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    SubjectRe: [PATCH v17 06/15] s390/vfio-ap: refresh guest's APCB by filtering APQNs assigned to mdev
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    On 1/12/22 06:52, Halil Pasic wrote:
    > On Tue, 11 Jan 2022 16:19:06 -0500
    > Tony Krowiak <akrowiak@linux.ibm.com> wrote:
    >
    >>> Also we could probably do the filtering incrementally. In a sense that
    >>> at a time only so much changes, and we know that the invariant was
    >>> preserved without that change. But that would probably end up trading
    >>> complexity for cycles. I will trust your judgment and your tests on this
    >>> matter.
    >> I am not entirely clear on what you are suggesting. I think you are
    >> suggesting that there may not be a need to look at every APQN
    >> assigned to the mdev when an adapter or domain is assigned or
    >> unassigned or a queue is probed or removed. Maybe you can clarify
    >> what you are suggesting here.
    > Exactly. For example if we have the following assigned
    > adapters:
    > 1, 2, 3
    > domains:
    > 1, 2, 3
    > and the operation we are trying to perform is assign domain 4, then it
    > is sufficient to have a look at the queues with the APQNs (1,4), (2,4)
    > and (3, 4). We don't have to examine all the 14 queues.
    >
    > When an unassign dapter is performed, there is no need to do the
    > re-filtering, because there is nothing that can pop-back or go away. And
    > on unassign domain is performed, then all we care about are the queues
    > of that domain on the filtered adapters.
    >
    > Similarly if after that successful assign the queue (3,4) gets removed
    > (from vfio_ap) and then added back again and probed, we only have to
    > look at the queues (3, 1), (3, 2), (3, 3).
    >
    > But I'm OK with the current design of this. It is certainly conceptually
    > simpler to say we have a master-copy and we filter that master-copy based
    > on the very same rules every time something changes. I'm really fine
    > either way as log as it works well. :D
    >
    > Regards,
    > Halil

    I spent a day messing with this and was able to make it work, so
    the next implementation will incorporate your idea here.


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