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

From: Pierre Morel
Date: Thu Aug 23 2018 - 06:41:25 EST


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