From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:43337) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bi16z-0001JT-RR for qemu-devel@nongnu.org; Thu, 08 Sep 2016 11:19:35 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1bi16v-0006oR-D9 for qemu-devel@nongnu.org; Thu, 08 Sep 2016 11:19:32 -0400 Received: from mx1.redhat.com ([209.132.183.28]:51688) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bi16v-0006oI-6u for qemu-devel@nongnu.org; Thu, 08 Sep 2016 11:19:29 -0400 Date: Thu, 8 Sep 2016 18:19:27 +0300 From: "Michael S. Tsirkin" Message-ID: <20160908181732-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> <20160908175237-mutt-send-email-mst@kernel.org> <20160908170447.2d864945.cornelia.huck@de.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20160908170447.2d864945.cornelia.huck@de.ibm.com> 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: Cornelia Huck Cc: Greg Kurz , qemu-devel@nongnu.org, "Aneesh Kumar K.V" On Thu, Sep 08, 2016 at 05:04:47PM +0200, Cornelia Huck wrote: > On Thu, 8 Sep 2016 18:00:28 +0300 > "Michael S. Tsirkin" wrote: > > > 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. > > I'd expect to get the message just once per device if we set the device > to broken (unless the guess continuously resets it again...) Which it can do, so we should limit that anyway. > Do we have > a generic print/log ratelimit infrastructure in qemu? There are actually two kinds of errors host side ones and ones triggered by guests. We should distinguish between them API-wise, then we will be able to limit the logging of those that guest can trigger. -- MST