From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:39079) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1T8Woi-00048M-Ft for qemu-devel@nongnu.org; Mon, 03 Sep 2012 09:35:58 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1T8Wob-0008C7-EP for qemu-devel@nongnu.org; Mon, 03 Sep 2012 09:35:52 -0400 Received: from mx1.redhat.com ([209.132.183.28]:45847) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1T8Wob-0008Bk-68 for qemu-devel@nongnu.org; Mon, 03 Sep 2012 09:35:45 -0400 Date: Mon, 3 Sep 2012 16:37:06 +0300 From: "Michael S. Tsirkin" Message-ID: <20120903133706.GE3855@redhat.com> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Subject: Re: [Qemu-devel] Symptoms of lost interrupts in virtio? List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Soren Hansen Cc: qemu-devel@nongnu.org On Mon, Sep 03, 2012 at 03:16:00PM +0200, Soren Hansen wrote: > Michael, > > In Ubuntu we're seeing a bug in qemu-kvm 1.0 where networking stops > working. It's described here: > > https://bugs.launchpad.net/ubuntu/+source/libvirt/+bug/997978 > > We've not been able to reproduce it ourselves, but the users who are > experiencing it say that it's fixed in 1.1. > > I've found this series of commits: > > a821ce5 virtio: order index/descriptor reads > 92045d8 virtio: add missing mb() on enable notification > a281ebc virtio: add missing mb() on notification > > where particularly the last one looks like a likely fix for the problem. > > The commit message isn't entirely clear about the symptoms it's meant > to fix, even though the behind-the-covers explanation is very > thorough. It's not clear to me, for instance, if the network would > stop working or if you'd just lose a couple of network packets? It can stop working. It's more likely to stop if event_idx is enabled. Try disabling and see what happens. > The commit message suggests it only happens on a very specific > processor type. Do you happen to remember which one? If it matches > what our affected users see, that could be clue as to whether this is > the same problem. I think it was reported on AMD systems. > Thanks in advance for your time. > > -- > Soren Hansen > Ubuntu Developer http://www.ubuntu.com/ > OpenStack Developer http://www.openstack.org/