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Date: Thu, 12 Jan 2017 15:25:46 -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 Thu, Jan 12, 2017 at 03:10:30PM +0200, Saeed Mahameed wrote:
> On Thu, Jan 12, 2017 at 4:09 AM, Martin KaFai Lau <kafai@...com> wrote:
> > This patch adds bpf_xdp_adjust_head() support to mlx5e.
>
> Hi Martin, Thanks for the patch !
>
> you can find some comments below.
>
> >
> > 1. rx_headroom is added to struct mlx5e_rq. It uses
> > an existing 4 byte hole in the struct.
> > 2. The adjusted data length is checked against
> > MLX5E_XDP_MIN_INLINE and MLX5E_SW2HW_MTU(rq->netdev->mtu).
> > 3. The macro MLX5E_SW2HW_MTU is moved from en_main.c to en.h.
> > MLX5E_HW2SW_MTU is also moved to en.h for symmetric reason
> > but it is not a must.
> >
> > Signed-off-by: Martin KaFai Lau <kafai@...com>
> > ---
> > drivers/net/ethernet/mellanox/mlx5/core/en.h | 4 ++
> > drivers/net/ethernet/mellanox/mlx5/core/en_main.c | 18 +++----
> > drivers/net/ethernet/mellanox/mlx5/core/en_rx.c | 63 ++++++++++++++---------
> > 3 files changed, 51 insertions(+), 34 deletions(-)
> >
> > diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en.h b/drivers/net/ethernet/mellanox/mlx5/core/en.h
> > index a473cea10c16..0d9dd860a295 100644
> > --- a/drivers/net/ethernet/mellanox/mlx5/core/en.h
> > +++ b/drivers/net/ethernet/mellanox/mlx5/core/en.h
> > @@ -51,6 +51,9 @@
> >
> > #define MLX5_SET_CFG(p, f, v) MLX5_SET(create_flow_group_in, p, f, v)
> >
> > +#define MLX5E_HW2SW_MTU(hwmtu) ((hwmtu) - (ETH_HLEN + VLAN_HLEN + ETH_FCS_LEN))
> > +#define MLX5E_SW2HW_MTU(swmtu) ((swmtu) + (ETH_HLEN + VLAN_HLEN + ETH_FCS_LEN))
> > +
> > #define MLX5E_MAX_NUM_TC 8
> >
> > #define MLX5E_PARAMS_MINIMUM_LOG_SQ_SIZE 0x6
> > @@ -369,6 +372,7 @@ struct mlx5e_rq {
> >
> > unsigned long state;
> > int ix;
> > + u16 rx_headroom;
> >
> > struct mlx5e_rx_am am; /* Adaptive Moderation */
> > struct bpf_prog *xdp_prog;
> > diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_main.c b/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
> > index f74ba73c55c7..aba3691e0919 100644
> > --- a/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
> > +++ b/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
> > @@ -343,9 +343,6 @@ static void mlx5e_disable_async_events(struct mlx5e_priv *priv)
> > synchronize_irq(mlx5_get_msix_vec(priv->mdev, MLX5_EQ_VEC_ASYNC));
> > }
> >
> > -#define MLX5E_HW2SW_MTU(hwmtu) (hwmtu - (ETH_HLEN + VLAN_HLEN + ETH_FCS_LEN))
> > -#define MLX5E_SW2HW_MTU(swmtu) (swmtu + (ETH_HLEN + VLAN_HLEN + ETH_FCS_LEN))
> > -
> > static inline int mlx5e_get_wqe_mtt_sz(void)
> > {
> > /* UMR copies MTTs in units of MLX5_UMR_MTT_ALIGNMENT bytes.
