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

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