netdev - Re: [PATCH v4 net-next 4/7] net: mvneta: add basic XDP support

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Date:   Wed, 16 Oct 2019 18:26:50 -0700
From:   Jakub Kicinski <jakub.kicinski@...ronome.com>
To:     Lorenzo Bianconi <lorenzo@...nel.org>
Cc:     netdev@...r.kernel.org, lorenzo.bianconi@...hat.com,
        davem@...emloft.net, thomas.petazzoni@...tlin.com,
        brouer@...hat.com, ilias.apalodimas@...aro.org,
        matteo.croce@...hat.com, mw@...ihalf.com
Subject: Re: [PATCH v4 net-next 4/7] net: mvneta: add basic XDP support

On Wed, 16 Oct 2019 23:03:09 +0200, Lorenzo Bianconi wrote:
> Add basic XDP support to mvneta driver for devices that rely on software
> buffer management. Currently supported verdicts are:
> - XDP_DROP
> - XDP_PASS
> - XDP_REDIRECT
> - XDP_ABORTED
> 
> - iptables drop:
> $iptables -t raw -I PREROUTING -p udp --dport 9 -j DROP
> $nstat -n && sleep 1 && nstat
> IpInReceives		151169		0.0
> IpExtInOctets		6953544		0.0
> IpExtInNoECTPkts	151165		0.0
> 
> - XDP_DROP via xdp1
> $./samples/bpf/xdp1 3
> proto 0:	421419 pkt/s
> proto 0:	421444 pkt/s
> proto 0:	421393 pkt/s
> proto 0:	421440 pkt/s
> proto 0:	421184 pkt/s
> 
> Tested-by: Matteo Croce <mcroce@...hat.com>
> Signed-off-by: Lorenzo Bianconi <lorenzo@...nel.org>

> +static int mvneta_xdp_setup(struct net_device *dev, struct bpf_prog *prog,
> +			    struct netlink_ext_ack *extack)
> +{
> +	struct mvneta_port *pp = netdev_priv(dev);
> +	struct bpf_prog *old_prog;
> +
> +	if (prog && dev->mtu > MVNETA_MAX_RX_BUF_SIZE) {
> +		NL_SET_ERR_MSG_MOD(extack, "Jumbo frames not supported on XDP");
> +		return -EOPNOTSUPP;
> +	}
> +
> +	if (netif_running(dev))
> +		mvneta_stop(dev);

Actually if pp->prog && prog you don't have to stop/start, right?
You just gotta restart if !!pp->prog != !!prog?

> +	old_prog = xchg(&pp->xdp_prog, prog);
> +	if (old_prog)
> +		bpf_prog_put(old_prog);
> +
> +	if (netif_running(dev))
> +		return mvneta_open(dev);
> +
> +	return 0;
> +}