From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:37812) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bi0oc-0008Gs-9F for qemu-devel@nongnu.org; Thu, 08 Sep 2016 11:00:35 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1bi0oY-0002Gl-Qr for qemu-devel@nongnu.org; Thu, 08 Sep 2016 11:00:34 -0400 Received: from mx1.redhat.com ([209.132.183.28]:37130) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bi0oY-0002GZ-LA for qemu-devel@nongnu.org; Thu, 08 Sep 2016 11:00:30 -0400 Date: Thu, 8 Sep 2016 18:00:28 +0300 From: "Michael S. Tsirkin" Message-ID: <20160908175237-mutt-send-email-mst@kernel.org> References: <147326875705.8546.11347276277137015855.stgit@bahia.lan> <147326876478.8546.16045138068342092499.stgit@bahia.lan> <20160908105926.0d968e64.cornelia.huck@de.ibm.com> <20160908111216.12a1b562@bahia> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20160908111216.12a1b562@bahia> Subject: Re: [Qemu-devel] [PATCH 1/2] virtio-9p: print error message and exit instead of BUG_ON() List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Greg Kurz Cc: Cornelia Huck , qemu-devel@nongnu.org, "Aneesh Kumar K.V" On Thu, Sep 08, 2016 at 11:12:16AM +0200, Greg Kurz wrote: > On Thu, 8 Sep 2016 10:59:26 +0200 > Cornelia Huck wrote: > > > On Wed, 07 Sep 2016 19:19:24 +0200 > > Greg Kurz wrote: > > > > > Calling assert() really makes sense when hitting a genuine bug, which calls > > > for a fix in QEMU. However, when something goes wrong because the guest > > > sends a malformed message, it is better to write down a more meaningul > > > error message and exit. > > > > > > Signed-off-by: Greg Kurz > > > --- > > > hw/9pfs/virtio-9p-device.c | 20 ++++++++++++++++++-- > > > 1 file changed, 18 insertions(+), 2 deletions(-) > > > > While this is an improvement over the current state, I don't think the > > guest should be able to kill qemu just by doing something stupid. > > > > Hi Connie, > > I'm glad you're pointing this out... this was also my impression, but > since there are a bunch of sanity checks in the virtio code that cause > QEMU to exit (even recently added like 1e7aed70144b), I did not dare > stand up :) It's true that it's broken in many places but we should just fix them all. A separate question is how to log such hardware/guest bugs generally. People already complained about disk filling up because of us printing errors on each such bug. Maybe print each message only N times, and then set a flag to skip the log until management tells us to restart logging again. > > The right way to go is to mark the virtio device as broken and stop > > doing any processing until the guest resets it. I think Stefan had a > > patch series doing that for some base virtio errors, but I'd have to > > search for it. > > > > I'd be glad to have a look and try to address this issue. > > Thanks ! > > -- > Greg