On Mon, Dec 18, 2023 at 6:37 AM David Hildenbrand <david@xxxxxxxxxx> wrote: > > On 14.12.23 05:13, David Stevens wrote: > > On Wed, Dec 13, 2023 at 5:44 PM David Hildenbrand <david@xxxxxxxxxx> wrote: > >> > >> 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 > > > > I'm working on enabling support for Linux s2Idle in our Android > > virtual machine, to restrict apps from running in the background > > without holding an Android partial wakelock. With the patch I recently > > sent out [1], since crosvm advertises native PCI power management for > > virtio devices, the Android guest can properly enter s2idle, and it > > can be woken up by incoming IO. However, one of the remaining problems > > is that when the host needs to reclaim memory from the guest via the > > virtio-balloon, there is nothing preventing the guest from entering > > s2idle before the balloon driver finishes returning memory to the > > host. > > Thanks for the information. So you also want to wakeup the VM when > wanting to get more memory from the VM? > > Using which mechanism would that wakeup happen? Likely not the device > itself? The wakeup would happen via the parent device's interrupt. I've sent a new version of this patch that uses the parent device's wakeup event instead of adding a new one. > > > > One alternative to this approach would be to add a virtballoon_suspend > > callback to abort suspend if the balloon is inflating/adjusting. > > However, it seems cleaner to just prevent suspend in the first place. > > Also, the PM notifier could also be used with very high priority, so the > device would respond early to PM_SUSPEND_PREPARE. One drawback of blocking suspend via a PM notifier is that the behavior isn't configurable by userspace, whereas wakeup events can be enabled/disabled by userspace. -David
