Il 29/07/2013 10:58, Kevin Wolf ha scritto: > Am 26.07.2013 um 10:43 hat Stefan Hajnoczi geschrieben: >> On Thu, Jul 25, 2013 at 07:53:33PM +0100, Alex Bligh wrote: >>> >>> >>> --On 25 July 2013 14:32:59 +0200 Jan Kiszka <jan.kis...@siemens.com> wrote: >>> >>>>> I would happily at a QEMUClock of each type to AioContext. They are after >>>>> all pretty lightweight. >>>> >>>> What's the point of adding tones of QEMUClock instances? Considering >>>> proper abstraction, how are they different for each AioContext? Will >>>> they run against different clock sources, start/stop at different times? >>>> If the answer is "they have different timer list", then fix this >>>> incorrect abstraction. >>> >>> Even if I fix the abstraction, there is a question of whether it is >>> necessary to have more than one timer list per AioContext, because >>> the timer list is fundamentally per clock-source. I am currently >>> just using QEMU_CLOCK_REALTIME as that's what the block drivers normally >>> want. Will block drivers ever want timers from a different clock source? >> >> block.c and block/qed.c use vm_clock because block drivers should not do >> guest I/O while the vm is stopped. This is especially true during live >> migration where it's important to hand off the image file from the >> source host to the destination host with good cache consistency. The >> source host is not allowed to modify the image file anymore once the >> destination host has resumed the guest. >> >> Block jobs use rt_clock because they aren't considered guest I/O. > > But considering your first paragraph, why is it safe to let block jobs > running while we're migrating? Do we really do that? It sounds unsafe to > me.
I think we should cancel them (synchronously) before the final bdrv_drain_all(). Paolo
