On Feb 17 16:25, Alexander Mikhalitsyn wrote:
> From: Alexander Mikhalitsyn <[email protected]>
> 
> Dear friends,
> 
> This patchset adds basic live migration support for
> QEMU emulated NVMe device.
> 
> Implementation has some limitations:
> - only one NVMe namespace is supported
> - SMART counters are not preserved
> - CMB is not supported
> - PMR is not supported
> - SPDM is not supported
> - SR-IOV is not supported
> - AERs are not fully supported
> 
> I believe this is something I can support in next patchset versions or
> separately on-demand (when usecase appears). But I wanted to share this
> first version as RFC to get some feedback on this in case if I'm approaching
> it wrong.
> 

Hi Alex,

Nice work!

As you have already identified, there are a lot of features that are
non-trivial to implement migration for. I am completely in favor of only
supporting migration on a very limited feature set (i.e., don't worry
about CMB, PMR, SPDM, SR-IOV, ZNS/FDP and so on). Focus on the bare
mandatory requirements. It would be preferable if the "is migration
possible?" test is an allowlist instead of a denylist. That makes sure
we don't add a feature down the road and forget to add it to the
denylist. I'm not 100% sure how to go about that at this point.

AERs are something we need to deal with. We should not drop events. I
don't think I have a problem with aborting enqueued AERs, but not the
events.

Finally, this at a minimum needs somekind of simple smoke test to catch
regressions. Preferably as part of the QEMU test suite itself, but if
that is hard to achieve, then I may be ok with an out-of-tree test that
maintainers can use.


Cheers,
Klaus

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