Commit aecd67b6 authored by Jesper Dangaard Brouer's avatar Jesper Dangaard Brouer Committed by Alexei Starovoitov
Browse files

xdp: base API for new XDP rx-queue info concept 



This patch only introduce the core data structures and API functions.
All XDP enabled drivers must use the API before this info can used.

There is a need for XDP to know more about the RX-queue a given XDP
frames have arrived on.  For both the XDP bpf-prog and kernel side.

Instead of extending xdp_buff each time new info is needed, the patch
creates a separate read-mostly struct xdp_rxq_info, that contains this
info.  We stress this data/cache-line is for read-only info.  This is
NOT for dynamic per packet info, use the data_meta for such use-cases.

The performance advantage is this info can be setup at RX-ring init
time, instead of updating N-members in xdp_buff.  A possible (driver
level) micro optimization is that xdp_buff->rxq assignment could be
done once per XDP/NAPI loop.  The extra pointer deref only happens for
program needing access to this info (thus, no slowdown to existing
use-cases).

Signed-off-by: default avatarJesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parent 5f103c5d

include/linux/filter.h

+2 −0
Original line number Diff line number Diff line
@@ -20,6 +20,7 @@ 
#include <linux/set_memory.h>

#include <linux/kallsyms.h>



#include <net/xdp.h>

#include <net/sch_generic.h>



#include <uapi/linux/filter.h>
@@ -503,6 +504,7 @@ struct xdp_buff { 
	void *data_end;

	void *data_meta;

	void *data_hard_start;

	struct xdp_rxq_info *rxq;

};



/* Compute the linear packet data range [data, data_end) which

include/net/xdp.h

0 → 100644
+47 −0
Original line number Diff line number Diff line 
/* include/net/xdp.h

 *

 * Copyright (c) 2017 Jesper Dangaard Brouer, Red Hat Inc.

 * Released under terms in GPL version 2.  See COPYING.

 */

#ifndef __LINUX_NET_XDP_H__

#define __LINUX_NET_XDP_H__



/**

 * DOC: XDP RX-queue information

 *

 * The XDP RX-queue info (xdp_rxq_info) is associated with the driver

 * level RX-ring queues.  It is information that is specific to how

 * the driver have configured a given RX-ring queue.

 *

 * Each xdp_buff frame received in the driver carry a (pointer)

 * reference to this xdp_rxq_info structure.  This provides the XDP

 * data-path read-access to RX-info for both kernel and bpf-side

 * (limited subset).

 *

 * For now, direct access is only safe while running in NAPI/softirq

 * context.  Contents is read-mostly and must not be updated during

 * driver NAPI/softirq poll.

 *

 * The driver usage API is a register and unregister API.

 *

 * The struct is not directly tied to the XDP prog.  A new XDP prog

 * can be attached as long as it doesn't change the underlying

 * RX-ring.  If the RX-ring does change significantly, the NIC driver

 * naturally need to stop the RX-ring before purging and reallocating

 * memory.  In that process the driver MUST call unregistor (which

 * also apply for driver shutdown and unload).  The register API is

 * also mandatory during RX-ring setup.

 */



struct xdp_rxq_info {

	struct net_device *dev;

	u32 queue_index;

	u32 reg_state;

} ____cacheline_aligned; /* perf critical, avoid false-sharing */



int xdp_rxq_info_reg(struct xdp_rxq_info *xdp_rxq,

		     struct net_device *dev, u32 queue_index);

void xdp_rxq_info_unreg(struct xdp_rxq_info *xdp_rxq);

void xdp_rxq_info_unused(struct xdp_rxq_info *xdp_rxq);



#endif /* __LINUX_NET_XDP_H__ */

net/core/Makefile

+1 −1
Original line number Diff line number Diff line
@@ -11,7 +11,7 @@ obj-$(CONFIG_SYSCTL) += sysctl_net_core.o 
obj-y		     += dev.o ethtool.o dev_addr_lists.o dst.o netevent.o \

			neighbour.o rtnetlink.o utils.o link_watch.o filter.o \

			sock_diag.o dev_ioctl.o tso.o sock_reuseport.o \

			fib_notifier.o

			fib_notifier.o xdp.o



obj-y += net-sysfs.o

obj-$(CONFIG_PROC_FS) += net-procfs.o

net/core/xdp.c

0 → 100644
+67 −0
Original line number Diff line number Diff line 
/* net/core/xdp.c

 *

 * Copyright (c) 2017 Jesper Dangaard Brouer, Red Hat Inc.

 * Released under terms in GPL version 2.  See COPYING.

 */

#include <linux/types.h>

#include <linux/mm.h>



#include <net/xdp.h>



#define REG_STATE_NEW		0x0

#define REG_STATE_REGISTERED	0x1

#define REG_STATE_UNREGISTERED	0x2

#define REG_STATE_UNUSED	0x3



void xdp_rxq_info_unreg(struct xdp_rxq_info *xdp_rxq)

{

	/* Simplify driver cleanup code paths, allow unreg "unused" */

	if (xdp_rxq->reg_state == REG_STATE_UNUSED)

		return;



	WARN(!(xdp_rxq->reg_state == REG_STATE_REGISTERED), "Driver BUG");



	xdp_rxq->reg_state = REG_STATE_UNREGISTERED;

	xdp_rxq->dev = NULL;

}

EXPORT_SYMBOL_GPL(xdp_rxq_info_unreg);



static void xdp_rxq_info_init(struct xdp_rxq_info *xdp_rxq)

{

	memset(xdp_rxq, 0, sizeof(*xdp_rxq));

}



/* Returns 0 on success, negative on failure */

int xdp_rxq_info_reg(struct xdp_rxq_info *xdp_rxq,

		     struct net_device *dev, u32 queue_index)

{

	if (xdp_rxq->reg_state == REG_STATE_UNUSED) {

		WARN(1, "Driver promised not to register this");

		return -EINVAL;

	}



	if (xdp_rxq->reg_state == REG_STATE_REGISTERED) {

		WARN(1, "Missing unregister, handled but fix driver");

		xdp_rxq_info_unreg(xdp_rxq);

	}



	if (!dev) {

		WARN(1, "Missing net_device from driver");

		return -ENODEV;

	}



	/* State either UNREGISTERED or NEW */

	xdp_rxq_info_init(xdp_rxq);

	xdp_rxq->dev = dev;

	xdp_rxq->queue_index = queue_index;



	xdp_rxq->reg_state = REG_STATE_REGISTERED;

	return 0;

}

EXPORT_SYMBOL_GPL(xdp_rxq_info_reg);



void xdp_rxq_info_unused(struct xdp_rxq_info *xdp_rxq)

{

	xdp_rxq->reg_state = REG_STATE_UNUSED;

}

EXPORT_SYMBOL_GPL(xdp_rxq_info_unused);

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