From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1LMped-0005uI-Pa for qemu-devel@nongnu.org; Tue, 13 Jan 2009 15:14:27 -0500 Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43) id 1LMpeb-0005r3-MJ for qemu-devel@nongnu.org; Tue, 13 Jan 2009 15:14:27 -0500 Received: from [199.232.76.173] (port=52893 helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1LMpeb-0005qX-4Z for qemu-devel@nongnu.org; Tue, 13 Jan 2009 15:14:25 -0500 Received: from yx-out-1718.google.com ([74.125.44.158]:40173) by monty-python.gnu.org with esmtp (Exim 4.60) (envelope-from ) id 1LMpea-0007Ng-IK for qemu-devel@nongnu.org; Tue, 13 Jan 2009 15:14:24 -0500 Received: by yx-out-1718.google.com with SMTP id 3so94474yxi.82 for ; Tue, 13 Jan 2009 12:14:22 -0800 (PST) Message-ID: <496CF614.5000405@codemonkey.ws> Date: Tue, 13 Jan 2009 14:14:12 -0600 From: Anthony Liguori MIME-Version: 1.0 References: <496C9813.7000609@suse.de> In-Reply-To: <496C9813.7000609@suse.de> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Subject: [Qemu-devel] Re: virtio breakage with 2.6.25 guest kernel Reply-To: qemu-devel@nongnu.org List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Alexander Graf Cc: kvm-devel , Mark McLoughlin , rusty@rustcorp.com.au, qemu-devel@nongnu.org Alexander Graf wrote: > Hi, > > while I don't fully understand the problem, here's what I experience so far: > > When using an openSUSE 11.0 kernel (2.6.25) in the guest, virtio on tap > breaks with current KVM git, while it used to work before (haven't > bisected, definitely worked in kvm-78, but is probably due to Anthony's > rewrite). It shows the following message (comes from qemu): > There were a couple of old-guest-breaking regressions. I think we've fixed all of them but there could be more. Are you using the latest kvm-userspace? Regards, Anthony Liguori > virtio-net header not in first element > > This is because qemu expects a message with mergeable rx bufs (12 > bytes), but if I see things correctly the old kernel doesn't support > that feature (sends 10 bytes). I put in some debug messages on IO > reads/writes in the qemu virtio handler and got these: > > virtio IO read: 0 = 0x100bba3 > virtio IO write: 0x4 = 0x100bba3 > virtio: setting features 0x100bba3 > > So I believe the feature masking is somewhat non-functional? Or did I > read the masking code in qemu's virtio-net wrong? > > Basically for me, current KVM git broke old guest support, which is a > clear regression and should not happen. Does anybody with more expertise > in virtio want to take on this? > > Alex >