> -----Original Message-----
> From: Maciej Fijalkowski <maciej.fijalkow...@intel.com>
> Sent: Tuesday, November 24, 2020 00:08
> To: Camelia Alexandra Groza <camelia.gr...@nxp.com>
> Cc: k...@kernel.org; bro...@redhat.com; sa...@kernel.org;
> da...@davemloft.net; Madalin Bucur (OSS)
> <madalin.bu...@oss.nxp.com>; Ioana Ciornei <ioana.cior...@nxp.com>;
> netdev@vger.kernel.org
> Subject: Re: [PATCH net-next v3 2/7] dpaa_eth: add basic XDP support
>
> On Fri, Nov 20, 2020 at 06:50:28PM +0000, Camelia Alexandra Groza wrote:
> > > -----Original Message-----
> > > From: Maciej Fijalkowski <maciej.fijalkow...@intel.com>
> > > Sent: Friday, November 20, 2020 02:19
> > > To: Camelia Alexandra Groza <camelia.gr...@nxp.com>
> > > Cc: k...@kernel.org; bro...@redhat.com; sa...@kernel.org;
> > > da...@davemloft.net; Madalin Bucur (OSS)
> > > <madalin.bu...@oss.nxp.com>; Ioana Ciornei <ioana.cior...@nxp.com>;
> > > netdev@vger.kernel.org
> > > Subject: Re: [PATCH net-next v3 2/7] dpaa_eth: add basic XDP support
> > >
> > > On Thu, Nov 19, 2020 at 06:29:31PM +0200, Camelia Groza wrote:
> > > > Implement the XDP_DROP and XDP_PASS actions.
> > > >
> > > > Avoid draining and reconfiguring the buffer pool at each XDP
> > > > setup/teardown by increasing the frame headroom and reserving
> > > > XDP_PACKET_HEADROOM bytes from the start. Since we always
> reserve
> > > an
> > > > entire page per buffer, this change only impacts Jumbo frame scenarios
> > > > where the maximum linear frame size is reduced by 256 bytes. Multi
> > > > buffer Scatter/Gather frames are now used instead in these scenarios.
> > > >
> > > > Allow XDP programs to access the entire buffer.
> > > >
> > > > The data in the received frame's headroom can be overwritten by the
> XDP
> > > > program. Extract the relevant fields from the headroom while they are
> > > > still available, before running the XDP program.
> > > >
> > > > Since the headroom might be resized before the frame is passed up to
> the
> > > > stack, remove the check for a fixed headroom value when building an
> skb.
> > > >
> > > > Allow the meta data to be updated and pass the information up the
> stack.
> > > >
> > > > Scatter/Gather frames are dropped when XDP is enabled.
> > > >
> > > > Acked-by: Madalin Bucur <madalin.bu...@oss.nxp.com>
> > > > Signed-off-by: Camelia Groza <camelia.gr...@nxp.com>
> > > > ---
> > > > Changes in v2:
> > > > - warn only once if extracting the timestamp from a received frame fails
> > > >
> > > > Changes in v3:
> > > > - drop received S/G frames when XDP is enabled
> > > >
> > > > drivers/net/ethernet/freescale/dpaa/dpaa_eth.c | 158
> > > ++++++++++++++++++++++---
> > > > drivers/net/ethernet/freescale/dpaa/dpaa_eth.h | 2 +
> > > > 2 files changed, 144 insertions(+), 16 deletions(-)
> > > >
> > > > diff --git a/drivers/net/ethernet/freescale/dpaa/dpaa_eth.c
> > > b/drivers/net/ethernet/freescale/dpaa/dpaa_eth.c
> > > > index 88533a2..102023c 100644
> > > > --- a/drivers/net/ethernet/freescale/dpaa/dpaa_eth.c
> > > > +++ b/drivers/net/ethernet/freescale/dpaa/dpaa_eth.c
