On 10/23, Magnus Karlsson wrote:
> On Thu, 19 Oct 2023 at 19:50, Stanislav Fomichev <sdf@xxxxxxxxxx> wrote:
> >
> > For zerocopy mode, tx_desc->addr can point to the arbitrary offset
>
> nit: the -> an
Thanks!
> > and carry some TX metadata in the headroom. For copy mode, there
> > is no way currently to populate skb metadata.
> >
> > Introduce new tx_metadata_len umem config option that indicates how many
> > bytes to treat as metadata. Metadata bytes come prior to tx_desc address
> > (same as in RX case).
> >
> > The size of the metadata has the same constraints as XDP:
> > - less than 256 bytes
> > - 4-byte aligned
> > - non-zero
> >
> > This data is not interpreted in any way right now.
> >
> > Signed-off-by: Stanislav Fomichev <sdf@xxxxxxxxxx>
> > ---
> > include/net/xdp_sock.h | 1 +
> > include/net/xsk_buff_pool.h | 1 +
> > include/uapi/linux/if_xdp.h | 1 +
> > net/xdp/xdp_umem.c | 4 ++++
> > net/xdp/xsk.c | 12 +++++++++++-
> > net/xdp/xsk_buff_pool.c | 1 +
> > net/xdp/xsk_queue.h | 17 ++++++++++-------
> > tools/include/uapi/linux/if_xdp.h | 1 +
> > 8 files changed, 30 insertions(+), 8 deletions(-)
> >
> > diff --git a/include/net/xdp_sock.h b/include/net/xdp_sock.h
> > index 7dd0df2f6f8e..5ae88a00f34a 100644
> > --- a/include/net/xdp_sock.h
> > +++ b/include/net/xdp_sock.h
> > @@ -30,6 +30,7 @@ struct xdp_umem {
> > struct user_struct *user;
> > refcount_t users;
> > u8 flags;
> > + u8 tx_metadata_len;
> > bool zc;
> > struct page **pgs;
> > int id;
> > diff --git a/include/net/xsk_buff_pool.h b/include/net/xsk_buff_pool.h
> > index b0bdff26fc88..1985ffaf9b0c 100644
> > --- a/include/net/xsk_buff_pool.h
> > +++ b/include/net/xsk_buff_pool.h
> > @@ -77,6 +77,7 @@ struct xsk_buff_pool {
> > u32 chunk_size;
> > u32 chunk_shift;
> > u32 frame_len;
> > + u8 tx_metadata_len; /* inherited from umem */
> > u8 cached_need_wakeup;
> > bool uses_need_wakeup;
> > bool dma_need_sync;
> > diff --git a/include/uapi/linux/if_xdp.h b/include/uapi/linux/if_xdp.h
> > index 8d48863472b9..2ecf79282c26 100644
> > --- a/include/uapi/linux/if_xdp.h
> > +++ b/include/uapi/linux/if_xdp.h
> > @@ -76,6 +76,7 @@ struct xdp_umem_reg {
> > __u32 chunk_size;
> > __u32 headroom;
> > __u32 flags;
> > + __u32 tx_metadata_len;
> > };
> >
> > struct xdp_statistics {
> > diff --git a/net/xdp/xdp_umem.c b/net/xdp/xdp_umem.c
> > index 06cead2b8e34..333f3d53aad4 100644
> > --- a/net/xdp/xdp_umem.c
> > +++ b/net/xdp/xdp_umem.c
> > @@ -199,6 +199,9 @@ static int xdp_umem_reg(struct xdp_umem *umem, struct xdp_umem_reg *mr)
> > if (headroom >= chunk_size - XDP_PACKET_HEADROOM)
> > return -EINVAL;
> >
> > + if (mr->tx_metadata_len > 256 || mr->tx_metadata_len % 4)
> > + return -EINVAL;
>
> Should be >= 256 since the final internal destination is a u8 and the
> documentation says "should be less than 256 bytes".
Thanks, will fix.
