On Fri, 2019-02-08 at 15:17 -0800, Saeed Mahameed wrote:

On Thu, 2019-02-07 at 19:08 +0000, Saeed Mahameed wrote:

quoted

So 
1) on dev_map_update_elem() we will call
dev->dev->ndo_bpf() to notify the device on the intention to
start/stop
redirect, and wait for it to create/destroy the HW resources
before/after actually updating the map

silly me, dev_map_update_elem must be atomic, we can't hook driver
resource allocation to it, it must come as a separate request
(syscall)
from user space to request to create XDP redirect resources.

Well, it is possible to render dev_map_update_elem non-atomic and fail
BPF programs who try to update it in the verifier
check_map_func_compatibility.

if you know of any case where devmap needs to be updated from the BPF
program please let me know.