netdev - Re: [RFC PATCH net-next v6 02/15] net: page_pool: create hooks for custom page providers

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Date: Thu, 28 Mar 2024 00:31:31 -0700
From: Christoph Hellwig <hch@...radead.org>
To: Mina Almasry <almasrymina@...gle.com>
Cc: Christoph Hellwig <hch@...radead.org>, shakeel.butt@...ux.dev,
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Subject: Re: [RFC PATCH net-next v6 02/15] net: page_pool: create hooks for
 custom page providers

On Tue, Mar 26, 2024 at 01:19:20PM -0700, Mina Almasry wrote:
> 
> Are you envisioning that dmabuf support would be added to the block
> layer

Yes.

> (which I understand is part of the VFS and not driver specific),

The block layer isn't really the VFS, it's just another core stack
like the network stack.

> or as part of the specific storage driver (like nvme for example)? If
> we can add dmabuf support to the block layer itself that sounds
> awesome. We may then be able to do devmem TCP on all/most storage
> devices without having to modify each individual driver.

I suspect we'll still need to touch the drivers to understand it,
but hopefully all the main infrastructure can live in the block layer.

> In your estimation, is adding dmabuf support to the block layer
> something technically feasible & acceptable upstream? I notice you
> suggested it so I'm guessing yes to both, but I thought I'd confirm.

I think so, and I know there has been quite some interest to at least
pre-register userspace memory so that the iommu overhead can be
pre-loaded.  It also is a much better interface for Peer to Peer
transfers than what we currently have.