Jan Kiszka wrote:
If migration disables dirty memory logging, it must keep the vga logging
enabled, and vice versa.
So we need some notifier callbacks on slot changes so that all users can
re-enable dirty logging after the update as required.
Simpler to do reference counting. When a user enables logging for a
memory range, the refcount for all slots containing that range gets
bumped. When a user enables logging for all of memory, a global
refcount is bumped. For a given slot, dirty logging is enabled if
either the slot logging refcount or the global logging refcount is nonzero.
That's sort of what's implemented in qemu-kvm.git. In qemu.git vga
logging does not get disabled, which is really broken. It prevents
optimizations like disabling logging when the screen is not displayed to
a human.
Where/how does the
migration code disable dirty logging?
Should be phase 3 of ram_save_live().
--
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.
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