On 11.12.23 12:43, David Stevens wrote:
From: David Stevens <stevensd@xxxxxxxxxxxx>
Hi David,
Add a wakeup event for when the balloon is inflating or deflating.
Userspace can enable this wakeup event to prevent the system from
suspending while the balloon is being adjusted. This allows
/sys/power/wakeup_count to be used without breaking virtio_balloon's
cooperative memory management.
Can you add/share some more details
Signed-off-by: David Stevens <stevensd@xxxxxxxxxxxx>
---
drivers/virtio/virtio_balloon.c | 59 +++++++++++++++++++++++++++------
1 file changed, 49 insertions(+), 10 deletions(-)
diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
index 1fe93e93f5bc..811d8937246a 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;
+ u32 adjustment_seqno;
Using a simple flag that gets set when updating the balloon size and
test-and-clear when testing for changes should be easier to get.
bool adjustment_balloon_size_changed;
or sth like that.
+ 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_seqno++;
+ if (!vb->adjustment_in_progress) {
+ vb->adjustment_in_progress = true;
+ pm_stay_awake(&vb->vdev->dev);
+ }
+ 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, u32 seqno)
+{
+ spin_lock(&vb->adjustment_lock);
+ if (vb->adjustment_seqno == seqno && vb->adjustment_in_progress) {
+ vb->adjustment_in_progress = false;
+ pm_relax(&vb->vdev->dev);
+ }
+ spin_unlock(&vb->adjustment_lock);
+}
+
static void virtballoon_changed(struct virtio_device *vdev)
{
struct virtio_balloon *vb = vdev->priv;
@@ -444,8 +474,7 @@ static void virtballoon_changed(struct virtio_device *vdev)
spin_lock_irqsave(&vb->stop_update_lock, flags);
if (!vb->stop_update) {
- queue_work(system_freezable_wq,
- &vb->update_balloon_size_work);
+ start_update_balloon_size(vb);
virtio_balloon_queue_free_page_work(vb);
}
spin_unlock_irqrestore(&vb->stop_update_lock, flags);
@@ -473,22 +502,29 @@ static void update_balloon_size_func(struct work_struct *work)
{
struct virtio_balloon *vb;
s64 diff;
+ u32 seqno;
vb = container_of(work, struct virtio_balloon,
update_balloon_size_work);
- diff = towards_target(vb);
- if (!diff)
- return;
+ spin_lock(&vb->adjustment_lock);
+ seqno = vb->adjustment_seqno;
+ spin_unlock(&vb->adjustment_lock);
- if (diff > 0)
- diff -= fill_balloon(vb, diff);
- else
- diff += leak_balloon(vb, -diff);
- update_balloon_size(vb);
+ diff = towards_target(vb);
+
+ if (diff) {
+ if (diff > 0)
+ diff -= fill_balloon(vb, diff);
+ else
+ diff += leak_balloon(vb, -diff);
+ update_balloon_size(vb);
+ }
if (diff)
queue_work(system_freezable_wq, work);
+ else
+ end_update_balloon_size(vb, seqno);
What if we stop the workqueue and unload the driver -- see
remove_common() -- won't you leave pm_stay_awake() wrongly set?
}
static int init_vqs(struct virtio_balloon *vb)
@@ -992,6 +1028,9 @@ static int virtballoon_probe(struct virtio_device *vdev)
goto out_unregister_oom;
}
+ spin_lock_init(&vb->adjustment_lock);
+ device_set_wakeup_capable(&vb->vdev->dev, true);
I'm a bit confused: Documentation/driver-api/pm/devices.rst documents
"
The :c:member:`power.can_wakeup` flag just records whether the device
(and its driver) can physically support wakeup events. The
:c:func:`device_set_wakeup_capable()` routine affects this flag.
"
...
"
Whether or not a device is capable of issuing wakeup events is a
hardware matter, and the kernel is responsible for keeping track of it.
"
But how is the virtio-balloon device capable of waking up the machine?
Your patch merely implies that the virtio-baloon device is capable to
prohbit going to sleep.
What am I missing?
--
Cheers,
David / dhildenb
