Subject: Re: [bpf-next V1-RFC PATCH 02/14] xdp/mlx5: setup xdp_rxq_info and extend with qtype

From: Jesper Dangaard Brouer <[email-masked]>
Date: Wed, 13 Dec 2017 14:44:39 +0100

On Wed, 13 Dec 2017 14:27:08 +0200
Tariq Toukan <[email-masked]> wrote:

> Hi Jesper,
> Thanks for taking care of the drop RQ.
> 
> In general, mlx5 part looks ok to me.
> Find a few comments below. Mostly pointing out some typos.
> 
> On 13/12/2017 1:19 PM, Jesper Dangaard Brouer wrote:
> > The mlx5 driver have a special drop-RQ queue (one per interface) that
> > simply drops all incoming traffic. It helps driver keep other HW
> > objects (flow steering) alive upon down/up operations.  It is
> > temporarily pointed by flow steering objects during the interface
> > setup, and when interface is down. It lacks many fields that are set
> > in a regular RQ (for example its state is never switched to
> > MLX5_RQC_STATE_RDY). (Thanks to Tariq Toukan for explaination).  
> typo: explanation

Fixed 

> > 
> > The XDP RX-queue info API is extended with a queue-type, and mlx5 uses
> > this kind of drop/sink-type (RXQ_TYPE_SINK) for this kind of sink queue.
> > 
> > Driver hook points for xdp_rxq_info:
> >   * init+reg: mlx5e_alloc_rq()
> >   * init+reg: mlx5e_alloc_drop_rq()
> >   * unreg   : mlx5e_free_rq()
> > 
> > Tested on actual hardware with samples/bpf program
> > 
> > Cc: Saeed Mahameed <[email-masked]>
> > Cc: Matan Barak <[email-masked]>
> > Cc: Tariq Toukan <[email-masked]>
> > Signed-off-by: Jesper Dangaard Brouer <[email-masked]>
> > ---
> >   drivers/net/ethernet/mellanox/mlx5/core/en.h      |    4 ++++
> >   drivers/net/ethernet/mellanox/mlx5/core/en_main.c |   14 +++++++++++++
> >   drivers/net/ethernet/mellanox/mlx5/core/en_rx.c   |    1 +
> >   include/net/xdp.h                                 |   23 +++++++++++++++++++++
> >   net/core/xdp.c                                    |    6 +++++
> >   5 files changed, 48 insertions(+)
> > 
> > diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en.h b/drivers/net/ethernet/mellanox/mlx5/core/en.h
> > index c0872b3284cb..fe10a042783b 100644
> > --- a/drivers/net/ethernet/mellanox/mlx5/core/en.h
> > +++ b/drivers/net/ethernet/mellanox/mlx5/core/en.h
> > @@ -46,6 +46,7 @@
> >   #include <linux/mlx5/transobj.h>
> >   #include <linux/rhashtable.h>
> >   #include <net/switchdev.h>
> > +#include <net/xdp.h>
> >   #include "wq.h"
> >   #include "mlx5_core.h"
> >   #include "en_stats.h"
> > @@ -568,6 +569,9 @@ struct mlx5e_rq {
> >   	u32                    rqn;
> >   	struct mlx5_core_dev  *mdev;
> >   	struct mlx5_core_mkey  umr_mkey;
> > +
> > +	/* XDP read-mostly */
> > +	struct xdp_rxq_info xdp_rxq;
> >   } ____cacheline_aligned_in_smp;
> >   
> >   struct mlx5e_channel {
> > diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_main.c b/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
> > index 0f5c012de52e..ea44b5f25e11 100644
> > --- a/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
> > +++ b/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
> > @@ -582,6 +582,12 @@ static int mlx5e_alloc_rq(struct mlx5e_channel *c,
> >   	rq->ix      = c->ix;
> >   	rq->mdev    = mdev;
> >   
> > +	/* XDP RX-queue info */
> > +	xdp_rxq_info_init(&rq->xdp_rxq);
> > +	rq->xdp_rxq.dev		= rq->netdev;
> > +	rq->xdp_rxq.queue_index = rq->ix;
> > +	xdp_rxq_info_reg(&rq->xdp_rxq);
> > +  
> You don't set type here. This is ok as long as the following hold:
> 1) RXQ_TYPE_DEFAULT is zero

True

> 2) xdp_rxq is zalloc'ed.

xdp_rxq memory area is part of rq allocation, but in
xdp_rxq_info_init() I memset/zero the area explicit.

