From mboxrd@z Thu Jan 1 00:00:00 1970 From: Michal Kubecek Subject: Re: Linux 4.14 - regression: broken tun/tap / bridge network with virtio - bisected Date: Fri, 8 Dec 2017 09:47:51 +0100 Message-ID: <20171208084751.tom4auppogz4lanz@unicorn.suse.cz> References: <9615150a-eb78-2f9d-798f-6aa460932aec@01019freenet.de> <2e2392b7-84c5-be89-b0e5-5bae3b2fdaed@01019freenet.de> <4efbaf24-f419-2c8e-c705-59a5242b0575@01019freenet.de> <881560f8-54ec-e946-50cb-b2e80ddb5f97@01019freenet.de> <73b7a7b0-4264-2bd0-9e65-69841377f09f@redhat.com> <401a0715-fd28-63a3-8dfd-e89835d70db0@01019freenet.de> <11c25b88-af9b-a1f7-b5f5-0420c75916d7@01019freenet.de> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Jason Wang , David Miller , netdev@vger.kernel.org To: Andreas Hartmann Return-path: Received: from mx2.suse.de ([195.135.220.15]:38646 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750927AbdLHIrx (ORCPT ); Fri, 8 Dec 2017 03:47:53 -0500 Content-Disposition: inline In-Reply-To: <11c25b88-af9b-a1f7-b5f5-0420c75916d7@01019freenet.de> Sender: netdev-owner@vger.kernel.org List-ID: On Fri, Dec 08, 2017 at 08:21:16AM +0100, Andreas Hartmann wrote: > > Thanks for this hint - I'm not using xdp. Therefore I rechecked my > bisect and detected a mistake. The rebisect now leads to > > > > [v2,RFC,11/13] net: Remove all references to SKB_GSO_UDP. [1] > > > > For the repeated bisect, I switched back to the original qemu 2.6.2 > (instead of 2.10.1), because problems can be seen reliably with 2.6.2. > > All my VMs are using virtio_net. BTW: I couldn't see the problems > (sometimes, the VM couldn't be stopped at all) if all my VMs are using > e1000 as interface instead. > > This finding now matches pretty much the responsible UDP-package which > caused the stall. I already mentioned it here [2]. > > To prove it, I reverted from the patch series "[PATCH v2 RFC 0/13] > Remove UDP Fragmentation Offload support" [3] > > 11/13 [v2,RFC,11/13] net: Remove all references to SKB_GSO_UDP. [4] > 12/13 [v2,RFC,12/13] inet: Remove software UFO fragmenting code. [5] > 13/13 [v2,RFC,13/13] net: Kill NETIF_F_UFO and SKB_GSO_UDP. [6] > > and applied it to Linux 4.14.4. It compiled fine and is running fine. > The vnet doesn't die anymore. Yet, I can't say if the qemu stop hangs > are gone, too. > > Obviously, there is something broken with the new UDP handling. Could > you please analyze this problem? I could test some more patches ... . Any chance your VMs were live migrated from pre-4.14 host kernel? If this is the case, you should try commit 0c19f846d582 ("net: accept UFO datagrams from tuntap and packet"). Or disabling UFO in the guest should work around the issue. Michal Kubecek