Subject: Re: [PATCH net-next v2 07/18] net: Register system page pool as an XDP memory model

From: Maciej Fijalkowski <[email-masked]>
Date: Thu, 17 Oct 2024 13:32:03 +0200

On Tue, Oct 15, 2024 at 04:53:39PM +0200, Alexander Lobakin wrote:
> From: Toke Høiland-Jørgensen <[email-masked]>
> 
> To make the system page pool usable as a source for allocating XDP
> frames, we need to register it with xdp_reg_mem_model(), so that page
> return works correctly. This is done in preparation for using the system
> page pool for the XDP live frame mode in BPF_TEST_RUN; for the same
> reason, make the per-cpu variable non-static so we can access it from
> the test_run code as well.

Again, to me BPF_TEST_RUN has nothing to do with libeth/idpf XDP support
:<

> 
> Signed-off-by: Toke Høiland-Jørgensen <[email-masked]>
> Signed-off-by: Alexander Lobakin <[email-masked]>
> ---
>  include/linux/netdevice.h |  1 +
>  net/core/dev.c            | 10 +++++++++-
>  2 files changed, 10 insertions(+), 1 deletion(-)
> 
> diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
> index 72f53e7610ec..692f21c28ea5 100644
> --- a/include/linux/netdevice.h
> +++ b/include/linux/netdevice.h
> @@ -3308,6 +3308,7 @@ struct softnet_data {
>  };
>  
>  DECLARE_PER_CPU_ALIGNED(struct softnet_data, softnet_data);
> +DECLARE_PER_CPU(struct page_pool *, system_page_pool);
>  
>  #ifndef CONFIG_PREEMPT_RT
>  static inline int dev_recursion_level(void)
> diff --git a/net/core/dev.c b/net/core/dev.c
> index b857abb5c0e9..773388f26d4f 100644
> --- a/net/core/dev.c
> +++ b/net/core/dev.c
> @@ -460,7 +460,7 @@ EXPORT_PER_CPU_SYMBOL(softnet_data);
>   * PP consumers must pay attention to run APIs in the appropriate context
>   * (e.g. NAPI context).
>   */
> -static DEFINE_PER_CPU(struct page_pool *, system_page_pool);
> +DEFINE_PER_CPU(struct page_pool *, system_page_pool);
>  
>  #ifdef CONFIG_LOCKDEP
>  /*
> @@ -12103,11 +12103,18 @@ static int net_page_pool_create(int cpuid)
>  		.nid = cpu_to_mem(cpuid),
>  	};
>  	struct page_pool *pp_ptr;
> +	int err;
>  
>  	pp_ptr = page_pool_create_percpu(&page_pool_params, cpuid);
>  	if (IS_ERR(pp_ptr))
>  		return -ENOMEM;
>  
> +	err = xdp_reg_page_pool(pp_ptr);
> +	if (err) {
> +		page_pool_destroy(pp_ptr);
> +		return err;
> +	}
> +
>  	per_cpu(system_page_pool, cpuid) = pp_ptr;
>  #endif
>  	return 0;
> @@ -12241,6 +12248,7 @@ static int __init net_dev_init(void)
>  			if (!pp_ptr)
>  				continue;
>  
> +			xdp_unreg_page_pool(pp_ptr);
>  			page_pool_destroy(pp_ptr);
>  			per_cpu(system_page_pool, i) = NULL;
>  		}
> -- 
> 2.46.2
>