Re: [libvirt] [PATCH 1/1][RESEND] ppc64 cpu features

On Mon, Apr 22, 2013 at 17:38:23 +0800, Li Zhang wrote: > On 2013年04月22日 17:10, Jiri Denemark wrote: >> If you want to add powernv feature just because you need to distinguish >> if the host supports KVM or not, there's much better way... In guest >> section of capabilities XML, KVM support is indicated by <domain >> type='kvm'> element. And that's what existing apps already use to detect >> KVM presence/absence. > As my understanding, there is still some difference from 'kvm' capability. > 'powernv' is only considered as one CPU feature of PPC64. > If other PPC platforms support KVM in the future, this feature can be > used to identify whether migration can be executed . :) Well, as I already said, unless there is a way to explicitly enable/disable powernv feature in guest CPU, I don't see any reason for exposing the feature to users/apps. We definitely don't want apps/users to detect support for migration (or anything else) by checking host CPU features. If migration is not supported, then any migration API can fail with VIR_ERR_OPERATION_UNSUPPORTED. That said, powernv feature can be used internally by libvirt to check if some configurations/operations are supported but it doesn't have to be exposed to users/apps. The CPU driver stuff is there for configuring *guest* CPU.

Jirka