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Date:   Wed, 8 Apr 2020 15:09:23 +0200
From:   Lorenzo Bianconi <lorenzo.bianconi@...hat.com>
To:     Jesper Dangaard Brouer <brouer@...hat.com>
Cc:     sameehj@...zon.com, Ilias Apalodimas <ilias.apalodimas@...aro.org>,
        netdev@...r.kernel.org, bpf@...r.kernel.org, zorik@...zon.com,
        akiyano@...zon.com, gtzalik@...zon.com,
        Toke Høiland-Jørgensen <toke@...hat.com>,
        Daniel Borkmann <borkmann@...earbox.net>,
        Alexei Starovoitov <alexei.starovoitov@...il.com>,
        John Fastabend <john.fastabend@...il.com>,
        Alexander Duyck <alexander.duyck@...il.com>,
        Jeff Kirsher <jeffrey.t.kirsher@...el.com>,
        David Ahern <dsahern@...il.com>,
        Willem de Bruijn <willemdebruijn.kernel@...il.com>,
        Lorenzo Bianconi <lorenzo@...nel.org>,
        Saeed Mahameed <saeedm@...lanox.com>
Subject: Re: [PATCH RFC v2 05/33] net: netsec: Add support for XDP frame size

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

Acked-by: Lorenzo Bianconi <lorenzo@...nel.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.
> 
> Signed-off-by: Ilias Apalodimas <ilias.apalodimas@...aro.org>
> Signed-off-by: Jesper Dangaard Brouer <brouer@...hat.com>
> ---
>  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);
> 
> 

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