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

Farhan Ali
2018-11-26T18:57:06Z

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
>