[Qemu-devel] [PATCH v2 0/5] vfio-ccw: support hsch/csch (kernel part)

[Cornelia Huck]

[This is the Linux kernel part, git tree is available at
https://git.kernel.org/pub/scm/linux/kernel/git/kvms390/vfio-ccw.git 
vfio-ccw-eagain-caps

The companion QEMU patches are available at
https://github.com/cohuck/qemu vfio-ccw-caps]

Currently, vfio-ccw only relays START SUBCHANNEL requests to the real
device. This tends to work well for the most common 'good path' scenarios;
however, as we emulate {HALT,CLEAR} SUBCHANNEL in QEMU, things like
clearing pending requests at the device is currently not supported.
This may be a problem for e.g. error recovery.

This patch series introduces capabilities (similar to what vfio-pci uses)
and exposes a new async region for handling hsch/csch.

New in v2 are two patches dealing with concurrency.

Lightly tested (I can interact with a dasd as before, and reserve/release
seems to work well.) Not sure if there is a better way to test this, ideas
welcome.

Changes v1->v2:
- New patch 1: make it safe to use the cp accessors at any time; this
  should avoid problems with unsolicited interrupt handling
- New patch 2: handle concurrent accesses to the io region; the idea is
  to return -EAGAIN to userspace more often (so it can simply retry)
- also handle concurrent accesses to the async io region
- change VFIO_REGION_TYPE_CCW
- merge events for halt and clear to a single async event; this turned out
  to make the code quite a bit simpler
- probably some small changes I forgot to note down


Cornelia Huck (5):
  vfio-ccw: make it safe to access channel programs
  vfio-ccw: concurrent I/O handling
  vfio-ccw: add capabilities chain
  s390/cio: export hsch to modules
  vfio-ccw: add handling for async channel instructions

 drivers/s390/cio/Makefile           |   3 +-
 drivers/s390/cio/ioasm.c            |   1 +
 drivers/s390/cio/vfio_ccw_async.c   |  91 ++++++++++++
 drivers/s390/cio/vfio_ccw_cp.c      |   3 +
 drivers/s390/cio/vfio_ccw_cp.h      |   2 +
 drivers/s390/cio/vfio_ccw_drv.c     |  46 ++++--
 drivers/s390/cio/vfio_ccw_fsm.c     | 122 +++++++++++++++-
 drivers/s390/cio/vfio_ccw_ops.c     | 211 +++++++++++++++++++++++-----
 drivers/s390/cio/vfio_ccw_private.h |  45 ++++++
 include/uapi/linux/vfio.h           |   4 +
 include/uapi/linux/vfio_ccw.h       |  12 ++
 11 files changed, 487 insertions(+), 53 deletions(-)
 create mode 100644 drivers/s390/cio/vfio_ccw_async.c

-- 
2.17.2