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Message-ID: <ZGZ66D8x5Nbp2iYO@google.com> Date: Thu, 18 May 2023 12:22:16 -0700 From: Stanislav Fomichev <sdf@...gle.com> To: Maciej Fijalkowski <maciej.fijalkowski@...el.com> Cc: bpf@...r.kernel.org, ast@...nel.org, daniel@...earbox.net, andrii@...nel.org, netdev@...r.kernel.org, magnus.karlsson@...el.com, tirthendu.sarkar@...el.com, bjorn@...nel.org Subject: Re: [PATCH bpf-next 01/21] xsk: prepare 'options' in xdp_desc for multi-buffer use On 05/18, Maciej Fijalkowski wrote: > From: Tirthendu Sarkar <tirthendu.sarkar@...el.com> > > Use the 'options' field in xdp_desc as a packet continuity marker. Since > 'options' field was unused till now and was expected to be set to 0, the > 'eop' descriptor will have it set to 0, while the non-eop descriptors > will have to set it to 1. This ensures legacy applications continue to > work without needing any change for single-buffer packets. > > Add helper functions and extend xskq_prod_reserve_desc() to use the > 'options' field. > > Signed-off-by: Tirthendu Sarkar <tirthendu.sarkar@...el.com> > --- > include/uapi/linux/if_xdp.h | 16 ++++++++++++++++ > net/xdp/xsk.c | 8 ++++---- > net/xdp/xsk_queue.h | 12 +++++++++--- > 3 files changed, 29 insertions(+), 7 deletions(-) > > diff --git a/include/uapi/linux/if_xdp.h b/include/uapi/linux/if_xdp.h > index a78a8096f4ce..4acc3a9430f3 100644 > --- a/include/uapi/linux/if_xdp.h > +++ b/include/uapi/linux/if_xdp.h > @@ -108,4 +108,20 @@ struct xdp_desc { > > /* UMEM descriptor is __u64 */ > > +/* Flag indicating that the packet continues with the buffer pointed out by the > + * next frame in the ring. The end of the packet is signalled by setting this > + * bit to zero. For single buffer packets, every descriptor has 'options' set > + * to 0 and this maintains backward compatibility. > + */ > +#define XDP_PKT_CONTD (1 << 0) > + > +/* Maximum number of descriptors supported as frags for a packet. So the total > + * number of descriptors supported for a packet is XSK_DESC_MAX_FRAGS + 1. The > + * max frags supported by skb is 16 for page sizes greater than 4K and 17 or This is now a config option CONFIG_MAX_SKB_FRAGS. Can we use it directly?
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