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Date: Mon, 12 Dec 2016 10:38:13 +0200
From: Mike Rapoport <rppt@...ux.vnet.ibm.com>
To: Jesper Dangaard Brouer <brouer@...hat.com>
Cc: "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
linux-mm <linux-mm@...ck.org>,
John Fastabend <john.fastabend@...il.com>,
Willem de Bruijn <willemdebruijn.kernel@...il.com>,
Björn Töpel <bjorn.topel@...el.com>,
"Karlsson, Magnus" <magnus.karlsson@...el.com>,
Alexander Duyck <alexander.duyck@...il.com>,
Mel Gorman <mgorman@...hsingularity.net>,
Tom Herbert <tom@...bertland.com>,
Brenden Blanco <bblanco@...mgrid.com>,
Tariq Toukan <tariqt@...lanox.com>,
Saeed Mahameed <saeedm@...lanox.com>,
Jesse Brandeburg <jesse.brandeburg@...el.com>,
Kalman Meth <METH@...ibm.com>
Subject: Re: Designing a safe RX-zero-copy Memory Model for Networking
Hello Jesper,
On Mon, Dec 05, 2016 at 03:31:32PM +0100, Jesper Dangaard Brouer wrote:
> Hi all,
>
> This is my design for how to safely handle RX zero-copy in the network
> stack, by using page_pool[1] and modifying NIC drivers. Safely means
> not leaking kernel info in pages mapped to userspace and resilience
> so a malicious userspace app cannot crash the kernel.
>
> Design target
> =============
>
> Allow the NIC to function as a normal Linux NIC and be shared in a
> safe manor, between the kernel network stack and an accelerated
> userspace application using RX zero-copy delivery.
>
> Target is to provide the basis for building RX zero-copy solutions in
> a memory safe manor. An efficient communication channel for userspace
> delivery is out of scope for this document, but OOM considerations are
> discussed below (`Userspace delivery and OOM`_).
Sorry, if this reply is a bit off-topic.
I'm working on implementation of RX zero-copy for virtio and I've dedicated
some thought about making guest memory available for physical NIC DMAs.
I believe this is quite related to your page_pool proposal, at least from
the NIC driver perspective, so I'd like to share some thoughts here.
The idea is to dedicate one (or more) of the NIC's queues to a VM, e.g.
using macvtap, and then propagate guest RX memory allocations to the NIC
using something like new .ndo_set_rx_buffers method.
What is your view about interface between the page_pool and the NIC
drivers?
Have you considered using "push" model for setting the NIC's RX memory?
>
> --
> Jesper Dangaard Brouer
> MSc.CS, Principal Kernel Engineer at Red Hat
> LinkedIn: http://www.linkedin.com/in/brouer
>
> Above document is taken at GitHub commit 47fa7c844f48fab8b
> https://github.com/netoptimizer/prototype-kernel/commit/47fa7c844f48fab8b
>
--
Sincerely yours,
Mike.
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