From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from pandora.armlinux.org.uk (pandora.armlinux.org.uk [78.32.30.218]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id B688C238D54; Tue, 6 May 2025 08:37:09 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=78.32.30.218 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1746520633; cv=none; b=qzDC+/eAsKGf4/qF6axN3PybmXx65weZZSeRMO6mUyrV9K/EAvt7u8NZyrr7UVyHLMqPzdzr6O/MTh1/1b7peIl//xTlKCxo0zlkWKNkOhSkjCBD4fZNYcSfUumedln59OKY9mf0UQWL2GFckZLI/B/iB6oMDymdyuSpMugVRKE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1746520633; c=relaxed/simple; bh=BPleUJ43gps1LzmAi+Cfbujv8xn2Wf6Mh4ei2dgpv04=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=fADgxlu4fdooq9paGKTrh3tRTuOnXP3x+gV5bEwiG/mlC8kAYn6OHi2ARMk8cTIL9iOgSqgOMvwD1yPmvY5GTv2OW1ojsedrGMGF9iXX77ubwCX3vgQAbnCMIaw2ogNqaN3W1GRSqwAXt6OuCK0H+mgsrHs3U9jfCcokaJ6nUww= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=armlinux.org.uk; spf=none smtp.mailfrom=armlinux.org.uk; dkim=pass (2048-bit key) header.d=armlinux.org.uk header.i=@armlinux.org.uk header.b=CdQNHlNC; arc=none smtp.client-ip=78.32.30.218 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=armlinux.org.uk Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=armlinux.org.uk Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=armlinux.org.uk header.i=@armlinux.org.uk header.b="CdQNHlNC" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=armlinux.org.uk; s=pandora-2019; h=Sender:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=3hvlZVFson57t3/jkjgd7DNP9CrsDWw/JGVHUYVHQz0=; b=CdQNHlNCfaFJOs//OjIoPGbRLF eYIaLZX2TzkNdE7txCL1rw42XUcU3h9GktlcJ+7Gm1OamfQttnzW5ZEDF+b9qfU2YWZ+NrD1/6cHp PiOxzYWCmdJL33gZ+EtuTTRmZCp9AogcxglGBGV99ugdcnJYL7G7v9bZ8FQM+fxNakrTgPhTWxmfW XUIogU0ixol87CShSu6Lx8OYXO9qFg5rok3Pcil2K+Y95ccpXzfB6x5K2uiWHJTw6k3seQ7hqzIzq 680DXTZ0fQ+doPEHILF2TvuTbeKeEgGRd6HO//pD8UqeIshSpW0yHpeGnMJO9xKGg8HV9E95I40lg YPmNnSLA==; Received: from shell.armlinux.org.uk ([fd8f:7570:feb6:1:5054:ff:fe00:4ec]:35116) by pandora.armlinux.org.uk with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.96) (envelope-from ) id 1uCDnS-0005UW-0D; Tue, 06 May 2025 09:37:02 +0100 Received: from linux by shell.armlinux.org.uk with local (Exim 4.96) (envelope-from ) id 1uCDnN-0004e7-2Q; Tue, 06 May 2025 09:36:57 +0100 Date: Tue, 6 May 2025 09:36:57 +0100 From: "Russell King (Oracle)" To: Andrew Lunn Cc: Heiner Kallweit , Alexandre Torgue , Alexei Starovoitov , Andrew Lunn , bpf@vger.kernel.org, Daniel Borkmann , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Jesper Dangaard Brouer , John Fastabend , Jon Hunter , linux-arm-kernel@lists.infradead.org, linux-stm32@st-md-mailman.stormreply.com, Maxime Coquelin , netdev@vger.kernel.org, Paolo Abeni , Thierry Reding Subject: Re: [PATCH net-next v2 2/4] net: stmmac: call phylink_carrier_*() in XDP functions Message-ID: References: Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: Russell King (Oracle) On Fri, May 02, 2025 at 06:54:49PM +0100, Russell King (Oracle) wrote: > On Fri, May 02, 2025 at 05:29:21PM +0200, Andrew Lunn wrote: > > On Fri, May 02, 2025 at 02:35:36PM +0100, Russell King (Oracle) wrote: > > > Phylink does not permit drivers to mess with the netif carrier, as > > > this will de-synchronise phylink with the MAC driver. Moreover, > > > setting and clearing the TE and RE bits via stmmac_mac_set() in this > > > path is also wrong as the link may not be up. > > > > > > Replace the netif_carrier_on(), netif_carrier_off() and > > > stmmac_mac_set() calls with the appropriate phylink_carrier_block() and > > > phylink_carrier_unblock() calls, thereby allowing phylink to manage the > > > netif carrier and TE/RE bits through the .mac_link_up() and > > > .mac_link_down() methods. > > > > > > This change will have the side effect of printing link messages to > > > the kernel log, even though the physical link hasn't changed state. > > > This matches the carrier state that userspace sees, which has always > > > "bounced". > > > > > > Note that RE should only be set after the DMA is ready to avoid the > > > receive FIFO between the MAC and DMA blocks overflowing, so > > > phylink_start() needs to be placed after DMA has been started. > > > > > > Signed-off-by: Russell King (Oracle) > > > --- > > > .../net/ethernet/stmicro/stmmac/stmmac_main.c | 20 +++++++++++-------- > > > 1 file changed, 12 insertions(+), 8 deletions(-) > > > > > > diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c > > > index