Patch "virtio_balloon: Give the balloon its own wakeup source" has been added to the 6.9-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    virtio_balloon: Give the balloon its own wakeup source

to the 6.9-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     virtio_balloon-give-the-balloon-its-own-wakeup-sourc.patch
and it can be found in the queue-6.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 30859bfc8a841eac49882a8fdec2c45d139f02c4
Author: David Stevens <stevensd@xxxxxxxxxxxx>
Date:   Thu Mar 21 10:24:44 2024 +0900

    virtio_balloon: Give the balloon its own wakeup source
    
    [ 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@xxxxxxxxxxxx>
    Acked-by: David Hildenbrand <david@xxxxxxxxxx>
    Message-Id: <20240321012445.1593685-2-stevensd@xxxxxxxxxx>
    Signed-off-by: Michael S. Tsirkin <mst@xxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

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))