> > > > @@ -53,6 +53,8 @@
> > > > #include <linux/dma-mapping.h>
> > > > #include <linux/sort.h>
> > > > #include <linux/phy_fixed.h>
> > > > +#include <linux/bpf.h>
> > > > +#include <linux/bpf_trace.h>
> > > > #include <soc/fsl/bman.h>
> > > > #include <soc/fsl/qman.h>
> > > > #include "fman.h"
> > > > @@ -177,7 +179,7 @@
> > > > #define DPAA_HWA_SIZE (DPAA_PARSE_RESULTS_SIZE +
> > > DPAA_TIME_STAMP_SIZE \
> > > > + DPAA_HASH_RESULTS_SIZE)
> > > > #define DPAA_RX_PRIV_DATA_DEFAULT_SIZE
> > > (DPAA_TX_PRIV_DATA_SIZE + \
> > > > - dpaa_rx_extra_headroom)
> > > > + XDP_PACKET_HEADROOM -
> > > DPAA_HWA_SIZE)
> > > > #ifdef CONFIG_DPAA_ERRATUM_A050385
> > > > #define DPAA_RX_PRIV_DATA_A050385_SIZE (DPAA_A050385_ALIGN
> -
> > > DPAA_HWA_SIZE)
> > > > #define DPAA_RX_PRIV_DATA_SIZE (fman_has_errata_a050385() ? \
> > > > @@ -1733,7 +1735,6 @@ static struct sk_buff *contig_fd_to_skb(const
> > > struct dpaa_priv *priv,
> > > > SKB_DATA_ALIGN(sizeof(struct skb_shared_info)));
> > > > if (WARN_ONCE(!skb, "Build skb failure on Rx\n"))
> > > > goto free_buffer;
> > > > - WARN_ON(fd_off != priv->rx_headroom);
> > > > skb_reserve(skb, fd_off);
> > > > skb_put(skb, qm_fd_get_length(fd));
> > > >
> > > > @@ -2349,12 +2350,62 @@ static enum qman_cb_dqrr_result
> > > rx_error_dqrr(struct qman_portal *portal,
> > > > return qman_cb_dqrr_consume;
> > > > }
> > > >
> > > > +static u32 dpaa_run_xdp(struct dpaa_priv *priv, struct qm_fd *fd,
> void
> > > *vaddr,
> > > > + unsigned int *xdp_meta_len)
> > > > +{
> > > > + ssize_t fd_off = qm_fd_get_offset(fd);
> > > > + struct bpf_prog *xdp_prog;
> > > > + struct xdp_buff xdp;
> > > > + u32 xdp_act;
> > > > +
> > > > + rcu_read_lock();
> > > > +
> > > > + xdp_prog = READ_ONCE(priv->xdp_prog);
> > > > + if (!xdp_prog) {
> > > > + rcu_read_unlock();
> > > > + return XDP_PASS;
> > > > + }
> > > > +
> > > > + xdp.data = vaddr + fd_off;
> > >
> > > I feel like a little drawing of xdp_buff layout would help me with
> > > understanding what is going on over here :)
> >
> > A region at the start of the buffer is reserved for storing hardware
> annotations and room for the XDP_PACKET_HEADROOM, before the actual
> data starts. So vaddr points to the start of the buffer, while fd offset
> provides
> the offset of the data inside the buffer. I don't feel that we are filling the
> xdp_buff in a majorly different way from other drivers, so please mention
> what is unclear here and I can provide more details.
>
> Okay, so fd_off tells me where the frame starts, from vaddr to vaddr +
> fd_off there might be some HW provided data, so you extract it and then
> you are free to go with setting the data_hard_start?
Yes, that's right.
> >
> > > > + xdp.data_meta = xdp.data;
> > > > + xdp.data_hard_start = xdp.data - XDP_PACKET_HEADROOM;
> > > > + xdp.data_end = xdp.data + qm_fd_get_length(fd);
> > > > + xdp.frame_sz = DPAA_BP_RAW_SIZE;
> > >
> > > Maybe you could fill xdp_buff outside of this function so that later on
> > > you could set xdp.rxq once per napi?
