[libvirt] [PATCH RFC 0/1] mdevctl: further config for vfio-ap

[Tony Krowiak]

On 6/7/19 10:56 AM, Cornelia Huck wrote:
> On Thu, 6 Jun 2019 12:45:29 -0400
> Matthew Rosato <mjrosato at linux.ibm.com> wrote:
> 
>> On 6/6/19 10:44 AM, Cornelia Huck wrote:
>>> This patch adds a very rough implementation of additional config data
>>> for mdev devices. The idea is to make it possible to specify some
>>> type-specific key=value pairs in the config file for an mdev device.
>>> If a device is started automatically, the device is stopped and restarted
>>> after applying the config.
>>>
>>> The code has still some problems, like not doing a lot of error handling
>>> and being ugly in general; but most importantly, I can't really test it,
>>> as I don't have the needed hardware. Feedback welcome; would be good to
>>> know if the direction is sensible in general.
>>
>> Hi Connie,
>>
>> This is very similar to what I was looking to do in zdev (config via
>> key=value pairs), so I like your general approach.
>>
>> I pulled your code and took it for a spin on an LPAR with access to
>> crypto cards:
>>
>> # mdevctl create-mdev `uuidgen` matrix vfio_ap-passthrough
>> # mdevctl set-additional-config <uuid> ap_adapters=0x4,0x5
>> # mdevctl set-additional-config <uuid> ap_domains=0x36
>> # mdevctl set-additional-config <uuid> ap_control_domains=0x37
>>
>> Assuming all valid inputs, this successfully creates the appropriate
>> mdev and what looks to be a valid mdevctl.d entry.  A subsequent reboot
>> successfully brings the same vfio_ap-passthrough device up again.
> 
> Cool, thanks for checking!

I also confirmed this. I realize this is a very early proof of concept,
if you will, but error handling could be an interesting endeavor in
the case of vfio_ap given the layers of configuration involved; for
example:

* The necessity for the vfio_ap module to be installed
* The necessity that the /sys/bus/ap/apmask and /sys/bus/ap/aqmask must
   be appropriately configured

> 
>>
>> Matt
>>
>>>
>>> Also available at
>>>
>>> https://github.com/cohuck/mdevctl conf-data
>>>
>>> Cornelia Huck (1):
>>>    allow to specify additional config data
>>>
>>>   mdevctl.libexec | 25 ++++++++++++++++++++++
>>>   mdevctl.sbin    | 56 ++++++++++++++++++++++++++++++++++++++++++++++++-
>>>   2 files changed, 80 insertions(+), 1 deletion(-)
>>>    
>>
>