Re: [libvirt] [PATCH] PowerPC : Do not allow an empty model spec for 'host-model'

On Friday 20 March 2015 01:51 PM, Ján Tomko wrote: Hi Jan, This commit does not break anything. It addresses a few corner cases not completely addressed by commits addce06 & 5e4f49ab8aa2. PowerPC pseries KVM is a paravirtualized platform, wherein there are only 2 allowed vcpu configurations of running a guest : 1) Native mode, where the guest sees the same vcpu model as the host -- this is reflected in libvirt by "host-passthrough" mode; 2) Compat mode, where the physical processor itself runs in binary compatibility with an older cpu model. This is marked in libvirt by "host-model" mode, which takes on an additional argument -- the guest CPU model which needs to be run. This was introduced by commit addce06. PowerKVM, being a paravirt platform, does not emulate a guest vcpu based on features copied from host. This behaviour is unlike x86 KVM. Hence , the host-model mode on PowerKVM needs to error out in case the model which needs to be run in binary compatibility is not specified by user. The reason for this commit was a bug seen even after 5e4f49ab8aa2. A null cpu model XML was causing an incorrect "best-fit" model (just like x86) to be passed to the VM after a save/restore. Hence the need for this check. Regards, -- Prerna Saxena Linux Technology Centre, IBM Systems and Technology Lab, Bangalore, India