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exec/memory: Introduce RAM_NAMED_FILE flag

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migrate_ignore_shared() is an optimization that avoids copying memory
that is visible and can be mapped on the target.  However, a
memory-backend-ram or a memory-backend-memfd block with the RAM_SHARED
flag set is not migrated when migrate_ignore_shared() is true.  This is
wrong, because the block has no named backing store, and its contents will
be lost.  To fix, ignore shared memory iff it is a named file.  Define a
new flag RAM_NAMED_FILE to distinguish this case.

Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Message-Id: <1686151116-253260-1-git-send-email-steven.sistare@oracle.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
This commit is contained in:
Steve Sistare 2023-06-07 08:18:36 -07:00 • committed by Philippe Mathieu-Daudé
parent 6fe4f6c941
commit b0182e537e
6 changed files with 15 additions and 4 deletions
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3
migration/ram.c
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@ -197,7 +197,8 @@ static bool postcopy_preempt_active(void)
bool ramblock_is_ignored(RAMBlock *block)
{
return !qemu_ram_is_migratable(block) ||
(migrate_ignore_shared() && qemu_ram_is_shared(block));
(migrate_ignore_shared() && qemu_ram_is_shared(block)
&& qemu_ram_is_named_file(block));
}
#undef RAMBLOCK_FOREACH