From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <netdev-owner@vger.kernel.org>
Received: from mx3-rdu2.redhat.com ([66.187.233.73]:52934 "EHLO mx1.redhat.com"
        rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP
        id S1751500AbeBROWJ (ORCPT <rfc822;netdev@vger.kernel.org>);
        Sun, 18 Feb 2018 09:22:09 -0500
Date: Sun, 18 Feb 2018 15:22:04 +0100
From: Jesper Dangaard Brouer <brouer@redhat.com>
To: Jason Wang <jasowang@redhat.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>, netdev@vger.kernel.org,
        John Fastabend <john.fastabend@gmail.com>,
        Alexei Starovoitov <alexei.starovoitov@gmail.com>,
        Daniel Borkmann <borkmann@iogearbox.net>,
        "David S. Miller" <davem@davemloft.net>, brouer@redhat.com,
        =?UTF-8?B?QmrDtnJuIFTDtnBlbA==?= <bjorn.topel@intel.com>,
        "Karlsson, Magnus" <magnus.karlsson@intel.com>
Subject: Re: [RFC net PATCH] virtio_net: disable XDP_REDIRECT in
 receive_mergeable() case
Message-ID: <20180218152204.671c21a8@redhat.com>
In-Reply-To: <25a9b6f0-e3f4-30b7-054a-d8e58d80cfcd@redhat.com>
References: <151873460188.31003.8350168978875601093.stgit@firesoul>
        <25a9b6f0-e3f4-30b7-054a-d8e58d80cfcd@redhat.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: 7bit
Sender: netdev-owner@vger.kernel.org
List-ID: <netdev.vger.kernel.org>

On Fri, 16 Feb 2018 13:31:37 +0800 Jason Wang <jasowang@redhat.com> wrote:

> > Besides the described bug:
> >
> > Update(1): There is also a OOM leak in the XDP_REDIRECT code, which
> > receive_small() is likely also affected by.

Found the issue behind this memory leak... page refcnt issues when
hitting xmit error paths.

> > Update(2): Also observed a guest crash when redirecting out an
> > another virtio_net device, when device is down.  

Also found reason behind this. It is not related to a "down" device.
It caused by redirect into a virtio_net device that does not have setup
sufficient XDP TX queues (which it assumes is one per CPU). I have a
preliminary fix patch.

> Will have a look at these issues. (Holiday in china now, so will do it 
> after).

No worry.  I can take care of this... I'll cleanup my patches and test
them Monday, should have patches ready Tuesday... as I want to make
sure they work in all the different error cases.

I'll be working on improvements for the XDP_REDIRECT code paths anyway
next week... in preparations for supporting the AF_XDP use case.

-- 
Best regards,
  Jesper Dangaard Brouer
  MSc.CS, Principal Kernel Engineer at Red Hat
  LinkedIn: http://www.linkedin.com/in/brouer