Re: [Qemu-devel] [PATCH 0/8 RFC] migration: Introduce side channel for RAM

[Paolo Bonzini <pbonzini@redhat.com>]

Il 03/10/2013 06:03, Lei Li ha scritto:
>>>
> 
> Hi Paolo,
> 
> When debugging the code, I realized that this problem might still
> exist. In the incoming part, it will qemu_fopen_pipe() in
> unix_accept_incoming_migration first to enable the load_hook
> callback, the check action of this RAM_SAVE_FLAG_HOOK flags would
> lead to 8 bytes taken. Turns out, it will break normal unix 
> migration (without unix-page-flipping), because no matter normal unix
> migration or unix-page-flipping migration, the incoming side has to
> check this 8-byes flags first to decide whether the load_hook is
> called, and normal unix migration did not send this 8-byte flags.

Why is the load_hook callback being called at all without page flipping?
 Without page flipping, the before_iterate and save_page hook will
return immediately (or depending on your code they may never be called),
so the RAM_SAVE_FLAG_HOOK will never be written to the Unix socket.

> I wonder if I didn't understand your suggestion correctly?

Perhaps you want to discuss this tomorrow morning on #qemu?

Paolo