Re: [Qemu-devel] [PATCH v4 0/6] vfio-ccw: support hsch/csch (kernel part)

[Cornelia Huck <cohuck@redhat.com>]

On Fri,  1 Mar 2019 10:38:56 +0100
Cornelia Huck <cohuck@redhat.com> 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-eagain-caps-v3
> 
> 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.
> 
> 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 v3->v4:
> - shrunk the capability offset, we don't need to accommodate as much as pci
> - make checks in patch 1 more consistent and less buggy
> - rebased on top of my current vfio-ccw branch
> 
> Changes v2->v3:
> - Unb0rked patch 1, improved scope
> - Split out the new mutex from patch 2 into new patch 3; added missing
>   locking and hopefully improved description
> - Patch 2 now reworks the state handling by splitting the BUSY state
>   into CP_PROCESSING and CP_PENDING
> - Patches 3 and 5 adapted on top of the reworked patches; hsch/csch
>   are allowed in CP_PENDING, but not in CP_PROCESSING (did not add
>   any R-b due to that)
> - Added missing free in patch 5
> - Probably some small changes I forgot to note down
> 
> 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 (6):
>   vfio-ccw: make it safe to access channel programs
>   vfio-ccw: rework ssch state handling
>   vfio-ccw: protect the I/O region
>   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   |  88 ++++++++++++
>  drivers/s390/cio/vfio_ccw_cp.c      |  21 ++-
>  drivers/s390/cio/vfio_ccw_cp.h      |   2 +
>  drivers/s390/cio/vfio_ccw_drv.c     |  57 ++++++--
>  drivers/s390/cio/vfio_ccw_fsm.c     | 143 +++++++++++++++++-
>  drivers/s390/cio/vfio_ccw_ops.c     | 215 +++++++++++++++++++++++-----
>  drivers/s390/cio/vfio_ccw_private.h |  48 ++++++-
>  include/uapi/linux/vfio.h           |   4 +
>  include/uapi/linux/vfio_ccw.h       |  12 ++
>  11 files changed, 537 insertions(+), 57 deletions(-)
>  create mode 100644 drivers/s390/cio/vfio_ccw_async.c
> 

Queued (with the touchups discussed in the thread) to the vfio-ccw
branch on kernel.org.