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

[Farhan Ali]

On 11/22/2018 11:54 AM, Cornelia Huck wrote:
> [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-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.
>
> 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.

Thanks
Farhan


> 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