i40e/i40evf: Add tracepoints
This patch adds tracepoints to the i40e and i40evf drivers to which BPF programs can be attached for feature testing and verification. It's expected that an attached BPF program will identify and count or log some interesting subset of traffic. The bcc-tools package is helpful there for containing all the BPF arcana in a handy Python wrapper. Though you can make these tracepoints log trace messages, the messages themselves probably won't be very useful (other to verify the tracepoint is being called while you're debugging your BPF program). The idea here is that tracepoints have such low performance cost when disabled that we can leave these in the upstream drivers. This may eventually enable the instrumentation of unmodified customer systems should the need arise to verify a NIC feature is working as expected. In general this enables one set of feature verification tools to be used on these drivers whether they're built with the kernel or separately. Users are advised against using these tracepoints for anything other than a diagnostic tool. They have a performance impact when enabled, and their exact placement and form may change as we see how well they work in practice for the purposes above. Change-ID: Id6014a7322c0e6d08068114dd20bd156f2f6435e Signed-off-by: Scott Peterson <scott.d.peterson@intel.com> Tested-by: Andrew Bowers <andrewx.bowers@intel.com> Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
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