netdev - Re: Regression in mvneta with XDP patches

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Date:   Mon, 11 Nov 2019 17:15:29 +0200
From:   Ilias Apalodimas <ilias.apalodimas@...aro.org>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     brouer@...hat.com, lorenzo@...nel.org,
        netdev <netdev@...r.kernel.org>
Subject: Re: Regression in mvneta with XDP patches

Hi Andrew,

On Mon, Nov 11, 2019 at 04:05:53PM +0100, Andrew Lunn wrote:
> On Mon, Nov 11, 2019 at 04:33:52PM +0200, Ilias Apalodimas wrote:
> > Hi Andrew,
> > 
> > On Mon, Nov 11, 2019 at 02:46:15PM +0100, Andrew Lunn wrote:
> > > Hi Lorenzo, Jesper, Ilias
> > > 
> > > I just found that the XDP patches to mvneta have caused a regression.
> > > 
> > > This one breaks networking:
> > 
> > Thaks for the report.
> > Looking at the DTS i can see 'buffer-manager' in it. The changes we made were
> > for the driver path software buffer manager. 
> > Can you confirm which one your hardware uses?
> 
> Hi Ilias
> 
> Ah, interesting.
> 
> # CONFIG_MVNETA_BM_ENABLE is not set
> 
> So in fact it is not being compiled in, so should be falling back to
> software buffer manager.
> 
> If i do enable it, then it works. So we are in a corner cases you
> probably never tested. Requested by DT, but not actually available.
> 

Correct, i don't think any of us had access to a hardware with BM
We did change some offsets of memory allocation in the swbm to make room for
skb_shared_info and the xdp headlen we need. 
Maybe we missed that on the 'fallback' scenario. I'll try to have a look on the
driver

> 	 Andrew

Thanks
/Ilias