On Wed, 22 Feb 2017 10:03:56 +0100
Paolo Bonzini <pbonz...@redhat.com> wrote:
> On 21/02/2017 18:54, Laszlo Ersek wrote:
> > Actually, QEMU segfaults. From the dmesg:
> >
> > [Tue Feb 21 18:47:28 2017] CPU 0/KVM[8298]: segfault at 48 ip
> > 00007fcb5dd02105 sp 00007fcb49efc270 error 4 in
> > qemu-system-x86_64[7fcb5dae3000+905000]
> >
> > Complete backtrace below. (Thread 11 seems to be the one
> > segfaulting.)
>
> Indeed. It's the virtio-blk device that is segfaulting, please try
> this one liner (haven't reproduced it, but it seems obvious with the
> backtrace and some sleep).
I hit this as well, the patch below resolves it.
Tested-by: Alex Williamson <alex.william...@redhat.com>
> commit c1aa478c7181c543606ca81404c59e126d66213d
> Author: Paolo Bonzini <pbonz...@redhat.com>
> Date: Wed Feb 22 10:02:37 2017 +0100
>
> virtio: check for vring setup in virtio_queue_empty
>
> If the vring has not been set up, there is nothing in the virtqueue.
> virtio_queue_host_notifier_aio_poll calls virtio_queue_empty even in
> this case; we have to filter it out just like virtio_queue_notify_aio_vq.
>
> Reported-by: Gerd Hoffmann <kra...@redhat.com>
> Signed-off-by: Paolo Bonzini <pbonz...@redhat.com>
>
> diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
> index 23483c7..e487e36 100644
> --- a/hw/virtio/virtio.c
> +++ b/hw/virtio/virtio.c
> @@ -2291,7 +2291,7 @@ static bool virtio_queue_host_notifier_aio_poll(void
> *opaque)
> VirtQueue *vq = container_of(n, VirtQueue, host_notifier);
> bool progress;
>
> - if (virtio_queue_empty(vq)) {
> + if (!vq->vring.desc || virtio_queue_empty(vq)) {
> return false;
> }
>
>
