Re: qemu-kvm.git now live

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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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