> >
> > I admit I haven't looked into exactly how much performance we would gain
> from this, but I don't think it would be enough to justify the code churn. We
> don't have a clean loop for processing the received frames like I see the
> Intel
> and ENA drivers have.
> >
> > > > +
> > > > + xdp_act = bpf_prog_run_xdp(xdp_prog, &xdp);
> > > > +
> > > > + /* Update the length and the offset of the FD */
> > > > + qm_fd_set_contig(fd, xdp.data - vaddr, xdp.data_end - xdp.data);
> > > > +
> > > > + switch (xdp_act) {
> > > > + case XDP_PASS:
> > > > + *xdp_meta_len = xdp.data - xdp.data_meta;
> > > > + break;
> > > > + default:
> > > > + bpf_warn_invalid_xdp_action(xdp_act);
> > > > + fallthrough;
> > > > + case XDP_ABORTED:
> > > > + trace_xdp_exception(priv->net_dev, xdp_prog, xdp_act);
> > > > + fallthrough;
> > > > + case XDP_DROP:
> > > > + /* Free the buffer */
> > > > + free_pages((unsigned long)vaddr, 0);
> > > > + break;
> > > > + }
> > > > +
> > > > + rcu_read_unlock();
> > > > +
> > > > + return xdp_act;
> > > > +}
> > > > +
> > > > static enum qman_cb_dqrr_result rx_default_dqrr(struct qman_portal
> > > *portal,
> > > > struct qman_fq *fq,
> > > > const struct
> > > > qm_dqrr_entry
> > > *dq,
> > > > bool sched_napi)
> > > > {
> > > > + bool ts_valid = false, hash_valid = false;
> > > > struct skb_shared_hwtstamps *shhwtstamps;
> > > > + unsigned int skb_len, xdp_meta_len = 0;
> > > > struct rtnl_link_stats64 *percpu_stats;
> > > > struct dpaa_percpu_priv *percpu_priv;
> > > > const struct qm_fd *fd = &dq->fd;
> > > > @@ -2362,12 +2413,14 @@ static enum qman_cb_dqrr_result
> > > rx_default_dqrr(struct qman_portal *portal,
> > > > enum qm_fd_format fd_format;
> > > > struct net_device *net_dev;
> > > > u32 fd_status, hash_offset;
> > > > + struct qm_sg_entry *sgt;
> > > > struct dpaa_bp *dpaa_bp;
> > > > struct dpaa_priv *priv;
> > > > - unsigned int skb_len;
> > > > struct sk_buff *skb;
> > > > int *count_ptr;
> > > > + u32 xdp_act;
> > > > void *vaddr;
> > > > + u32 hash;
> > > > u64 ns;
> > > >
> > > > fd_status = be32_to_cpu(fd->status);
> > > > @@ -2423,35 +2476,67 @@ static enum qman_cb_dqrr_result
> > > rx_default_dqrr(struct qman_portal *portal,
> > > > count_ptr = this_cpu_ptr(dpaa_bp->percpu_count);
> > > > (*count_ptr)--;
> > > >
> > > > - if (likely(fd_format == qm_fd_contig))
> > > > + /* Extract the timestamp stored in the headroom before running
> > > XDP */
> > > > + if (priv->rx_tstamp) {
> > > > + if (!fman_port_get_tstamp(priv->mac_dev->port[RX],
> > > > vaddr,
> > > &ns))
> > > > + ts_valid = true;
> > > > + else
> > > > + WARN_ONCE(1, "fman_port_get_tstamp failed!\n");
> > > > + }
> > > > +
> > > > + /* Extract the hash stored in the headroom before running XDP */
> > > > + if (net_dev->features & NETIF_F_RXHASH && priv->keygen_in_use
> > > &&
> > > > + !fman_port_get_hash_result_offset(priv->mac_dev->port[RX],
> > > > + &hash_offset)) {
> > > > + hash = be32_to_cpu(*(u32 *)(vaddr + hash_offset));
> > > > + hash_valid = true;
> > > > + }
> > > > +
> > > > + if (likely(fd_format == qm_fd_contig)) {
> > > > + xdp_act = dpaa_run_xdp(priv, (struct qm_fd *)fd, vaddr,
> > > > + &xdp_meta_len);
> > > > + if (xdp_act != XDP_PASS) {
> > > > + percpu_stats->rx_packets++;
> > > > + percpu_stats->rx_bytes += qm_fd_get_length(fd);
> > > > + return qman_cb_dqrr_consume;
> > > > + }
> > > > skb = contig_fd_to_skb(priv, fd);
> > > > - else
> > > > + } else {
> > > > + /* XDP doesn't support S/G frames. Return the fragments
> > > > to
> > > the
> > > > + * buffer pool and release the SGT.
