Re: [PATCH v9 0/5] KVM statistics data fd-based binary interface

Paolo Bonzini
2021-06-15T07:06:51Z

On 15/06/21 07:25, Leon Romanovsky wrote:
> Sorry for my naive questions, but how does telemetry get statistics
> for hypervisors? Why is KVM different from hypervisors or NIC's statistics
> or any other high speed devices (RDMA) that generate tons of data?

Right now, the only way is debugfs but it's slow, and it's disabled when
using lockdown mode; this series is a way to fix this.

I sense that there is another question in there; are you wondering if
another mechanism should be used, for example netlink? The main issue
there is how to identify a VM, since KVM file descriptors don't have a
name. Using a pid works (sort of) for debugfs, but pids are not
appropriate for a stable API. Using a file descriptor as in this series
requires collaboration from the userspace program; howver, once the file
descriptor has been transmitted via SCM_RIGHTS, telemetry can read it
forever without further IPC, and there is proper privilege separation.

Paolo