Re: [PATCH RESEND net-next v4 0/4] net/mlx5e: Add GBP VxLAN HW offload support

[Gavin Li]

On 3/8/2023 12:58 AM, Alexander Lobakin wrote:
> External email: Use caution opening links or attachments
>
>
> From: Gavin Li <gavinl@xxxxxxxxxx>
> Date: Tue, 7 Mar 2023 17:19:35 +0800
>
> > On 3/6/2023 10:47 PM, Alexander Lobakin wrote:
> > > External email: Use caution opening links or attachments
> > >
> > >
> > > From: Gavin Li <gavinl@xxxxxxxxxx>
> > > Date: Mon, 6 Mar 2023 05:02:58 +0200
> > >
> > > > Patch-1: Remove unused argument from functions.
> > > > Patch-2: Expose helper function vxlan_build_gbp_hdr.
> > > > Patch-3: Add helper function for encap_info_equal for tunnels with
> > > > options.
> > > > Patch-4: Add HW offloading support for TC flows with VxLAN GBP
> > > > encap/decap
> > > >           in mlx ethernet driver.
> > > >
> > > > Gavin Li (4):
> > > >     vxlan: Remove unused argument from vxlan_build_gbp_hdr( ) and
> > > >       vxlan_build_gpe_hdr( )
> > > > ---
> > > > changelog:
> > > > v2->v3
> > > > - Addressed comments from Paolo Abeni
> > > > - Add new patch
> > > > ---
> > > >     vxlan: Expose helper vxlan_build_gbp_hdr
> > > > ---
> > > > changelog:
> > > > v1->v2
> > > > - Addressed comments from Alexander Lobakin
> > > > - Use const to annotate read-only the pointer parameter
> > > > ---
> > > >     net/mlx5e: Add helper for encap_info_equal for tunnels with options
> > > > ---
> > > > changelog:
> > > > v3->v4
> > > > - Addressed comments from Alexander Lobakin
> > > > - Fix vertical alignment issue
> > > > v1->v2
> > > > - Addressed comments from Alexander Lobakin
> > > > - Replace confusing pointer arithmetic with function call
> > > > - Use boolean operator NOT to check if the function return value is
> > > > not zero
> > > > ---
> > > >     net/mlx5e: TC, Add support for VxLAN GBP encap/decap flows offload
> > > > ---
> > > > changelog:
> > > > v3->v4
> > > > - Addressed comments from Simon Horman
> > > > - Using cast in place instead of changing API
> > > I don't remember me acking this. The last thing I said is that in order
> > > to avoid cast-aways you need to use _Generic(). 2 times. IIRC you said
> > > "Ack" and that was the last message in that thread.
> > > Now this. Without me in CCs, so I noticed it accidentally.
> > > ???
> > Not asked by you but you said you were OK if I used cast-aways. So I did
> > the
> >
> > change in V3 and reverted back to using cast-away in V4.
> My last reply was[0]:
>
> "
> 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.
>
> [...]
>
> [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
> "
>
> Where did I say here I'm fine with W/As in the drivers? I mentioned two
> options: cast-away in THE GENERIC INLINE, not the driver, or, more
> preferred, following the way of container_of_const().
> Then your reply[1]:
>
> "ACK"
>
> What did you ack then if you picked neither of those 2 options?

I had fixed it with "cast-away in THE GENERIC INLINE" in V3 and got 
comments and concern

from Simon Horman. So, it was reverted.

"But I really do wonder if this patch masks rather than fixes the 
problem."----From Simon.

I thought you were OK to revert the changes based on the reply.

From my understanding, the function always return a non-const pointer 
regardless the type of the

 input one, which is slightly different from your examples.

Any comments, Simon?

If both or you are OK with option #1, I'll follow.

> > > > v2->v3
> > > > - Addressed comments from Alexander Lobakin
> > > > - Remove the WA by casting away
> > > > v1->v2
> > > > - Addressed comments from Alexander Lobakin
> > > > - Add a separate pair of braces around bitops
> > > > - Remove the WA by casting away
> > > > - Fit all log messages into one line
> > > > - Use NL_SET_ERR_MSG_FMT_MOD to print the invalid value on error
> > > > ---
> > > >
> > > >    .../ethernet/mellanox/mlx5/core/en/tc_tun.h   |  3 +
> > > >    .../mellanox/mlx5/core/en/tc_tun_encap.c      | 32 ++++++++
> > > >    .../mellanox/mlx5/core/en/tc_tun_geneve.c     | 24 +-----
> > > >    .../mellanox/mlx5/core/en/tc_tun_vxlan.c      | 76 ++++++++++++++++++-
> > > >    drivers/net/vxlan/vxlan_core.c                | 27 +------
> > > >    include/linux/mlx5/device.h                   |  6 ++
> > > >    include/linux/mlx5/mlx5_ifc.h                 | 13 +++-
> > > >    include/net/vxlan.h                           | 19 +++++
> > > >    8 files changed, 149 insertions(+), 51 deletions(-)
> > > Thanks,
> > > Olek
> [0]
> https://lore.kernel.org/netdev/aefe00f0-2a15-9a43-2451-6d01e74cc48a@xxxxxxxxx
> [1]
> https://lore.kernel.org/netdev/ca729a48-35a1-ef05-59d3-ef1539003051@xxxxxxxxxx
>
> Thanks,
> Olek