linux-kernel - Re: [PATCH v3 00/14] Adding GAUDI NIC code to habanalabs driver

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Date:   Wed, 16 Sep 2020 11:02:39 +0300
From:   Oded Gabbay <oded.gabbay@...il.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     David Miller <davem@...emloft.net>,
        "Linux-Kernel@...r. Kernel. Org" <linux-kernel@...r.kernel.org>,
        netdev@...r.kernel.org, SW_Drivers <SW_Drivers@...ana.ai>,
        Jakub Kicinski <kuba@...nel.org>, Andrew Lunn <andrew@...n.ch>,
        Florian Fainelli <f.fainelli@...il.com>
Subject: Re: [PATCH v3 00/14] Adding GAUDI NIC code to habanalabs driver

On Wed, Sep 16, 2020 at 10:41 AM Greg Kroah-Hartman
<gregkh@...uxfoundation.org> wrote:
>
> On Wed, Sep 16, 2020 at 09:36:23AM +0300, Oded Gabbay wrote:
> > On Wed, Sep 16, 2020 at 9:25 AM Greg Kroah-Hartman
> > <gregkh@...uxfoundation.org> wrote:
> > >
> > > On Tue, Sep 15, 2020 at 11:49:12PM +0300, Oded Gabbay wrote:
> > > > On Tue, Sep 15, 2020 at 11:42 PM David Miller <davem@...emloft.net> wrote:
> > > > >
> > > > > From: Oded Gabbay <oded.gabbay@...il.com>
> > > > > Date: Tue, 15 Sep 2020 20:10:08 +0300
> > > > >
> > > > > > This is the second version of the patch-set to upstream the GAUDI NIC code
> > > > > > into the habanalabs driver.
> > > > > >
> > > > > > The only modification from v2 is in the ethtool patch (patch 12). Details
> > > > > > are in that patch's commit message.
> > > > > >
> > > > > > Link to v2 cover letter:
> > > > > > https://lkml.org/lkml/2020/9/12/201
> > > > >
> > > > > I agree with Jakub, this driver definitely can't go-in as it is currently
> > > > > structured and designed.
> > > > Why is that ?
> > > > Can you please point to the things that bother you or not working correctly?
> > > > I can't really fix the driver if I don't know what's wrong.
> > > >
> > > > In addition, please read my reply to Jakub with the explanation of why
> > > > we designed this driver as is.
> > > >
> > > > And because of the RDMA'ness of it, the RDMA
> > > > > folks have to be CC:'d and have a chance to review this.
> > > > As I said to Jakub, the driver doesn't use the RDMA infrastructure in
> > > > the kernel and we can't connect to it due to the lack of H/W support
> > > > we have
> > > > Therefore, I don't see why we need to CC linux-rdma.
> > > > I understood why Greg asked me to CC you because we do connect to the
> > > > netdev and standard eth infrastructure, but regarding the RDMA, it's
> > > > not really the same.
> > >
> > > Ok, to do this "right" it needs to be split up into separate drivers,
> > > hopefully using the "virtual bus" code that some day Intel will resubmit
> > > again that will solve this issue.
> > Hi Greg,
> > Can I suggest an alternative for the short/medium term ?
> >
> > In an earlier email, Jakub said:
> > "Is it not possible to move the files and still build them into a single
> > module?"
> >
> > I thought maybe that's a good way to progress here ?
>
> Cross-directory builds of a single module are crazy.  Yes, they work,
> but really, that's a mess, and would never suggest doing that.
>
> > First, split the content to Ethernet and RDMA.
> > Then move the Ethernet part to drivers/net but build it as part of
> > habanalabs.ko.
> > Regarding the RDMA code, upstream/review it in a different patch-set
> > (maybe they will want me to put the files elsewhere).
> >
> > What do you think ?
>
> I think you are asking for more work there than just splitting out into
> separate modules :)
>
> thanks,
>
> greg k-h
Hi Greg,

If cross-directory building is out of the question, what about
splitting into separate modules ? And use cross-module notifiers/calls
? I did that with amdkfd and amdgpu/radeon a couple of years back. It
worked (that's the best thing I can say about it).
The main problem with this "virtual bus" thing is that I'm not
familiar with it at all and from my experience I imagine it would take
a considerable time and effort to upstream this infrastructure work.
This could delay the NIC code for a couple of years, which by then
this won't be relevant at all.

So I'm trying to find some middle ground here on how to proceed.

Thanks,
Oded