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From: sdf@google.com
To: Jesper Dangaard Brouer <brouer@redhat.com>
Cc: bpf@vger.kernel.org, netdev@vger.kernel.org,
	xdp-hints@xdp-project.net, larysa.zaremba@intel.com,
	memxor@gmail.com, Lorenzo Bianconi <lorenzo@kernel.org>,
	mtahhan@redhat.com,
	Alexei Starovoitov <alexei.starovoitov@gmail.com>,
	Daniel Borkmann <borkmann@iogearbox.net>,
	Andrii Nakryiko <andrii.nakryiko@gmail.com>,
	dave@dtucker.co.uk, Magnus Karlsson <magnus.karlsson@intel.com>,
	bjorn@kernel.org
Subject: [xdp-hints] Re: [PATCH RFCv2 bpf-next 00/18] XDP-hints: XDP gaining access to HW offload hints via BTF
Date: Mon, 3 Oct 2022 16:55:14 -0700	[thread overview]
Message-ID: <Yzt2YhbCBe8fYHWQ@google.com> (raw)
In-Reply-To: <166256538687.1434226.15760041133601409770.stgit@firesoul>

On 09/07, Jesper Dangaard Brouer wrote:
> This patchset expose the traditional hardware offload hints to XDP and
> rely on BTF to expose the layout to users.

> Main idea is that the kernel and NIC drivers simply defines the struct
> layouts they choose to use for XDP-hints. These XDP-hints structs gets
> naturally and automatically described via BTF and implicitly exported to
> users. NIC drivers populate and records their own BTF ID as the last
> member in XDP metadata area (making it easily accessible by AF_XDP
> userspace at a known negative offset from packet data start).

> Naming conventions for the structs (xdp_hints_*) is used such that
> userspace can find and decode the BTF layout and match against the
> provided BTF IDs. Thus, no new UAPI interfaces are needed for exporting
> what XDP-hints a driver supports.

> The patch "i40e: Add xdp_hints_union" introduce the idea of creating a
> union named "xdp_hints_union" in every driver, which contains all
> xdp_hints_* struct this driver can support. This makes it easier/quicker
> to find and parse the relevant BTF types.  (Seeking input before fixing
> up all drivers in patchset).


> The main different from RFC-v1:
>   - Drop idea of BTF "origin" (vmlinux, module or local)
>   - Instead to use full 64-bit BTF ID that combine object+type ID

> I've taken some of Alexandr/Larysa's libbpf patches and integrated
> those.

> Patchset exceeds netdev usually max 15 patches rule. My excuse is three
> NIC drivers (i40e, ixgbe and mvneta) gets XDP-hints support and which
> required some refactoring to remove the SKB dependencies.

Hey Jesper,

I took a quick look at the series. Do we really need the enum with the  
flags?
We might eventually hit that "first 16 bits are reserved" issue?

Instead of exposing enum with the flags, why not solve it as follows:
a. We define UAPI struct xdp_rx_hints with _all_ possible hints
b. Each device defines much denser <device>_xdp_rx_hints struct with the
    metadata that it supports
c. The subset of fields in <device>_xdp_rx_hints should match the ones from
    xdp_rx_hints (we essentially standardize on the field names/sizes)
d. We expose <device>_xdp_rx_hints btf id via netlink for each device
e. libbpf will query and do offset relocations for
    xdp_rx_hints -> <device>_xdp_rx_hints at load time

Would that work? Then it seems like we can replace bitfields with the  
following:

   if (bpf_core_field_exists(struct xdp_rx_hints, vlan_tci)) {
     /* use that hint */
   }

All we need here is for libbpf to, again, do xdp_rx_hints ->
<device>_xdp_rx_hints translation before it evaluates  
bpf_core_field_exists()?

Thoughts? Any downsides? Am I missing something?

Also, about the TX side: I feel like the same can be applied there,
the program works with xdp_tx_hints and libbpf will rewrite to
<device>_xdp_tx_hints. xdp_tx_hints might have fields like "has_tx_vlan:1";
those, presumably, can be relocatable by libbpf as well?

  parent reply	other threads:[~2022-10-03 23:55 UTC|newest]

