netdev - Re: [RFC PATCH net-next v5 1/2] net: introduce abstraction for network memory

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Date: Wed, 10 Jan 2024 10:45:00 -0800
From: Shakeel Butt <shakeelb@...gle.com>
To: Mina Almasry <almasrymina@...gle.com>
Cc: linux-kernel@...r.kernel.org, netdev@...r.kernel.org, 
	"David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, 
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, Jason Gunthorpe <jgg@...dia.com>, 
	Christian König <christian.koenig@....com>, 
	Yunsheng Lin <linyunsheng@...wei.com>, Willem de Bruijn <willemdebruijn.kernel@...il.com>
Subject: Re: [RFC PATCH net-next v5 1/2] net: introduce abstraction for
 network memory

On Mon, Jan 8, 2024 at 5:15 PM Mina Almasry <almasrymina@...gle.com> wrote:
>
> Add the netmem_ref type, an abstraction for network memory.
>
> To add support for new memory types to the net stack, we must first
> abstract the current memory type. Currently parts of the net stack
> use struct page directly:
>
> - page_pool
> - drivers
> - skb_frag_t
>
> Originally the plan was to reuse struct page* for the new memory types,
> and to set the LSB on the page* to indicate it's not really a page.
> However, for compiler type checking we need to introduce a new type.
>
> netmem_ref is introduced to abstract the underlying memory type.
> Currently it's a no-op abstraction that is always a struct page
> underneath. In parallel there is an undergoing effort to add support
> for devmem to the net stack:
>
> https://lore.kernel.org/netdev/20231208005250.2910004-1-almasrymina@google.com/
>
> netmem_ref can be pointers to different underlying memory types, and the
> low bits are set to indicate the memory type. Helpers are provided
> to convert netmem pointers to the underlying memory type (currently only
> struct page). In the devmem series helpers are provided so that calling
> code can use netmem without worrying about the underlying memory type
> unless absolutely necessary.
>
> Signed-off-by: Mina Almasry <almasrymina@...gle.com>
>

Reviewed-by: Shakeel Butt <shakeelb@...gle.com>