Re: [Qemu-devel] [PATCH 2/2] qxl: add QXL_IO_UPDATE_MEM for guest S3&S4 support

[Alon Levy <alevy@redhat.com>]

On Mon, Jun 27, 2011 at 09:28:45AM +0300, yhalperi wrote:
> On 06/26/2011 08:47 PM, Alon Levy wrote:
> >On Sun, Jun 26, 2011 at 12:59:06PM -0400, Yonit Halperin wrote:
> >>Sorry for the late response, wasn't available.
> >>I'm afraid  that (1) and (2) will indeed wakeup the worker, but will not assure emptying the command ring, as it depends on the client pipe size.
> >>
> >
> >I actually can't figure out what wakeup does (that's what both NOTIFY and
> >NOTIFY_CURSOR do, see hw/qxl.c).
> It turns on an event the worker is waiting for on epoll_wait.
Ah, ok. So it will only read up to the pipe size like you said.

> 
> What we did in prepare_to_sleep before was
> >call flush_all_qxl_commands, which reads the command and cursor rings until
> >they are empty (calling flush_cursor_commands and flush_display_commands), waiting
> >whenever the pipe is too large. (avoiding this wait still needs to be done, but
> >after ensuring suspend is correct).
> >
> >More to the point this flush is done from handle_dev_destroy_surfaces, but
> >this is not good enough since this also destroys the surfaces, before we have
> >a chance to actually render the surfaces.
> >
> >Perhaps RED_WORKER_MESSAGE_STOP should do a flush_all_qxl_commands?
> >
> We can do it as long as it doesn't affect migration - does STOP
> happens before or after savevm? If it happens after - we can't touch
> the command ring, i.e., we can't call flush. And even if it happens
> before - do we really want to call flush during migration and
> presumably slow it down?
But if we don't then the client connected before migration doesn't get some of
the messages it was supposed to get.

stop is called before hw/qxl.c:qxl_pre_save, from
ui/spice-display.c:qemu_spice_vm_change_state_handler


> 
> Cheers,
> Yonit.
> 
> >>
> >>----- Original Message -----
> >>From: "Alon Levy"<alevy@redhat.com>
> >>To: "Gerd Hoffmann"<kraxel@redhat.com>
> >>Cc: qemu-devel@nongnu.org, yhalperi@redhat.com
> >>Sent: Wednesday, June 22, 2011 11:57:54 AM
> >>Subject: Re: [Qemu-devel] [PATCH 2/2] qxl: add QXL_IO_UPDATE_MEM for guest S3&S4 support
> >>
> >>On Wed, Jun 22, 2011 at 11:13:19AM +0200, Gerd Hoffmann wrote:
> >>>   Hi,
> >>>
> >>>>>worker call.  We can add a I/O command to ask qxl to push the
> >>>>>release queue head to the release ring.
> >>>>
> >>>>So you suggest to replace QXL_IO_UPDATE_MEM with what, two io commands instead
> >>>>of using the val parameter?
> >>>
> >>>I'd like to (a) avoid updating the libspice-server API if possible
> >>>and (b) have one I/O command for each logical step.  So going into
> >>>S3 could look like this:
> >>>
> >>>   (0) stop putting new commands into the rings
> >>>   (1) QXL_IO_NOTIFY_CMD
> >>>   (2) QXL_IO_NOTIFY_CURSOR
> >>>       qxl calls notify(), to make the worker thread empty the command
> >>>       rings before it processes the next dispatcher request.
> >>>   (3) QXl_IO_FLUSH_SURFACES (to be implemented)
> >>>       qxl calls stop()+start(), spice-server renders all surfaces,
> >>>       thereby flushing state to device memory.
> >>>   (4) QXL_IO_DESTROY_ALL_SURFACES
> >>>       zap surfaces
> >>>   (5) QXL_IO_FLUSH_RELEASE (to be implemented)
> >>>       push release queue head into the release ring, so the guest
> >>>       will see it and can release everything.
> >>>
> >>>(1)+(2)+(4) exist already.
> >>>(3)+(5) can be done without libspice-server changes.
> >>>
> >>>Looks workable?
> >>
> >>yeah. Yonit?
> >>
> >>>
> >>>cheers,
> >>>   Gerd
> >>>
> >>>
> >>
> 
>