Thread overview: 57+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-09-07 15:45 [xdp-hints] " Jesper Dangaard Brouer
2022-09-07 15:45 ` [xdp-hints] [PATCH RFCv2 bpf-next 01/18] libbpf: factor out BTF loading from load_module_btfs() Jesper Dangaard Brouer
2022-09-07 15:45 ` [xdp-hints] [PATCH RFCv2 bpf-next 02/18] libbpf: try to load vmlinux BTF from the kernel first Jesper Dangaard Brouer
2022-09-07 15:45 ` [xdp-hints] [PATCH RFCv2 bpf-next 03/18] libbpf: patch module BTF obj+type ID into BPF insns Jesper Dangaard Brouer
2022-09-07 15:45 ` [xdp-hints] [PATCH RFCv2 bpf-next 04/18] net: create xdp_hints_common and set functions Jesper Dangaard Brouer
2022-09-09 10:49   ` [xdp-hints] " Burakov, Anatoly
2022-09-09 14:13     ` Jesper Dangaard Brouer
2022-09-07 15:45 ` [xdp-hints] [PATCH RFCv2 bpf-next 05/18] net: add net_device feature flag for XDP-hints Jesper Dangaard Brouer
2022-09-07 15:45 ` [xdp-hints] [PATCH RFCv2 bpf-next 06/18] xdp: controlling XDP-hints from BPF-prog via helper Jesper Dangaard Brouer
2022-09-07 15:45 ` [xdp-hints] [PATCH RFCv2 bpf-next 07/18] i40e: Refactor i40e_ptp_rx_hwtstamp Jesper Dangaard Brouer
2022-09-07 15:45 ` [xdp-hints] [PATCH RFCv2 bpf-next 08/18] i40e: refactor i40e_rx_checksum with helper Jesper Dangaard Brouer
2022-09-07 15:45 ` [xdp-hints] [PATCH RFCv2 bpf-next 09/18] bpf: export btf functions for modules Jesper Dangaard Brouer
2022-09-07 15:45 ` [xdp-hints] [PATCH RFCv2 bpf-next 10/18] btf: Add helper for kernel modules to lookup full BTF ID Jesper Dangaard Brouer
2022-09-07 15:45 ` [xdp-hints] [PATCH RFCv2 bpf-next 11/18] i40e: add XDP-hints handling Jesper Dangaard Brouer
2022-09-07 15:46 ` [xdp-hints] [PATCH RFCv2 bpf-next 12/18] net: use XDP-hints in xdp_frame to SKB conversion Jesper Dangaard Brouer
2022-09-07 15:46 ` [xdp-hints] [PATCH RFCv2 bpf-next 13/18] mvneta: add XDP-hints support Jesper Dangaard Brouer
2022-09-07 15:46 ` [xdp-hints] [PATCH RFCv2 bpf-next 14/18] i40e: Add xdp_hints_union Jesper Dangaard Brouer
2022-09-07 15:46 ` [xdp-hints] [PATCH RFCv2 bpf-next 15/18] ixgbe: enable xdp-hints Jesper Dangaard Brouer
2022-09-07 15:46 ` [xdp-hints] [PATCH RFCv2 bpf-next 16/18] ixgbe: add rx timestamp xdp hints support Jesper Dangaard Brouer
2022-09-07 15:46 ` [xdp-hints] [PATCH RFCv2 bpf-next 17/18] xsk: AF_XDP xdp-hints support in desc options Jesper Dangaard Brouer
2022-09-08  8:06   ` [xdp-hints] " Magnus Karlsson
2022-09-08 10:10     ` Maryam Tahhan
2022-09-08 15:04       ` Jesper Dangaard Brouer
2022-09-09  6:43         ` Magnus Karlsson
2022-09-09  8:12           ` Maryam Tahhan
2022-09-09  9:42             ` Jesper Dangaard Brouer
2022-09-09 10:14               ` Magnus Karlsson
2022-09-09 12:35                 ` Jesper Dangaard Brouer
2022-09-09 12:44                   ` Magnus Karlsson
2022-09-07 15:46 ` [xdp-hints] [PATCH RFCv2 bpf-next 18/18] ixgbe: AF_XDP xdp-hints processing in ixgbe_clean_rx_irq_zc Jesper Dangaard Brouer
2022-09-08  9:30 ` [xdp-hints] Re: [PATCH RFCv2 bpf-next 00/18] XDP-hints: XDP gaining access to HW offload hints via BTF Alexander Lobakin
2022-09-09 13:48   ` Jesper Dangaard Brouer
2022-10-03 23:55 ` sdf [this message]
2022-10-04  9:29   ` Jesper Dangaard Brouer
2022-10-04 18:26     ` Stanislav Fomichev
2022-10-05  0:25       ` Martin KaFai Lau
2022-10-05  0:59         ` Jakub Kicinski
2022-10-05  1:02           ` Stanislav Fomichev
2022-10-05  1:24             ` Jakub Kicinski
2022-10-05  2:15               ` Stanislav Fomichev
2022-10-05 19:26                 ` Martin KaFai Lau
2022-10-06  9:14                   ` Magnus Karlsson
2022-10-06 15:29                     ` Jesper Dangaard Brouer
2022-10-11  6:29                       ` Martin KaFai Lau
2022-10-11 11:57                         ` Jesper Dangaard Brouer
2022-10-05 10:06             ` Toke Høiland-Jørgensen
2022-10-05 18:47               ` sdf
2022-10-06  8:19                 ` Maryam Tahhan
2022-10-06 17:22                   ` sdf
2022-10-05 14:19             ` Jesper Dangaard Brouer
2022-10-06 14:59               ` Jakub Kicinski
2022-10-05 13:43         ` Jesper Dangaard Brouer
2022-10-05 16:29       ` Jesper Dangaard Brouer
2022-10-05 18:43         ` sdf
2022-10-06 17:47           ` Jesper Dangaard Brouer
2022-10-07 15:05             ` David Ahern
2022-10-05 13:14     ` Burakov, Anatoly

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