net: mana: Fix race on per-CQ variable napi work_done

After calling napi_complete_done(), the NAPIF_STATE_SCHED bit may be
cleared, and another CPU can start napi thread and access per-CQ variable,
cq->work_done. If the other thread (for example, from busy_poll) sets
it to a value >= budget, this thread will continue to run when it should
stop, and cause memory corruption and panic.

To fix this issue, save the per-CQ work_done variable in a local variable
before napi_complete_done(), so it won't be corrupted by a possible
concurrent thread after napi_complete_done().

Also, add a flag bit to advertise to the NIC firmware: the NAPI work_done
variable race is fixed, so the driver is able to reliably support features
like busy_poll.

Cc: [email protected]
Fixes: e1b5683ff62e ("net: mana: Move NAPI from EQ to CQ")
Signed-off-by: Haiyang Zhang <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Paolo Abeni <[email protected]>

0 files changed, 0 insertions, 0 deletions