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migration/ram: Fix error handling in ram_write_tracking_start() 

If something goes wrong during uffd_change_protection(), we would miss
to unregister uffd-wp and not release our reference. Fix it by
performing the uffd_change_protection(true) last.

Note that a uffd_change_protection(false) on the recovery path without a
prior uffd_change_protection(false) is fine.

Fixes: 278e2f551a ("migration: support UFFD write fault processing in ram_save_iterate()")
Cc: qemu-stable@nongnu.org
Reviewed-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
This commit is contained in:
David Hildenbrand 2023-01-05 13:45:25 +01:00 committed by Juan Quintela
parent 5f19a44919
commit 72ef3a3708
1 changed files with 3 additions and 2 deletions
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5
migration/ram.c
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@ -1896,13 +1896,14 @@ int ram_write_tracking_start(void)
block->max_length, UFFDIO_REGISTER_MODE_WP, NULL)) {
goto fail;
}
block->flags |= RAM_UF_WRITEPROTECT;
memory_region_ref(block->mr);
/* Apply UFFD write protection to the block memory range */
if (uffd_change_protection(rs->uffdio_fd, block->host,
block->max_length, true, false)) {
goto fail;
}
block->flags |= RAM_UF_WRITEPROTECT;
memory_region_ref(block->mr);
trace_ram_write_tracking_ramblock_start(block->idstr, block->page_size,
block->host, block->max_length);