On Fri, Nov 20, 2020 at 06:54:42PM +0000, Camelia Alexandra Groza wrote:
> > -----Original Message-----
> > From: Maciej Fijalkowski <[email protected]>
> > Sent: Friday, November 20, 2020 01:51
> > To: Camelia Alexandra Groza <[email protected]>
> > Cc: [email protected]; [email protected]; [email protected];
> > [email protected]; Madalin Bucur (OSS)
> > <[email protected]>; Ioana Ciornei <[email protected]>;
> > [email protected]
> > Subject: Re: [PATCH net-next v3 4/7] dpaa_eth: add XDP_TX support
> >
> > On Thu, Nov 19, 2020 at 06:29:33PM +0200, Camelia Groza wrote:
> > > Use an xdp_frame structure for managing the frame. Store a backpointer
> > to
> > > the structure at the start of the buffer before enqueueing. Use the XDP
> > > API for freeing the buffer when it returns to the driver on the TX
> > > confirmation path.
> >
[...]
> > > static u32 dpaa_run_xdp(struct dpaa_priv *priv, struct qm_fd *fd, void
> > *vaddr,
> > > - unsigned int *xdp_meta_len)
> > > + struct dpaa_fq *dpaa_fq, unsigned int
> > *xdp_meta_len)
> > > {
> > > ssize_t fd_off = qm_fd_get_offset(fd);
> > > struct bpf_prog *xdp_prog;
> > > + struct xdp_frame *xdpf;
> > > struct xdp_buff xdp;
> > > u32 xdp_act;
> > >
> > > @@ -2370,7 +2470,8 @@ static u32 dpaa_run_xdp(struct dpaa_priv *priv,
> > struct qm_fd *fd, void *vaddr,
> > > 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;
> > > + xdp.frame_sz = DPAA_BP_RAW_SIZE - DPAA_TX_PRIV_DATA_SIZE;
> > > + xdp.rxq = &dpaa_fq->xdp_rxq;
> > >
> > > xdp_act = bpf_prog_run_xdp(xdp_prog, &xdp);
> > >
> > > @@ -2381,6 +2482,22 @@ static u32 dpaa_run_xdp(struct dpaa_priv *priv,
> > struct qm_fd *fd, void *vaddr,
> > > case XDP_PASS:
> > > *xdp_meta_len = xdp.data - xdp.data_meta;
> > > break;
> > > + case XDP_TX:
> > > + /* We can access the full headroom when sending the frame
> > > + * back out
> >
> > And normally why a piece of headroom is taken away? I probably should
> > have
> > started from the basic XDP support patch, but if you don't mind, please
> > explain it a bit.
>
> I mentioned we require DPAA_TX_PRIV_DATA_SIZE bytes at the start of the
> buffer in order to make sure we have enough space for our private info.
What is your private info?
>
> When setting up the xdp_buff, this area is reserved from the frame size
> exposed to the XDP program.
> - xdp.frame_sz = DPAA_BP_RAW_SIZE;
> + xdp.frame_sz = DPAA_BP_RAW_SIZE - DPAA_TX_PRIV_DATA_SIZE;
>
> After the XDP_TX verdict, we're sure that DPAA_TX_PRIV_DATA_SIZE bytes at the
> start of the buffer are free and we can use the full headroom how it suits
> us, hence the increase of the frame size back to DPAA_BP_RAW_SIZE.
Not at the *end* of the buffer?
>
> Thanks for all your feedback.
>
> > > + */
> > > + xdp.data_hard_start = vaddr;
> > > + xdp.frame_sz = DPAA_BP_RAW_SIZE;
> > > + xdpf = xdp_convert_buff_to_frame(&xdp);
> > > + if (unlikely(!xdpf)) {
> > > + free_pages((unsigned long)vaddr, 0);
> > > + break;
> > > + }
> > > +
> > > + if (dpaa_xdp_xmit_frame(priv->net_dev, xdpf))
> > > + xdp_return_frame_rx_napi(xdpf);
> > > +
> > > + break;
> > > default:
> > > bpf_warn_invalid_xdp_action(xdp_act);
> > > fallthrough;
> > > @@ -2415,6 +2532,7 @@ static enum qman_cb_dqrr_result
