On 09.04.25 11:56, Alexey Kardashevskiy wrote:
On 7/4/25 17:49, Chenyi Qiang wrote:
RamDiscardManager is an interface used by virtio-mem to adjust VFIO
mappings in relation to VM page assignment. It manages the state of
populated and discard for the RAM. To accommodate future scnarios for
managing RAM states, such as private and shared states in confidential
VMs, the existing RamDiscardManager interface needs to be generalized.
Introduce a parent class, GenericStateManager, to manage a pair of
"GenericState" is the same as "State" really. Call it RamStateManager.
opposite states with RamDiscardManager as its child. The changes include
- Define a new abstract class GenericStateChange.
- Extract six callbacks into GenericStateChangeClass and allow the child
classes to inherit them.
- Modify RamDiscardManager-related helpers to use GenericStateManager
ones.
- Define a generic StatChangeListener to extract fields from
"e" missing in StateChangeListener.
RamDiscardManager listener which allows future listeners to embed it
and avoid duplication.
- Change the users of RamDiscardManager (virtio-mem, migration, etc.) to
switch to use GenericStateChange helpers.
It can provide a more flexible and resuable framework for RAM state
management, facilitating future enhancements and use cases.
I fail to see how new interface helps with this. RamDiscardManager
manipulates populated/discarded. It would make sense may be if the new
class had more bits per page, say private/shared/discarded but it does
not. And PrivateSharedManager cannot coexist with RamDiscard. imho this
is going in a wrong direction.
Agreed.
In the future, we will have virtio-mem co-exist with guest_memfd.
Both are information sources, and likely we'd have some instance on top,
that merges these sources to identify if anybody needs to be notified.
Until we figure out how that would look like, I would suggest to keep it
as is.
Maybe, in the future we would have a single RamDiscardManager and
multiple RamDiscardSources per RAMBlock.
The sources notify the manager, and the manager can ask other sources to
merge the information.
--
Cheers,
David / dhildenb
