Open Stack

Hi,

I was recently informed of a situation that came up when an engineer
added an SR-IOV nic to a compute node that was hosting some guests that
had VFs attached. Unfortunately, adding the card shuffled the PCI
addresses causing some degree of havoc. Basically, the PCI addresses
associated with the previously allocated VFs were no longer valid. 

I tend to consider this a non-issue. The expectation that hosts have
relatively static hardware configuration (and kernel/driver configs for
that matter) is the price you pay for having pets with direct hardware
access. That being said, this did come as a surprise to some of those
involved and I don't think we have any messaging around this or advice
on how to deal with situations like this.

So what should we do? I can't quite see altering OpenStack to deal with
this situation (or even how that could work). Has anyone done any
research into this problem, even if it is how to recover or extricate
a guest that is no longer valid? It seems that at the very least we
could use some stern warnings in the docs.

Cheers,

Brent
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