> >   	rq->xdp_prog = params->xdp_prog ?
> > bpf_prog_inc(params->xdp_prog) : NULL; if (IS_ERR(rq->xdp_prog)) {
> >   		err = PTR_ERR(rq->xdp_prog);
> > @@ -695,6 +701,7 @@ static int mlx5e_alloc_rq(struct mlx5e_channel
> > *c, err_rq_wq_destroy:
> >   	if (rq->xdp_prog)
> >   		bpf_prog_put(rq->xdp_prog);
> > +	xdp_rxq_info_unreg(&rq->xdp_rxq);
> >   	mlx5_wq_destroy(&rq->wq_ctrl);
> >   
> >   	return err;
> > @@ -707,6 +714,8 @@ static void mlx5e_free_rq(struct mlx5e_rq *rq)
> >   	if (rq->xdp_prog)
> >   		bpf_prog_put(rq->xdp_prog);
> >   
> > +	xdp_rxq_info_unreg(&rq->xdp_rxq);
> > +
> >   	switch (rq->wq_type) {
> >   	case MLX5_WQ_TYPE_LINKED_LIST_STRIDING_RQ:
> >   		mlx5e_rq_free_mpwqe_info(rq);
> > @@ -2768,6 +2777,11 @@ static int mlx5e_alloc_drop_rq(struct
> > mlx5_core_dev *mdev, if (err)
> >   		return err;
> >   
> > +	/* XDP RX-queue info for "Drop-RQ", packets never reach
> > XDP */
> > +	xdp_rxq_info_init(&rq->xdp_rxq);
> > +	xdp_rxq_info_type(&rq->xdp_rxq, RXQ_TYPE_SINK);
> > +	xdp_rxq_info_reg(&rq->xdp_rxq);
> > +
> >   	rq->mdev = mdev;
> >   
> >   	return 0;
> > diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_rx.c
> > b/drivers/net/ethernet/mellanox/mlx5/core/en_rx.c index
> > 5b499c7a698f..7b38480811d4 100644 ---
> > a/drivers/net/ethernet/mellanox/mlx5/core/en_rx.c +++
> > b/drivers/net/ethernet/mellanox/mlx5/core/en_rx.c @@ -812,6 +812,7
> > @@ static inline int mlx5e_xdp_handle(struct mlx5e_rq *rq,
> > xdp_set_data_meta_invalid(&xdp); xdp.data_end = xdp.data + *len;
> >   	xdp.data_hard_start = va;
> > +	xdp.rxq = &rq->xdp_rxq;
> >   
> >   	act = bpf_prog_run_xdp(prog, &xdp);
> >   	switch (act) {
> > diff --git a/include/net/xdp.h b/include/net/xdp.h
> > index e4acd198fd60..5be560d943e1 100644
> > --- a/include/net/xdp.h
> > +++ b/include/net/xdp.h
> > @@ -36,10 +36,33 @@ struct xdp_rxq_info {
> >   	struct net_device *dev;
> >   	u32 queue_index;
> >   	u32 reg_state;
> > +	u32 qtype;
> >   } ____cacheline_aligned; /* perf critical, avoid false-sharing */
> >   
> >   void xdp_rxq_info_init(struct xdp_rxq_info *xdp_rxq);
> >   void xdp_rxq_info_reg(struct xdp_rxq_info *xdp_rxq);
> >   void xdp_rxq_info_unreg(struct xdp_rxq_info *xdp_rxq);
> >   
> > +/**
> > + * DOC: XDP RX-queue type
> > + *
> > + * The XDP RX-queue info can have associated a type.
> > + *
> > + * @RXQ_TYPE_DEFAULT: default no specifik queue type need to be
> > specified  
> 
> typo: specific

Thanks, this is a Danish typo (it's spelled that way in Danish).
 
> > + *
> > + * @RXQ_TYPE_SINK: indicate a fake queue that never reach XDP RX
> > + *	code.  Some drivers have a need to maintain a lower layer
> > + *	RX-queue as a sink queue, while reconfiguring other
> > RX-queues.
> > + */
> > +#define RXQ_TYPE_DEFAULT	0
> > +#define RXQ_TYPE_SINK		1
> > +#define RXQ_TYPE_MAX		RXQ_TYPE_SINK  
> 
> Definitions of incremental numbers, enum might be best here, you can 
> give them some enum type and use it in xdp_rxq_info->qtype.

I use defines to make the below BUILD_BUG_ON work, as enums does not
get expanded to their values in the C-preprocessor stage.

> > +
> > +static inline
> > +void xdp_rxq_info_type(struct xdp_rxq_info *xdp_rxq, u32 qtype)
> > +{
> > +	BUILD_BUG_ON(qtype > RXQ_TYPE_MAX);
> > +	xdp_rxq->qtype = qtype;
> > +}
> > +
> >   #endif /* __LINUX_NET_XDP_H__ */
> > diff --git a/net/core/xdp.c b/net/core/xdp.c
> > index a9d2dd7b1ede..2a111f5987f6 100644
> > --- a/net/core/xdp.c
> > +++ b/net/core/xdp.c
> > @@ -32,8 +32,14 @@ EXPORT_SYMBOL_GPL(xdp_rxq_info_init);
> >   
> >   void xdp_rxq_info_reg(struct xdp_rxq_info *xdp_rxq)
> >   {
> > +	if (xdp_rxq->qtype == RXQ_TYPE_SINK)
> > +		goto skip_content_check;
> > +
> > +	/* Check information setup by driver code */
> >   	WARN(!xdp_rxq->dev, "Missing net_device from driver");
> >   	WARN(xdp_rxq->queue_index == U32_MAX, "Miss queue_index from driver"); +
> > +skip_content_check:
> >   	WARN(!(xdp_rxq->reg_state == REG_STATE_NEW),"API violation, miss init");
> >     xdp_rxq->reg_state = REG_STATE_REGISTRED;  
> typo: REGISTERED (introduced in a previous patch)

Thanks for catching that! :-)

-- 
Best regards,
  Jesper Dangaard Brouer
  MSc.CS, Principal Kernel Engineer at Red Hat
  LinkedIn: http://www.linkedin.com/in/brouer