* Anthony Liguori <anthony@xxxxxxxxxxxxx> wrote: > > - Easy default reference to guest instances, and a way for tools to > > reference them symbolically as well in the multi-guest case. Preferably > > something trustable and kernel-provided - not some indirect information > > like a PID file created by libvirt-manager or so. > > A guest is not a KVM concept. [...] Well, in a sense a guest is a KVM concept too: it's in essence represented via the 'vcpu state attached to a struct mm' abstraction that is attached to the /dev/kvm file descriptor attached to a Linux process. Multiple vcpus can be started by the same process to represent SMP, but the whole guest notion is present: a Linux MM that carries KVM state. In that sense when we type 'perf kvm list' we'd like to get a list of all currently present guests that the developer has permission to profile: i.e. we'd like a list of all [debuggable] Linux tasks that have a KVM instance attached to them. A convenient way to do that would be to use the Qemu process's ->comm[] name, and to have a KVM ioctl that gets us a list of all vcpus that the querying task has ptrace permission to. [the standard permission check we do for instrumentation] No need for communication with Qemu for that - just an ioctl, and an always-guaranteed result that works fine on a whole-system and on a per user basis as well. Thanks, Ingo -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
