Re: [PATCH net] net: stmmac: Correct byte order of perfect_match

[Maxime Chevallier <maxime.chevallier@bootlin.com>]

Hello Simon,

On Tue, 23 Jul 2024 14:29:27 +0100
Simon Horman <horms@kernel.org> wrote:

> The perfect_match parameter of the update_vlan_hash operation is __le16,
> and is correctly converted from host byte-order in the lone caller,
> stmmac_vlan_update().
> 
> However, the implementations of this caller, dwxgmac2_update_vlan_hash()
> and dwxgmac2_update_vlan_hash(), both treat this parameter as host byte
> order, using the following pattern:
> 
> 	u32 value = ...
> 	...
> 	writel(value | perfect_match, ...);
> 
> This is not correct because both:
> 1) value is host byte order; and
> 2) writel expects a host byte order value as it's first argument
> 
> I believe that this will break on big endian systems. And I expect it
> has gone unnoticed by only being exercised on little endian systems.
> 
> The approach taken by this patch is to update the callback, and it's
> caller to simply use a host byte order value.
> 
> Flagged by Sparse.
> Compile tested only.
> 
> Fixes: c7ab0b8088d7 ("net: stmmac: Fallback to VLAN Perfect filtering if HASH is not available")
> Signed-off-by: Simon Horman <horms@kernel.org>

Reviewed-by: Maxime Chevallier <maxime.chevallier@bootlin.com>

Thanks,

Maxime