linux-kernel - Re: [RFC PATCH v12 01/17] dlb: add skeleton for DLB driver

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Message-ID: <YcRN9zwkP4nw4Dh8@lunn.ch>
Date:   Thu, 23 Dec 2021 11:22:47 +0100
From:   Andrew Lunn <andrew@...n.ch>
To:     "Chen, Mike Ximing" <mike.ximing.chen@...el.com>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "arnd@...db.de" <arnd@...db.de>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "Williams, Dan J" <dan.j.williams@...el.com>,
        "pierre-louis.bossart@...ux.intel.com" 
        <pierre-louis.bossart@...ux.intel.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "kuba@...nel.org" <kuba@...nel.org>
Subject: Re: [RFC PATCH v12 01/17] dlb: add skeleton for DLB driver

On Thu, Dec 23, 2021 at 05:15:34AM +0000, Chen, Mike Ximing wrote:
> 
> 
> > -----Original Message-----
> > From: Andrew Lunn <andrew@...n.ch>
> > Sent: Wednesday, December 22, 2021 4:27 PM
> > To: Chen, Mike Ximing <mike.ximing.chen@...el.com>
> > Cc: linux-kernel@...r.kernel.org; arnd@...db.de; gregkh@...uxfoundation.org; Williams, Dan J
> > <dan.j.williams@...el.com>; pierre-louis.bossart@...ux.intel.com; netdev@...r.kernel.org;
> > davem@...emloft.net; kuba@...nel.org
> > Subject: Re: [RFC PATCH v12 01/17] dlb: add skeleton for DLB driver
> > 
> > > > pointing to skbufs? How are the lifetimes of skbufs managed? How do
> > > > you get skbufs out of the NIC? Are you using XDP?
> > >
> > > This is not a network accelerator in the sense that it does not have
> > > direct access to the network sockets/ports. We do not use XDP.
> > 
> > So not using XDP is a problem. I looked at previous versions of this patch, and it is all DPDK. But DPDK is
> > not in mainline, XDP is. In order for this to be merged into mainline you need a mainline user of it.
> > 
> > Maybe you should abandon mainline, and just get this driver merged into the DPDK fork of Linux?
> > 
> Hi Andrew,
> 
> I am not sure why not using XDP is a problem. As mentioned earlier, the
> DLB driver is not a part of network stack.  
> 
> DPDK is one of applications that can make a good use of DLB, but is not the
> only one. We have applications that access DLB directly via the kernel driver API
> without using DPDK.

Cool. Please can you point at a repo for the code? As i said, we just
need a userspace user, which gives us a good idea how the hardware is
supposed to be used, how the kAPI is to be used, and act as a good
test case for when kernel modifications are made. But it needs to be
pure mainline.

There have been a few good discussion on LWN about accelerators
recently. Worth reading.

	  Andrew