Re: [Qemu-devel] [PATCH v2 23/25] console: make screendump async

[Marc-André Lureau]

Hi

On Mon, Jan 23, 2017 at 4:04 PM Gerd Hoffmann <address@hidden> wrote:

>   Hi,
> >
> > If you only ref, you could have the image being modified while it is
> > being saved asynchronously, this could result in tearing artefacts,
> > no?
>
> Yes, but you have that problem _anyway_.  screendump qmp command can run
> in parallel to guest vcpu, so it can race with guest display updates
> today.  Assuming they happen as simple framebuffer writes and therefore
> don't involve vmexit + grabbing big qemu lock.
>

Agreed, fwiw, I implemented a coroutine-based ppm_save in the qapi-async
branch:
https://github.com/elmarco/qemu/commit/6f45a28ce737eab1d0ce4639f7b015a51a43674c

btw, is it supported to reenter the main_loop in hmp_screendump_sync()
(Paolo)?

(the alternative is probably to block hmp until the async command is
finished. This would eventually be interesting if more qmp commands used
from hmp are converted to be async)
-- 
Marc-André Lureau