On Wed, Mar 15, 2017 at 03:06:33PM +0100, Andrew Jones wrote: > On Wed, Mar 15, 2017 at 02:36:45PM +0100, Christoffer Dall wrote: > > > If QEMU wants to know > > > whether or not the host it's running on is heterogeneous, then > > > it can just query sysfs, rather than ask KVM. > > > > > > > Can it? Is this information available in a reliable way from userspace? > > I don't know much (anything) about it, but, afaict, yes. See > https://lkml.org/lkml/2017/1/19/380 The "capacity" of a CPU does *not* tell you if your system is hetereogeneous. Two vastly different CPU implementations can stumble upon the same capacity, and two identical implementations could be assigned close but not identical capacities. The "capacity" is purely a scheduler heuristic, and should not be relied upon for functional correctness. We have a sysfs interface to see the MIDR and REVIDR of (online) CPUs, which can tell you. See Documentation/arm64/cpu-feature-registers.txt. Whether a system is heterogeneous can change at runtime, as CPUs can be brought online very late (e.g. if booted with maxcpus capped, or if we get "real" hotplug in future). Thanks, Mark. _______________________________________________ kvmarm mailing list kvmarm@xxxxxxxxxxxxxxxxxxxxx https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
