On Mon, Dec 18, 2023 at 12:33 PM David Hildenbrand <david@xxxxxxxxxx> wrote: > > On 18.12.23 16:18, David Stevens wrote: > > From: David Stevens <stevensd@xxxxxxxxxxxx> > > > > A virtio_balloon's parent device may be configured so that a > > configuration change interrupt is a wakeup event. Extend the processing > > of such a wakeup event until the balloon finishes inflating or deflating > > by calling pm_stay_awake/pm_relax in the virtio_balloon driver. Note > > that these calls are no-ops if the parent device doesn't support wakeup > > events or if the wakeup events are not enabled. > > > > This change allows the guest to use system power states such as s2idle > > without running the risk the virtio_balloon's cooperative memory > > management becoming unresponsive to the host's requests. > > > > Signed-off-by: David Stevens <stevensd@xxxxxxxxxxxx> > > --- > > v1 -> v2: > > - Use adjustment_signal_pending flag instead of a sequence number > > - Call pm_stay_awake/pm_relax on parent device instead of adding a wake > > event to the virtio balloon device > > > > drivers/virtio/virtio_balloon.c | 57 +++++++++++++++++++++++++++------ > > 1 file changed, 47 insertions(+), 10 deletions(-) > > > > diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c > > index 1fe93e93f5bc..a3c11159cbe0 100644 > > --- a/drivers/virtio/virtio_balloon.c > > +++ b/drivers/virtio/virtio_balloon.c > > @@ -119,6 +119,11 @@ struct virtio_balloon { > > /* Free page reporting device */ > > struct virtqueue *reporting_vq; > > struct page_reporting_dev_info pr_dev_info; > > + > > + /* State for keeping the wakeup_source active while adjusting the balloon */ > > + spinlock_t adjustment_lock; > > + bool adjustment_signal_pending; > > + bool adjustment_in_progress; > > }; > > > > static const struct virtio_device_id id_table[] = { > > @@ -437,6 +442,31 @@ static void virtio_balloon_queue_free_page_work(struct virtio_balloon *vb) > > queue_work(vb->balloon_wq, &vb->report_free_page_work); > > } > > > > +static void start_update_balloon_size(struct virtio_balloon *vb) > > +{ > > + unsigned long flags; > > + > > + spin_lock_irqsave(&vb->adjustment_lock, flags); > > + vb->adjustment_signal_pending = true; > > + if (!vb->adjustment_in_progress) { > > + vb->adjustment_in_progress = true; > > + pm_stay_awake(vb->vdev->dev.parent); > > + } > > + spin_unlock_irqrestore(&vb->adjustment_lock, flags); > > + > > + queue_work(system_freezable_wq, &vb->update_balloon_size_work); > > +} > > + > > +static void end_update_balloon_size(struct virtio_balloon *vb) > > +{ > > + spin_lock(&vb->adjustment_lock); > > + if (!vb->adjustment_signal_pending && vb->adjustment_in_progress) { > > How could vb->adjustment_in_progress ever not be set at this point? > > > + vb->adjustment_in_progress = false; > > + pm_relax(vb->vdev->dev.parent); > > + } > > + spin_unlock(&vb->adjustment_lock); > > +} > > + > > LGTM, although I wonder what happens when calling pm_stay_awake() etc. > on a parent device that is not wakeup-even-capable? If the parent device is not wakeup capable or if wakeup isn't enabled, then the vb->vdev->dev.parent->power.wakeup pointer will be NULL, so the NULL checks in __pm_relax/__pm_stay_awake will immediately return. -David