Re: [PATCH v4 0/8] s390x/vfio-ccw: Channel Path Handling [KVM]

[Eric Farman <farman@linux.ibm.com>]

On 5/5/20 8:56 AM, Cornelia Huck wrote:
> On Tue,  5 May 2020 14:27:37 +0200
> Eric Farman <farman@linux.ibm.com> wrote:
> 
>> Here is a new pass at the channel-path handling code for vfio-ccw.
>> Changes from previous versions are recorded in git notes for each patch.
>> Patches 5 through 7 got swizzled a little bit, in order to better
>> compartmentalize the code they define. Basically, the IRQ definitions
>> were moved from patch 7 to 5, and then patch 6 was placed ahead of
>> patch 5.
>>
>> I have put Conny's r-b's on patches 1, 3, 4, (new) 5, and 8, and believe
>> I have addressed all comments from v3, with two exceptions:
>>
>>> I'm wondering if we should make this [vfio_ccw_schib_region_{write,release}]
>>> callback optional (not in this patch).  
>>
>> I have that implemented on top of this series, and will send later as part
>> of a larger cleanup series.
> 
> Good, sounds reasonable.
> 
>>
>>> One thing though that keeps coming up: do we need any kind of
>>> serialization? Can there be any confusion from concurrent reads from
>>> userspace, or are we sure that we always provide consistent data?  
>>
>> I _think_ this is in good shape, though as suggested another set of
>> eyeballs would be nice. There is still a problem on the main
>> interrupt/FSM path, which I'm not attempting to address here.
> 
> I'll try to think about it some more.

Re: interrupt/FSM, I now have two separate patches that each straighten
things out on their own.  And a handful of debug patches that probably
only make things worse.  :)  I'll get one/both of those meaningful
patches sent to the list so we can have that discussion separately from
this code.

> 
>>
>> With this code plus the corresponding QEMU series (posted momentarily)
>> applied I am able to configure off/on a CHPID (for example, by issuing
>> "chchp -c 0/1 xx" on the host), and the guest is able to see both the
>> events and reflect the updated path masks in its structures.
>>
>> v3: https://lore.kernel.org/kvm/20200417023001.65006-1-farman@linux.ibm.com/
>> v2: https://lore.kernel.org/kvm/20200206213825.11444-1-farman@linux.ibm.com/
>> v1: https://lore.kernel.org/kvm/20191115025620.19593-1-farman@linux.ibm.com/
>>
>> Eric Farman (3):
>>   vfio-ccw: Refactor the unregister of the async regions
>>   vfio-ccw: Refactor IRQ handlers
>>   vfio-ccw: Add trace for CRW event
>>
>> Farhan Ali (5):
>>   vfio-ccw: Introduce new helper functions to free/destroy regions
>>   vfio-ccw: Register a chp_event callback for vfio-ccw
>>   vfio-ccw: Introduce a new schib region
>>   vfio-ccw: Introduce a new CRW region
>>   vfio-ccw: Wire up the CRW irq and CRW region
>>
>>  Documentation/s390/vfio-ccw.rst     |  38 ++++++-
>>  drivers/s390/cio/Makefile           |   2 +-
>>  drivers/s390/cio/vfio_ccw_chp.c     | 148 +++++++++++++++++++++++++
>>  drivers/s390/cio/vfio_ccw_drv.c     | 165 ++++++++++++++++++++++++++--
>>  drivers/s390/cio/vfio_ccw_ops.c     |  65 ++++++++---
>>  drivers/s390/cio/vfio_ccw_private.h |  16 +++
>>  drivers/s390/cio/vfio_ccw_trace.c   |   1 +
>>  drivers/s390/cio/vfio_ccw_trace.h   |  30 +++++
>>  include/uapi/linux/vfio.h           |   3 +
>>  include/uapi/linux/vfio_ccw.h       |  18 +++
>>  10 files changed, 458 insertions(+), 28 deletions(-)
>>  create mode 100644 drivers/s390/cio/vfio_ccw_chp.c
>>
>