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Date: Wed, 2 Jul 2025 11:32:08 -0700
From: Jakub Kicinski <kuba@kernel.org>
To: Dragos Tatulea <dtatulea@nvidia.com>
Cc: <almasrymina@google.com>, <asml.silence@gmail.com>, Andrew Lunn
 <andrew+netdev@lunn.ch>, "David S. Miller" <davem@davemloft.net>, "Eric
 Dumazet" <edumazet@google.com>, Paolo Abeni <pabeni@redhat.com>, Simon
 Horman <horms@kernel.org>, Saeed Mahameed <saeedm@nvidia.com>,
 <tariqt@nvidia.com>, <cratiu@nvidia.com>, <netdev@vger.kernel.org>,
 <linux-kernel@vger.kernel.org>
Subject: Re: [RFC net-next 1/4] net: Allow non parent devices to be used for
 ZC DMA
Message-ID: <20250702113208.5adafe79@kernel.org>
In-Reply-To: <20250702172433.1738947-2-dtatulea@nvidia.com>
References: <20250702172433.1738947-1-dtatulea@nvidia.com>
	<20250702172433.1738947-2-dtatulea@nvidia.com>
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On Wed, 2 Jul 2025 20:24:23 +0300 Dragos Tatulea wrote:
> For zerocopy (io_uring, devmem), there is an assumption that the
> parent device can do DMA. However that is not always the case:
> for example mlx5 SF devices have an auxiliary device as a parent.

Noob question -- I thought that the point of SFs was that you can pass
them thru to a VM. How do they not have DMA support? Is it added on
demand by the mediated driver or some such?