Material for next QEMU release

Coroutines in the block layer [Kevin]

Programming model to simplify block drivers without blocking QEMU threads

Generic copy-on-read [Stefan]

Populate image file to avoid fetching same block from backing file again later

Generic image streaming [Stefan]

Make block_stream commands available for all image formats that support backing files

Live block copy

Copy the contents of an image file while a guest is using it
Mostly a libvirt feature based on QEMU's blockdev-snapshot-sync and block_stream

In-place qcow2 <-> qed conversion [Devin, GSoC 2011]:

Fast conversion between qcow2 and qed image formats without copy all data
Patches currently being reviewed and merged

VMDK enhancements [Fam, GSoC 2011]

Implement latest VMDK specs to support modern image files
Patches currently being reviewed and merged

Block I/O limits [Zhi Yong]

Resource control for guest I/O bandwidth/iops consumption

Runtime WCE toggling [?]

wce=none|on|off and run-time guest toggling support
Prerequisite to switching away from cache=writethrough by default

Future changes

Cow overlay [Dong Xu "Robert"]

Allow live block copy and image streaming to raw destination files

snapshot_blkdev and Backup API [Jes, Jagane]

Support for consistent disk snapshots and dirty block tracking
Allow backup software to integrate with QEMU

-blockdev [Markus?]

Explicit user control over block device trees
Perhaps base this on QEMU Object Model right away

QCOW3

Extend qcow2 format to address current and future image format challenges
- Feature bits for fine-grained file format extensions
- Sub-clusters to reduce metadata size and fragmentation
- Zero clusters for efficient sparse images and copy-on-read
- luks-like key scheme that allows changing passphrase without re-encrypting data

iSCSI/NBD/Remote block device integration

Enable remote access to disk images for live migration and other tasks
Still unclear what will be done in this area

Pre/post block copy based on image streaming

Working block migration that works with a separate migration thread

Avoid blocking QEMU threads

Today loss of NFS connectivity can hang guests
It's critical never to block the vcpu thread
The iothread should also not block while the qemu mutex is held
All blocking operations must be done asynchronously or in a worker thread

virtio-scsi [Paolo/Stefan]

The next step after virtio-blk, full SCSI command set and appears as SCSI HBA in guest
Real /dev/sda devices in guest
No more modifying guest drivers to add simple storage protocol features

tcm_vhost [Stefan]

Directly connect virtio-scsi with Linux in-kernel SCSI target
Pass-through of host SCSI devices

qcow2 online resize [Zhi Yong]

Handle snapshots
Support shrinking

qed online resize [Zhi Yong]

Support shrinking

Future changes

Cow overlay [Dong Xu "Robert"]

* Allow live block copy and image streaming to raw destination files

snapshot_blkdev and Backup API [Jes, Jagane]

* Support for consistent disk snapshots and dirty block tracking
* Allow backup software to integrate with QEMU

-blockdev [Markus?]

* Explicit user control over block device trees
* Perhaps base this on QEMU Object Model right away

QCOW3

* Extend qcow2 format to address current and future image format challenges
 * Feature bits for fine-grained file format extensions
 * Sub-clusters to reduce metadata size and fragmentation
 * Zero clusters for efficient sparse images and copy-on-read
 * luks-like key scheme that allows changing passphrase without re-encrypting data

iSCSI/NBD/Remote block device integration

* Enable remote access to disk images for live migration and other tasks
* Still unclear what will be done in this area

Pre/post block copy based on image streaming

* Working block migration that works with a separate migration thread

Avoid blocking QEMU threads

* Today loss of NFS connectivity can hang guests
* It's critical never to block the vcpu thread
* The iothread should also not block while the qemu mutex is held
* All blocking operations must be done asynchronously or in a worker thread

virtio-scsi [Paolo/Stefan]

* The next step after virtio-blk, full SCSI command set and appears as SCSI HBA in guest
* Real /dev/sda devices in guest
* No more modifying guest drivers to add simple storage protocol features

tcm_vhost [Stefan]

* Directly connect virtio-scsi with Linux in-kernel SCSI target
* Pass-through of host SCSI devices

qcow2 online resize

* Handle snapshots
* Support shrinking

qed online resize

* Support shrinking