f59a2363f150..ac27ea679b23 100644 > > > --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c > > > +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c > > > @@ -6922,6 +6922,11 @@ void stmmac_xdp_release(struct net_device *dev) > > > /* Ensure tx function is not running */ > > > netif_tx_disable(dev); > > > > > > + /* Take down the software link. stmmac_xdp_open() must be called after > > > + * this function to release this block. > > > + */ > > > + phylink_carrier_block(priv->phylink); > > > + > > > /* Disable NAPI process */ > > > stmmac_disable_all_queues(priv); > > > > > > @@ -6937,14 +6942,10 @@ void stmmac_xdp_release(struct net_device *dev) > > > /* Release and free the Rx/Tx resources */ > > > free_dma_desc_resources(priv, &priv->dma_conf); > > > > > > - /* Disable the MAC Rx/Tx */ > > > - stmmac_mac_set(priv, priv->ioaddr, false); > > > - > > > /* set trans_start so we don't get spurious > > > * watchdogs during reset > > > */ > > > netif_trans_update(dev); > > > - netif_carrier_off(dev); > > > } > > > > > > > > int stmmac_xdp_open(struct net_device *dev) > > > @@ -7026,25 +7027,28 @@ int stmmac_xdp_open(struct net_device *dev) > > > hrtimer_setup(&tx_q->txtimer, stmmac_tx_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); > > > } > > > > > > - /* Enable the MAC Rx/Tx */ > > > - stmmac_mac_set(priv, priv->ioaddr, true); > > > - > > > /* Start Rx & Tx DMA Channels */ > > > stmmac_start_all_dma(priv); > > > > > > + /* Allow phylink to bring the software link back up. > > > + * stmmac_xdp_release() must have been called prior to this. > > > + */ > > > > This is counter intuitive. Why is release called before open? > > Indeed - and that should've been caught in the review where XDP was > being added. > > > Looking into stmmac_xdp_set_prog() i think i get it. Even if there is > > not a running XDP prog, stmmac_xdp_release() is called, and then > > stmmac_xdp_open(). > > If there is a change of "do we have an XDP prog" state, then > stmmac_xdp_release() is called to free all the current contexts to > do with queue/descriptor management, and then stmmac_xdp_open() is > called thereafter. These are doing a subset of .ndo_open/.ndo_release > and I think that's where they're getting their naming from. > > The only possible sequence is: > > stmmac_open() > then, on each XDP prog addition or removal, but not replacement: > stmmac_xdp_release() > stmmac_xdp_open() > finally, > stmmac_release() > > > Maybe these two functions need better names? prepare and commit? > > Yes, it's all counter intuitive, and there are various things about the > XDP code that make it hard to follow. > > For example, stmmac_xdp_set_prog() leads you to think, because of the > way the need_update variable is set, that looking for references to > xdp_prog would show one where all the dependents are, but no, there's > stmmac_xdp_is_enabled(), which is nice and readable, but could've > been used in stmmac_xdp_set_prog() to make it more obvious what to > grep for. > > Incidentally, if stmmac_xdp_open() fails to re-grab the interrupts, > then it calls phylink_stop(), stmmac_hw_teardown(), and > free_dma_desc_resources(). > > If one then set the interface administratively down, stmmac_release() > gets called, which again calls phylink_stop(), free_dma_desc_resources() > and stmmac_release_ptp(). > > stmmac_release_ptp() disables/unprepares clk_ptp_ref, and unregisters > the PTP stuff. stmmac_hw_teardown() also disables/unprepares > clk_ptp_ref, so we probably unbalance the clk API in this case... > and probably much other stuff. > > Calling free_dma_desc_resources() twice calls functios such as > free_dma_tx_desc_resources() twice, and it looks like that's not going > to be healthy, calling dma_free_coherent() with the same arguments, > double-releasing memory. Same for kfree(). Probably same for the RX > stuff. > > Basically, if one messes with XDP in this driver, expect things to go > bang and kill the kernel if something goes wrong with the whole > xdp_release+xdp_open dance. > > Honestly, this needs a rewrite, but I currently know nowt about XDP. > > So, I'd suggest that the names of these functions is the least of the > problems here. Well, this series has been discarded from patchwork. Shrug. I won't be posting another version, stmmac can remain broken. I don't have a suggestion on better names for these functions. -- RMK's Patch system: https://www.armlinux.org.uk/developer/patches/ FTTP is here! 80Mbps down 10Mbps up. Decent connectivity at last!