Re: [PATCH v1 0/3] migration: Fixes to the 'background-snapshot' code

[Peter Xu]

On Fri, Mar 19, 2021 at 05:52:46PM +0300, Andrey Gruzdev wrote:
> Changes v0->v1:
>  * Using qemu_real_host_page_size instead of TARGET_PAGE_SIZE for host
>    page size in ram_block_populate_pages()
>  * More elegant implementation of ram_block_populate_pages()
> 
> This patch series contains:
>  * Fix to the issue with occasionally truncated non-iterable device state
>  * Solution to compatibility issues with virtio-balloon device
>  * Fix to the issue when discarded or never populated pages miss UFFD
>    write protection and get into migration stream in dirty state
> 
> Andrey Gruzdev (3):
>   migration: Fix missing qemu_fflush() on buffer file in
>     bg_migration_thread
>   migration: Inhibit virtio-balloon for the duration of background
>     snapshot
>   migration: Pre-fault memory before starting background snasphot

Unless Andrey would like to respin a new version, this version looks good to me
(I don't think the adding new helper issue in patch 1 is a blocker):

Reviewed-by: Peter Xu <peterx@redhat.com>

I'm also looking into introducing UFFD_FEATURE_WP_UNALLOCATED so as to
wr-protect page holes too for a uffd-wp region when the feature bit is set.
With that feature we should be able to avoid pre-fault as what we do in the
last patch of this series.  However even if that can work out, we'll still need
this for old kernel anyways.

Thanks,

-- 
Peter Xu