On 09/07/2018 17:50, Halil Pasic wrote:
On 07/09/2018 05:21 AM, Pierre Morel wrote:
On 03/07/2018 01:10, Halil Pasic wrote:
On 06/29/2018 11:11 PM, Tony Krowiak wrote:
This patch provides documentation describing the AP architecture and
design concepts behind the virtualization of AP devices. It also
includes an example of how to configure AP devices for exclusive
use of KVM guests.
Signed-off-by: Tony Krowiak <akrowiak@xxxxxxxxxxxxx>
I don't like the design of external interfaces except for:
* cpu model features, and
* reset handling.
In particular:
...snip...
4) If I were to act out the role of the administrator, I would
prefer to think of
specifying or changing the access controls of a guest in respect to
AP (that is
setting the AP matrix) as a single atomic operation -- which either
succeeds or fails.
The operation should succeed for any valid configuration, and fail
for any invalid
on.
The current piecemeal approach seems even less fitting if we
consider changing the
access controls of a running guest. AFAIK changing access controls
for a running
guest is possible, and I don't see a reason why should we
artificially prohibit this.
I think the current sysfs interface for manipulating the matrix is
good for
manual playing around, but I would prefer having an interface that
is better
suited for programs (e.g. ioctl).
I disagree with using ioctl.
Why? What speaks against ioctl?
Using a sysfs interface is easy and can be done using any interpreted
language.
It has become the standard way to configure drivers.
Even the existing interface must be consolidated, it exist and is
functional.
For what I understood, the problem is to have an atomic update of the
matrix to avoid possible dead-lock
when two admin tasks try to configure a matrix for a guest.
The problematic is a userland problem it is not a kernel problem.
We have several possibilities to avoid this problem but still keep a
sysfs interface:
- the admin tasks may use a lock
- the admin task may use a policy like freeing owned resources if they
can not get all resources.
Using a step by step configuration allows to easily know the missing
resource in case of failure.
Regards,
Pierre
I agree that the current implementation is not right.
The configuration of APM and AQM should always be guarantied as coherent
within the host but it can be done doing the right checks when using
the sysfs.
I'm glad we agree on this one at least.
Regards,
Halil
--
Pierre Morel
Linux/KVM/QEMU in Böblingen - Germany
