netdev - Re: [PATCH net 1/3] net: fec: dynamically set the NETDEV_XDP_ACT_NDO

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Date: Wed, 5 Jul 2023 01:41:37 +0200
From: Andrew Lunn <andrew@...n.ch>
To: wei.fang@....com
Cc: davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
	pabeni@...hat.com, ast@...nel.org, daniel@...earbox.net,
	hawk@...nel.org, john.fastabend@...il.com, shenwei.wang@....com,
	xiaoning.wang@....com, netdev@...r.kernel.org, linux-imx@....com,
	linux-kernel@...r.kernel.org, bpf@...r.kernel.org
Subject: Re: [PATCH net 1/3] net: fec: dynamically set the
 NETDEV_XDP_ACT_NDO_XMIT feature of XDP

On Tue, Jul 04, 2023 at 04:29:14PM +0800, wei.fang@....com wrote:
> From: Wei Fang <wei.fang@....com>
> 
> When a XDP program is installed or uninstalled, fec_restart() will
> be invoked to reset MAC and buffer descriptor rings. It's reasonable
> not to transmit any packet during the process of reset. However, the
> NETDEV_XDP_ACT_NDO_XMIT bit of xdp_features is enabled by default,
> that is to say, it's possible that the fec_enet_xdp_xmit() will be
> invoked even if the process of reset is not finished. In this case,
> the redirected XDP frames might be dropped and available transmit BDs
> may be incorrectly deemed insufficient. So this patch disable the
> NETDEV_XDP_ACT_NDO_XMIT feature by default and dynamically configure
> this feature when the bpf program is installed or uninstalled.

I don't know much about XDP, so please excuse what might be a stupid
question.

Is this a generic issue? Should this
xdp_features_clear_redirect_target(dev) /
xdp_features_set_redirect_target(dev, false) be done in the core?

	Andrew