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

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Date:   Tue, 22 Nov 2022 12:38:51 +0100
From:   Alexander Lobakin <alexandr.lobakin@...el.com>
To:     Horatiu Vultur <horatiu.vultur@...rochip.com>
Cc:     Alexander Lobakin <alexandr.lobakin@...el.com>,
        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

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()?

> +		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