have the feature, but if you guess wrong you may get an error from the hardware) > I'm still not seeing what's wrong with depending on the version > number since other features are also depending on the version > number. Every feature where we have to guess based on version number is due to a bug in qemu for not providing enough information for libvirt to probe for the feature's existence. We hate those features, and I have been lobbying hard on the qemu list that all NEW features should be discoverable. rdma is one such feature - I recall you making changes in your series there so that it is discoverable in response to my early review comments - so now please USE that methodology from libvirt.