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Date: Sat, 14 Jan 2017 14:15:50 +0200
From: Saeed Mahameed <saeedm@....mellanox.co.il>
To: Martin KaFai Lau <kafai@...com>
Cc: Linux Netdev List <netdev@...r.kernel.org>,
Saeed Mahameed <saeedm@...lanox.com>,
Tariq Toukan <tariqt@...lanox.com>,
Kernel Team <kernel-team@...com>
Subject: Re: [PATCH net-next] net/mlx5e: Support bpf_xdp_adjust_head()
On Sat, Jan 14, 2017 at 12:31 AM, Martin KaFai Lau <kafai@...com> wrote:
> On Fri, Jan 13, 2017 at 03:58:46PM +0200, Saeed Mahameed wrote:
>> >> > @@ -680,7 +687,7 @@ static inline void mlx5e_xmit_xdp_frame(struct mlx5e_rq *rq,
>> >> > memset(wqe, 0, sizeof(*wqe));
>> >> >
>> >> > /* copy the inline part */
>> >> > - memcpy(eseg->inline_hdr_start, data, MLX5E_XDP_MIN_INLINE);
>> >> > + memcpy(eseg->inline_hdr_start, xdp->data, MLX5E_XDP_MIN_INLINE);
>> >> > eseg->inline_hdr_sz = cpu_to_be16(MLX5E_XDP_MIN_INLINE);
>> >> >
>> >> > dseg = (struct mlx5_wqe_data_seg *)cseg + (MLX5E_XDP_TX_DS_COUNT - 1);
>> >> > @@ -706,22 +713,16 @@ static inline void mlx5e_xmit_xdp_frame(struct mlx5e_rq *rq,
>> >> > static inline bool mlx5e_xdp_handle(struct mlx5e_rq *rq,
>> >> > const struct bpf_prog *prog,
>> >> > struct mlx5e_dma_info *di,
>> >> > - void *data, u16 len)
>> >> > + struct xdp_buff *xdp)
>> >> > {
>> >> > - struct xdp_buff xdp;
>> >> > u32 act;
>> >> >
>> >> > - if (!prog)
>> >> > - return false;
>> >> > -
>> >> > - xdp.data = data;
>> >> > - xdp.data_end = xdp.data + len;
>> >> > - act = bpf_prog_run_xdp(prog, &xdp);
>> >> > + act = bpf_prog_run_xdp(prog, xdp);
>> >> > switch (act) {
>> >> > case XDP_PASS:
>> >> > return false;
>> >> > case XDP_TX:
>> >> > - mlx5e_xmit_xdp_frame(rq, di, MLX5_RX_HEADROOM, len);
>> >> > + mlx5e_xmit_xdp_frame(rq, di, xdp);
>> >> > return true;
>> >> > default:
>> >> > bpf_warn_invalid_xdp_action(act);
>> >> > @@ -737,18 +738,19 @@ static inline
>> >> > struct sk_buff *skb_from_cqe(struct mlx5e_rq *rq, struct mlx5_cqe64 *cqe,
>> >> > u16 wqe_counter, u32 cqe_bcnt)
>> >> > {
>> >> > + const struct bpf_prog *xdp_prog;
>> >> > struct mlx5e_dma_info *di;
>> >> > struct sk_buff *skb;
>> >> > void *va, *data;
>> >> > - bool consumed;
>> >> > + u16 rx_headroom = rq->rx_headroom;
>> >> >
>> >> > di = &rq->dma_info[wqe_counter];
>> >> > va = page_address(di->page);
>> >> > - data = va + MLX5_RX_HEADROOM;
>> >> > + data = va + rx_headroom;
>> >> >
>> >> > dma_sync_single_range_for_cpu(rq->pdev,
>> >> > di->addr,
>> >> > - MLX5_RX_HEADROOM,
>> >> > + rx_headroom,
>> >> > rq->buff.wqe_sz,
>> >> > DMA_FROM_DEVICE);
>> >> > prefetch(data);
>> >> > @@ -760,11 +762,26 @@ struct sk_buff *skb_from_cqe(struct mlx5e_rq *rq, struct mlx5_cqe64 *cqe,
>> >> > }
>> >> >
>> >> > rcu_read_lock();
>> >> > - consumed = mlx5e_xdp_handle(rq, READ_ONCE(rq->xdp_prog), di, data,
>> >> > - cqe_bcnt);
>> >> > + xdp_prog = READ_ONCE(rq->xdp_prog);
>> >> > + if (xdp_prog) {
>> >> > + struct xdp_buff xdp;
>> >> > + bool consumed;
>> >> > +
>> >> > + xdp.data = data;
>> >> > + xdp.data_end = xdp.data + cqe_bcnt;
>> >> > + xdp.data_hard_start = va;
>> >> > +
>> >> > + consumed = mlx5e_xdp_handle(rq, xdp_prog, di, &xdp);
>> >> > +
>> >> > + if (consumed) {
>> >> > + rcu_read_unlock();
>> >> > + return NULL; /* page/packet was consumed by XDP */
>> >> > + }
>> >> > +
>> >> > + rx_headroom = xdp.data - xdp.data_hard_start;
>> >> > + cqe_bcnt = xdp.data_end - xdp.data;
>> >> > + }
>> >>
>> >> This whole new logic belongs to mlx5e_xdp_handle, I would like to keep
>> >> xdp related code in one place.
