6.9-stable review patch. If anyone has any objections, please let me know.
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From: David Stevens stevensd@chromium.org
[ Upstream commit 810d831bbbf3cbd86e5aa91c8485b4d35186144d ]
Wakeup sources don't support nesting multiple events, so sharing a single object between multiple drivers can result in one driver overriding the wakeup event processing period specified by another driver. Have the virtio balloon driver use the wakeup source of the device it is bound to rather than the wakeup source of the parent device, to avoid conflicts with the transport layer.
Note that although the virtio balloon's virtio_device itself isn't what actually wakes up the device, it is responsible for processing wakeup events. In the same way that EPOLLWAKEUP uses a dedicated wakeup_source to prevent suspend when userspace is processing wakeup events, a dedicated wakeup_source is necessary when processing wakeup events in a higher layer in the kernel.
Fixes: b12fbc3f787e ("virtio_balloon: stay awake while adjusting balloon") Signed-off-by: David Stevens stevensd@chromium.org Acked-by: David Hildenbrand david@redhat.com Message-Id: 20240321012445.1593685-2-stevensd@google.com Signed-off-by: Michael S. Tsirkin mst@redhat.com Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/virtio/virtio_balloon.c | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-)
diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c index 1f5b3dd31fcfc..89bc8da80519f 100644 --- a/drivers/virtio/virtio_balloon.c +++ b/drivers/virtio/virtio_balloon.c @@ -450,7 +450,7 @@ static void start_update_balloon_size(struct virtio_balloon *vb) vb->adjustment_signal_pending = true; if (!vb->adjustment_in_progress) { vb->adjustment_in_progress = true; - pm_stay_awake(vb->vdev->dev.parent); + pm_stay_awake(&vb->vdev->dev); } spin_unlock_irqrestore(&vb->adjustment_lock, flags);
@@ -462,7 +462,7 @@ static void end_update_balloon_size(struct virtio_balloon *vb) spin_lock_irq(&vb->adjustment_lock); if (!vb->adjustment_signal_pending && vb->adjustment_in_progress) { vb->adjustment_in_progress = false; - pm_relax(vb->vdev->dev.parent); + pm_relax(&vb->vdev->dev); } spin_unlock_irq(&vb->adjustment_lock); } @@ -1029,6 +1029,15 @@ static int virtballoon_probe(struct virtio_device *vdev)
spin_lock_init(&vb->adjustment_lock);
+ /* + * The virtio balloon itself can't wake up the device, but it is + * responsible for processing wakeup events passed up from the transport + * layer. Wakeup sources don't support nesting/chaining calls, so we use + * our own wakeup source to ensure wakeup events are properly handled + * without trampling on the transport layer's wakeup source. + */ + device_set_wakeup_capable(&vb->vdev->dev, true); + virtio_device_ready(vdev);
if (towards_target(vb))