> > @@ -534,9 +531,13 @@ static int mlx5e_create_rq(struct mlx5e_channel *c,
> > goto err_rq_wq_destroy;
> > }
> >
> > - rq->buff.map_dir = DMA_FROM_DEVICE;
> > - if (rq->xdp_prog)
> > + if (rq->xdp_prog) {
> > rq->buff.map_dir = DMA_BIDIRECTIONAL;
> > + rq->rx_headroom = XDP_PACKET_HEADROOM;
> > + } else {
> > + rq->buff.map_dir = DMA_FROM_DEVICE;
> > + rq->rx_headroom = MLX5_RX_HEADROOM;
> > + }
> >
> > switch (priv->params.rq_wq_type) {
> > case MLX5_WQ_TYPE_LINKED_LIST_STRIDING_RQ:
> > @@ -586,7 +587,7 @@ static int mlx5e_create_rq(struct mlx5e_channel *c,
> > byte_count = rq->buff.wqe_sz;
> >
> > /* calc the required page order */
> > - frag_sz = MLX5_RX_HEADROOM +
> > + frag_sz = rq->rx_headroom +
> > byte_count /* packet data */ +
> > SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
> > frag_sz = SKB_DATA_ALIGN(frag_sz);
> > @@ -3153,11 +3154,6 @@ static int mlx5e_xdp_set(struct net_device *netdev, struct bpf_prog *prog)
> > bool reset, was_opened;
> > int i;
> >
> > - if (prog && prog->xdp_adjust_head) {
> > - netdev_err(netdev, "Does not support bpf_xdp_adjust_head()\n");
> > - return -EOPNOTSUPP;
> > - }
> > -
> > mutex_lock(&priv->state_lock);
> >
> > if ((netdev->features & NETIF_F_LRO) && prog) {
> > diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_rx.c b/drivers/net/ethernet/mellanox/mlx5/core/en_rx.c
> > index 0e2fb3ed1790..914e00132e08 100644
> > --- a/drivers/net/ethernet/mellanox/mlx5/core/en_rx.c
> > +++ b/drivers/net/ethernet/mellanox/mlx5/core/en_rx.c
> > @@ -264,7 +264,7 @@ int mlx5e_alloc_rx_wqe(struct mlx5e_rq *rq, struct mlx5e_rx_wqe *wqe, u16 ix)
> > if (unlikely(mlx5e_page_alloc_mapped(rq, di)))
> > return -ENOMEM;
> >
> > - wqe->data.addr = cpu_to_be64(di->addr + MLX5_RX_HEADROOM);
> > + wqe->data.addr = cpu_to_be64(di->addr + rq->rx_headroom);
> > return 0;
> > }
> >
> > @@ -646,8 +646,7 @@ static inline void mlx5e_xmit_xdp_doorbell(struct mlx5e_sq *sq)
> >
> > static inline void mlx5e_xmit_xdp_frame(struct mlx5e_rq *rq,
> > struct mlx5e_dma_info *di,
> > - unsigned int data_offset,
> > - int len)
> > + const struct xdp_buff *xdp)
> > {
> > struct mlx5e_sq *sq = &rq->channel->xdp_sq;
> > struct mlx5_wq_cyc *wq = &sq->wq;
> > @@ -659,9 +658,17 @@ static inline void mlx5e_xmit_xdp_frame(struct mlx5e_rq *rq,
> > struct mlx5_wqe_eth_seg *eseg = &wqe->eth;
> > struct mlx5_wqe_data_seg *dseg;
> >
> > + ptrdiff_t data_offset = xdp->data - xdp->data_hard_start;
> > dma_addr_t dma_addr = di->addr + data_offset + MLX5E_XDP_MIN_INLINE;
> > - unsigned int dma_len = len - MLX5E_XDP_MIN_INLINE;
> > - void *data = page_address(di->page) + data_offset;
> > + unsigned int dma_len = xdp->data_end - xdp->data;
> > +
> > + if (unlikely(dma_len < MLX5E_XDP_MIN_INLINE ||
>
> I don't think this can happen, MLX5E_XDP_MIN_INLINE is 18 bytes and
> should not get bigger in the future,
> Also i don't think it is possible for XDP prog to xmit packets smaller
> than 18 bytes, let's remove this
The bpf_xdp_adjust_head() only checks for a min of ETH_HLEN which is 14.
Hence, <18 bytes is still possible here.
>
> > + MLX5E_SW2HW_MTU(rq->netdev->mtu) < dma_len)) {
> > + rq->stats.xdp_drop++;
> > + mlx5e_page_release(rq, di, true);
> > + return;
> > + }
> > + dma_len -= MLX5E_XDP_MIN_INLINE;
>
> Move this to after the below sanity check, it is better to separate
> logic from pre-conditions
Will do.
>
> >
> > if (unlikely(!mlx5e_sq_has_room_for(sq, MLX5E_XDP_TX_WQEBBS))) {
> > if (sq->db.xdp.doorbell) {
> > @@ -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.
Thanks,
--Martin
>
> > rcu_read_unlock();
> > - if (consumed)
> > - return NULL; /* page/packet was consumed by XDP */
> >
> > skb = build_skb(va, RQ_PAGE_SIZE(rq));
> > if (unlikely(!skb)) {
> > @@ -777,7 +794,7 @@ 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;
> > --
> > 2.5.1
> >
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