linux-kernel - Re: [PATCH net-next v3 4/5] page_pool: disable sync for cpu for dmabuf memory provider

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Message-ID: <20241210194745.7a0a319e@kernel.org>
Date: Tue, 10 Dec 2024 19:47:45 -0800
From: Jakub Kicinski <kuba@...nel.org>
To: Mina Almasry <almasrymina@...gle.com>
Cc: netdev@...r.kernel.org, Pavel Begunkov <asml.silence@...il.com>, Kaiyuan
 Zhang <kaiyuanz@...gle.com>, Willem de Bruijn <willemb@...gle.com>,
 Samiullah Khawaja <skhawaja@...gle.com>, linux-doc@...r.kernel.org,
 linux-kernel@...r.kernel.org, "David S. Miller" <davem@...emloft.net>, Eric
 Dumazet <edumazet@...gle.com>, Paolo Abeni <pabeni@...hat.com>, Simon
 Horman <horms@...nel.org>, Jonathan Corbet <corbet@....net>, Jesper
 Dangaard Brouer <hawk@...nel.org>, Ilias Apalodimas
 <ilias.apalodimas@...aro.org>
Subject: Re: [PATCH net-next v3 4/5] page_pool: disable sync for cpu for
 dmabuf memory provider

On Mon,  9 Dec 2024 17:23:07 +0000 Mina Almasry wrote:
> -static inline void page_pool_dma_sync_for_cpu(const struct page_pool *pool,
> -					      const struct page *page,
> -					      u32 offset, u32 dma_sync_size)
> +static inline void
> +page_pool_dma_sync_netmem_for_cpu(const struct page_pool *pool,
> +				  const netmem_ref netmem, u32 offset,
> +				  u32 dma_sync_size)
>  {
> +	if (pool->mp_priv)

Let's add a dedicated bit to skip sync. The io-uring support feels
quite close. Let's not force those guys to have to rejig this.

> +		return;
> +
>  	dma_sync_single_range_for_cpu(pool->p.dev,
> -				      page_pool_get_dma_addr(page),
> +				      page_pool_get_dma_addr_netmem(netmem),
>  				      offset + pool->p.offset, dma_sync_size,
>  				      page_pool_get_dma_dir(pool));
>  }
>  
> +static inline void page_pool_dma_sync_for_cpu(const struct page_pool *pool,
> +					      struct page *page, u32 offset,
> +					      u32 dma_sync_size)
> +{
> +	page_pool_dma_sync_netmem_for_cpu(pool, page_to_netmem(page), offset,
> +					  dma_sync_size);

I have the feeling Olek won't thank us for this extra condition and
bit clearing. If driver calls page_pool_dma_sync_for_cpu() we don't
have to check the new bit / mp_priv. Let's copy & paste the
dma_sync_single_range_for_cpu() call directly here.