Re: [libvirt] What is the strategy to update the CPU Models in src/cpu/cpu_map.xml based on?

On Wed, May 30, 2018 at 18:55:02 +0800, Dou Liyang wrote: > Hi Jiri, > > At 05/30/2018 06:14 PM, Jiri Denemark wrote: >> [Dropping random people from Cc] >> >> On Wed, May 30, 2018 at 18:00:56 +0800, Dou Liyang wrote: >>> Hi All, >>> >>> I am not sure about the update strategy of CPU models in libvirt. >>> >>> IMO, It's depend on the CPU model in qemu-kvm, if some CPU models >>> were updated in qemu-kvm. Then, we should modify the src/cpu/cpu_map.xml >>> of libvirt to synchronize? >> >> No, we never change existing CPU models in cpu_map.xml to make sure the >> same CPU model is the same across libvirt versions. Not to mention that >> QEMU only changes existing CPU models for new machine type (for the same >> compatibility reason) so we can't just change our CPU models since we >> don't know what machine type their going to be used with. Libvirt will >> handle the differences in runtime by remembering any additionally >> enabled or disabled features once domain starts to make sure the exact >> same CPU is recreated after, e.g., migration. >> > > I see. > > Btw, If we found there is a wrong feature in the existing CPU models, > what should we do? What do you mean by wrong feature?

> If we add a new CPU model, what we refer to? CPU models spec or > hypervisors' code(eg, qemu-kvm) QEMU code for CPU model and if new CPUID features are required for that model the CPU vendor's specification of the new features is useful too.

Jirka