Re: [RFC PATCH v2 0/9] s390x/vfio-ccw: Channel Path Handling

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

On 2/7/20 4:12 AM, Cornelia Huck wrote:
> On Thu,  6 Feb 2020 22:38:16 +0100
> Eric Farman <farman@linux.ibm.com> wrote:
> 
>> Here is a new pass at the channel-path handling code for vfio-ccw.
>> This was initially developed by Farhan Ali this past summer, and
>> picked up by me.  For my own benefit/sanity, I made a small changelog
>> in the commit message for each patch, describing the changes I've
>> made to his original code beyond just rebasing to master, rather than
>> a giant list appended here.
>>
>> I had been encountering a host crash which I think was triggered by
>> this code rather than existing within it.  I'd sent a potential fix
>> for that separately, but need more diagnosis.  So while that is
>> outstanding, I think I've gotten most (but probably not all) comments
>> from v1 addressed within.
>>
>> With this, and the corresponding QEMU series (to be 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.
>>
>> For reasons that are hopefully obvious, issuing chchp within the guest
>> only works for the logical vary.  Configuring it off/on does not work,
>> which I think is fine.
> 
> Before I delve into this: While the basic architecture here (and in the
> QEMU part) is still similar, you changed things like handling multiple
> CRWs? That's at least the impression I got from a very high-level skim.

I hope so.  :)

I'm not chaining any CRWs together using the CRW.C flag, since that will
expose other more interesting problems if we go beyond two.  It should
help handle the "guest processes one while another is added" scenario,
even though I've got some racing during the management of the list itself.

> 
>>
>> v1: https://lore.kernel.org/kvm/20191115025620.19593-1-farman@linux.ibm.com/
>>
>> Eric Farman (4):
>>   vfio-ccw: Refactor the unregister of the async regions
>>   vfio-ccw: Refactor IRQ handlers
>>   vfio-ccw: Add trace for CRW event
>>   vfio-ccw: Remove inline get_schid() routine
>>
>> 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     |  31 ++++-
>>  drivers/s390/cio/Makefile           |   2 +-
>>  drivers/s390/cio/vfio_ccw_chp.c     | 136 ++++++++++++++++++++
>>  drivers/s390/cio/vfio_ccw_drv.c     | 186 ++++++++++++++++++++++++++--
>>  drivers/s390/cio/vfio_ccw_fsm.c     |   8 +-
>>  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       |  19 +++
>>  11 files changed, 463 insertions(+), 34 deletions(-)
>>  create mode 100644 drivers/s390/cio/vfio_ccw_chp.c
>>
>