Re: [RFC PATCH v2 4/9] vfio-ccw: Introduce a new schib region

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

On 2/14/20 7:32 AM, Cornelia Huck wrote:
> On Thu,  6 Feb 2020 22:38:20 +0100
> Eric Farman <farman@linux.ibm.com> wrote:
> 
>> From: Farhan Ali <alifm@linux.ibm.com>
>>
>> The schib region can be used by userspace to get the subchannel-
>> information block (SCHIB) for the passthrough subchannel.
>> This can be useful to get information such as channel path
>> information via the SCHIB.PMCW fields.
>>
>> Signed-off-by: Farhan Ali <alifm@linux.ibm.com>
>> Signed-off-by: Eric Farman <farman@linux.ibm.com>
>> ---
>>
>> Notes:
>>     v1->v2:
>>      - Add new region info to Documentation/s390/vfio-ccw.rst [CH]
>>      - Add a block comment to struct ccw_schib_region [CH]
>>     
>>     v0->v1: [EF]
>>      - Clean up checkpatch (#include, whitespace) errors
>>      - Remove unnecessary includes from vfio_ccw_chp.c
>>      - Add ret=-ENOMEM in error path for new region
>>      - Add call to vfio_ccw_unregister_dev_regions() during error exit
>>        path of vfio_ccw_mdev_open()
>>      - New info on the module prologue
>>      - Reorder cleanup of regions
>>
>>  Documentation/s390/vfio-ccw.rst     | 16 +++++-
>>  drivers/s390/cio/Makefile           |  2 +-
>>  drivers/s390/cio/vfio_ccw_chp.c     | 75 +++++++++++++++++++++++++++++
>>  drivers/s390/cio/vfio_ccw_drv.c     | 20 ++++++++
>>  drivers/s390/cio/vfio_ccw_ops.c     | 14 +++++-
>>  drivers/s390/cio/vfio_ccw_private.h |  3 ++
>>  include/uapi/linux/vfio.h           |  1 +
>>  include/uapi/linux/vfio_ccw.h       | 10 ++++
>>  8 files changed, 137 insertions(+), 4 deletions(-)
>>  create mode 100644 drivers/s390/cio/vfio_ccw_chp.c
>>
>> diff --git a/Documentation/s390/vfio-ccw.rst b/Documentation/s390/vfio-ccw.rst
>> index fca9c4f5bd9c..b805dc995fc8 100644
>> --- a/Documentation/s390/vfio-ccw.rst
>> +++ b/Documentation/s390/vfio-ccw.rst
>> @@ -231,6 +231,19 @@ This region is exposed via region type VFIO_REGION_SUBTYPE_CCW_ASYNC_CMD.
>>  
>>  Currently, CLEAR SUBCHANNEL and HALT SUBCHANNEL use this region.
>>  
>> +vfio-ccw schib region
>> +---------------------
>> +
>> +The vfio-ccw schib region is used to return Subchannel-Information
>> +Block (SCHIB) data to userspace::
>> +
>> +  struct ccw_schib_region {
>> +  #define SCHIB_AREA_SIZE 52
>> +         __u8 schib_area[SCHIB_AREA_SIZE];
>> +  } __packed;
>> +
>> +This region is exposed via region type VFIO_REGION_SUBTYPE_CCW_SCHIB.
> 
> Also mention that reading this triggers a stsch() updating the schib?

Yeah, I tucked that in the uapi header, but it should be mentioned here too.

> 
>> +
>>  vfio-ccw operation details
>>  --------------------------
>>  
> 
> (...)
> 
>> diff --git a/drivers/s390/cio/vfio_ccw_chp.c b/drivers/s390/cio/vfio_ccw_chp.c
>> new file mode 100644
>> index 000000000000..826d08379fe3
>> --- /dev/null
>> +++ b/drivers/s390/cio/vfio_ccw_chp.c
>> @@ -0,0 +1,75 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +/*
>> + * Channel path related status regions for vfio_ccw
>> + *
>> + * Copyright IBM Corp. 2019
> 
> Should the year be updated?

Probably.  :)

> 
>> + *
>> + * Author(s): Farhan Ali <alifm@linux.ibm.com>
>> + */
> 
> (...)
>