netdev - Re: [PATCH net-next v6 12/12] net/mlx5e: Add TX support for netmems

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Message-ID: <CAHS8izNQ+eRH3L-npJXDO7cCYo82jPL0jROBnYXu2U7Kko65Kg@mail.gmail.com>
Date: Thu, 19 Jun 2025 15:19:35 -0700
From: Mina Almasry <almasrymina@...gle.com>
To: Dragos Tatulea <dtatulea@...dia.com>
Cc: Stanislav Fomichev <stfomichev@...il.com>, Mark Bloch <mbloch@...dia.com>, 
	"David S. Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, 
	Eric Dumazet <edumazet@...gle.com>, Andrew Lunn <andrew+netdev@...n.ch>, 
	Simon Horman <horms@...nel.org>, saeedm@...dia.com, gal@...dia.com, leonro@...dia.com, 
	tariqt@...dia.com, Leon Romanovsky <leon@...nel.org>, 
	Jesper Dangaard Brouer <hawk@...nel.org>, Ilias Apalodimas <ilias.apalodimas@...aro.org>, 
	Richard Cochran <richardcochran@...il.com>, Alexei Starovoitov <ast@...nel.org>, 
	Daniel Borkmann <daniel@...earbox.net>, John Fastabend <john.fastabend@...il.com>, 
	Stanislav Fomichev <sdf@...ichev.me>, netdev@...r.kernel.org, linux-rdma@...r.kernel.org, 
	linux-kernel@...r.kernel.org, bpf@...r.kernel.org
Subject: Re: [PATCH net-next v6 12/12] net/mlx5e: Add TX support for netmems

On Thu, Jun 19, 2025 at 9:07 AM Dragos Tatulea <dtatulea@...dia.com> wrote:
> > You have to test ncdevmem tx on a platform with iommu enabled. Only in
> > this case the netmem_dma_unmap_page_attrs() may cause a problem, and
> > even then it's not a sure thing. It depends on the type of iommu and
> > type of dmabuf i think.
> >
> Is it worth adding a WARN_ON_ONCE(netmem_is_net_iov())
> in netmem_dma_unmap_page_attrs() after addr check to catch these kinds
> of misuse?
>

I would say it's worth it, but it's the same challenge you point to in
your reply: netmem_dma_unmap_page_attrs currently doesn't take in a
netmem, and it may be a big refactor not worth it if it's callers also
don't have a reference to the netmem readily available to pass it.

-- 
Thanks,
Mina