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Date: Fri, 13 Jan 2017 15:58:46 +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 Fri, Jan 13, 2017 at 1:25 AM, Martin KaFai Lau <kafai@...com> wrote:
> 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.
>
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);
Thanks,
Saeed.
> 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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