Regarding to the recent Intel IAA/DSA/QAT support on migration

[Peter Xu <peterx@redhat.com>]

Copy qemu-devel.

On Wed, Feb 07, 2024 at 04:07:40PM +0800, Peter Xu wrote:
> Hi,
> 
> I'm sending this email just to leave a generic comment to the recent
> migration efforts to enable these new Intel technologies.
> 
> The relevant patchsets (latest version so far) we're discussing are:
> 
>   [PATCH v3 0/4] Live Migration Acceleration with IAA Compression
>   https://lore.kernel.org/r/20240103112851.908082-1-yuan1.liu@intel.com
>   
>   [PATCH v3 00/20] Use Intel DSA accelerator to offload zero page checking in multifd live migration.
>   https://lore.kernel.org/r/20240104004452.324068-1-hao.xiang@bytedance.com
>   
>   [PATCH 0/5] *** Implement using Intel QAT to offload ZLIB
>   https://lore.kernel.org/r/20231231205804.2366509-1-bryan.zhang@bytedance.com
> 
> I want to comment in a generic way since this should apply to all these
> series:
> 
>   - A heads-up that multifd code is rapidly changing recently, I apologize
>     that you'll need a rebase.  It's just that it's probably much better to
>     do this before anything lands there.
> 
>     IIUC the good thing is we found that send_prepare() doesn't need to be
>     changed that much, however there's still some change; please refer to
>     the new code (I'll prepare a pull tomorrow to include most of the
>     changes, and we should have a major thread race fixed too with Fabiano
>     & Avihai's help). I hope this will also provide some kind of isolation
>     to e.g. other works that may touch other areas.  E.g., I hope fixed-ram
>     won't need to conflict much with any of the above series now.
> 
>   - When posting the new patchset (if there is a plan..), please make sure
>     we have:
> 
>     - Proper unit tests for the new code (probably mostly software
>       fallbacks to be tested on the new libraries being introduced; just to
>       make sure the new library code paths can get some torture please).
> 
>     - Proper documentation for the new code.  Please feel free to start
>       creating your own .rst file under docs/devel/migration/, we can try
>       to merge them later.  It should help avoid conflictions.  Please also
>       link the new file into index.rst there.
> 
>       IMHO the document can contain many things, the important ones could
>       start from: who should enable such feature; what one can get from
>       having it enabled; what is the HW requirement to enable it; how
>       should one tune the new parameters, and so on... some links to the
>       technology behinds it would be nice too to be referenced.
> 
>     - Try to add new code (especially HW/library based) into new file.
>       I see that QPL & QAT already proposed its own files (multifd-pql.c,
>       multifd-qatzip.c) which is great.
> 
>       Xiang, please also consider doing so for the DSA based zero page
>       detection.  It can be called multifd-zero-page.c, for example, and
>       you can create it when working on the
>       offload-zero-page-detect-to-multifd patchset already.
> 
>     - Please provide someone who can potentially maintain this code if ever
>       possible.  Pushing these code upstream is great, but maintaining will
>       also take effort.  It might be impractical this keeps growing for
>       migration maintainers (currently Fabiano and myself), so we may like
>       to have people covering these areas, especially when the new codes
>       are not directly relevant to migration framework.
> 
>       I'd suggest for each of the project we can add an entry in
>       MAINTAINERS below "Migration" section, adding relevant files (and
>       these files should exist in both the new section and "Migration").  I
>       am not sure whether Bytedance would be able to cover this, or we
>       should try to find someone from Intel?  If you're willing to add
>       yourself to maintain such codes, please attach the maintainers file
>       change together with the series.  It will be very much appreciated.
> 
> Thanks,
> 
> -- 
> Peter Xu

-- 
Peter Xu