netdev - Re: [PATCH iwl-net] i40e: Fix XDP program unloading while removing the driver

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Message-ID: <20240531182549.GR491852@kernel.org>
Date: Fri, 31 May 2024 19:25:49 +0100
From: Simon Horman <horms@...nel.org>
To: Michal Kubiak <michal.kubiak@...el.com>
Cc: intel-wired-lan@...ts.osuosl.org, maciej.fijalkowski@...el.com,
	netdev@...r.kernel.org, Wojciech Drewek <wojciech.drewek@...el.com>
Subject: Re: [PATCH iwl-net] i40e: Fix XDP program unloading while removing
 the driver

On Thu, May 16, 2024 at 06:41:08PM +0200, Michal Kubiak wrote:
> The commit 6533e558c650 ("i40e: Fix reset path while removing
> the driver") introduced a new PF state "__I40E_IN_REMOVE" to block
> modifying the XDP program while the driver is being removed.
> Unfortunately, such a change is useful only if the ".ndo_bpf()"
> callback was called out of the rmmod context because unloading the
> existing XDP program is also a part of driver removing procedure.
> In other words, from the rmmod context the driver is expected to
> unload the XDP program without reporting any errors. Otherwise,
> the kernel warning with callstack is printed out to dmesg.
> 
> Example failing scenario:
>  1. Load the i40e driver.
>  2. Load the XDP program.
>  3. Unload the i40e driver (using "rmmod" command).
> 
> Fix this by improving checks in ".ndo_bpf()" to determine if that
> callback was called from the removing context and if the kernel
> wants to unload the XDP program. Allow for unloading the XDP program
> in such a case.
> 
> Fixes: 6533e558c650 ("i40e: Fix reset path while removing the driver")
> Reviewed-by: Wojciech Drewek <wojciech.drewek@...el.com>
> Signed-off-by: Michal Kubiak <michal.kubiak@...el.com>

Reviewed-by: Simon Horman <horms@...nel.org>