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Date: Thu, 16 Nov 2023 04:01:01 +0100
From: Larysa Zaremba <larysa.zaremba@...el.com>
To: Maciej Fijalkowski <maciej.fijalkowski@...el.com>
CC: <bpf@...r.kernel.org>, <ast@...nel.org>, <daniel@...earbox.net>,
<andrii@...nel.org>, <martin.lau@...ux.dev>, <song@...nel.org>, <yhs@...com>,
<john.fastabend@...il.com>, <kpsingh@...nel.org>, <sdf@...gle.com>,
<haoluo@...gle.com>, <jolsa@...nel.org>, David Ahern <dsahern@...il.com>,
Jakub Kicinski <kuba@...nel.org>, Willem de Bruijn <willemb@...gle.com>,
Jesper Dangaard Brouer <hawk@...nel.org>, Anatoly Burakov
<anatoly.burakov@...el.com>, Alexander Lobakin <alexandr.lobakin@...el.com>,
Magnus Karlsson <magnus.karlsson@...il.com>, Maryam Tahhan
<mtahhan@...hat.com>, <xdp-hints@...-project.net>, <netdev@...r.kernel.org>,
Willem de Bruijn <willemdebruijn.kernel@...il.com>, Alexei Starovoitov
<alexei.starovoitov@...il.com>, Tariq Toukan <tariqt@...lanox.com>, "Saeed
Mahameed" <saeedm@...lanox.com>
Subject: Re: [PATCH bpf-next v7 08/18] ice: Support XDP hints in AF_XDP ZC
mode
On Thu, Nov 16, 2023 at 01:49:36PM +0100, Maciej Fijalkowski wrote:
> On Wed, Nov 15, 2023 at 06:52:50PM +0100, Larysa Zaremba wrote:
> > In AF_XDP ZC, xdp_buff is not stored on ring,
> > instead it is provided by xsk_buff_pool.
> > Space for metadata sources right after such buffers was already reserved
> > in commit 94ecc5ca4dbf ("xsk: Add cb area to struct xdp_buff_xsk").
> >
> > Some things (such as pointer to packet context) do not change on a
> > per-packet basis, so they can be set at the same time as RX queue info.
> > On the other hand, RX descriptor is unique for each packet, but is already
> > known when setting DMA addresses. This minimizes performance impact of
> > hints on regular packet processing.
> >
> > Update AF_XDP ZC packet processing to support XDP hints.
> >
> > Co-developed-by: Maciej Fijalkowski <maciej.fijalkowski@...el.com>
> > Signed-off-by: Maciej Fijalkowski <maciej.fijalkowski@...el.com>
> > Signed-off-by: Larysa Zaremba <larysa.zaremba@...el.com>
> > ---
> > drivers/net/ethernet/intel/ice/ice_base.c | 13 +++++++++++++
> > drivers/net/ethernet/intel/ice/ice_xsk.c | 17 +++++++++++------
> > 2 files changed, 24 insertions(+), 6 deletions(-)
> >
> > diff --git a/drivers/net/ethernet/intel/ice/ice_base.c b/drivers/net/ethernet/intel/ice/ice_base.c
> > index 2d83f3c029e7..d3396c1c87a9 100644
> > --- a/drivers/net/ethernet/intel/ice/ice_base.c
> > +++ b/drivers/net/ethernet/intel/ice/ice_base.c
> > @@ -519,6 +519,18 @@ static int ice_setup_rx_ctx(struct ice_rx_ring *ring)
> > return 0;
> > }
> >
> > +static void ice_xsk_pool_fill_cb(struct ice_rx_ring *ring)
> > +{
> > + void *ctx_ptr = &ring->pkt_ctx;
> > + struct xsk_cb_desc desc = {};
> > +
> > + desc.src = &ctx_ptr;
> > + desc.off = offsetof(struct ice_xdp_buff, pkt_ctx) -
> > + sizeof(struct xdp_buff);
>
> Took me a while to figure out this offset calculation:D
>
Do you have a suggestion, how to make it easier to understand?
> > + desc.bytes = sizeof(ctx_ptr);
> > + xsk_pool_fill_cb(ring->xsk_pool, &desc);
> > +}
> > +
> > /**
> > * ice_vsi_cfg_rxq - Configure an Rx queue
> > * @ring: the ring being configured
> > @@ -553,6 +565,7 @@ int ice_vsi_cfg_rxq(struct ice_rx_ring *ring)
> > if (err)
> > return err;
> > xsk_pool_set_rxq_info(ring->xsk_pool, &ring->xdp_rxq);
>
> A good place for XSK_CHECK_PRIV_TYPE() ?
