On Tue, Oct 18, 2011 at 06:49:57PM +0200, Jan Kiszka wrote:
> On 2011-10-18 18:40, Avi Kivity wrote:
> > On 10/18/2011 04:30 PM, Avi Kivity wrote:
> >> This takes a while to reproduce, let me talk to gdb for a bit.
> >>
> >
> > a vcpu exit causes kvm_flush_coalesced_mmio_buffer() to run, which does
> > a bitblt, which is cirrus_do_copy(), which goes to vga_hw_update, which
>
> Why does it have to do vga_hw_update? Why can't it set some flag for the
> next requested screen update or so? Just thinking, haven't looked at the
> code yet.
bottomhalf?
>
> Do you think that only cirrus is affected by this pattern?
>
> > does vga_update_display(), which calls
> > qemu_flush_coalesced_mmio_buffer(), which is not reentrant.
> >
> > It's easy to make qemu_flush_coalesced_mmio_buffer reentrant:
> >
> > if (s->coalesced_flush_in_progress) {
> > return;
> > }
> >
> > it isn't very pretty and is also a lie. Other ideas?
> >
> > I'll probably commit this soon to avoid the regression, to be replaced
> > by a better fix when we find it.
> >
>
> Agreed. Unless we can avoid that recursion at devices level, there is
> likely no alternative.
>
> Jan
>
> --
> Siemens AG, Corporate Technology, CT T DE IT 1
> Corporate Competence Center Embedded Linux
>
