Re: [PATCH v5 10/13] s390: vfio-ap: sysfs interface to view matrix mdev matrix

From: Pierre Morel
Date: Tue Jun 05 2018 - 08:41:02 EST


On 30/05/2018 16:28, Tony Krowiak wrote:
On 05/24/2018 05:10 AM, Pierre Morel wrote:
On 23/05/2018 16:38, Tony Krowiak wrote:
On 05/16/2018 03:55 AM, Pierre Morel wrote:
On 07/05/2018 17:11, Tony Krowiak wrote:
Provides a sysfs interface to view the AP matrix configured for the
mediated matrix device.

The relevant sysfs structures are:

/sys/devices/vfio_ap
... [matrix]
...... [mdev_supported_types]
......... [vfio_ap-passthrough]
............ [devices]
...............[$uuid]
.................. matrix

To view the matrix configured for the mediated matrix device,
print the matrix file:

This is the configured matrix, not the one used by the guest.
Nothing in the patches protect against binding a queue and assigning
a new AP when the guest runs.
The card and queue will be showed by this entry.

Of course, as stated above, this is the matrix configured for the
mediated matrix device. Are you suggesting here that the driver
should prevent assigning a new adapter or domain while a guest is
running? Couldn't this be a step in the process for hot (un)plugging
AP queues?

No, I mean what is the point to show this?
It is not what the guest sees.
Has it any use case?

The point is to display the matrix so one can view the AP queues that
have been assigned to the mediated matrix device. This is the only way
to view the matrix. Do you not find value in being able to see what
has been assigned to the mediated matrix device?

Two things:
1) I think it is better to retrieve the individual masks
2) As I said above, what you show is not the effective mask used by the guest




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