[PATCH net-next v4 04/33] mvneta: add XDP frame size to driver

Jesper Dangaard Brouer
2020-05-14T10:49:33Z

This marvell driver mvneta uses PAGE_SIZE frames, which makes it
really easy to convert. Driver updates rxq and now frame_sz
once per NAPI call.

This driver takes advantage of page_pool PP_FLAG_DMA_SYNC_DEV that
can help reduce the number of cache-lines that need to be flushed
when doing DMA sync for_device. Due to xdp_adjust_tail can grow the
area accessible to the by the CPU (can possibly write into), then max
sync length *after* bpf_prog_run_xdp() needs to be taken into account.

For XDP_TX action the driver is smart and does DMA-sync. When growing
tail this is still safe, because page_pool have DMA-mapped the entire
page size.

Cc: thomas.petazzoni@bootlin.com
Acked-by: Lorenzo Bianconi <lorenzo@kernel.org>
Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
---
drivers/net/ethernet/marvell/mvneta.c | 25 +++++++++++++++----------
1 file changed, 15 insertions(+), 10 deletions(-)

diff --git a/drivers/net/ethernet/marvell/mvneta.c b/drivers/net/ethernet/marvell/mvneta.c
index 51889770958d..37947949345c 100644
--- a/drivers/net/ethernet/marvell/mvneta.c
+++ b/drivers/net/ethernet/marvell/mvneta.c
@@ -2148,12 +2148,17 @@ mvneta_run_xdp(struct mvneta_port *pp, struct mvneta_rx_queue *rxq,
struct bpf_prog *prog, struct xdp_buff *xdp,
struct mvneta_stats *stats)
{
- unsigned int len;
+ unsigned int len, sync;
+ struct page *page;
u32 ret, act;

len = xdp->data_end - xdp->data_hard_start - pp->rx_offset_correction;
act = bpf_prog_run_xdp(prog, xdp);

+ /* Due xdp_adjust_tail: DMA sync for_device cover max len CPU touch */
+ sync = xdp->data_end - xdp->data_hard_start - pp->rx_offset_correction;
+ sync = max(sync, len);
+
switch (act) {
case XDP_PASS:
stats->xdp_pass++;
@@ -2164,9 +2169,8 @@ mvneta_run_xdp(struct mvneta_port *pp, struct mvneta_rx_queue *rxq,
err = xdp_do_redirect(pp->dev, xdp, prog);
if (unlikely(err)) {
ret = MVNETA_XDP_DROPPED;
- page_pool_put_page(rxq->page_pool,
- virt_to_head_page(xdp->data), len,
- true);
+ page = virt_to_head_page(xdp->data);
+ page_pool_put_page(rxq->page_pool, page, sync, true);
} else {
ret = MVNETA_XDP_REDIR;
stats->xdp_redirect++;
@@ -2175,10 +2179,10 @@ mvneta_run_xdp(struct mvneta_port *pp, struct mvneta_rx_queue *rxq,
}
case XDP_TX:
ret = mvneta_xdp_xmit_back(pp, xdp);
- if (ret != MVNETA_XDP_TX)
- page_pool_put_page(rxq->page_pool,
- virt_to_head_page(xdp->data), len,
- true);
+ if (ret != MVNETA_XDP_TX) {
+ page = virt_to_head_page(xdp->data);
+ page_pool_put_page(rxq->page_pool, page, sync, true);
+ }
break;
default:
bpf_warn_invalid_xdp_action(act);
@@ -2187,8 +2191,8 @@ mvneta_run_xdp(struct mvneta_port *pp, struct mvneta_rx_queue *rxq,
trace_xdp_exception(pp->dev, prog, act);
/* fall through */
case XDP_DROP:
- page_pool_put_page(rxq->page_pool,
- virt_to_head_page(xdp->data), len, true);
+ page = virt_to_head_page(xdp->data);
+ page_pool_put_page(rxq->page_pool, page, sync, true);
ret = MVNETA_XDP_DROPPED;
stats->xdp_drop++;
break;
@@ -2320,6 +2324,7 @@ static int mvneta_rx_swbm(struct napi_struct *napi,
rcu_read_lock();
xdp_prog = READ_ONCE(pp->xdp_prog);
xdp_buf.rxq = &rxq->xdp_rxq;
+ xdp_buf.frame_sz = PAGE_SIZE;

/* Fairness NAPI loop */
while (rx_proc < budget && rx_proc < rx_todo) {