[Qemu-devel] [PATCH RFC] external backup api

[Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>]

Hi all.

This is the early begin of the series which aims to add external backup
api. This is needed to allow backup software use our dirty bitmaps.

Vmware and Parallels Cloud Server have this feature.

There is only one patch here, about querying dirty bitmap from qemu by
qmp command. It is just an updated and clipped (hmp command removed) old
my patch "[PATCH RFC v3 01/14] qmp: add query-block-dirty-bitmap".

Before writing the whole thing I'd like to discuss the details. Or, may
be there are existing plans on this topic, or may be someone already
works on it?

I see it like this:

=====

- add qmp commands for dirty-bitmap functions: create_successor, abdicate,
reclaime.
- make create-successor command transaction-able
- add query-block-dirty-bitmap qmp command

then, external backup:

qmp transaction {
    external-snapshot
    bitmap-create-successor
}

qmp query frozen bitmap, not acquiring aio context.

do external backup, using snapshot and bitmap

if (success backup)
    qmp bitmap-abdicate
else
    qmp bitmap-reclaime

qmp merge snapshot
=====


In the following patch query-bitmap acquires aio context. This must be
ofcourse dropped for frozen bitmap.
But to make it in true way, I think, I should check somehow that this is
not just frozen bitmap, but the bitmap frozen by qmp command, to avoid
incorrect quering of bitmap frozen by internal backup (or other
mechanizm).. May be, it is not necessary.



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1.8.3.1