linux-kernel - Re: [PATCH net-next v3 4/7] net: lan966x: Update rxq memory model

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Date:   Tue, 22 Nov 2022 22:23:16 +0100
From:   Horatiu Vultur <horatiu.vultur@...rochip.com>
To:     Alexander Lobakin <alexandr.lobakin@...el.com>
CC:     <netdev@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <bpf@...r.kernel.org>, <davem@...emloft.net>,
        <edumazet@...gle.com>, <kuba@...nel.org>, <pabeni@...hat.com>,
        <ast@...nel.org>, <daniel@...earbox.net>, <hawk@...nel.org>,
        <john.fastabend@...il.com>, <UNGLinuxDriver@...rochip.com>
Subject: Re: [PATCH net-next v3 4/7] net: lan966x: Update rxq memory model

The 11/22/2022 12:38, Alexander Lobakin wrote:
> 
> From: Horatiu Vultur <horatiu.vultur@...rochip.com>
> Date: Mon, 21 Nov 2022 22:28:47 +0100
> 
> > By default the rxq memory model is MEM_TYPE_PAGE_SHARED but to be able
> > to reuse pages on the TX side, when the XDP action XDP_TX it is required
> > to update the memory model to PAGE_POOL.
> >
> > Signed-off-by: Horatiu Vultur <horatiu.vultur@...rochip.com>
> > ---
> >  .../net/ethernet/microchip/lan966x/lan966x_fdma.c  | 14 ++++++++++++++
> >  1 file changed, 14 insertions(+)
> >
> > diff --git a/drivers/net/ethernet/microchip/lan966x/lan966x_fdma.c b/drivers/net/ethernet/microchip/lan966x/lan966x_fdma.c
> > index 384ed34197d58..483d1470c8362 100644
> > --- a/drivers/net/ethernet/microchip/lan966x/lan966x_fdma.c
> > +++ b/drivers/net/ethernet/microchip/lan966x/lan966x_fdma.c
> > @@ -78,8 +78,22 @@ static int lan966x_fdma_rx_alloc_page_pool(struct lan966x_rx *rx)
> >               .max_len = rx->max_mtu -
> >                          SKB_DATA_ALIGN(sizeof(struct skb_shared_info)),
> >       };
> > +     struct lan966x_port *port;
> > +     int i;
> >
> >       rx->page_pool = page_pool_create(&pp_params);
> > +
> > +     for (i = 0; i < lan966x->num_phys_ports; ++i) {
> > +             if (!lan966x->ports[i])
> > +                     continue;
> > +
> > +             port = lan966x->ports[i];
> > +
> > +             xdp_rxq_info_unreg_mem_model(&port->xdp_rxq);
> 
> xdp_rxq_info_unreg_mem_model() can emit a splat if currently the
> corresponding xdp_rxq_info is not registered[0]. Can't we face it
> here if called from lan966x_fdma_init()?

We will not face that issue here because before lan966x_fdma_init is
called, we call lan966x_xdp_port_init which registers xdp_rxq_info.

> 
> > +             xdp_rxq_info_reg_mem_model(&port->xdp_rxq, MEM_TYPE_PAGE_POOL,
> > +                                        rx->page_pool);
> > +     }
> > +
> >       return PTR_ERR_OR_ZERO(rx->page_pool);
> >  }
> >
> > --
> > 2.38.0
> 
> Thanks,
> Olek

-- 
/Horatiu