netdev - Re: [RFC PATCH net-next v5 08/14] memory-provider: dmabuf devmem memory provider

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Message-ID: <dd4a6633-36d0-4654-a5e1-2824de29c130@gmail.com>
Date: Tue, 13 Feb 2024 13:19:43 +0000
From: Pavel Begunkov <asml.silence@...il.com>
To: Mina Almasry <almasrymina@...gle.com>,
 Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
 Martin KaFai Lau <martin.lau@...ux.dev>, Song Liu <song@...nel.org>,
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 Willem de Bruijn <willemb@...gle.com>, Kaiyuan Zhang <kaiyuanz@...gle.com>
Subject: Re: [RFC PATCH net-next v5 08/14] memory-provider: dmabuf devmem
 memory provider

On 12/18/23 02:40, Mina Almasry wrote:
> Implement a memory provider that allocates dmabuf devmem in the form of
> net_iov.
> 
> The provider receives a reference to the struct netdev_dmabuf_binding
> via the pool->mp_priv pointer. The driver needs to set this pointer for
> the provider in the net_iov.
> 
> The provider obtains a reference on the netdev_dmabuf_binding which
> guarantees the binding and the underlying mapping remains alive until
> the provider is destroyed.
> 
> Usage of PP_FLAG_DMA_MAP is required for this memory provide such that
> the page_pool can provide the driver with the dma-addrs of the devmem.
> 
> Support for PP_FLAG_DMA_SYNC_DEV is omitted for simplicity & p.order !=
> 0.
> 
> Signed-off-by: Willem de Bruijn <willemb@...gle.com>
> Signed-off-by: Kaiyuan Zhang <kaiyuanz@...gle.com>
> Signed-off-by: Mina Almasry <almasrymina@...gle.com>
> 
> ---
...
> +
> +static bool mp_dmabuf_devmem_release_page(struct page_pool *pool,
> +					  struct netmem *netmem)
> +{
> +	WARN_ON_ONCE(!netmem_is_net_iov(netmem));
> +
> +	page_pool_clear_pp_info(netmem);
> +
> +	netdev_free_dmabuf(netmem_to_net_iov(netmem));
> +
> +	/* We don't want the page pool put_page()ing our net_iovs. */
> +	return false;
> +}
> +
> +const struct memory_provider_ops dmabuf_devmem_ops = {
> +	.init			= mp_dmabuf_devmem_init,
> +	.destroy		= mp_dmabuf_devmem_destroy,
> +	.alloc_pages		= mp_dmabuf_devmem_alloc_pages,
> +	.release_page		= mp_dmabuf_devmem_release_page,
> +};
> +EXPORT_SYMBOL(dmabuf_devmem_ops);

It might make sense to move all these functions together with
new code from core/dev.c into a new file

-- 
Pavel Begunkov