Re: [qemu-s390x] [PATCH v3 0/6] vfio-ccw: support hsch/csch (kernel part)

[Eric Farman]

On 02/06/2019 09:00 AM, Cornelia Huck wrote:
> On Wed, 30 Jan 2019 14:22:06 +0100
> Cornelia Huck <address@hidden> 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
>
> I've pushed out the changes I've made so far (patch 1) to
> vfio-ccw-eagain-caps-v3.5. I'll wait a bit for more comments before
> sending a new version.

Thanks for that branch...  For patch 1 in v3.5:

Reviewed-by: Eric Farman <address@hidden>

> > The companion QEMU patches are available at
> > https://github.com/cohuck/qemu vfio-ccw-caps
> > This is the previously posted v2 version, which should continue to work.]
>
> I would not mind if somebody looked at those as well :)

Not precluding anyone else from doing so :) ... I'd planned on looking 
at them as I get into the meat of patches 4-6 on the kernel side, where 
the overlap occurs.  I'm getting close.  :)

FWIW, I've been running with both series for the last week or two, along 
with some host kernel traces to prove things got executed the way I 
thought, and it's seemed to be working well.  So that makes me 
optimistic for the later patches.

 - Eric

> > 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 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      |  20 ++-
> >   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     | 210 +++++++++++++++++++++++-----
> >   drivers/s390/cio/vfio_ccw_private.h |  48 ++++++-
> >   include/uapi/linux/vfio.h           |   4 +
> >   include/uapi/linux/vfio_ccw.h       |  12 ++
> >   11 files changed, 531 insertions(+), 57 deletions(-)
> >   create mode 100644 drivers/s390/cio/vfio_ccw_async.c