netdev - RE: [PATCH] ethernet: ice: avoid gcc-9 integer overflow warning

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Date:   Wed, 15 Feb 2023 10:58:46 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Arnd Bergmann' <arnd@...nel.org>,
        Jesse Brandeburg <jesse.brandeburg@...el.com>,
        Tony Nguyen <anthony.l.nguyen@...el.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        "Martyna Szapar-Mudlaw" <martyna.szapar-mudlaw@...ux.intel.com>
CC:     Arnd Bergmann <arnd@...db.de>,
        Marcin Szycik <marcin.szycik@...ux.intel.com>,
        Amritha Nambiar <amritha.nambiar@...el.com>,
        Michal Swiatkowski <michal.swiatkowski@...ux.intel.com>,
        Wojciech Drewek <wojciech.drewek@...el.com>,
        "intel-wired-lan@...ts.osuosl.org" <intel-wired-lan@...ts.osuosl.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH] ethernet: ice: avoid gcc-9 integer overflow warning

From: Arnd Bergmann
> Sent: 14 February 2023 13:20
> 
> From: Arnd Bergmann <arnd@...db.de>
> 
> With older compilers like gcc-9, the calculation of the vlan
> priority field causes a warning from the byteswap:
> 
...
> 
> Fixes: 34800178b302 ("ice: Add support for VLAN priority filters in switchdev")
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> ---
>  drivers/net/ethernet/intel/ice/ice_tc_lib.c | 10 ++++------
>  1 file changed, 4 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/net/ethernet/intel/ice/ice_tc_lib.c b/drivers/net/ethernet/intel/ice/ice_tc_lib.c
> index 6b48cbc049c6..e9932446185c 100644
> --- a/drivers/net/ethernet/intel/ice/ice_tc_lib.c
> +++ b/drivers/net/ethernet/intel/ice/ice_tc_lib.c
> @@ -1453,10 +1453,9 @@ ice_parse_cls_flower(struct net_device *filter_dev, struct ice_vsi *vsi,
>  		}
> 
>  		if (match.mask->vlan_priority) {
> +			u16 prio = (match.key->vlan_priority << VLAN_PRIO_SHIFT) & VLAN_PRIO_MASK;
>  			fltr->flags |= ICE_TC_FLWR_FIELD_VLAN_PRIO;
> -			headers->vlan_hdr.vlan_prio =
> -				cpu_to_be16((match.key->vlan_priority <<
> -					     VLAN_PRIO_SHIFT) & VLAN_PRIO_MASK);
> +			headers->vlan_hdr.vlan_prio = cpu_to_be16(prio);
>  		}

Is there something that will do:
	unsigned int pri = match.key->vlan_priority & (VLAN_PRIO_MASK >> VLAN_PRIO_SHIFT);
	headers->vlan_hdr.vlan_prio = pri << (VLAN_PRIO_SHIFT ^ (le ? 8 : 0));

	David

-
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