Re: [PATCH v9 12/22] s390: vfio-ap: sysfs interfaces to configure control domains

[Pierre Morel]

On 23/08/2018 11:26, Halil Pasic wrote:
> On 08/22/2018 09:16 PM, Tony Krowiak wrote:
> > On 08/22/2018 01:11 PM, Halil Pasic wrote:
> > > On 08/22/2018 05:48 PM, Christian Borntraeger wrote:
> > > > On 08/22/2018 05:34 PM, Pierre Morel wrote:
> > > > > On 22/08/2018 17:11, Christian Borntraeger wrote:
> > > > > > On 08/22/2018 01:03 PM, Pierre Morel wrote:
> > > > > > > > That's interesting.
...
> > > > So you have changed the code to not automatically make a usage domain a
> > > > control domain in the bitfield (and you could still use it as a usage
> > > > domain). Correct?

Yes.

> > > I tested basically the same yesterday, with the same results.
> > >
> > > > I think this is probably expected. the "usage implies control" seems to
> > > > be a convention implemented by HMC (lpar) and z/VM but millicode offers
> > > > the bits to have usage-only domains. As LPAR and z/VM will always 
> > > > enable
> > > > any usage-domain to also be a control domain we should do the same.

I think it is the reasonable thing to do.

> > > I'm fine either way, but slightly prefer higher level management 
> > > software
> > > and not the kernel accommodating this convention.

Please, we do not need this in a first version just make it easy
stick with what HMC does.

> > > with read access to, let's say a regular file. For me, all options 
> > > (rw, r, and w)
> > > do make sense, and if I had to pick the one that makes the least 
> > > sense I would
> > > pick write only. The convention is in these terms making read-only 
> > > illegal. But
> > > should 'usage only domains' ever get identified as something somebody 
> > > wants to do
> > > we can just add an attribute for that. So I'm fine either way.

We do not need to introduce new features now.

regards,
Pierre


--
Pierre Morel
Linux/KVM/QEMU in BÃblingen - Germany