On Thursday 30 Mar 2023 at 15:43:37 (-0700), David Dai wrote: > This service allows guests to query the host for frequency of the CPU > that the vCPU is currently running on. I assume the intention here is to achieve scale invariance in the guest to ensure its PELT signals represent how much work is actually being done. If so, it's likely the usage of activity monitors will be superior for this type of thing as that may allow us to drop the baked-in assumption about vCPU pinning. IIRC, AMUs v2 (arm64-specific obv) have extended support for virtualization, so I'd suggest looking into supporting that first. And assuming we also want to support this on hardware that don't have AMUs, or don't have the right virt extensions, then the only thing I can think of is to have the VMM expose non-architectural AMUs to the guest, maybe emulated using PMUs. If the guest uses Linux, it'll need to grow support for non-architectural AMUs which is its own can of worms though. Thanks, Quentin
