Re: [PATCH v1] qemu: monitor: substitute missing model name for host-passthrough

On 9/16/20 3:03 AM, Michal Privoznik wrote: > On 9/15/20 10:25 PM, Collin Walling wrote: >> One more ping in attempt to get this in the right direction. Otherwise >> I'll post my next idea and we can go from there :) > > I agree with Peter that while the idea might look correct it's too deep. > >> >> Thinking about this issue, should a host-passthough CPU definition be >> permitted for the baseline & comparison commands? The model represented >> under this mode is not considered migration safe and it may make sense >> to simply fail early since these commands aim to construct/determine a >> migratable CPU model, respectively. > > Honestly, I don't know much about this CPU models area, but is that true > even for two identical hosts? Say I have two desktops next to each > other, with the same CPU and I want to migrate. I could use host model, > couldn't I? > "Host-model" is an alias for a CPU model that closely represents the capabilities of the host machine (on s390, because this model is defined by the hypervisor, it can also be called the "hypervisor CPU model" -- not an important detail). However, a guest running with the host-passthrough mode is not considered migration safe as that guest may covertly run with features/capabilities that are not directly exposed to the hypervisor.

From what I understand regarding the hypervisor-cpu-compare and hypervisor-cpu-baseline commands is that they aim to assist with determining the migratability of guests based on their CPU model and feature set (usually along with a host CPU in the equation as well).