[Qemu-devel] [RFC 00/13] dataplane: use block layer

[Stefan Hajnoczi <stefanha@redhat.com>]

This series adds image format, QMP 'transation', and QMP 'block_resize' support
to dataplane.  This is done by replacing custom Linux AIO code with QEMU block
layer APIs.

In order for block layer APIs to be safe, bdrv_drain_all() is modified to be
aware of device emulation threads (like dataplane).
BlockDevOps->drain_threads_cb() is introduced as a way to stop device emulation
threads temporarily.  Device emulation threads may resume after this main loop
iteration completes, which is enough to allow code running under the QEMU
global mutex a chance to use the block device temporarily.

bdrv_get_aio_context() is dropped in favor of a thread-local AioContext
pointer.  This allows qemu_bh_new(), qemu_aio_wait(), and friends to
automatically use the right AioContext.  When we introduce a BlockDriverState
lock in the future, it will be possible to use block devices from multiple
threads arbitrarily (right now we only allow it if bdrv_drain_all() is used).

Three open issues:

 * Timers only work in the main loop, so I/O throttling is ignored and QED is
   unsafe with x-data-plane=on.

 * Need to test with NBD, Gluster, and other non-file protocols.

 * Need to compare performance against custom Linux AIO code.

Paolo Bonzini (2):
  exec: do not use qemu/tls.h
  qemu-thread: add TLS wrappers

Stefan Hajnoczi (11):
  block: fix bdrv_flush() ordering in bdrv_close()
  dataplane: sync virtio.c and vring.c virtqueue state
  block: add BlockDevOps->drain_threads_cb()
  virtio-blk: implement BlockDevOps->drain_threads_cb()
  block: add thread_aio_context TLS variable
  block: drop bdrv_get_aio_context()
  main-loop: use thread-local AioContext
  block: disable I/O throttling outside main loop
  dataplane: use block layer for I/O
  dataplane: drop ioq Linux AIO request queue
  block: drop raw_get_aio_fd()

 async.c                             |   2 +
 block.c                             |  22 ++-
 block/raw-posix.c                   |  38 +----
 block/raw-win32.c                   |   2 +-
 configure                           |  21 +++
 cpus.c                              |   2 +
 exec.c                              |  10 +-
 hw/block/dataplane/Makefile.objs    |   2 +-
 hw/block/dataplane/ioq.c            | 117 ---------------
 hw/block/dataplane/ioq.h            |  57 -------
 hw/block/dataplane/virtio-blk.c     | 290 ++++++++++++------------------------
 hw/block/virtio-blk.c               |  12 ++
 hw/virtio/dataplane/vring.c         |   8 +-
 include/block/aio.h                 |   4 +
 include/block/block.h               |  17 ++-
 include/block/block_int.h           |   7 -
 include/exec/cpu-all.h              |  14 +-
 include/hw/virtio/dataplane/vring.h |   2 +-
 include/qemu/tls.h                  | 125 +++++++++++++---
 main-loop.c                         |  15 +-
 tests/Makefile                      |   3 +
 tests/test-tls.c                    |  87 +++++++++++
 util/qemu-thread-win32.c            |  17 +++
 23 files changed, 408 insertions(+), 466 deletions(-)
 delete mode 100644 hw/block/dataplane/ioq.c
 delete mode 100644 hw/block/dataplane/ioq.h
 create mode 100644 tests/test-tls.c

-- 
1.8.1.4