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

[Cornelia Huck]

On Fri, 7 Jun 2019 14:30:48 -0400
Tony Krowiak <akrowiak at linux.ibm.com> wrote:

> 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; 

I agree; that's why I mostly ignored it for now :)

> 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

What do you think about outsourcing that configuration to some
s390-specific tool (probably something in s390-tools)? While we can
(and should) rely on driverctl for vfio-ccw, this does not look like
something that can be easily served by some generic tooling.

> 
> >   
> >>
> >> 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(-)
> >>>      
> >>  
> >   
>