> > > > + */
> > > > + if (READ_ONCE(priv->xdp_prog)) {
> > > > + WARN_ONCE(1, "S/G frames not supported under
> > > XDP\n");
> > > > + sgt = vaddr + qm_fd_get_offset(fd);
> > > > + dpaa_release_sgt_members(sgt);
> > > > + free_pages((unsigned long)vaddr, 0);
> > > > + return qman_cb_dqrr_consume;
> > > > + }
> > > > skb = sg_fd_to_skb(priv, fd);
> > > > + }
> > > > if (!skb)
> > > > return qman_cb_dqrr_consume;
> > > >
> > > > - if (priv->rx_tstamp) {
> > > > + if (xdp_meta_len)
> > > > + skb_metadata_set(skb, xdp_meta_len);
> > >
> > > This is working on a single buffer, right? So there's no need to clear
> > > xdp_meta_len?
> >
> > I don't think I understand what you mean. Are you saying I shouldn't be
> initializing xdp_meta_len to 0? This receive path is used when XDP is disabled
> as well, in which case we don't propagate the metadata.
>
> What I meant was that if this function would operate on many buffers then
> we would have to clear the xdp_meta_len, so that next buffers wouldn't get
> the value from previous bufs, but I suppose that this rx_default_dqrr
> callback is called once per each buffer.
Yes, rx_default_dqrr is processing only one buffer.
> >
> > > > +
> > > > + /* Set the previously extracted timestamp */
> > > > + if (ts_valid) {
> > > > shhwtstamps = skb_hwtstamps(skb);
> > > > memset(shhwtstamps, 0, sizeof(*shhwtstamps));
> > > > -
> > > > - if (!fman_port_get_tstamp(priv->mac_dev->port[RX],
> > > > vaddr,
> > > &ns))
> > > > - shhwtstamps->hwtstamp = ns_to_ktime(ns);
> > > > - else
> > > > - dev_warn(net_dev->dev.parent,
> > > "fman_port_get_tstamp failed!\n");
> > > > + shhwtstamps->hwtstamp = ns_to_ktime(ns);
> > > > }
> > > >
> > > > skb->protocol = eth_type_trans(skb, net_dev);
> > > >
> > > > - if (net_dev->features & NETIF_F_RXHASH && priv->keygen_in_use
> > > &&
> > > > - !fman_port_get_hash_result_offset(priv->mac_dev->port[RX],
> > > > - &hash_offset)) {
> > > > + /* Set the previously extracted hash */
> > > > + if (hash_valid) {
> > > > enum pkt_hash_types type;
> > > >
> > > > /* if L4 exists, it was used in the hash generation */
> > > > type = be32_to_cpu(fd->status) & FM_FD_STAT_L4CV ?
> > > > PKT_HASH_TYPE_L4 : PKT_HASH_TYPE_L3;
> > > > - skb_set_hash(skb, be32_to_cpu(*(u32 *)(vaddr +
> > > hash_offset)),
> > > > - type);
> > > > + skb_set_hash(skb, hash, type);
> > > > }
> > > >
> > > > skb_len = skb->len;
> > > > @@ -2671,6 +2756,46 @@ static int dpaa_eth_stop(struct net_device
> > > *net_dev)
> > > > return err;
> > > > }
