On 31 May 2019, at 4:49, Björn Töpel wrote:

On 2019-05-30 20:57, Jonathan Lemon wrote:

quoted

Currently, the AF_XDP code uses a separate map in order to
determine if an xsk is bound to a queue.  Instead of doing this,
have bpf_map_lookup_elem() return the queue_id, as a way of
indicating that there is a valid entry at the map index.

Rearrange some xdp_sock members to eliminate structure holes.

Signed-off-by: Jonathan Lemon <redacted>
---
  include/net/xdp_sock.h                            |  6 +++---
  kernel/bpf/verifier.c                             |  6 +++++-
  kernel/bpf/xskmap.c                               |  4 +++-
  .../selftests/bpf/verifier/prevent_map_lookup.c   | 15 ---------------
  4 files changed, 11 insertions(+), 20 deletions(-)

diff --git a/include/net/xdp_sock.h b/include/net/xdp_sock.h
index d074b6d60f8a..7d84b1da43d2 100644
--- a/include/net/xdp_sock.h
+++ b/include/net/xdp_sock.h

@@ -57,12 +57,12 @@ struct xdp_sock {
  	struct net_device *dev;
  	struct xdp_umem *umem;
  	struct list_head flush_node;
-	u16 queue_id;
-	struct xsk_queue *tx ____cacheline_aligned_in_smp;
-	struct list_head list;
+	u32 queue_id;

Why the increase of size?

Currently xskmaps are defined as size=4, so the returned pointer for
bpf must have that many bytes.  I was kicking around the idea of using
a union and returning { qid, zc }, but Alexei pointed out that doesn't
make a good API.

Besides, queue_index in struct xdp_rxq_info is already a u32.
-- 
Jonathan