Re: [Qemu-devel] assert hit on master with q35 machine type

[Stefan Hajnoczi <stefanha@redhat.com>]

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On Mon, Jan 09, 2017 at 01:08:53PM +0000, Dr. David Alan Gilbert wrote:
> copying in Stefan since it's his commit.
> 
> * Doug Goldstein (cardoe@cardoe.com) wrote:
> > I'm currently hitting an assert on master. I've bisected the change down
> > to aff8fd18f1786fc5af259a9bc0077727222f51ca but obviously that's a false
> > positive because that adds the assert for the condition. So obviously
> > the issue was introduced prior to this. As another data point the issue
> > only occurs with q35 machines and will only happen with pc-q35-2.7 and
> > pc-q35-2.8 (and obviously the aliased q35). If I use pc-q35-2.6 it does
> > not hit.
> > 
> > The message is: qemu-system-x86_64:
> > /home/doug/work/qemu/hw/virtio/virtio.c:214:
> > virtio_queue_set_notification: Assertion `vq->notification_disabled > 0'
> > failed.
> > 
> > But that clearly just shows its the assert that was added in that
> > commit. To create the machine I use the following command line:
> > 
> > ./work/qemu/x86_64-softmmu/qemu-system-x86_64 -enable-kvm -M pc-q35-2.8
> > -device intel-iommu -cpu host -m 2048 -smp 2 -drive
> > if=pflash,format=raw,file=/tmp/tmp.Sno2BP3saP -global
> > isa-debugcon.iobase=0x402 -debugcon file:/tmp/tmp.KCrwM98Mus -monitor
> > stdio -chardev socket,host=127.0.0.1,port=4455,id=S0,server,nowait
> > -device isa-serial,chardev=S0 -device piix3-usb-uhci -device usb-tablet
> > -netdev id=net0,type=tap -device virtio-net-pci,netdev=net0 -boot
> > order=n -device qxl-vga -gdb tcp::1234
> > 
> > It happens almost right away. Let me know how I can help track this down
> > further.

I can't reproduce the assertion failure.

Are you able to provide a backtrace (e.g. launch QEMU under gdb and then
use the 'bt' command after the assertion failure is raised)?

Thanks,
Stefan

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