Seems so, have not noticed that it was missing :(
>
> > + ice_xsk_pool_fill_cb(ring);
> >
> > dev_info(dev, "Registered XDP mem model MEM_TYPE_XSK_BUFF_POOL on Rx ring %d\n",
> > ring->q_index);
> > diff --git a/drivers/net/ethernet/intel/ice/ice_xsk.c b/drivers/net/ethernet/intel/ice/ice_xsk.c
> > index 906e383e864a..a690e34ea8ae 100644
> > --- a/drivers/net/ethernet/intel/ice/ice_xsk.c
> > +++ b/drivers/net/ethernet/intel/ice/ice_xsk.c
> > @@ -433,7 +433,7 @@ int ice_xsk_pool_setup(struct ice_vsi *vsi, struct xsk_buff_pool *pool, u16 qid)
> >
> > /**
> > * ice_fill_rx_descs - pick buffers from XSK buffer pool and use it
> > - * @pool: XSK Buffer pool to pull the buffers from
> > + * @rx_ring: rx ring
> > * @xdp: SW ring of xdp_buff that will hold the buffers
> > * @rx_desc: Pointer to Rx descriptors that will be filled
> > * @count: The number of buffers to allocate
> > @@ -445,19 +445,24 @@ int ice_xsk_pool_setup(struct ice_vsi *vsi, struct xsk_buff_pool *pool, u16 qid)
> > *
> > * Returns the amount of allocated Rx descriptors
> > */
> > -static u16 ice_fill_rx_descs(struct xsk_buff_pool *pool, struct xdp_buff **xdp,
> > +static u16 ice_fill_rx_descs(struct ice_rx_ring *rx_ring, struct xdp_buff **xdp,
>
> Might be lack of caffeine on my side, but I don't see a reason for passing
> rx_ring down to ice_fill_rx_descs() ?
>
> I see I introduced this in the code example previously but it must have
> been some leftover from previous hacking...
>
> Help!
It is lack of caffeine on both sides. I have missed the fact that indeed, we do
not need rx_ring here.
>
> > union ice_32b_rx_flex_desc *rx_desc, u16 count)
> > {
> > dma_addr_t dma;
> > u16 buffs;
> > int i;
> >
> > - buffs = xsk_buff_alloc_batch(pool, xdp, count);
> > + buffs = xsk_buff_alloc_batch(rx_ring->xsk_pool, xdp, count);
> > for (i = 0; i < buffs; i++) {
> > dma = xsk_buff_xdp_get_dma(*xdp);
> > rx_desc->read.pkt_addr = cpu_to_le64(dma);
> > rx_desc->wb.status_error0 = 0;
> >
> > + /* Put private info that changes on a per-packet basis
> > + * into xdp_buff_xsk->cb.
> > + */
> > + ice_xdp_meta_set_desc(*xdp, rx_desc);
> > +
> > rx_desc++;
> > xdp++;
> > }
> > @@ -488,8 +493,7 @@ static bool __ice_alloc_rx_bufs_zc(struct ice_rx_ring *rx_ring, u16 count)
> > xdp = ice_xdp_buf(rx_ring, ntu);
> >
> > if (ntu + count >= rx_ring->count) {
> > - nb_buffs_extra = ice_fill_rx_descs(rx_ring->xsk_pool, xdp,
> > - rx_desc,
> > + nb_buffs_extra = ice_fill_rx_descs(rx_ring, xdp, rx_desc,
> > rx_ring->count - ntu);
> > if (nb_buffs_extra != rx_ring->count - ntu) {
> > ntu += nb_buffs_extra;
> > @@ -502,7 +506,7 @@ static bool __ice_alloc_rx_bufs_zc(struct ice_rx_ring *rx_ring, u16 count)
> > ice_release_rx_desc(rx_ring, 0);
> > }
> >
> > - nb_buffs = ice_fill_rx_descs(rx_ring->xsk_pool, xdp, rx_desc, count);
> > + nb_buffs = ice_fill_rx_descs(rx_ring, xdp, rx_desc, count);
> >
> > ntu += nb_buffs;
> > if (ntu == rx_ring->count)
> > @@ -752,6 +756,7 @@ static int ice_xmit_xdp_tx_zc(struct xdp_buff *xdp,
> > * @xdp: xdp_buff used as input to the XDP program
> > * @xdp_prog: XDP program to run
> > * @xdp_ring: ring to be used for XDP_TX action
> > + * @rx_desc: packet descriptor
>
> leftover comment from previous approach
>
Will fix.
> > *
> > * Returns any of ICE_XDP_{PASS, CONSUMED, TX, REDIR}
> > */
> > --
> > 2.41.0
> >
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