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Re: [qemu-s390x] [PATCH 0/3] vfio-ccw: support hsch/csch (kernel part)

From: Farhan Ali
Subject: Re: [qemu-s390x] [PATCH 0/3] vfio-ccw: support hsch/csch (kernel part)
Date: Mon, 26 Nov 2018 13:57:06 -0500
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.4.0

On 11/22/2018 11:54 AM, Cornelia Huck wrote:
[This is the Linux kernel part, git tree is available at

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.

Very lightly tested (I can interact with a dasd as before; I have not
found a reliable way to trigger hsch/csch in the Linux dasd guest driver.)

I was able to trigger the guest DASD driver to issue a csch instruction, and from my brief testing it seems to be working just like it would on the LPAR. (I basically tested with 2 threads trying to issue DASD device reserve and release ioctls, on the same DASD device, in a busy loop).

I am going to spend some time doing a deeper review.


Cornelia Huck (3):
   vfio-ccw: add capabilities chain
   s390/cio: export hsch to modules
   vfio-ccw: add handling for asnyc channel instructions

  drivers/s390/cio/Makefile           |   3 +-
  drivers/s390/cio/ioasm.c            |   1 +
  drivers/s390/cio/vfio_ccw_async.c   |  88 +++++++++++++
  drivers/s390/cio/vfio_ccw_drv.c     |  48 +++++--
  drivers/s390/cio/vfio_ccw_fsm.c     | 158 +++++++++++++++++++++-
  drivers/s390/cio/vfio_ccw_ops.c     | 195 ++++++++++++++++++++++++----
  drivers/s390/cio/vfio_ccw_private.h |  44 +++++++
  include/uapi/linux/vfio.h           |   5 +
  include/uapi/linux/vfio_ccw.h       |  12 ++
  9 files changed, 509 insertions(+), 45 deletions(-)
  create mode 100644 drivers/s390/cio/vfio_ccw_async.c

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