Re: [net-next,5/8] cadence: macb: add XDP support for gem
From: Jakub Kicinski <kuba@kernel.org>
Date: 2026-01-19 19:36:26
This is an AI-generated review of your patch. The human sending this email has considered the AI review valid, or at least plausible. For local reproduction steps see https://netdev-ai.bots.linux.dev/ai-local.html --- cadence: macb: add XDP support for gem This commit introduces XDP support for the macb/gem driver with XDP_PASS, XDP_DROP, and XDP_REDIRECT verdicts.
quoted hunk ↗ jump to hunk
diff --git a/drivers/net/ethernet/cadence/macb_main.c b/drivers/net/ethernet/cadence/macb_main.c index 89f0c4dc3884..1f62100a4c4d 100644 --- a/drivers/net/ethernet/cadence/macb_main.c +++ b/drivers/net/ethernet/cadence/macb_main.c
[ ... ]
-static int gem_create_page_pool(struct macb_queue *queue)
+static int gem_create_page_pool(struct macb_queue *queue, int qid)
{
struct page_pool_params pp_params = {
.order = 0,
.flags = PP_FLAG_DMA_MAP | PP_FLAG_DMA_SYNC_DEV,
.pool_size = queue->bp->rx_ring_size,
.nid = NUMA_NO_NODE,
- .dma_dir = DMA_FROM_DEVICE,
+ .dma_dir = rcu_access_pointer(queue->bp->prog)
+ ? DMA_BIDIRECTIONAL
+ : DMA_FROM_DEVICE,The page pool is created with DMA direction based on whether an XDP program is attached at creation time. However, gem_xdp_setup() below allows attaching XDP programs to a running interface without recreating the page pool. If the interface is opened without XDP (page pool uses DMA_FROM_DEVICE), and then an XDP program is attached via ndo_bpf, the pool will still use DMA_FROM_DEVICE. For XDP redirect, DMA_BIDIRECTIONAL is needed for proper cache coherency on non-cache-coherent architectures. The stmmac driver handles this by calling stmmac_xdp_release() and stmmac_xdp_open() when XDP program state changes on a running interface, which recreates the page pool with the correct DMA direction. Should gem_xdp_setup() reset the interface (or at least the page pools) when attaching or detaching XDP programs on a running interface to ensure the DMA direction matches? [ ... ]
+static int gem_xdp_setup(struct net_device *dev, struct bpf_prog *prog,
+ struct netlink_ext_ack *extack)
+{
+ struct macb *bp = netdev_priv(dev);
+ struct bpf_prog *old_prog;
+
+ if (prog && !gem_xdp_valid_mtu(bp, dev->mtu)) {
+ NL_SET_ERR_MSG_MOD(extack, "MTU too large for XDP");
+ return -EOPNOTSUPP;
+ }
+
+ old_prog = rcu_replace_pointer(bp->prog, prog, lockdep_rtnl_is_held());
+ if (old_prog)
+ bpf_prog_put(old_prog);
+
+ return 0;
+}This function swaps the XDP program via RCU but does not reset the interface or recreate the page pools. This relates to the DMA direction concern above.