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From: Maryam Tahhan <mtahhan@redhat.com>
To: Magnus Karlsson <magnus.karlsson@gmail.com>,
	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>,
	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 17/18] xsk: AF_XDP xdp-hints support in desc options
Date: Thu, 8 Sep 2022 11:10:31 +0100	[thread overview]
Message-ID: <b5f0d10d-2d4e-34d6-1e45-c206cb6f5d26@redhat.com> (raw)
In-Reply-To: <CAJ8uoz3UcC2tnMtG8W6a3HpCKgaYSzSCqowLFQVwCcsr+NKBOQ@mail.gmail.com>

On 08/09/2022 09:06, Magnus Karlsson wrote:
> On Wed, Sep 7, 2022 at 5:48 PM Jesper Dangaard Brouer <brouer@redhat.com> wrote:
>>
>> From: Maryam Tahhan <mtahhan@redhat.com>
>>
>> Simply set AF_XDP descriptor options to XDP flags.
>>
>> Jesper: Will this really be acceptable by AF_XDP maintainers?
> 
> Maryam, you guessed correctly that dedicating all these options bits
> for a single feature will not be ok :-). E.g., I want one bit for the
> AF_XDP multi-buffer support and who knows what other uses there might
> be for this options field in the future. Let us try to solve this in
> some other way. Here are some suggestions, all with their pros and
> cons.
> 

TBH it was Jespers question :)

> * Put this feature flag at a known place in the metadata area, for
> example just before the BTF ID. No need to fill this in if you are not
> redirecting to AF_XDP, but at a redirect to AF_XDP, the XDP flags are
> copied into this u32 in the metadata area so that user-space can
> consume it. Will cost 4 bytes of the metadata area though.

If Jesper agrees I think this approach would make sense. Trying to
translate encodings into some other flags for AF_XDP I think will lead
to a growing set of translations as more options come along.
The other thing to be aware of is just making sure to clear/zero the 
metadata space in the buffers at some point (ideally when the descriptor 
is returned from the application) so when the buffers are used again
they are already in a "reset" state.

> 
> * Instead encode this information into each metadata entry in the
> metadata area, in some way so that a flags field is not needed (-1
> signifies not valid, or whatever happens to make sense). This has the
> drawback that the user might have to look at a large number of entries
> just to find out there is nothing valid to read. To alleviate this, it
> could be combined with the next suggestion.
> 
> * Dedicate one bit in the options field to indicate that there is at
> least one valid metadata entry in the metadata area. This could be
> combined with the two approaches above. However, depending on what
> metadata you have enabled, this bit might be pointless. If some
> metadata is always valid, then it serves no purpose. But it might if
> all enabled metadata is rarely valid, e.g., if you get an Rx timestamp
> on one packet out of one thousand.
> 
>> Signed-off-by: Maryam Tahhan <mtahhan@redhat.com>
>> ---
>>   include/uapi/linux/if_xdp.h |    2 +-
>>   net/xdp/xsk.c               |    2 +-
>>   net/xdp/xsk_queue.h         |    3 ++-
>>   3 files changed, 4 insertions(+), 3 deletions(-)
>>
>> diff --git a/include/uapi/linux/if_xdp.h b/include/uapi/linux/if_xdp.h
>> index a78a8096f4ce..9335b56474e7 100644
>> --- a/include/uapi/linux/if_xdp.h
>> +++ b/include/uapi/linux/if_xdp.h
>> @@ -103,7 +103,7 @@ struct xdp_options {
>>   struct xdp_desc {
>>          __u64 addr;
>>          __u32 len;
>> -       __u32 options;
>> +       __u32 options; /* set to the values of xdp_hints_flags*/
>>   };
>>
>>   /* UMEM descriptor is __u64 */
>> diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c
>> index 5b4ce6ba1bc7..32095d78f06b 100644
>> --- a/net/xdp/xsk.c
>> +++ b/net/xdp/xsk.c
>> @@ -141,7 +141,7 @@ static int __xsk_rcv_zc(struct xdp_sock *xs, struct xdp_buff *xdp, u32 len)
>>          int err;
>>
>>          addr = xp_get_handle(xskb);
>> -       err = xskq_prod_reserve_desc(xs->rx, addr, len);
>> +       err = xskq_prod_reserve_desc(xs->rx, addr, len, xdp->flags);
>>          if (err) {
>>                  xs->rx_queue_full++;
>>                  return err;
>> diff --git a/net/xdp/xsk_queue.h b/net/xdp/xsk_queue.h
>> index fb20bf7207cf..7a66f082f97e 100644
>> --- a/net/xdp/xsk_queue.h
>> +++ b/net/xdp/xsk_queue.h
>> @@ -368,7 +368,7 @@ static inline u32 xskq_prod_reserve_addr_batch(struct xsk_queue *q, struct xdp_d
>>   }
>>
>>   static inline int xskq_prod_reserve_desc(struct xsk_queue *q,
>> -                                        u64 addr, u32 len)
>> +                                        u64 addr, u32 len, u32 flags)
>>   {
>>          struct xdp_rxtx_ring *ring = (struct xdp_rxtx_ring *)q->ring;
>>          u32 idx;
>> @@ -380,6 +380,7 @@ static inline int xskq_prod_reserve_desc(struct xsk_queue *q,
>>          idx = q->cached_prod++ & q->ring_mask;
>>          ring->desc[idx].addr = addr;
>>          ring->desc[idx].len = len;
>> +       ring->desc[idx].options = flags;
>>
>>          return 0;
>>   }
>>
>>
> 


  reply	other threads:[~2022-09-08 10:10 UTC|newest]

Thread overview: 57+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-09-07 15:45 [xdp-hints] [PATCH RFCv2 bpf-next 00/18] XDP-hints: XDP gaining access to HW offload hints via BTF 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 [this message]
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
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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