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Date: Fri, 13 Jan 2017 14:31:41 -0800
From: Martin KaFai Lau <kafai@...com>
To: Saeed Mahameed <saeedm@....mellanox.co.il>
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 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)
{
+ 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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