Subject: Re: [PATCH v2 net-next] net: socionext: get rid of huge dma sync in netsec_alloc_rx_data

From: Lorenzo Bianconi <[email-masked]>
Date: Fri, 10 Jan 2020 16:34:13 +0100

> On Fri, Jan 10, 2020 at 02:57:44PM +0100, Lorenzo Bianconi wrote:
> > Socionext driver can run on dma coherent and non-coherent devices.
> > Get rid of huge dma_sync_single_for_device in netsec_alloc_rx_data since
> > now the driver can let page_pool API to managed needed DMA sync
> > 
> > Signed-off-by: Lorenzo Bianconi <[email-masked]>
> > ---
> > Changes since v1:
> > - rely on original frame size for dma sync
> > ---
> >  drivers/net/ethernet/socionext/netsec.c | 43 +++++++++++++++----------
> >  1 file changed, 26 insertions(+), 17 deletions(-)
> > 

[...]

> > @@ -883,6 +881,8 @@ static u32 netsec_xdp_xmit_back(struct netsec_priv *priv, struct xdp_buff *xdp)
> >  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;
> 
> We need to account for XDP expanding the headers as well here. 
> So something like max(xdp->data_end(before bpf), xdp->data_end(after bpf)) -
> xdp->data (original)

correct, the corner case that is not covered at the moment is when data_end is
moved forward by the bpf program. I will fix it in v3. Thx

Regards,
Lorenzo

> 
> >  	u32 ret = NETSEC_XDP_PASS;
> >  	int err;
> >  	u32 act;
> > @@ -896,7 +896,9 @@ static u32 netsec_run_xdp(struct netsec_priv *priv, struct bpf_prog *prog,
> >  	case XDP_TX:
> >  		ret = netsec_xdp_xmit_back(priv, xdp);
> >  		if (ret != NETSEC_XDP_TX)
> > -			xdp_return_buff(xdp);
> > +			__page_pool_put_page(dring->page_pool,
> > +				     virt_to_head_page(xdp->data),
> > +				     len, true);
> >  		break;
> >  	case XDP_REDIRECT:
> >  		err = xdp_do_redirect(priv->ndev, xdp, prog);
> > @@ -904,7 +906,9 @@ static u32 netsec_run_xdp(struct netsec_priv *priv, struct bpf_prog *prog,
> >  			ret = NETSEC_XDP_REDIR;
> >  		} else {
> >  			ret = NETSEC_XDP_CONSUMED;
> > -			xdp_return_buff(xdp);
> > +			__page_pool_put_page(dring->page_pool,
> > +				     virt_to_head_page(xdp->data),
> > +				     len, true);
> >  		}
> >  		break;
> >  	default:
> > @@ -915,7 +919,9 @@ 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;
> > -		xdp_return_buff(xdp);
> > +		__page_pool_put_page(dring->page_pool,
> > +				     virt_to_head_page(xdp->data),
> > +				     len, true);
> >  		break;
> >  	}
> >  
> > @@ -1014,7 +1020,8 @@ static int netsec_process_rx(struct netsec_priv *priv, int budget)
> >  			 * cache state. Since we paid the allocation cost if
> >  			 * building an skb fails try to put the page into cache
> >  			 */
> > -			page_pool_recycle_direct(dring->page_pool, page);
> > +			__page_pool_put_page(dring->page_pool, page,
> > +					     pkt_len, true);
> 
> Same here, a bpf prog with XDP_PASS verdict might change lenghts
> 
> >  			netif_err(priv, drv, priv->ndev,
> >  				  "rx failed to build skb\n");
> >  			break;
> > @@ -1272,17 +1279,19 @@ static int netsec_setup_rx_dring(struct netsec_priv *priv)
> >  {
> >  	struct netsec_desc_ring *dring = &priv->desc_ring[NETSEC_RING_RX];
> >  	struct bpf_prog *xdp_prog = READ_ONCE(priv->xdp_prog);
> > -	struct page_pool_params pp_params = { 0 };
> > +	struct page_pool_params pp_params = {
> > +		.order = 0,
> > +		/* internal DMA mapping in page_pool */
> > +		.flags = PP_FLAG_DMA_MAP | PP_FLAG_DMA_SYNC_DEV,
> > +		.pool_size = DESC_NUM,
> > +		.nid = NUMA_NO_NODE,
> > +		.dev = priv->dev,
> > +		.dma_dir = xdp_prog ? DMA_BIDIRECTIONAL : DMA_FROM_DEVICE,
> > +		.offset = NETSEC_RXBUF_HEADROOM,
> > +		.max_len = NETSEC_RX_BUF_SIZE,
> > +	};
> >  	int i, err;
> >  
> > -	pp_params.order = 0;
> > -	/* internal DMA mapping in page_pool */
> > -	pp_params.flags = PP_FLAG_DMA_MAP;
> > -	pp_params.pool_size = DESC_NUM;
> > -	pp_params.nid = NUMA_NO_NODE;
> > -	pp_params.dev = priv->dev;
> > -	pp_params.dma_dir = xdp_prog ? DMA_BIDIRECTIONAL : DMA_FROM_DEVICE;
> > -
> >  	dring->page_pool = page_pool_create(&pp_params);
> >  	if (IS_ERR(dring->page_pool)) {
> >  		err = PTR_ERR(dring->page_pool);
> > -- 
> > 2.21.1
> > 
> 
> Thanks
> /Ilias