On Fr, 2016-11-11 at 17:28 +0100, Jiri Slaby wrote:> On 11/09/2016, 09:01 AM, Gerd Hoffmann wrote:
> > On Di, 2016-11-08 at 22:37 +0200, Michael S. Tsirkin wrote:
> >> On Mon, Nov 07, 2016 at 09:43:24AM +0100, Jiri Slaby wrote:
> >>> Hi,
> >>>
> >>> I can relatively easily reproduce this bug:
> >
> > How?
>
> Run dmesg -w in the qemu window (virtio_gpu) to see a lot of output.
fbcon? Or xorg/wayland with terminal app?
> Run pps [1] without exit(0); on e.g. serial console.
> Wait a bit. The lot of output causes the BUG.
>
> [1] https://github.com/jirislaby/collected_sources/blob/master/pps.c
>
> >>> BUG: 'list_empty(&vgdev->free_vbufs)' is true!
> >
> >> The following might be helpful for debugging - if kernel still
will
> >> not stop panicing, we are looking at some kind
> >> of memory corruption.
> >
> > Looking carefully through the code I think it isn't impossible to
> > trigger this, but you need for that:
> >
> > (1) command queue full (quite possible),
> > (2) cursor queue full too (unlikely), and
> > (3) multiple threads trying to submit commands and waiting for free
> > space in the command queue (possible with virgl enabled).
>
> I use -vga virtio with no -display option, so no virtgl, I suppose:
> [drm] virgl 3d acceleration not available
>
> > Do things improve if you allocate some extra bufs?
> >
> > int virtio_gpu_alloc_vbufs(struct virtio_gpu_device *vgdev)
> > {
> > struct virtio_gpu_vbuffer *vbuf;
> > - int i, size, count = 0;
> > + int i, size, count = 16;
>
> This seems to help.
>
> thanks,