linux-kernel - Re: [RFC net-next 1/4] net: Allow non parent devices to be used for ZC DMA

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <fszmowhndjnms4dyqt2nvnoisoml27e3eddbxg3pwgqrkywpop@g7u75aair6la>
Date: Tue, 8 Jul 2025 14:26:54 +0000
From: Dragos Tatulea <dtatulea@...dia.com>
To: Pavel Begunkov <asml.silence@...il.com>, 
	Parav Pandit <parav@...dia.com>, Jakub Kicinski <kuba@...nel.org>
Cc: "almasrymina@...gle.com" <almasrymina@...gle.com>, 
	Andrew Lunn <andrew+netdev@...n.ch>, "David S. Miller" <davem@...emloft.net>, 
	Eric Dumazet <edumazet@...gle.com>, Paolo Abeni <pabeni@...hat.com>, Simon Horman <horms@...nel.org>, 
	Saeed Mahameed <saeedm@...dia.com>, Tariq Toukan <tariqt@...dia.com>, 
	Cosmin Ratiu <cratiu@...dia.com>, "netdev@...r.kernel.org" <netdev@...r.kernel.org>, 
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [RFC net-next 1/4] net: Allow non parent devices to be used for
 ZC DMA

On Tue, Jul 08, 2025 at 12:08:48PM +0100, Pavel Begunkov wrote:
> On 7/4/25 14:11, Dragos Tatulea wrote:
> > On Thu, Jul 03, 2025 at 01:58:50PM +0200, Parav Pandit wrote:
> > > 
> > > > From: Jakub Kicinski <kuba@...nel.org>
> > > > Sent: 03 July 2025 02:23 AM
> ...>> In an offline discussion, Dragos mentioned that io_uring already
> > > operates at the queue level, may be some ideas can be picked up
> > > from io_uring?
> > The problem for devmem is that the device based API is already set in
> > stone so not sure how we can change this. Maybe Mina can chime in.
> > 
> > To sum the conversation up, there are 2 imperfect and overlapping
> > solutions:
> > 
> > 1) For the common case of having a single PCI device per netdev, going one
> >     parent up if the parent device is not DMA capable would be a good
> >     starting point.
> > 
> > 2) For multi-PF netdev [0], a per-queue get_dma_dev() op would be ideal
> >     as it provides the right PF device for the given queue. io_uring
> >     could use this but devmem can't. Devmem could use 1. but the
> >     driver has to detect and block the multi PF case.
> > 
> > I think we need both. Either that or a netdev op with an optional queue
> > parameter. Any thoughts?
> 
> No objection from zcrx for either approach, but it sounds like a good
> idea to have something simple for 1) sooner than later, and perhaps
> marked as a fix.
>
Sounds good. This is light enough to be a single patch.

Will tackle multi-PF netdev in a subsequent series.

Thanks,
Dragos