netdev - Re: [Xen-devel] xennet_start

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Message-ID: <20170125154546.GF2212@oracle.com>
Date:   Wed, 25 Jan 2017 10:45:46 -0500
From:   Sowmini Varadhan <sowmini.varadhan@...cle.com>
To:     Paul Durrant <Paul.Durrant@...rix.com>
Cc:     Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
        Wei Liu <wei.liu2@...rix.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "xen-devel@...ts.xenproject.org" <xen-devel@...ts.xenproject.org>
Subject: Re: [Xen-devel] xennet_start_xmit assumptions

On (01/25/17 15:06), Paul Durrant wrote:
> 
>   Making netfront cope with a fully non-linear skb looks like it would
> be quite intrusive and probably not worth it so I opted for just doing
> the ETH_HLEN pull-tail if necessary. Can you check it works for you?

I tested it, and it works fine, but note that DaveM's comments in 
this thread: the DKI is that we *must* provide at least the hard_header_len
in the non-paged part of the skb. So might not even be necessary to handle
the fully non-linear skb (though it's probably prudent to check
and bail for this, as your patch does)

I just posted an RFC patch for fixing the pf_packet layer,
just in case other drivers like xen_netfront dont explicitly
check for this
   http://patchwork.ozlabs.org/patch/719236/