>> >>
>> >> move the xdp_buff initialization back to there and keep the xdp_prog
>> >> check in mlx5e_xdp_handle;
>> >> + xdp_prog = READ_ONCE(rq->xdp_prog);
>> >> + if (!xdp_prog)
>> >> + return false
>> >>
>> >> you can remove "const struct bpf_prog *prog" parameter from
>> >> mlx5e_xdp_handle and take it directly from rq.
>> >>
>> >> if you need va for xdp_buff you can pass it as a paramter to
>> >> mlx5e_xdp_handle as well:
>> >> mlx5e_xdp_handle(rq, di, va, data, cqe_bcnt);
>> >> Make sense ?
>> > I moved them because xdp.data could be adjusted which then
>> > rx_headroom and cqe_bcnt have to be adjusted accordingly
>> > in skb_from_cqe() also.
>> >
>> > I understand your point. After another quick thought,
>> > the adjusted xdp.data is the only one that we want in skb_from_cqe().
>> > I will try to make mlx5e_xdp_handle() to return the adjusted xdp.data
>> > instead of bool.
>> >
>>
>> hmm, You also need the adjusted cqe_bcnt! this will make
>> mlx5e_xdp_handle stuffed with parameters,
>>
>> what if, in skb_from_cqe we warp data, rx_headroom and cqe_bcnt in one struct.
>>
>> struct mlx5e_rx_buff {
>> void *data;
>> u6 headroom;
>> u32 bcnt;
>> }
>>
>> initialize it at the start of skb_from_cqe:
>>
>> struct mlx5e_rx_buff rxb;
>>
>> rxb.headroom = rq->headroom;
>> rxb.data = va + rxb.headroom;
>> rxb.bcnt = cqe_bcnt;
>>
>> pass it to mlx5e_xdp_handle(rq, di, va, &rxb) in case xdp_prog is ON
>> and rxb needs adjustment.
>>
>> At the end use it to build the SKB:
>> skb = build_skb(va, RQ_PAGE_SIZE(rq));
>> skb_reserve(skb, rxb.headroom);
>> skb_put(skb, rxb.bcnt);
> How about something like this without introducing a new struct?
>
> -static inline bool mlx5e_xdp_handle(struct mlx5e_rq *rq,
> - const struct bpf_prog *prog,
> - struct mlx5e_dma_info *di,
> - void *data, u16 len)
> +static inline int mlx5e_xdp_handle(struct mlx5e_rq *rq,
> + struct mlx5e_dma_info *di,
> + void *va, u16 *rx_headroom, u32 *len)
Also good.
> {
> + const struct bpf_prog *prog = READ_ONCE(rq->xdp_prog);
> struct xdp_buff xdp;
> u32 act;
>
> if (!prog)
> return false;
>
> - xdp.data = data;
> - xdp.data_end = xdp.data + len;
> + xdp.data = va + *rx_headroom;
> + xdp.data_end = xdp.data + *len;
> + xdp.data_hard_start = va;
> +
> act = bpf_prog_run_xdp(prog, &xdp);
> switch (act) {
> case XDP_PASS:
> + *rx_headroom = xdp.data - xdp.data_hard_start;
> + *len = xdp.data_end - xdp.data;
> return false;
> case XDP_TX:
> - mlx5e_xmit_xdp_frame(rq, di, MLX5_RX_HEADROOM, len);
> + mlx5e_xmit_xdp_frame(rq, di, &xdp);
> return true;
> default:
> bpf_warn_invalid_xdp_action(act);
> @@ -740,15 +751,16 @@ struct sk_buff *skb_from_cqe(struct mlx5e_rq *rq, struct mlx5_cqe64 *cqe,
> struct mlx5e_dma_info *di;
> struct sk_buff *skb;
> void *va, *data;
> + u16 rx_headroom = rq->rx_headroom;
> bool consumed;
>
> di = &rq->dma_info[wqe_counter];
> va = page_address(di->page);
> - data = va + MLX5_RX_HEADROOM;
> + data = va + rx_headroom;
>
> dma_sync_single_range_for_cpu(rq->pdev,
> di->addr,
> - MLX5_RX_HEADROOM,
> + rx_headroom,
> rq->buff.wqe_sz,
> DMA_FROM_DEVICE);
> prefetch(data);
> @@ -760,8 +772,7 @@ struct sk_buff *skb_from_cqe(struct mlx5e_rq *rq, struct mlx5_cqe64 *cqe,
> }
>
> rcu_read_lock();
> - consumed = mlx5e_xdp_handle(rq, READ_ONCE(rq->xdp_prog), di, data,
> - cqe_bcnt);
> + consumed = mlx5e_xdp_handle(rq, di, va, &rx_headroom, &cqe_bcnt);
> rcu_read_unlock();
> if (consumed)
> return NULL; /* page/packet was consumed by XDP */
> @@ -777,7 +788,7 @@ struct sk_buff *skb_from_cqe(struct mlx5e_rq *rq, struct mlx5_cqe64 *cqe,
> page_ref_inc(di->page);
> mlx5e_page_release(rq, di, true);
>
> - skb_reserve(skb, MLX5_RX_HEADROOM);
> + skb_reserve(skb, rx_headroom);
> skb_put(skb, cqe_bcnt);
>
> return skb;
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