netdev - Re: [RFC PATCH 00/13] Ultra Ethernet driver introduction

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Message-ID: <20250311145557.GG7027@unreal>
Date: Tue, 11 Mar 2025 16:55:57 +0200
From: Leon Romanovsky <leon@...nel.org>
To: Bernard Metzler <BMT@...ich.ibm.com>
Cc: Parav Pandit <parav@...dia.com>,
	Nikolay Aleksandrov <nikolay@...abrica.net>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"shrijeet@...abrica.net" <shrijeet@...abrica.net>,
	"alex.badea@...sight.com" <alex.badea@...sight.com>,
	"eric.davis@...adcom.com" <eric.davis@...adcom.com>,
	"rip.sohan@....com" <rip.sohan@....com>,
	"dsahern@...nel.org" <dsahern@...nel.org>,
	"roland@...abrica.net" <roland@...abrica.net>,
	"winston.liu@...sight.com" <winston.liu@...sight.com>,
	"dan.mihailescu@...sight.com" <dan.mihailescu@...sight.com>,
	Kamal Heib <kheib@...hat.com>,
	"parth.v.parikh@...sight.com" <parth.v.parikh@...sight.com>,
	Dave Miller <davem@...hat.com>,
	"ian.ziemba@....com" <ian.ziemba@....com>,
	"andrew.tauferner@...nelisnetworks.com" <andrew.tauferner@...nelisnetworks.com>,
	"welch@....com" <welch@....com>,
	"rakhahari.bhunia@...sight.com" <rakhahari.bhunia@...sight.com>,
	"kingshuk.mandal@...sight.com" <kingshuk.mandal@...sight.com>,
	"linux-rdma@...r.kernel.org" <linux-rdma@...r.kernel.org>,
	"kuba@...nel.org" <kuba@...nel.org>,
	Paolo Abeni <pabeni@...hat.com>, Jason Gunthorpe <jgg@...dia.com>
Subject: Re: [RFC PATCH 00/13] Ultra Ethernet driver introduction

On Tue, Mar 11, 2025 at 02:20:07PM +0000, Bernard Metzler wrote:
> 
> 
> > -----Original Message-----
> > From: Parav Pandit <parav@...dia.com>
> > Sent: Sunday, March 9, 2025 4:22 AM
> > To: Leon Romanovsky <leon@...nel.org>; Nikolay Aleksandrov
> > <nikolay@...abrica.net>
> > Cc: netdev@...r.kernel.org; shrijeet@...abrica.net;
> > alex.badea@...sight.com; eric.davis@...adcom.com; rip.sohan@....com;
> > dsahern@...nel.org; Bernard Metzler <BMT@...ich.ibm.com>;
> > roland@...abrica.net; winston.liu@...sight.com;
> > dan.mihailescu@...sight.com; Kamal Heib <kheib@...hat.com>;
> > parth.v.parikh@...sight.com; Dave Miller <davem@...hat.com>;
> > ian.ziemba@....com; andrew.tauferner@...nelisnetworks.com;
> > welch@....com; rakhahari.bhunia@...sight.com;
> > kingshuk.mandal@...sight.com; linux-rdma@...r.kernel.org;
> > kuba@...nel.org; Paolo Abeni <pabeni@...hat.com>; Jason Gunthorpe
> > <jgg@...dia.com>
> > Subject: [EXTERNAL] RE: [RFC PATCH 00/13] Ultra Ethernet driver
> > introduction
> > 
> > 
> > 
> > > From: Leon Romanovsky <leon@...nel.org>
> > > Sent: Sunday, March 9, 2025 12:17 AM
> > >
> > > On Fri, Mar 07, 2025 at 01:01:50AM +0200, Nikolay Aleksandrov wrote:
> > > > Hi all,
> > >
> > > <...>
> > >
> > > > Ultra Ethernet is a new RDMA transport.
> > >
> > > Awesome, and now please explain why new subsystem is needed when
> > > drivers/infiniband already supports at least 5 different RDMA
> > transports
> > > (OmniPath, iWARP, Infiniband, RoCE v1 and RoCE v2).
> > >
> > 6th transport is drivers/infiniband/hw/efa (srd).
> > 
> > > Maybe after this discussion it will be very clear that new subsystem
> > is needed,
> > > but at least it needs to be stated clearly.
> 
> I am not sure if a new subsystem is what this RFC calls
> for, but rather a discussion about the proper integration of
> a new RDMA transport into the Linux kernel.

<...>

> The different API semantics of UET may further call
> for either extending verbs to cover it as well, or exposing a
> new non-verbs API (libfabrics), or both.

So you should start from there (UAPI) by presenting the device model and
how the verbs API needs to be extended, so it will be possible to evaluate
how to fit that model into existing Linux kernel codebase.

RDNA subsystem provides multiple type of QPs and operational models, some of them
are indeed follow IB style, but not all of them (SRD, DC e.t.c).

Thanks

> 
> Thanks,
> Bernard.
> 
> 
> > >
> > > An please CC RDMA maintainers to any Ultra Ethernet related
> > discussions as it
> > > is more RDMA than Ethernet.
> > >
> > > Thanks
>