On 2011-10-19 11:04, Avi Kivity wrote: > > On 10/18/2011 09:50 PM, Jan Kiszka wrote: >> On 2011-10-18 19:34, Avi Kivity wrote: >>> On 10/18/2011 06:49 PM, 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. >>> >>> Maybe it's a remnant from the days where it asked the host hardware to >>> do the blt. > >> If it's no longer needed - drop it? Already for other reasons like >> efficiency. > > I think it actually is needed - it calls qemu_console_copy() to do the > copy. Which incidentally means the the coalesced flush, had it worked, > would be a bug: it would bring pending mmio writes in front of a > currently executing bitblt. I don't think we can regard my hack as a > fix for that. Maybe we need to revert the original patch. Or make sure > the flush only happens from the display thread.
I hope we can avoid the old scheme as it hurts when trying to make progress /wrt scalability. Will have a look if we can avoid the recursion in some reasonable way at device level here. Jan -- Siemens AG, Corporate Technology, CT T DE IT 1 Corporate Competence Center Embedded Linux
