From: Jakub Kicinski <kuba@kernel.org>
To: Qingfang Deng <dqfext@gmail.com>
Cc: Andrew Lunn <andrew+netdev@lunn.ch>,
"David S. Miller" <davem@davemloft.net>,
Eric Dumazet <edumazet@google.com>,
Paolo Abeni <pabeni@redhat.com>,
linux-ppp@vger.kernel.org, netdev@vger.kernel.org,
linux-kernel@vger.kernel.org, Felix Fietkau <nbd@nbd.name>
Subject: Re: [PATCH net-next] ppp: enable TX scatter-gather
Date: Mon, 15 Sep 2025 18:10:15 -0700 [thread overview]
Message-ID: <20250915181015.67588ec2@kernel.org> (raw)
In-Reply-To: <20250912095928.1532113-1-dqfext@gmail.com>
On Fri, 12 Sep 2025 17:59:27 +0800 Qingfang Deng wrote:
> When chan->direct_xmit is true, and no compressors are in use, PPP
> prepends its header to a skb, and calls dev_queue_xmit directly. In this
> mode the skb does not need to be linearized.
> Enable NETIF_F_SG and NETIF_F_FRAGLIST, and add .ndo_fix_features()
> callback to conditionally disable them if a linear skb is required.
> This is required to support PPPoE GSO.
Seems a bit racy. We can't netdev_update_features() under the spin lock
so there's going to be a window of time where datapath will see new
state but netdev flags won't be cleared, yet?
We either need to add a explicit linearization check in the xmit path,
or always reset the flags to disabled before we start tweaking the
config and re-enable after config (tho the latter feels like a bit of
a hack).
--
pw-bot: cr
next prev parent reply other threads:[~2025-09-16 1:10 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-09-12 9:59 [PATCH net-next] ppp: enable TX scatter-gather Qingfang Deng
2025-09-16 1:10 ` Jakub Kicinski [this message]
2025-09-16 2:57 ` Qingfang Deng
2025-09-16 14:57 ` Jakub Kicinski
2025-09-17 11:00 ` Qingfang Deng
2025-09-17 21:14 ` Jakub Kicinski
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