Implement the outgoing migration side for the 'mapped-ram' capability.
A bitmap is introduced to track which pages have been written in the
migration file. Pages are written at a fixed location for every
ramblock. Zero pages are ignored as they'd be zero in the destination
migration as well.
The migration stream is altered to put the dirty pages for a ramblock
after its header instead of having a sequential stream of pages that
follow the ramblock headers.
Without mapped-ram (current): With mapped-ram (new):
--------------------- --------------------------------
| ramblock 1 header | | ramblock 1 header |
--------------------- --------------------------------
| ramblock 2 header | | ramblock 1 mapped-ram header |
--------------------- --------------------------------
| ... | | padding to next 1MB boundary |
--------------------- | ... |
| ramblock n header | --------------------------------
--------------------- | ramblock 1 pages |
| RAM_SAVE_FLAG_EOS | | ... |
--------------------- --------------------------------
| stream of pages | | ramblock 2 header |
| (iter 1) | --------------------------------
| ... | | ramblock 2 mapped-ram header |
--------------------- --------------------------------
| RAM_SAVE_FLAG_EOS | | padding to next 1MB boundary |
--------------------- | ... |
| stream of pages | --------------------------------
| (iter 2) | | ramblock 2 pages |
| ... | | ... |
--------------------- --------------------------------
| ... | | ... |
--------------------- --------------------------------
| RAM_SAVE_FLAG_EOS |
--------------------------------
| ... |
--------------------------------
where:
- ramblock header: the generic information for a ramblock, such as
idstr, used_len, etc.
- ramblock mapped-ram header: the new information added by this
feature: bitmap of pages written, bitmap size and offset of pages
in the migration file.
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Fabiano Rosas <farosas@suse.de>
Link: https://lore.kernel.org/r/20240229153017.2221-10-farosas@suse.de
Signed-off-by: Peter Xu <peterx@redhat.com>
c2d5c4a7cb