[PATCH net-next v4 05/33] net: netsec: Add support for XDP frame size

Jesper Dangaard Brouer
2020-05-14T10:49:39Z

From: Ilias Apalodimas <ilias.apalodimas@linaro.org>

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.

Signed-off-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
Acked-by: Lorenzo Bianconi <lorenzo@kernel.org>
---
drivers/net/ethernet/socionext/netsec.c | 30 ++++++++++++++++++------------
1 file changed, 18 insertions(+), 12 deletions(-)

diff --git a/drivers/net/ethernet/socionext/netsec.c b/drivers/net/ethernet/socionext/netsec.c
index a5a0fb60193a..e1f4be4b3d69 100644
--- a/drivers/net/ethernet/socionext/netsec.c
+++ b/drivers/net/ethernet/socionext/netsec.c
@@ -884,23 +884,28 @@ static u32 netsec_run_xdp(struct netsec_priv *priv, struct bpf_prog *prog,
struct xdp_buff *xdp)
{
struct netsec_desc_ring *dring = &priv->desc_ring[NETSEC_RING_RX];
- unsigned int len = xdp->data_end - xdp->data;
+ unsigned int sync, len = xdp->data_end - xdp->data;
u32 ret = NETSEC_XDP_PASS;
+ struct page *page;
int err;
u32 act;

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 - NETSEC_RXBUF_HEADROOM;
+ sync = max(sync, len);
+
switch (act) {
case XDP_PASS:
ret = NETSEC_XDP_PASS;
break;
case XDP_TX:
ret = netsec_xdp_xmit_back(priv, xdp);
- if (ret != NETSEC_XDP_TX)
- page_pool_put_page(dring->page_pool,
- virt_to_head_page(xdp->data), len,
- true);
+ if (ret != NETSEC_XDP_TX) {
+ page = virt_to_head_page(xdp->data);
+ page_pool_put_page(dring->page_pool, page, sync, true);
+ }
break;
case XDP_REDIRECT:
err = xdp_do_redirect(priv->ndev, xdp, prog);
@@ -908,9 +913,8 @@ static u32 netsec_run_xdp(struct netsec_priv *priv, struct bpf_prog *prog,
ret = NETSEC_XDP_REDIR;
} else {
ret = NETSEC_XDP_CONSUMED;
- page_pool_put_page(dring->page_pool,
- virt_to_head_page(xdp->data), len,
- true);
+ page = virt_to_head_page(xdp->data);
+ page_pool_put_page(dring->page_pool, page, sync, true);
}
break;
default:
@@ -921,8 +925,8 @@ static u32 netsec_run_xdp(struct netsec_priv *priv, struct bpf_prog *prog,
/* fall through -- handle aborts by dropping packet */
case XDP_DROP:
ret = NETSEC_XDP_CONSUMED;
- page_pool_put_page(dring->page_pool,
- virt_to_head_page(xdp->data), len, true);
+ page = virt_to_head_page(xdp->data);
+ page_pool_put_page(dring->page_pool, page, sync, true);
break;
}

@@ -936,10 +940,14 @@ static int netsec_process_rx(struct netsec_priv *priv, int budget)
struct netsec_rx_pkt_info rx_info;
enum dma_data_direction dma_dir;
struct bpf_prog *xdp_prog;
+ struct xdp_buff xdp;
u16 xdp_xmit = 0;
u32 xdp_act = 0;
int done = 0;

+ xdp.rxq = &dring->xdp_rxq;
+ xdp.frame_sz = PAGE_SIZE;
+
rcu_read_lock();
xdp_prog = READ_ONCE(priv->xdp_prog);
dma_dir = page_pool_get_dma_dir(dring->page_pool);
@@ -953,7 +961,6 @@ static int netsec_process_rx(struct netsec_priv *priv, int budget)
struct sk_buff *skb = NULL;
u16 pkt_len, desc_len;
dma_addr_t dma_handle;
- struct xdp_buff xdp;
void *buf_addr;

if (de->attr & (1U << NETSEC_RX_PKT_OWN_FIELD)) {
@@ -1002,7 +1009,6 @@ static int netsec_process_rx(struct netsec_priv *priv, int budget)
xdp.data = desc->addr + NETSEC_RXBUF_HEADROOM;
xdp_set_data_meta_invalid(&xdp);
xdp.data_end = xdp.data + pkt_len;
- xdp.rxq = &dring->xdp_rxq;

if (xdp_prog) {
xdp_result = netsec_run_xdp(priv, xdp_prog, &xdp);