Messages in this thread | | | Date | Thu, 16 Feb 2023 16:19:53 +0100 | Subject | Re: [PATCH net-next v1 3/3] net/mlx5e: TC, Add support for VxLAN GBP encap/decap flows offload | From | Alexander Lobakin <> |
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From: Gavin Li <gavinl@nvidia.com> Date: Thu, 16 Feb 2023 16:40:33 +0800
> > On 2/16/2023 1:01 AM, Alexander Lobakin wrote: >> External email: Use caution opening links or attachments >> >> >> From: Gavin Li <gavinl@nvidia.com> >> Date: Wed, 15 Feb 2023 16:30:04 +0800 >> >>> On 2/15/2023 11:36 AM, Gavin Li wrote: >>>> External email: Use caution opening links or attachments >>>> >>>> >>>> On 2/14/2023 11:26 PM, Alexander Lobakin wrote: >>>>> External email: Use caution opening links or attachments >>>>> >>>>> >>>>> From: Gavin Li <gavinl@nvidia.com> >>>>> Date: Tue, 14 Feb 2023 15:41:37 +0200 >> [...] >> >>>>>> @@ -96,6 +99,70 @@ static int mlx5e_gen_ip_tunnel_header_vxlan(char >>>>>> buf[], >>>>>> udp->dest = tun_key->tp_dst; >>>>>> vxh->vx_flags = VXLAN_HF_VNI; >>>>>> vxh->vx_vni = vxlan_vni_field(tun_id); >>>>>> + if (tun_key->tun_flags & TUNNEL_VXLAN_OPT) { >>>>>> + md = ip_tunnel_info_opts((struct ip_tunnel_info >>>>>> *)e->tun_info); >>>>>> + vxlan_build_gbp_hdr(vxh, tun_key->tun_flags, >>>>>> + (struct vxlan_metadata *)md); >>>>> Maybe constify both ip_tunnel_info_opts() and vxlan_build_gbp_hdr() >>>>> arguments instead of working around by casting away? >>>> ACK. Sorry for the confusion---I misunderstood the comment. >>> This ip_tunnel_info_opts is tricky to use const to annotate the arg >>> because it will have to cast from const to non-const again upon >>> returning. >> It's okay to cast away for the `void *` returned. >> Alternatively, use can convert it to a macro and use >> __builtin_choose_expr() or _Generic to return const or non-const >> depending on whether the argument is constant. That's what was recently >> done for container_of() IIRC. > > I've fixed vxlan_build_gbp_hdr in V2. For ip_tunnel_info_opts, it's > confusing to me. > > It would be as below after constifying the parameter. > > static inline void *ip_tunnel_info_opts(const struct ip_tunnel_info *info) > { > return (void *)(info + 1); > } > Is there any value gained by this change?
You wouldn't need to W/A it each time in each driver, just do it once in the inline itself. I did it once in __skb_header_pointer()[0] to be able to pass data pointer as const to optimize code a bit and point out explicitly that the function doesn't modify the packet anyhow, don't see any reason to not do the same here. Or, as I said, you can use macros + __builtin_choose_expr() or _Generic. container_of_const() uses the latter[1]. A __builtin_choose_expr() variant could rely on the __same_type() macro to check whether the pointer passed from the driver const or not.
> >> >>>>>> + } >>>>>> + >>>>>> + return 0; >>>>>> +} >> [...] >> >> Thanks, >> Olek
[0] https://elixir.bootlin.com/linux/v6.2-rc8/source/include/linux/skbuff.h#L3992 [1] https://elixir.bootlin.com/linux/v6.2-rc8/source/include/linux/container_of.h#L33
Thanks, Olek
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