Re: [PATCH v5 00/11] migration: fast snapshot load

[Peter Xu <peterx@redhat.com>]

Hey, Aadeshveer,

On Sun, Aug 16, 2026 at 11:16:20PM +0530, Aadeshveer Singh wrote:
> v4 -> v5
> - Modify pending_bmap(Patch 6) to use variable size for better
>   efficient atomic state management
> - Added a comment(Patch 7) explaining postcopy_mapped_ram_load_page
>   explaining why cases where guest page is larger than host page are
>   disabled following what remote postcopy follows
> - Add a new check(Patch 9) in migrate_prepare to bail out if migrate
>   was used with fast snapshot load enabled, as suggested by Peter

There're something you didn't mention but we discussed it only during the
meeting about host/guest psize problem.  For this time, I'll do it for you.
Aadeshveer, please remember to mention such conclusions and findings in the
future when you will be working on other patches.

The quick summary: Aadeshveer found postcopy doesn't support guest psize >
host psize since the start, which will already fail the set capabilities in
postcopy_ram_supported_by_host().  It means we can also skip supporting
that in fast snapshot load.

Personally, I still prefer removal of all such guest psize > host psize
handlings in your current code; postcopy_place_page() isn't ready, so the
current code won't work anyway for that setup.  With it removed, then we
can stick pending_bmap with host psize, which can also cause less confusion
and make it easier to read.  But I think it's not a huge deal, and AFAIU
the code works as expected.  So I think it's fine for now.

If you're going to prepare a small series on top of this, please consider
reverting those changes back to the simple version with one patch on top.

Other than that, thanks for your hard work in the past few months!  Since I
believe this code still should function all well, I queued it for 11.2.

-- 
Peter Xu