From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Michael S. Tsirkin" Subject: Re: regression: UFO removal breaks kvm live migration Date: Wed, 8 Nov 2017 18:01:22 +0200 Message-ID: <20171108174633-mutt-send-email-mst@kernel.org> References: <446b71fc-6ffc-2bb0-bae1-69424805de91@redhat.com> <20171108.203231.310648804772108001.davem@davemloft.net> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Cc: jasowang@redhat.com, willemdebruijn.kernel@gmail.com, mkubecek@suse.cz, netdev@vger.kernel.org, vyasevic@redhat.com To: David Miller Return-path: Received: from mx1.redhat.com ([209.132.183.28]:59360 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752608AbdKHQBZ (ORCPT ); Wed, 8 Nov 2017 11:01:25 -0500 Content-Disposition: inline In-Reply-To: <20171108.203231.310648804772108001.davem@davemloft.net> Sender: netdev-owner@vger.kernel.org List-ID: On Wed, Nov 08, 2017 at 08:32:31PM +0900, David Miller wrote: > From: Jason Wang > Date: Wed, 8 Nov 2017 17:25:48 +0900 > > > On 2017年11月08日 17:08, Willem de Bruijn wrote: > >> That won't help in the short term. I'm still reading up to see if > >> there are > >> any other options besides reimplement or advertise-but-drop, such as > >> an implicit trigger that would make the guest renegotiate. It's > >> unlikely, but > >> worth a look.. > > > > Yes, this looks hard. And even if we can manage to do this, it looks > > an overkill since it will impact all guest after migration. > > Like Willem I would much prefer "advertise-but-drop" if it works. > > In the long term feature renegotiation triggers are a must. > > There is no way for us to remove features otherwise. Isn't this like most userspace ABI issues? Once you add them it's very hard to remove them, even with negotiation - too much userspace just does if (ret) exit(); > In my opinion this will even make migrations more powerful. I agree. Not sure how to avoid packet drops when doing this though. And dropping a ton of TX packets isn't nice at all since TX packets is what teaches the network about the new location of the VM. -- MST