qxl: don't render stuff when the vm is stopped.

This patch fixes the local qxl renderer to not kick spice-server in case
the vm is stopped.  First it is pointless because we render evevything
when the vm is stopped.  Thus there is nothing to render anyway because
a stopped guest can hardly queue more commands.  Second we avoid
triggering an assert in spice-server.

With this patch applied it is possible to take screen shots (via
screendump monitor command) from a qxl gpu even in case the guest
is stopped.

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
---
 hw/qxl-render.c |   12 +++++-------
 1 files changed, 5 insertions(+), 7 deletions(-)

On Wed, Feb 15, 2012 at 02:11:06PM +0100, Gerd Hoffmann wrote:
> This patch fixes the local qxl renderer to not kick spice-server in case
> the vm is stopped.  First it is pointless because we render evevything
*everything
> when the vm is stopped.  Thus there is nothing to render anyway because
> a stopped guest can hardly queue more commands.  Second we avoid
> triggering an assert in spice-server.
> 
> With this patch applied it is possible to take screen shots (via
> screendump monitor command) from a qxl gpu even in case the guest
> is stopped.
> 

Ack, just a minor request for the comment below.

> Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
> ---
>  hw/qxl-render.c |   12 +++++-------
>  1 files changed, 5 insertions(+), 7 deletions(-)
> 
> diff --git a/hw/qxl-render.c b/hw/qxl-render.c
> index 133d093..7084143 100644
> --- a/hw/qxl-render.c
> +++ b/hw/qxl-render.c
> @@ -121,19 +121,17 @@ void qxl_render_update(PCIQXLDevice *qxl)
>          dpy_resize(vga->ds);
>      }
>  
> -    if (!qxl->guest_primary.commands) {
> -        return;
> -    }
> -    qxl->guest_primary.commands = 0;
> -
>      update.left   = 0;
>      update.right  = qxl->guest_primary.surface.width;
>      update.top    = 0;
>      update.bottom = qxl->guest_primary.surface.height;
>  
>      memset(dirty, 0, sizeof(dirty));
> -    qxl_spice_update_area(qxl, 0, &update,
> -                          dirty, ARRAY_SIZE(dirty), 1, QXL_SYNC);
> +    if (runstate_is_running() && qxl->guest_primary.commands) {
> +        qxl->guest_primary.commands = 0;
> +        qxl_spice_update_area(qxl, 0, &update,
> +                              dirty, ARRAY_SIZE(dirty), 1, QXL_SYNC);
> +    }

Can you update the comment to note that you are also changing it so even
when there is no qxl_spice_update_area call you still honor the redraw
request?

>      if (redraw) {
>          memset(dirty, 0, sizeof(dirty));
>          dirty[0] = update;
> -- 
> 1.7.1
> 
>

On 02/15/2012 03:36 PM, Gerd Hoffmann wrote:
> On 02/15/12 14:22, Yonit Halperin wrote:
>> Hi,
>> On 02/15/2012 03:11 PM, Gerd Hoffmann wrote:
>>> This patch fixes the local qxl renderer to not kick spice-server in case
>>> the vm is stopped.  First it is pointless because we render evevything
>>> when the vm is stopped.  Thus there is nothing to render anyway because
>>> a stopped guest can hardly queue more commands.
>> hmm...When the vm is stopped we render only commands that we already
>> read. We don't do more reading from the command ring.
>
> Ah, ok.
>
>> So there may be
>> other pending commands that were not rendered. That is why I
>> suggested allowing rendering when the vm is stopped. But
>> not allowing it during loading the vm during migration.
>
> I'd prefer to keep things simple: let the spice worker run when the
> guest runs, no exceptions.
>
> We may leave some unrendered commands in the ring then.  Ok.  Is that a
> problem for some reason?  Note that the guest may have more commands
> queued which spice-server simply doesn't see yet due to the ring being
> full.  If we stop the guest the wrong moment we can end up with a
> half-done screen update operation no matter what.

Ok. Then ack after correcting the patch comment.

Thanks,
Yonit.
>
> cheers,
>    Gerd
>