netdev - Re: [PATCH net] net: thunder_bgx: Fix netdev structure allocation

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Message-ID: <ZruI940YZCETGNGq@gmail.com>
Date: Tue, 13 Aug 2024 09:25:27 -0700
From: Breno Leitao <leitao@...ian.org>
To: Marc Zyngier <maz@...nel.org>
Cc: linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	netdev@...r.kernel.org, Sunil Goutham <sgoutham@...vell.com>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>
Subject: Re: [PATCH net] net: thunder_bgx: Fix netdev structure allocation

Hello Marc,

On Mon, Aug 12, 2024 at 03:13:22PM +0100, Marc Zyngier wrote:
> Commit 94833addfaba ("net: thunderx: Unembed netdev structure") had
> a go at dynamically allocating the netdev structures for the thunderx_bgx
> driver.  This change results in my ThunderX box catching fire (to be fair,
> it is what it does best).

Should I be proud of it? :-)

> The issues with this change are that:
> 
> - bgx_lmac_enable() is called *after* bgx_acpi_register_phy() and
>   bgx_init_of_phy(), both expecting netdev to be a valid pointer.
> 
> - bgx_init_of_phy() populates the MAC addresses for *all* LMACs
>   attached to a given BGX instance, and thus needs netdev for each of
>   them to have been allocated.
> 
> There is a few things to be said about how the driver mixes LMAC and
> BGX states which leads to this sorry state, but that's beside the point.
> 
> To address this, go back to a situation where all netdev structures
> are allocated before the driver starts relying on them, and move the
> freeing of these structures to driver removal. Someone brave enough
> can always go and restructure the driver if they want.
> 
> Fixes: 94833addfaba ("net: thunderx: Unembed netdev structure")
> Signed-off-by: Marc Zyngier <maz@...nel.org>

Reviewed-by: Breno Leitao <leitao@...ian.org>

Thanks for taming my fiery commit.