Re: [PATCH net-next v3 5/7] net: lan966x: Update dma_dir of page_pool_params

Horatiu Vultur
2022-11-22T21:20:25Z

The 11/22/2022 12:43, Alexander Lobakin wrote:
>
> From: Horatiu Vultur <horatiu.vultur@microchip.com>
> Date: Mon, 21 Nov 2022 22:28:48 +0100
>
> > To add support for XDP_TX it is required to be able to write to the DMA
> > area therefore it is required that the pages will be mapped using
> > DMA_BIDIRECTIONAL flag.
> > Therefore check if there are any xdp programs on the interfaces and in
> > that case set DMA_BIDRECTIONAL otherwise use DMA_FROM_DEVICE.
> > Therefore when a new XDP program is added it is required to redo the
> > page_pool.
> >
> > Signed-off-by: Horatiu Vultur <horatiu.vultur@microchip.com>
> > ---
> > .../ethernet/microchip/lan966x/lan966x_fdma.c | 29 ++++++++++++++----
> > .../ethernet/microchip/lan966x/lan966x_main.h | 2 ++
> > .../ethernet/microchip/lan966x/lan966x_xdp.c | 30 +++++++++++++++++++
> > 3 files changed, 55 insertions(+), 6 deletions(-)
>
> [...]
>
> > diff --git a/drivers/net/ethernet/microchip/lan966x/lan966x_xdp.c b/drivers/net/ethernet/microchip/lan966x/lan966x_xdp.c
> > index 8ebde1eb6a09c..05c5a28206558 100644
> > --- a/drivers/net/ethernet/microchip/lan966x/lan966x_xdp.c
> > +++ b/drivers/net/ethernet/microchip/lan966x/lan966x_xdp.c
> > @@ -11,6 +11,8 @@ static int lan966x_xdp_setup(struct net_device *dev, struct netdev_bpf *xdp)
> > struct lan966x_port *port = netdev_priv(dev);
> > struct lan966x *lan966x = port->lan966x;
> > struct bpf_prog *old_prog;
> > + bool old_xdp, new_xdp;
> > + int err;
> >
> > if (!lan966x->fdma) {
> > NL_SET_ERR_MSG_MOD(xdp->extack,
> > @@ -18,7 +20,20 @@ static int lan966x_xdp_setup(struct net_device *dev, struct netdev_bpf *xdp)
> > return -EOPNOTSUPP;
> > }
> >
> > + old_xdp = lan966x_xdp_present(lan966x);
> > old_prog = xchg(&port->xdp_prog, xdp->prog);
> > + new_xdp = lan966x_xdp_present(lan966x);
> > +
> > + if (old_xdp != new_xdp)
> > + goto out;
>
> Shouldn't it be the other way around? E.g. when there's no prog and
> you're installing it or there is a prog and we're removing it from
> the interface, DMA dir must be changed, so we reload the Pools, but
> if `old_xdp == new_xdp` we should just hotswap them and goto out?

Argh! Yes, it needs to be the other way around.
>
> > +
> > + err = lan966x_fdma_reload_page_pool(lan966x);
> > + if (err) {
> > + xchg(&port->xdp_prog, old_prog);
> > + return err;
> > + }
> > +
> > +out:
> > if (old_prog)
> > bpf_prog_put(old_prog);
> >
>
> [...]
>
> > --
> > 2.38.0
>
> Thanks,
> Olek

--
/Horatiu